LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 LM2727/LM2737 N-Channel FET Synchronous Buck Regulator Controller for Low Output Voltages Check for Samples: LM2727, LM2737 FEATURES DESCRIPTION * * * The LM2727 and LM2737 are high-speed, synchronous, switching regulator controllers. They are intended to control currents of 0.7A to 20A with up to 95% conversion efficiencies. The LM2727 employs output over-voltage and under-voltage latchoff. For applications where latch-off is not desired, the LM2737 can be used. Power up and down sequencing is achieved with the power-good flag, adjustable soft-start and output enable features. The LM2737 and LM2737 operate from a low-current 5V bias and can convert from a 2.2V to 16V power rail. Both parts utilize a fixed-frequency, voltage-mode, PWM control architecture and the switching frequency is adjustable from 50kHz to 2MHz by adjusting the value of an external resistor. Current limit is achieved by monitoring the voltage drop across the on-resistance of the low-side MOSFET, which enhances low duty-cycle operation. The wide range of operating frequencies gives the power supply designer the flexibility to fine-tune component size, cost, noise and efficiency. The adaptive, nonoverlapping MOSFET gate-drivers and high-side bootstrap structure helps to further maximize efficiency. The high-side power FET drain voltage can be from 2.2V to 16V and the output voltage is adjustable down to 0.6V. 1 2 * * * * * * * Input Power from 2.2V to 16V Output Voltage Adjustable Down to 0.6V Power Good flag, Adjustable Soft-Start and Output Enable for Easy Power Sequencing Output Over-Voltage and Under-Voltage LatchOff (LM2727) Output Over-Voltage and Under-Voltage Flag (LM2737) Reference Accuracy: 1.5% (0C - 125C) Current Limit Without Sense Resistor Soft Start Switching Frequency from 50 kHz to 2 MHz TSSOP-14 Package APPLICATIONS * * * * * Cable Modems Set-Top Boxes/ Home Gateways DDR Core Power High-Efficiency Distributed Power Local Regulation of Core Power Typical Application +5V 0.1P RIN 10: CIN 2.2PF RFADJ Q1 VCC HG BOOT SD CSS 12n CIN1,2 10PF 6.3V Si4884DY 1.5 PH 6.1 A, 9.6 m: RCS VO = 1.2V@5A ISEN PWGD LM27x7 FREQ 63.4k VIN = 3.3V CBOOT D1 LG SS PGND SGND PGND EAO 2.2k Q2 L1 Si4884DY RFB2 10k + CO1,2 2200PF 6.3V, 2.8A FB RFB1 10k CC1 CC2 180p 2.2p RC1 392k 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2002-2013, Texas Instruments Incorporated LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Connection Diagram 1 2 3 5 6 7 HG LG PGND SGND Vcc PWGD ISEN PGND LM27x7 4 BOOT SD FREQ FB SS EAO 14 13 12 11 10 9 8 Figure 1. 14-Lead Plastic TSSOP JA = 155C/W See Package Number PW0014A PIN DESCRIPTION BOOT (Pin 1) - Supply rail for the N-channel MOSFET gate drive. The voltage should be at least one gate threshold above the regulator input voltage to properly turn on the high-side N-FET. LG (Pin 2) - Gate drive for the low-side N-channel MOSFET. This signal is interlocked with HG to avoid shoot-through problems. PGND (Pins 3, 13) - Ground for FET drive circuitry. It should be connected to system ground. SGND (Pin 4) - Ground for signal level circuitry. It should be connected to system ground. VCC (Pin 5) - Supply rail for the controller. PWGD (Pin 6) - Power Good. This is an open drain output. The pin is pulled low when the chip is in UVP, OVP, or UVLO mode. During normal operation, this pin is connected to VCC or other voltage source through a pull-up resistor. ISEN (Pin 7) - Current limit threshold setting. This sources a fixed 50A current. A resistor of appropriate value should be connected between this pin and the drain of the low-side FET. EAO (Pin 8) - Output of the error amplifier. The voltage level on this pin is compared with an internally generated ramp signal to determine the duty cycle. This pin is necessary for compensating the control loop. SS (Pin 9) - Soft start pin. A capacitor connected between this pin and ground sets the speed at which the output voltage ramps up. Larger capacitor value results in slower output voltage ramp but also lower inrush current. FB (Pin 10) - This is the inverting input of the error amplifier, which is used for sensing the output voltage and compensating the control loop. FREQ (Pin 11) - The switching frequency is set by connecting a resistor between this pin and ground. SD (Pin 12) - IC Logic Shutdown. When this pin is pulled low the chip turns off the high side switch and turns on the low side switch. While this pin is low, the IC will not start up. An internal 20A pull-up connects this pin to VCC. HG (Pin 14) - Gate drive for the high-side N-channel MOSFET. This signal is interlocked with LG to avoid shoot-through problems. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 2 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 Absolute Maximum Ratings (1) (2) VCC 7V BOOTV 21V Junction Temperature 150C Storage Temperature -65C to 150C Soldering Information Lead Temperature (soldering, 10sec) 260C Infrared or Convection (20sec) 235C ESD Rating (1) (2) (3) (3) 2 kV Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device operates correctly. Opearting Ratings do not imply ensured performance limits. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. The human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin. Operating Ratings Supply Voltage (VCC) 4.5V to 5.5V -40C to +125C Junction Temperature Range Thermal Resistance (JA) 155C/W Electrical Characteristics VCC = 5V unless otherwise indicated. Typicals and limits appearing in plain type apply for TA=TJ=+25C. Limits appearing in boldface type apply over full Operating Temperature Range. Datasheet min/max specification limits are ensured by design, test, or statistical analysis. Symbol VFB_ADJ VON Parameter Conditions FB Pin Voltage UVLO Thresholds Min Typ Max VCC = 4.5V, 0C to +125C 0.591 0.6 0.609 VCC = 5V, 0C to +125C 0.591 0.6 0.609 VCC = 5.5V, 0C to +125C 0.591 0.6 0.609 VCC = 4.5V, -40C to +125C 0.589 0.6 0.609 VCC = 5V, -40C to +125C 0.589 0.6 0.609 VCC = 5.5V, -40C to +125C 0.589 0.6 0.609 Rising Falling 4.2 3.6 Units V V SD = 5V, FB = 0.55V Fsw = 600kHz 1 1.5 2 SD = 5V, FB = 0.65V Fsw = 600kHz 0.8 1.7 2.2 Shutdown VCC Current SD = 0V 0.15 0.4 0.7 tPWGD1 PWGD Pin Response Time FB Voltage Going Up 6 tPWGD2 PWGD Pin Response Time FB Voltage Going Down 6 s 20 A IQ-V5 ISD ISS-ON ISS-OC ISEN-TH Operating VCC Current mA SD Pin Internal Pull-up Current SS Pin Source Current SS Voltage = 2.5V 0C to +125C -40C to +125C SS Pin Sink Current During Over Current SS Voltage = 2.5V ISEN Pin Source Current Trip Point 0C to +125C -40C to +125C 8 5 11 11 s 15 15 95 35 28 50 50 Product Folder Links: LM2727 LM2737 A A 65 65 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated mA A 3 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Electrical Characteristics (continued) VCC = 5V unless otherwise indicated. Typicals and limits appearing in plain type apply for TA=TJ=+25C. Limits appearing in boldface type apply over full Operating Temperature Range. Datasheet min/max specification limits are ensured by design, test, or statistical analysis. Symbol Parameter Conditions Min Typ Max Units ERROR AMPLIFIER GBW G Error Amplifier Unity Gain Bandwidth 5 MHz Error Amplifier DC Gain 60 dB SR Error Amplifier Slew Rate 6 V/A IFB FB Pin Bias Current FB = 0.55V FB = 0.65V IEAO EAO Pin Current Sourcing and Sinking VEAO = 2.5, FB = 0.55V VEAO = 2.5, FB = 0.65V 2.8 0.8 mA VEA Error Amplifier Maximum Swing Minimum Maximum 1.2 3.2 V BOOT Pin Quiescent Current BOOTV = 12V, EN = 0 0C to +125C -40C to +125C 95 95 0 0 15 30 100 155 nA GATE DRIVE IQ-BOOT 160 215 A RDS1 Top FET Driver Pull-Up ON resistance BOOT-SW = 5V@350mA 3 RDS2 Top FET Driver Pull-Down ON resistance BOOT-SW = 5V@350mA 2 RDS3 Bottom FET Driver Pull-Up ON resistance BOOT-SW = 5V@350mA 3 RDS4 Bottom FET Driver Pull-Down ON resistance BOOT-SW = 5V@350mA 2 OSCILLATOR fOSC D PWM Frequency Max Duty Cycle RFADJ = 590k 50 RFADJ = 88.7k 300 RFADJ = 42.2k, 0C to +125C 500 600 700 RFADJ = 42.2k, -40C to +125C 490 600 700 RFADJ = 17.4k 1400 RFADJ = 11.3k 2000 fPWM = 300kHz fPWM = 600kHz 90 88 kHz % LOGIC INPUTS AND OUTPUTS VSD-IH SD Pin Logic High Trip Point VSD-IL SD Pin Logic Low Trip Point 0C to +125C -40C to +125C 1.3 1.25 1.6 1.6 PWGD Pin Trip Points FB Voltage Going Down 0C to +125C -40C to +125C 0.413 0.410 0.430 0.430 0.446 0.446 V FB Voltage Going Up 0C to +125C -40C to +125C 0.691 0.688 0.710 0.710 0.734 0.734 V VPWGD-TH-LO VPWGD-TH-HI VPWGD-HYS 4 2.6 PWGD Pin Trip Points PWGD Hysteresis (LM2737 only) FB Voltage Going Down FB Voltage Going Up Submit Documentation Feedback 35 110 3.5 V V mV Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 Typical Performance Characteristics Efficiency (VO = 1.5V) FSW = 300kHz, TA = 25C Efficiency (VO = 3.3V) FSW = 300kHz, TA = 25C 100 100 Vin = 5V Vin = 3.3V 90 90 EFFICIENCY (%) EFFICIENCY (%) 80 Vin = 5V 70 60 50 Vin = 12V 40 80 70 50 40 30 30 0.1 20 0.2 1 3 5 9 7 0.5 2 4 6 8 10 OUTPUT CURRENT (A) OUTPUT CURRENT (A) Figure 2. Figure 3. VCC Operating Current vs Temperature FSW = 600kHz, No-Load Bootpin Current vs Temperature for BOOTV = 12V FSW = 600kHz, Si4826DY FET, No-Load 30.3 1.64 1.62 30.1 Without Bootstrap (Vboot = 12V) 1.6 BOOT PIN CURRENT (mA) OPEARTING CURRENT(mA) Vin = 12V 60 1.58 1.56 With Bootstrap (Vboot = 5V) 1.54 1.52 1.5 29.9 29.7 29.5 29.3 29.1 1.48 28.9 1.46 0 20 35 55 75 95 115 AMBIENT TEMPERATURE ( C) Figure 4. Figure 5. Bootpin Current vs Temperature with 5V Bootstrap FSW = 600kHz, Si4826DY FET, No-Load PWM Frequency vs Temperature for RFADJ = 43.2k 8.6 630 8.4 628 8.2 626 PWM FREQUENCY (kHz) BOOT PIN CURRENT (mA) 0 10 20 25 35 45 55 65 75 85 95105115 125 AMBIENT TEMPERATURE (oC) o 8 7.8 7.6 7.4 7.2 624 622 620 618 616 614 7 0 10 20 25 35 45 55 65 75 85 95 105115125 612 o AMBIENT TEMPERATURE ( C) Figure 6. 0 10 20 25 35 45 55 65 75 85 95 105115 125 AMBIENT TEMPERATURE (oC) Figure 7. Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 5 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) RFADJ vs PWM Frequency (in 100 to 800kHz range), TA = 25C RFADJ vs PWM Frequency (in 900 to 2000kHz range), TA = 25C 500 30 400 RF-ADJ (k:) RF-ADJ (k:) 25 300 200 20 15 100 0 100 150 200 250 300 350 400450 500 600 700 800 10 9001000110012001300140015001600170018001900 PWM FREQUENCY (kHz) PWM FREQUENCY (kHz) Figure 8. Figure 9. VCC Operating Current Plus Boot Current vs PWM Frequency (Si4826DY FET, TA = 25C) Switch Waveforms (HG Falling) VIN = 5V, VO = 1.8V IO = 3A, CSS = 10nF FSW = 600kHz 40 VCC PLUS BOOT CURRENT 35 30 25 20 15 10 5 0 100 300 500 700 9001100 13001500 17001900 PWM FREQUENCY (kHz) 6 Figure 10. Figure 11. Switch Waveforms (HG Rising) VIN = 5V, VO = 1.8V IO = 3A, FSW = 600kHz Start-Up (No-Load) VIN = 10V, VO = 1.2V CSS = 10nF, FSW = 300kHz Figure 12. Figure 13. Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 Typical Performance Characteristics (continued) Start-Up (Full-Load) VIN = 10V, VO = 1.2V IO = 10A, CSS = 10nF FSW = 300kHz Start Up (No-Load, 10x CSS) VIN = 10V, VO = 1.2V CSS = 100nF, FSW = 300kHz Figure 14. Figure 15. Start Up (Full Load, 10x CSS) VIN = 10V, VO = 1.2V IO = 10A, CSS = 100nF FSW = 300kHz Shutdown VIN = 10V, VO = 1.2V IO = 10A, CSS = 10nF FSW = 300kHz Figure 16. Figure 17. Start Up (Full Load, 10x CSS) VIN = 10V, VO = 1.2V IO = 10A, CSS = 100nF FSW = 300kHz Load Transient Response (IO = 0 to 4A) VIN = 12V, VO = 1.2V FSW = 300kHz Figure 18. Figure 19. Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 7 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) 8 Load Transient Response (IO = 4 to 0A) VIN = 12V, VO = 1.2V FSW = 300kHz Line Transient Response (VIN =5V to 12V) VO = 1.2V, IO = 5A FSW = 300kHz Figure 20. Figure 21. Line Transient Response (VIN =12V to 5V) VO = 1.2V, IO = 5A FSW = 300kHz Line Transient Response VO = 1.2V, IO = 5A FSW = 300kHz Figure 22. Figure 23. Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 Block Diagram SD FREQ Vcc CLOCK & RAMP UVLO PGND PGND SGND 20PA off LOGIC BOOT SHUT DOWN LATCH 10Ps DELAY HG PWGD 3.05V 10PA HIGH LOW LG 0.708V tol.=+/-2% 0.42V tol.=+/-2% hyst.=12% S OUTPUT CLAMP HI: 3.25V LO: 1.25V SS 3.25V oc 95P$ R 1.25V R>S SS CMP off off SYNCHRONOUS DRIVER LOGIC PWM 50PA BG = 0.6V ISEN ILIM EA oc FB EAO Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 9 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com APPLICATION INFORMATION THEORY OF OPERATION The LM2727 is a voltage-mode, high-speed synchronous buck regulator with a PWM control scheme. It is designed for use in set-top boxes, thin clients, DSL/Cable modems, and other applications that require high efficiency buck converters. It has power good (PWRGD), output shutdown (SD), over voltage protection (OVP) and under voltage protection (UVP). The over-voltage and under-voltage signals are OR gated to drive the Power Good signal and a shutdown latch, which turns off the high side gate and turns on the low side gate if pulled low. Current limit is achieved by sensing the voltage VDS across the low side FET. During current limit the high side gate is turned off and the low side gate turned on. The soft start capacitor is discharged by a 95A source (reducing the maximum duty cycle) until the current is under control. The LM2737 does not latch off during UVP or OVP, and uses the HIGH and LOW comparators for the powergood function only. START UP When VCC exceeds 4.2V and the enable pin EN sees a logic high the soft start capacitor begins charging through an internal fixed 10A source. During this time the output of the error amplifier is allowed to rise with the voltage of the soft start capacitor. This capacitor, Css, determines soft start time, and can be determined approximately by: (1) An application for a microprocessor might need a delay of 3ms, in which case CSS would be 12nF. For a different device, a 100ms delay might be more appropriate, in which case CSS would be 400nF. (390 10%) During soft start the PWRGD flag is forced low and is released when the voltage reaches a set value. At this point this chip enters normal operation mode, the Power Good flag is released, and the OVP and UVP functions begin to monitor Vo. NORMAL OPERATION While in normal operation mode, the LM2727/37 regulates the output voltage by controlling the duty cycle of the high side and low side FETs. The equation governing output voltage is: (2) The PWM frequency is adjustable between 50kHz and 2MHz and is set by an external resistor, RFADJ, between the FREQ pin and ground. The resistance needed for a desired frequency is approximately: (3) MOSFET GATE DRIVERS The LM2727/37 has two gate drivers designed for driving N-channel MOSFETs in a synchronous mode. Power for the drivers is supplied through the BOOTV pin. For the high side gate (HG) to fully turn on the top FET, the BOOTV voltage must be at least one VGS(th) greater than Vin. (BOOTV 2*Vin) This voltage can be supplied by a separate, higher voltage source, or supplied from a local charge pump structure. In a system such as a desktop computer, both 5V and 12V are usually available. Hence if Vin was 5V, the 12V supply could be used for BOOTV. 12V is more than 2*Vin, so the HG would operate correctly. For a BOOTV of 12V, the initial gate charging current is 2A, and the initial gate discharging current is typically 6A. 10 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 5V Cb BOOTV + HG Vo LM27x7 + LG Figure 24. BOOTV Supplied by Charge Pump In a system without a separate, higher voltage, a charge pump (bootstrap) can be built using a diode and small capacitor, Figure 24. The capacitor serves to maintain enough voltage between the top FET gate and source to control the device even when the top FET is on and its source has risen up to the input voltage level. The LM2727/37 gate drives use a BiCMOS design. Unlike some other bipolar control ICs, the gate drivers have rail-to-rail swing, ensuring no spurious turn-on due to capacitive coupling. POWER GOOD SIGNAL The power good signal is the or-gated flag representing over-voltage and under-voltage protection. If the output voltage is 18% over it's nominal value, VFB = 0.7V, or falls 30% below that value, VFB = 0.41V, the power good flag goes low. The converter then turns off the high side gate, and turns on the low side gate. Unlike the output (LM2727 only) the power good flag is not latched off. It will return to a logic high whenever the feedback pin voltage is between 70% and 118% of 0.6V. UVLO The 4.2V turn-on threshold on VCC has a built in hysteresis of 0.6V. Therefore, if VCC drops below 3.6V, the chip enters UVLO mode. UVLO consists of turning off the top FET, turning on the bottom FET, and remaining in that condition until VCC rises above 4.2V. As with shutdown, the soft start capacitor is discharged through a FET, ensuring that the next start-up will be smooth. CURRENT LIMIT Current limit is realized by sensing the voltage across the low side FET while it is on. The RDSON of the FET is a known value, hence the current through the FET can be determined as: VDS = I * RDSON (4) The current limit is determined by an external resistor, RCS, connected between the switch node and the ISEN pin. A constant current of 50A is forced through Rcs, causing a fixed voltage drop. This fixed voltage is compared against VDS and if the latter is higher, the current limit of the chip has been reached. RCS can be found by using the following: RCS = RDSON(LOW) * ILIM/50A (5) For example, a conservative 15A current limit in a 10A design with a minimum RDSON of 10m would require a 3.3k resistor. Because current sensing is done across the low side FET, no minimum high side on-time is necessary. In the current limit mode the LM2727/37 will turn the high side off and the keep low side on for as long as necessary. The chip also discharges the soft start capacitor through a fixed 95A source. In this way, smooth ramping up of the output voltage as with a normal soft start is ensured. The output of the LM2727/37 internal error amplifier is limited by the voltage on the soft start capacitor. Hence, discharging the soft start capacitor reduces the maximum duty cycle D of the controller. During severe current limit, this reduction in duty cycle will reduce the output voltage, if the current limit conditions lasts for an extended time. During the first few nanoseconds after the low side gate turns on, the low side FET body diode conducts. This causes an additional 0.7V drop in VDS. The range of VDS is normally much lower. For example, if RDSON were 10m and the current through the FET was 10A, VDS would be 0.1V. The current limit would see 0.7V as a 70A current and enter current limit immediately. Hence current limit is masked during the time it takes for the high side switch to turn off and the low side switch to turn on. Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 11 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com UVP/OVP The output undervoltage protection and overvoltage protection mechanisms engage at 70% and 118% of the target output voltage, respectively. In either case, the LM2727 will turn off the high side switch and turn on the low side switch, and discharge the soft start capacitor through a MOSFET switch. The chip remains in this state until the shutdown pin has been pulled to a logic low and then released. The UVP function is masked only during the first charging of the soft start capacitor, when voltage is first applied to the VCC pin. In contrast, the LM2737 is designed to continue operating during UVP or OVP conditions, and to resume normal operation once the fault condition is cleared. As with the LM2727, the powergood flag goes low during this time, giving a logic-level warning signal. SHUT DOWN If the shutdown pin SD is pulled low, the LM2727/37 discharges the soft start capacitor through a MOSFET switch. The high side switch is turned off and the low side switch is turned on. The LM2727/37 remains in this state until SD is released. DESIGN CONSIDERATIONS The following is a design procedure for all the components needed to create the circuit shown in Figure 26 in the Example Circuits section, a 5V in to 1.2V out converter, capable of delivering 10A with an efficiency of 85%. The switching frequency is 300kHz. The same procedures can be followed to create the circuit shown in Figure 26, Figure 27, and to create many other designs with varying input voltages, output voltages, and output currents. INPUT CAPACITOR The input capacitors in a Buck switching converter are subjected to high stress due to the input current waveform, which is a square wave. Hence input caps are selected for their ripple current capability and their ability to withstand the heat generated as that ripple current runs through their ESR. Input rms ripple current is approximately: (6) The power dissipated by each input capacitor is: (7) Here, n is the number of capacitors, and indicates that power loss in each cap decreases rapidly as the number of input caps increase. The worst-case ripple for a Buck converter occurs during full load, when the duty cycle D = 50%. In the 5V to 1.2V case, D = 1.2/5 = 0.24. With a 10A maximum load the ripple current is 4.3A. The Sanyo 10MV5600AX aluminum electrolytic capacitor has a ripple current rating of 2.35A, up to 105C. Two such capacitors make a conservative design that allows for unequal current sharing between individual caps. Each capacitor has a maximum ESR of 18m at 100 kHz. Power loss in each device is then 0.05W, and total loss is 0.1W. Other possibilities for input and output capacitors include MLCC, tantalum, OSCON, SP, and POSCAPS. INPUT INDUCTOR The input inductor serves two basic purposes. First, in high power applications, the input inductor helps insulate the input power supply from switching noise. This is especially important if other switching converters draw current from the same supply. Noise at high frequency, such as that developed by the LM2727 at 1MHz operation, could pass through the input stage of a slower converter, contaminating and possibly interfering with its operation. An input inductor also helps shield the LM2727 from high frequency noise generated by other switching converters. The second purpose of the input inductor is to limit the input current slew rate. During a change from no-load to full-load, the input inductor sees the highest voltage change across it, equal to the full load current times the input capacitor ESR. This value divided by the maximum allowable input current slew rate gives the minimum input inductance: 12 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 (8) In the case of a desktop computer system, the input current slew rate is the system power supply or "silver box" output current slew rate, which is typically about 0.1A/s. Total input capacitor ESR is 9m, hence V is 10*0.009 = 90 mV, and the minimum inductance required is 0.9H. The input inductor should be rated to handle the DC input current, which is approximated by: (9) In this case IIN-DC is about 2.8A. One possible choice is the TDK SLF12575T-1R2N8R2, a 1.2H device that can handle 8.2Arms, and has a DCR of 7m. OUTPUT INDUCTOR The output inductor forms the first half of the power stage in a Buck converter. It is responsible for smoothing the square wave created by the switching action and for controlling the output current ripple. (Io) The inductance is chosen by selecting between tradeoffs in efficiency and response time. The smaller the output inductor, the more quickly the converter can respond to transients in the load current. As shown in the efficiency calculations, however, a smaller inductor requires a higher switching frequency to maintain the same level of output current ripple. An increase in frequency can mean increasing loss in the FETs due to the charging and discharging of the gates. Generally the switching frequency is chosen so that conduction loss outweighs switching loss. The equation for output inductor selection is: (10) Plugging in the values for output current ripple, input voltage, output voltage, switching frequency, and assuming a 40% peak-to-peak output current ripple yields an inductance of 1.5H. The output inductor must be rated to handle the peak current (also equal to the peak switch current), which is (Io + 0.5*Io). This is 12A for a 10A design. The Coilcraft D05022-152HC is 1.5H, is rated to 15Arms, and has a DCR of 4m. OUTPUT CAPACITOR The output capacitor forms the second half of the power stage of a Buck switching converter. It is used to control the output voltage ripple (Vo) and to supply load current during fast load transients. In this example the output current is 10A and the expected type of capacitor is an aluminum electrolytic, as with the input capacitors. (Other possibilities include ceramic, tantalum, and solid electrolyte capacitors, however the ceramic type often do not have the large capacitance needed to supply current for load transients, and tantalums tend to be more expensive than aluminum electrolytic.) Aluminum capacitors tend to have very high capacitance and fairly low ESR, meaning that the ESR zero, which affects system stability, will be much lower than the switching frequency. The large capacitance means that at switching frequency, the ESR is dominant, hence the type and number of output capacitors is selected on the basis of ESR. One simple formula to find the maximum ESR based on the desired output voltage ripple, Vo and the designed output current ripple, Io, is: (11) In this example, in order to maintain a 2% peak-to-peak output voltage ripple and a 40% peak-to-peak inductor current ripple, the required maximum ESR is 6m. Three Sanyo 10MV5600AX capacitors in parallel will give an equivalent ESR of 6m. The total bulk capacitance of 16.8mF is enough to supply even severe load transients. Using the same capacitors for both input and output also keeps the bill of materials simple. Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 13 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com MOSFETS MOSFETS are a critical part of any switching controller and have a direct impact on the system efficiency. In this case the target efficiency is 85% and this is the variable that will determine which devices are acceptable. Loss from the capacitors, inductors, and the LM2727 itself are detailed in the Efficiency section, and come to about 0.54W. To meet the target efficiency, this leaves 1.45W for the FET conduction loss, gate charging loss, and switching loss. Switching loss is particularly difficult to estimate because it depends on many factors. When the load current is more than about 1 or 2 amps, conduction losses outweigh the switching and gate charging losses. This allows FET selection based on the RDSON of the FET. Adding the FET switching and gate-charging losses to the equation leaves 1.2W for conduction losses. The equation for conduction loss is: PCnd = D(I2o * RDSON *k) + (1-D)(I2o * RDSON *k) (12) The factor k is a constant which is added to account for the increasing RDSON of a FET due to heating. Here, k = 1.3. The Si4442DY has a typical RDSON of 4.1m. When plugged into the equation for PCND the result is a loss of 0.533W. If this design were for a 5V to 2.5V circuit, an equal number of FETs on the high and low sides would be the best solution. With the duty cycle D = 0.24, it becomes apparent that the low side FET carries the load current 76% of the time. Adding a second FET in parallel to the bottom FET could improve the efficiency by lowering the effective RDSON. The lower the duty cycle, the more effective a second or even third FET can be. For a minimal increase in gate charging loss (0.054W) the decrease in conduction loss is 0.15W. What was an 85% design improves to 86% for the added cost of one SO-8 MOSFET. CONTROL LOOP COMPONENTS The circuit is this design example and the others shown in the Example Circuits section have been compensated to improve their DC gain and bandwidth. The result of this compensation is better line and load transient responses. For the LM2727, the top feedback divider resistor, Rfb2, is also a part of the compensation. For the 10A, 5V to 1.2V design, the values are: Cc1 = 4.7pF 10%, Cc2 = 1nF 10%, Rc = 229k 1%. These values give a phase margin of 63 and a bandwidth of 29.3kHz. SUPPORT CAPACITORS AND RESISTORS The Cinx capacitors are high frequency bypass devices, designed to filter harmonics of the switching frequency and input noise. Two 1F ceramic capacitors with a sufficient voltage rating (10V for the Circuit of Figure 26) will work well in almost any case. Rbypass and Cbypass are standard filter components designed to ensure smooth DC voltage for the chip supply and for the bootstrap structure, if it is used. Use 10 for the resistor and a 2.2F ceramic for the cap. Cb is the bootstrap capacitor, and should be 0.1F. (In the case of a separate, higher supply to the BOOTV pin, this 0.1F cap can be used to bypass the supply.) Using a Schottky device for the bootstrap diode allows the minimum drop for both high and low side drivers. The On Semiconductor BAT54 or MBR0520 work well. Rp is a standard pull-up resistor for the open-drain power good signal, and should be 10k. If this feature is not necessary, it can be omitted. RCS is the resistor used to set the current limit. Since the design calls for a peak current magnitude (Io + 0.5 * Io) of 12A, a safe setting would be 15A. (This is well below the saturation current of the output inductor, which is 25A.) Following the equation from the Current Limit section, use a 3.3k resistor. RFADJ is used to set the switching frequency of the chip. Following the equation in the Theory of Operation section, the closest 1% tolerance resistor to obtain fSW = 300kHz is 88.7k. CSS depends on the users requirements. Based on the equation for CSS in the Theory of Operation section, for a 3ms delay, a 12nF capacitor will suffice. 14 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 EFFICIENCY CALCULATIONS A reasonable estimation of the efficiency of a switching controller can be obtained by adding together the loss is each current carrying element and using the equation: (13) The following shows an efficiency calculation to complement the Circuit of Figure 26. Output power for this circuit is 1.2V x 10A = 12W. Chip Operating Loss PIQ = IQ-VCC *VCC (14) 2mA x 5V = 0.01W FET Gate Charging Loss PGC = n * VCC * QGS * fOSC (15) The value n is the total number of FETs used. The Si4442DY has a typical total gate charge, QGS, of 36nC and an rds-on of 4.1m. For a single FET on top and bottom: 2*5*36E-9*300,000 = 0.108W FET Switching Loss PSW = 0.5 * Vin * IO * (tr + tf)* fOSC (16) -9 The Si4442DY has a typical rise time tr and fall time tf of 11 and 47ns, respectively. 0.5*5*10*58E *300,000 = 0.435W FET Conduction Loss PCn = 0.533W (17) Input Capacitor Loss (18) (19) 2 4.28 *0.018/2 = 0.084W Input Inductor Loss PLin = I2in * DCRinput-L (20) (21) 2 2.82 *0.007 = 0.055W Output Inductor Loss PLout = I2o * DCRoutput-L (22) 2 10 *0.004 = 0.4W System Efficiency (23) Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 15 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Example Circuits +5V D1 Rin 10 Cin 2.2u Rfadj 0.1u Q1 BOOT SD Css 12n 2.7 uH 14.4 A, 4.5 m: Rcs ISEN PWGD LM27x7 LG SS PGND SGND PGND Lin + Cin1,2 2 x 10 uF 25V, 3.3A Cinx 1uF 25V HG Vcc FREQ 88.7k 1.2 uH 8.2 A, 6.9 m: Cboot Vin = 12V Vo = 3.3V@10A L1 1.8k Q2 + Co1-4 4 x 100 uF 10V, 55 m: Rfb2 49.9k Rc2 Cc3 FB EAO 8.45k 470p Rfb1 11k Cc1 Cc2 6.8p Rc1 143.3k 270p Figure 25. 5V-16V to 3.3V, 10A, 300kHz This circuit and the one featured on the front page have been designed to deliver high current and high efficiency in a small package, both in area and in height The tallest component in this circuit is the inductor L1, which is 6mm tall. The compensation has been designed to tolerate input voltages from 5 to 16V. D1 1.2 uH 8.2 A, 6.9 m: Cboot Rin 10 0.1u Cinx1, 2 2x1uF 10V Q1 Cin 2.2u Rfadj Vcc HG SD BOOT PWGD Css 12n 1.5 uH 15 A, 4 m: ISEN LM27x7 FREQ 88.7k Rcs SS LG 1.5k SGND Vin = 5V Lin Cin1,2 2 x 5600uF 10V, 2.35A Vo = 1.2V@10A L1 Q2 PGND PGND EAO + Rfb2 4.99k + Co1-3 3 x 5600 uF 10V, 3.1A 18 m: FB Rfb1 4.99k Cc1 Cc2 270p 4.7p Rc1 229k Figure 26. 5V to 1.2V, 10A, 300kHz This circuit design, detailed in the Design Considerations section, uses inexpensive aluminum capacitors and offthe-shelf inductors. It can deliver 10A at better than 85% efficiency. Large bulk capacitance on input and output ensure stable operation. 16 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 +12V Vin = 5V Cc 0.1u Rin 10 Cin 2.2u Vcc SD BOOT PWGD Rfadj Css 12n LG SS PGND SGND PGND EAO Cin1 100 uF 10V, 1.9A 2.2 uH 6.1A, 12 m: Rcs ISEN LM27x7 FREQ 43.2k + Q1/Q2 HG Vo = 1.8V@3A L1 2.7k + Rfb2 4.99k Co1 1 x 220 uF 4V, 55 m: FB Rfb1 2.49k Cc1 Cc2 10p 560p Rc1 51.1k Figure 27. 5V to 1.8V, 3A, 600kHz The example circuit of Figure 27 has been designed for minimum component count and overall solution size. A switching frequency of 600kHz allows the use of small input/output capacitors and a small inductor. The availability of separate 5V and 12V supplies (such as those available from desk-top computer supplies) and the low current further reduce component count. Using the 12V supply to power the MOSFET drivers eliminates the bootstrap diode, D1. At low currents, smaller FETs or dual FETs are often the most efficient solutions. Here, the Si4826DY, an asymmetric dual FET in an SO-8 package, yields 92% efficiency at a load of 2A. 1 uH 4.5 A, 7.5 m: +5V D1 Cboot Rin 10 Cin 2.2u Rfadj Vcc Css 12n Q1 HG BOOT SD PWGD Rcs 1 uH 11 A, 3.7 m: 3.3k L1 ISEN FREQ 49.9k Vin = 3.3V Lin 0.1u LG LM27x7 Q2 SS PGND SGND PGND EAO Cinx 1uF 10V + Cin1 1 x 5600 uF 10V, 2.35A Vo = 0.8V@5A Rfb2 4.99k + Co1,2 2 x 4700 uF 16V, 2.8A FB Rfb1 14.9k Cc1 Cc2 680p 4.7p Rc1 147k Figure 28. 3.3V to 0.8V, 5A, 500kHz The circuit of Figure 28 demonstrates the LM2727 delivering a low output voltage at high efficiency (87%) A separate 5V supply is required to run the chip, however the input voltage can be as low as 2.2 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 17 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com +5V D1 1uH 6.4A, 7.3 m: Cboot Rin 10 Vin = 5 to 15V Lin 0.1u + Vcc Cin 2.2u SD BOOT PWGD Rfadj Rcs ISEN LM27x7 FREQ 17.4k LG SS PGND SGND PGND EAO + Rfb2 10k Rc2 66.5 22p Co1 1 x 15uF 25V 3.1mohm Cc3 680p Rfb1 4.99k Cc1 Cc2 Vo = 1.8V@1A L1 1.5k FB Css 1 x 15uF 25V, 3.3A Q1/Q2 3.3uH 4.1A, 17.4 m: HG Rc1 39n 680p 10.7k 1uH 6.4 A, 7.3 m: Vin = 5 to 15V Lin +5V D1 Cboot Rin 10 0.1u Vcc Cin 2.2u HG SD BOOT PWGD Rfadj FREQ 17.4k Rcs ISEN LM27x7 LG SS PGND SGND PGND Vo = 3.3V@1A L1 1.5k Rfb2 10k Rc2 EAO + Cin1 1 x 15uF 25V, 3.3A Q1/Q2 4.7uH 3.4A, 26 m: + Co1 1 x 15uF 25V 3.1 m: Cc3 FB 54.9 820p Cc1 Cc2 1n 27p Rfb1 2.21k Rc1 12.1k Figure 29. 1.8V and 3.3V, 1A, 1.4MHz, Simultaneous The circuits in Figure 29 are intended for ADSL applications, where the high switching frequency keeps noise out of the data transmission range. In this design, the 1.8 and 3.3V outputs come up simultaneously by using the same softstart capacitor. Because two current sources now charge the same capacitor, the capacitance must be doubled to achieve the same softstart time. (Here, 40nF is used to achieve a 5ms softstart time.) A common softstart capacitor means that, should one circuit enter current limit, the other circuit will also enter current limit. In addition, if both circuits are built with the LM2727, a UVP or OVP fault on one circuit will cause both circuits to latch off. The additional compensation components Rc2 and Cc3 are needed for the low ESR, all ceramic output capacitors, and the wide (3x) range of Vin. 18 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 To 2nd LM27x7 Vin = 11 to 13V +5V LM78L05 D1 1uH, 6.4A 7.3 m: Cboot 0.1u Cin 2.2u BOOT SD LM27x7 FREQ 32.5k Css 12n Rcs + Cinx 10uF 16V Cin1 680uF 16V, 1.54A Vo = 3.3V@3A ISEN PWGD Rfadj Q1/Q2 4.2uH, 5.5A 15 m: HG Vcc 2k LG SS PGND SGND PGND + Rfb2 10k 2.37k 4.7n Rfb1 2.21k Cc1 Cc2 Cox 10uF 25V Co1,2 2 x 680uF 16V 1.54A Cc3 Rc2 FB EAO Vin = 11 to 13V Lin Rc1 8.2p 52.3k 1n Figure 30. 12V Unregulated to 3.3V, 3A, 750kHz This circuit shows the LM27x7 paired with a cost effective solution to provide the 5V chip power supply, using no extra components other than the LM78L05 regulator itself. The input voltage comes from a 'brick' power supply which does not regulate the 12V line tightly. Additional, inexpensive 10uF ceramic capacitors (Cinx and Cox) help isolate devices with sensitive databands, such as DSL and cable modems, from switching noise and harmonics. +5V (low current source) Cboot D1 Vin = 12V 0.1u Cin 2.2u Rfadj Vcc HG SD BOOT PWGD FREQ 267k Css 12n ISEN LM27x7 SS SGND + Cin1 680uF 16V 1.54A Vo = 5V@1.8A L1 LG D2 PGND Rfb2 10k PGND Rc2 EAO Cinx 10uF 16V Q1 47uH 2.7A 53 m: Cc3 + Co1,2 2 x 680uF 16V 26 m: Cox 10uF 6.3V FB 750 22n Cc1 Cc2 3.9n 56p Rfb1 1.37k Rc1 61.9k Figure 31. 12V to 5V, 1.8A, 100kHz In situations where low cost is very important, the LM27x7 can also be used as an asynchronous controller, as shown in the above circuit. Although a a schottky diode in place of the bottom FET will not be as efficient, it will cost much less than the FET. The 5V at low current needed to run the LM27x7 could come from a zener diode or inexpensive regulator, such as the one shown in Figure 30. Because the LM27x7 senses current in the low side MOSFET, the current limit feature will not function in an asynchronous design. The ISEN pin should be left open in this case. Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 19 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Table 1. Bill of Materials for Typical Application Circuit ID U1 Part Number Type Synchronous Controller LM2727 Q1, Q2 Si4884DY L1 RLF7030T-1R5N6R1 N-MOSFET Cin1, Cin2 C2012X5R1J106M MLCC Capacitor Cinx C3216X7R1E105K Co1, Co2 6MV2200WG Cboot VJ1206X104XXA Inductor Size Parameters Qty. Vendor TSSOP-14 TSSOP-14 1 Texas Instruments SO-8 30V, 4.1m, 36nC 1 Vishay 7.1x7.1x3.2mm 1.5H, 6.1A 9.6m 1 TDK 0805 10F 6.3V 2 TDK 1206 1F, 25V 1 TDK 10mm D 20mm H 2200F 6.3V125m 2 Sanyo Capacitor 1206 0.1F, 25V 1 Vishay AL-E Cin C3216X7R1E225K Capacitor 1206 0.1F, 25V 1 TDK Css VJ1206X123KXX Capacitor 1206 12nF, 25V 1 Vishay Cc1 VJ1206A2R2KXX Capacitor 1206 2.2pF 10% 1 Vishay Cc2 VJ1206A181KXX Capacitor 1206 180pF 10% 1 Vishay Rin CRCW1206100J Resistor 1206 10 5% 1 Vishay Rfadj CRCW12066342F Resistor 1206 63.4k 1% 1 Vishay Rc1 CRCW12063923F Resistor 1206 392k 1% 1 Vishay Rfb1 CRCW12061002F Resistor 1206 10k 1% 1 Vishay Rfb2 CRCW12061002F Resistor 1206 10k 1% 1 Vishay Rcs CRCW1206222J Resistor 1206 2.2k 5% 1 Vishay Table 2. Bill of Materials for Circuit of Figure 25 (Identical to BOM for 1.5V except as noted below) ID Part Number Size Parameters Qty. Vendor L1 RLF12560T-2R7N110 Inductor Type 12.5x12.8x6mm 2.7H, 14.4A 4.5m 1 TDK Co1, Co2, Co3, Co4 10TPB100M POSCAP 7.3x4.3x2.8mm 100F 10V 1.9Arms 4 Sanyo Cc1 VJ1206A6R8KXX Capacitor 1206 6.8pF 10% 1 Vishay Cc2 VJ1206A271KXX Capacitor 1206 270pF 10% 1 Vishay Cc3 VJ1206A471KXX Capacitor 1206 470pF 10% 1 Vishay Rc2 CRCW12068451F Resistor 1206 8.45k 1% 1 Vishay Rfb1 CRCW12061102F Resistor 1206 11k 1% 1 Vishay Qty. Vendor 1 Texas Instruments Table 3. Bill of Materials for Circuit of Figure 26 ID 20 Part Number Type Synchronous Controller Size Parameters U1 LM2727 Q1 Si4442DY N-MOSFET SO-8 30V, 4.1m, @ 4.5V, 36nC 1 Vishay Q2 Si4442DY N-MOSFET SO-8 30V, 4.1m, @ 4.5V, 36nC 1 Vishay D1 BAT-54 SOT-23 30V 1 Vishay Lin SLF12575T-1R2N8R2 Inductor 12.5x12.5x7.5mm 12H, 8.2A, 6.9m 1 Coilcraft L1 D05022-152HC Inductor 22.35x16.26x8mm 1.5H, 15A,4m 1 Coilcraft 16mm D 25mm H 5600F10V 2.35Arms 2 Sanyo Schottky Diode Cin1, Cin2 10MV5600AX Aluminum Electrolytic Cinx TSSOP-14 C3216X7R1E105K Capacitor 1206 1F, 25V 1 TDK Co1, Co2, Co3 10MV5600AX Aluminum Electrolytic 16mm D 25mm H 5600F10V 2.35Arms 2 Sanyo Cboot VJ1206X104XXA Capacitor 1206 0.1F, 25V 1 Vishay Cin C3216X7R1E225K Capacitor 1206 2.2F, 25V 1 TDK Css VJ1206X123KXX Capacitor 1206 12nF, 25V 1 Vishay Cc1 VJ1206A4R7KXX Capacitor 1206 4.7pF 10% 1 Vishay Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 Table 3. Bill of Materials for Circuit of Figure 26 (continued) ID Part Number Size Parameters Qty. Vendor Cc2 VJ1206A102KXX Capacitor Type 1206 1nF 10% 1 Vishay Rin CRCW1206100J Resistor 1206 10 5% 1 Vishay Rfadj CRCW12068872F Resistor 1206 88.7k 1% 1 Vishay Rc1 CRCW12062293F Resistor 1206 229k 1% 1 Vishay Rfb1 CRCW12064991F Resistor 1206 4.99k 1% 1 Vishay Rfb2 CRCW12064991F Resistor 1206 4.99k 1% 1 Vishay Rcs CRCW1206152J Resistor 1206 1.5k 5% 1 Vishay Qty. Vendor 1 Texas Instruments 30V, 24m/ 8nC Top 16.5m/ 15nC 1 Vishay Table 4. Bill of Materials for Circuit of Figure 27 ID Part Number U1 LM2727 Type Q1/Q2 Si4826DY L1 DO3316P-222 Inductor 12.95x9.4x 5.21mm 2.2H, 6.1A, 12m 1 Coilcraft Cin1 10TPB100ML POSCAP 7.3x4.3x3.1mm 100F 10V 1.9Arms 1 Sanyo Co1 4TPB220ML POSCAP 7.3x4.3x3.1mm 220F 4V 1.9Arms 1 Sanyo Cc C3216X7R1E105K Capacitor 1206 1F, 25V 1 TDK Cin C3216X7R1E225K Capacitor 1206 2.2F, 25V 1 TDK Css VJ1206X123KXX Capacitor 1206 12nF, 25V 1 Vishay Cc1 VJ1206A100KXX Capacitor 1206 10pF 10% 1 Vishay Cc2 VJ1206A561KXX Capacitor 1206 560pF 10% 1 Vishay Rin CRCW1206100J Resistor 1206 10 5% 1 Vishay Rfadj CRCW12064222F Resistor 1206 42.2k 1% 1 Vishay Rc1 CRCW12065112F Resistor 1206 51.1k 1% 1 Vishay Rfb1 CRCW12062491F Resistor 1206 2.49k 1% 1 Vishay Rfb2 CRCW12064991F Resistor 1206 4.99k 1% 1 Vishay Rcs CRCW1206272J Resistor 1206 2.7k 5% 1 Vishay Qty. Vendor 1 Texas Instruments Synchronous Controller Asymetric Dual N-MOSFET Size Parameters TSSOP-14 SO-8 Table 5. Bill of Materials for Circuit of Figure 28 ID Part Number U1 LM2727 Type Q1 Si4884DY N-MOSFET SO-8 30V, 13.5m, @ 4.5V 15.3nC 1 Vishay Q2 Si4884DY N-MOSFET SO-8 30V, 13.5m, @ 4.5V 15.3nC 1 Vishay SOT-23 30V 1 Vishay 7.29x7.29 3.51mm 1H, 11A 3.7m 1 Pulse 12x12x4.5 mm 1H, 11A, 3.7m 1 Pulse 16mm D 25mm H 5600F 10V 2.35Arms 1 Sanyo Synchronous Controller D1 BAT-54 Lin P1166.102T Schottky Diode Inductor Inductor L1 P1168.102T Cin1 10MV5600AX Aluminum Electrolytic Size Parameters TSSOP-14 Cinx C3216X7R1E105K Capacitor 1206 1F, 25V 1 TDK Co1, Co2, Co3 16MV4700WX Aluminum Electrolytic 12.5mm D 30mm H 4700F 16V 2.8Arms 2 Sanyo Cboot VJ1206X104XXA Capacitor 1206 0.1F, 25V 1 Vishay Cin C3216X7R1E225K Capacitor 1206 2.2F, 25V 1 TDK Css VJ1206X123KXX Capacitor 1206 12nF, 25V 1 Vishay Cc1 VJ1206A4R7KXX Capacitor 1206 4.7pF 10% 1 Vishay Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 21 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Table 5. Bill of Materials for Circuit of Figure 28 (continued) ID Part Number Size Parameters Qty. Vendor Cc2 VJ1206A681KXX Capacitor Type 1206 680pF 10% 1 Vishay Rin CRCW1206100J Resistor 1206 10 5% 1 Vishay Rfadj CRCW12064992F Resistor 1206 49.9k 1% 1 Vishay Rc1 CRCW12061473F Resistor 1206 147k 1% 1 Vishay Rfb1 CRCW12061492F Resistor 1206 14.9k 1% 1 Vishay Rfb2 CRCW12064991F Resistor 1206 4.99k 1% 1 Vishay Rcs CRCW1206332J Resistor 1206 3.3k 5% 1 Vishay Qty. Vendor 1 Texas Instruments 30V, 24m/ 8nC Top 16.5m/ 15nC 1 Vishay Table 6. Bill of Materials for Circuit of Figure 29 ID Part Number U1 LM2727 Type Q1/Q2 Si4826DY Assymetric Dual N-MOSFET Schottky Diode Synchronous Controller Size Parameters TSSOP-14 SO-8 D1 BAT-54 SOT-23 30V 1 Vishay Lin RLF7030T-1R0N64 Inductor 6.8x7.1x3.2mm 1H, 6.4A, 7.3m 1 TDK Inductor L1 RLF7030T-3R3M4R1 6.8x7.1x3.2mm 3.3H, 4.1A, 17.4m 1 TDK Cin1 C4532X5R1E156M MLCC 1812 15F 25V 3.3Arms 1 Sanyo Co1 C4532X5R1E156M MLCC 1812 15F 25V 3.3Arms 1 Sanyo Cboot VJ1206X104XXA Capacitor 1206 0.1F, 25V 1 TDK Cin C3216X7R1E225K Capacitor 1206 2.2F, 25V 1 TDK Css VJ1206X393KXX Capacitor 1206 39nF, 25V 1 Vishay Cc1 VJ1206A220KXX Capacitor 1206 22pF 10% 1 Vishay Cc2 VJ1206A681KXX Capacitor 1206 680pF 10% 1 Vishay Cc3 VJ1206A681KXX Capacitor 1206 680pF 10% 1 Vishay Rin CRCW1206100J Resistor 1206 10 5% 1 Vishay Rfadj CRCW12061742F Resistor 1206 17.4k 1% 1 Vishay Rc1 CRCW12061072F Resistor 1206 10.7k 1% 1 Vishay Rc2 CRCW120666R5F Resistor 1206 66.5 1% 1 Vishay Rfb1 CRCW12064991F Resistor 1206 4.99k 1% 1 Vishay Rfb2 CRCW12061002F Resistor 1206 10k 1% 1 Vishay Rcs CRCW1206152J Resistor 1206 1.5k 5% 1 Vishay Vendor Table 7. Bill of Materials for 3.3V Circuit of Figure 29 (Identical to BOM for 1.8V except as noted below) 22 ID Part Number L1 RLF7030T-4R7M3R4 Cc1 VJ1206A270KXX Cc2 Cc3 Rc1 Type Size Parameters Qty. 6.8x7.1x 3.2mm 4.7H, 3.4A, 26m 1 TDK Capacitor 1206 27pF 10% 1 Vishay VJ1206X102KXX Capacitor 1206 1nF 10% 1 Vishay VJ1206A821KXX Capacitor 1206 820pF 10% 1 Vishay CRCW12061212F Resistor 1206 12.1k 1% 1 Vishay Inductor Rc2 CRCW12054R9F Resistor 1206 54.9 1% 1 Vishay Rfb1 CRCW12062211F Resistor 1206 2.21k 1% 1 Vishay Rfb2 CRCW12061002F Resistor 1206 10k 1% 1 Vishay Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 Table 8. Bill of Materials for Circuit of Figure 30 ID Part Number U1 LM2727 Synchronous Controller Type Qty. Vendor TSSOP-14 Size U2 LM78L05 Q1/Q2 Si4826DY D1 BAT-54 1 Texas Instrument s Voltage Regulator SO-8 1 Texas Instrument s Assymetric Dual N-MOSFET SO-8 30V, 24m/ 8nC Top 16.5m/ 15nC 1 Vishay SOT-23 30V 1 Vishay TDK Schottky Diode Parameters Lin RLF7030T-1R0N64 Inductor 6.8x7.1x3.2mm 1H, 6.4A, 7.3m 1 L1 SLF12565T-4R2N5R5 Inductor 12.5x12.5x6.5mm 4.2H, 5.5A, 15m 1 TDK Cin1 16MV680WG D: 10mm L: 12.5mm 680F 16V 3.4Arms 1 Sanyo Al-E Cinx C3216X5R1C106M MLCC 1210 10F 16V 3.4Arms 1 TDK Co1 Co2 16MV680WG MLCC 1812 15F 25V 3.3Arms 1 Sanyo Vishay Cox C3216X5R10J06M MLCC 1206 10F 6.3V 2.7A Cboot VJ1206X104XXA Capacitor 1206 0.1F, 25V 1 TDK Cin C3216X7R1E225K Capacitor 1206 2.2F, 25V 1 TDK Css VJ1206X123KXX Capacitor 1206 12nF, 25V 1 Vishay Cc1 VJ1206A8R2KXX Capacitor 1206 8.2pF 10% 1 Vishay Cc2 VJ1206X102KXX Capacitor 1206 1nF 10% 1 Vishay Cc3 VJ1206X472KXX Capacitor 1206 4.7nF 10% 1 Vishay Rfadj CRCW12063252F Resistor 1206 32.5k 1% 1 Vishay Rc1 CRCW12065232F Resistor 1206 52.3k 1% 1 Vishay Rc2 CRCW120662371F Resistor 1206 2.37 1% 1 Vishay Rfb1 CRCW12062211F Resistor 1206 2.21k 1% 1 Vishay Rfb2 CRCW12061002F Resistor 1206 10k 1% 1 Vishay Rcs CRCW1206202J Resistor 1206 2k 5% 1 Vishay Table 9. Bill of Materials for Circuit of Figure 31 ID Part Number U1 LM2727 Q1 Si4894DY D2 MBRS330T3 L1 SLF12565T-470M2R4 D1 MBR0520 Cin1 16MV680WG Cinx C3216X5R1C106M Co1, Co2 16MV680WG Cox C3216X5R10J06M Cboot Type Synchronous Controller Size Parameters TSSOP-14 Qty. Vendor 1 Texas Instruments N-MOSFET SO-8 30V, 15m, 11.5nC 1 Vishay Schottky Diode SO-8 30V, 3A 1 ON TDK Inductor 12.5x12.8x 4.7mm 47H, 2.7A 53m 1 Schottky Diode 1812 20V 0.5A 1 ON Al-E 1206 680F, 16V, 1.54Arms 1 Sanyo MLCC 1206 10F, 16V, 3.4Arms 1 TDK Sanyo Al-E D: 10mm L: 12.5mm 680F 16V 26m 2 MLCC 1206 10F, 6.3V 2.7A 1 TDK VJ1206X104XXA Capacitor 1206 0.1F, 25V 1 Vishay Cin C3216X7R1E225K Capacitor 1206 2.2F, 25V 1 TDK Css VJ1206X123KXX Capacitor 1206 12nF, 25V 1 Vishay Cc1 VJ1206A561KXX Capacitor 1206 56pF 10% 1 Vishay Cc2 VJ1206X392KXX Capacitor 1206 3.9nF 10% 1 Vishay Cc3 VJ1206X223KXX Capacitor 1206 22nF 10% 1 Vishay Rfadj CRCW12062673F Resistor 1206 267k 1% 1 Vishay Rc1 CRCW12066192F Resistor 1206 61.9k 1% 1 Vishay Rc2 CRCW12067503F Resistor 1206 750k 1% 1 Vishay Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 23 LM2727, LM2737 SNVS205D - AUGUST 2002 - REVISED MARCH 2013 www.ti.com Table 9. Bill of Materials for Circuit of Figure 31 (continued) 24 ID Part Number Size Parameters Qty. Vendor Rfb1 CRCW12061371F Resistor Type 1206 1.37k 1% 1 Vishay Rfb2 CRCW12061002F Resistor 1206 10k 1% 1 Vishay Rcs CRCW1206122F Resistor 1206 1.2k 5% 1 Vishay Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 LM2727, LM2737 www.ti.com SNVS205D - AUGUST 2002 - REVISED MARCH 2013 REVISION HISTORY Changes from Revision C (March 2013) to Revision D * Page Changed layout of National Data Sheet to TI format .......................................................................................................... 23 Submit Documentation Feedback Copyright (c) 2002-2013, Texas Instruments Incorporated Product Folder Links: LM2727 LM2737 25 PACKAGE OPTION ADDENDUM www.ti.com 7-Nov-2017 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (C) Device Marking (4/5) LM2727MTC/NOPB ACTIVE TSSOP PW 14 94 Green (RoHS & no Sb/Br) CU NIPDAU | CU SN Level-1-260C-UNLIM 0 to 125 2727 MTC LM2727MTCX/NOPB ACTIVE TSSOP PW 14 2500 Green (RoHS & no Sb/Br) CU NIPDAU | CU SN Level-1-260C-UNLIM 0 to 125 2727 MTC LM2737MTC/NOPB ACTIVE TSSOP PW 14 94 Green (RoHS & no Sb/Br) CU NIPDAU | CU SN Level-1-260C-UNLIM -40 to 125 2737 MTC LM2737MTCX NRND TSSOP PW 14 2500 TBD Call TI Call TI -40 to 125 2737 MTC LM2737MTCX/NOPB ACTIVE TSSOP PW 14 2500 Green (RoHS & no Sb/Br) CU NIPDAU | CU SN Level-1-260C-UNLIM -40 to 125 2737 MTC (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 7-Nov-2017 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. 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Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 30-Apr-2016 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM2727MTCX/NOPB TSSOP PW 14 2500 330.0 12.4 6.95 5.6 1.6 8.0 12.0 Q1 LM2737MTCX TSSOP PW 14 2500 330.0 12.4 6.95 5.6 1.6 8.0 12.0 Q1 LM2737MTCX/NOPB TSSOP PW 14 2500 330.0 12.4 6.95 5.6 1.6 8.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 30-Apr-2016 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2727MTCX/NOPB TSSOP PW 14 2500 367.0 367.0 35.0 LM2737MTCX TSSOP PW 14 2500 367.0 367.0 35.0 LM2737MTCX/NOPB TSSOP PW 14 2500 367.0 367.0 35.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated (TI) reserves the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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