A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver FEATURES AND BENEFITS DESCRIPTION * * * * * * * * * * * The A6214 is a single-IC switching regulator that provides constant-current output to drive high-power LEDs. It integrates a high-side N-channel DMOS switch for DC-to-DC step- down (buck) conversion. A true average current is output using a cycle-by-cycle, controlled on-time method. * * * * * * AEC-Q100 qualified Supply voltage 4.5 to 55 V 2 A maximum output over operating temperature range Integrated MOSFET switch Able to use either Schottky or silicon low-side diode True average output current control Internal control loop compensation Integrated 5 V, 10 mA regulator for driving external load PWM dimming via direct logic input down to 0.1% at 200 Hz Standalone internal PWM dimming (A6216) Analog dimming for brightness calibration and thermal foldback Low-power shutdown (1 A typical) Fault flag output (A6216) LED string open and short protection Cycle-by-cycle current limit Undervoltage lockout (UVLO) and thermal shutdown (TSD) Robust protection against: Adjacent pin-to-pin short Pin-to-GND short Component open/short faults PACKAGES: Output current is user-selectable by an external current sense resistor. Output voltage is automatically adjusted to drive various numbers of LEDs in a single string. This ensures the optimal system efficiency. LED dimming is accomplished by a direct logic input pulse-width-modulation (PWM) signal at the Enable pin. Alternatively, an Analog Dimming input can be used to calibrate the LED current, or implement thermal foldback in conjunction with external NTC thermistor. The A6216 has the added capability to generate its own PWM dimming frequency and duty cycle in stand-alone mode. The A6214 is provided in a compact 10-pin narrow SOIC package (suffix LK). The A6216 is in 16-pin TSSOP (suffix LP), both with exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with 100% matte-tin leadframe plating. APPLICATIONS: A6214: 10-Pin SOICN (suffix LK) Automotive lighting * Daytime running lights * Front and rear fog lights * Turn/stop lights * Map light * Dimmable interior lights Not to scale A6216: 16-Pin eTSSOP (suffix LP) Not to scale VIN (4.5 to 55 V) CIN 1 GND RON External PWM dimming signal External analog dimming signal 2 EN/PWM 3 4 ADIM 5 C2 VIN TON A6214 SW BOOT EN CSH ADIM CSL VCC GND 10 9 8 L1 CBOOT RSENSE D1 LED+ 7 6 CLED GND Figure 1: A6214 (LK Package) Typical Application Circuit A6214-16-DS, Rev. 4 January 21, 2013 November 1, 2016 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver VIN (4.5 to 55 V) CIN External PWM dimming signal External analog dimming signal 1 RON GND EN/PWM 2 3 4 ADIM VCC CBIAS FULL = "HIGH" = 100% Duty Cycle FULL = "LOW" = DR controls Duty Cycle 5 R1* R2* FULL 6 7 8 VIN A6216 TON SW BOOT CBOOT CSH ADIM CSL VCC GND L1 15 RSENSE D1 14 EN/PWM LED+ 13 CLED 12 DR FAULT GND FPWM FULL 16 RANGE VCC 11 10 FAULT GND R3* 9 RANGE = "HIGH" = 0 to 100% Duty Cycle RANGE = "LOW" = 0 to 30% Duty Cycle RANGE * R1, R2, R3 used in stand-alone mode for internal PWM dimming Figure 2: A6216 (LP Package) Typical Application Circuit SELECTION GUIDE Part Number Internal PWM and FAULT Flag Package Packing A6214KLKTR-T No 10-pin SOICN with exposed thermal pad 3000 pieces per 13-in reel A6216KLPTR-T Yes 16-pin TSSOP with exposed thermal pad 4000 pieces per 13-in reel Table of Contents Features and Benefits Description Applications Packages Typical Application Circuit (A6214) Typical Application Circuit (A6216) Selection Guide Specifications Absolute Maximum Ratings Thermal Characteristics 1 1 1 1 1 2 2 3 3 3 Pinout Diagrams and Terminal List Tables Functional Block Diagrams Electrical Characteristics Characteristic Performance Functional Description Application Circuit Diagrams System Failure Detection and Protection Package Outline Drawings 4 5 7 9 11 18 21 23 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS Characteristic Supply Voltage Bootstrap Drive Voltage Switching Voltage Symbol Notes Rating Unit VIN -0.3 to 60 V VBOOT -0.3 to VIN + 8 V VSW Continuous Pulsed, t < 20 ns -1.5 to VIN + 0.3 V -0.3 to VIN + 3 V Enable and TON Voltage VEN , VTON -0.3 to VIN + 0.3 V Linear Regulator Terminal VCC -0.3 to 7 V VADIM -0.3 to 7 V VCSH, VCSL -0.3 to VIN + 0.3 V -0.3 to 7 V -0.3 to VCC + 0.3 V -40 to 125 C ADIM Pin Voltage Current Sense Voltages FAULT, FULL, RANGE, and FPWM Voltages DR Pin Voltage VFAULT, VFULL, VRANGE, VFPWM VDR A6216 only A6216 only; DR pin voltage must not be higher than VCC even when device is off (VCC = 0 V) Operating Ambient Temperature TA Maximum Junction Temperature TJ(max) 150 C Tstg -55 to 150 C Storage Temperature K temperature range for automotive THERMAL CHARACTERISTICS*: May require derating at maximum conditions; see application section for optimization Characteristic Symbol Test Conditions* A6214 Package LK Package Thermal Resistance (Junction to Ambient) Package Thermal Resistance (Junction to Pad) RJA A6216 Package LP RJP Value Unit On 4-layer PCB based on JEDEC standard 35 C/W On 4-layer PCB based on JEDEC standard 34 C/W On 2-layer PCB with 3.8 in.2 of copper area each side 43 C/W 2 C/W *Additional thermal information available on the AllegroTM website. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver Pinout Diagram for A6214 (LK Package) 10 SW VIN 1 TON 2 EN 3 9 BOOT PAD 8 CSH ADIM 4 7 CSL VCC 5 6 GND Pinout Diagram for A6216 (LP Package) ADIM 4 VCC 5 Function 1 VIN Supply voltage input voltage for IC and buck regulator 2 TON Regulator on-time setting resistor terminal. Connect a resistor between VIN and TON to set the switching frequency. 3 EN/PWM 4 ADIM Analog dimming control voltage input 5 VCC Internal IC bias regulator output. Connect 1uF MLCC to GND. Can be used to supply up to 10mA for external load. 6 GND Ground terminal 7 CSL Current Sense (Lower end) feedback input for LED current 8 CSH Current Sense (Higher end) feedback input for LED current 9 BOOT 10 SW Switched output terminal - PAD Exposed pad for enhanced thermal dissipation; connect to GND Logic input for Enable and PWM dimming DMOS gate driver bootstrap terminal Terminal List Table for A6216 (LP Package) 1 VIN Supply voltage input voltage for IC and buck regulator 2 TON Regulator on-time setting resistor terminal. Connect a resistor between VIN and TON to set the switching frequency 13 CSL 3 EN/PWM 12 GND 4 ADIM Analog dimming control voltage input 5 VCC Internal IC bias regulator output. Connect 1uF MLCC to GND. Can be used to supply up to 10mA for external load 6 DR 7 GND Ground terminal 8 FULL Selects 100% dimming duty cycle or DR control of duty cycle 9 RANGE Selects DR control range, high range gives DR control from 5% to 100%, low range gives DR control from 5% to 33%. 10 FPWM Dimming PWM frequency control. In stand-alone mode, connect a resistor to GND to set the dimming PWM frequency 11 FAULT Open-drain output which is pulled low in case of fault. Connect through an external pull-up resistor to the desired logic level. 12 GND Ground terminal 13 CSL Current Sense (Lower end) feedback input for LED current 14 CSH Current Sense (Higher end) feedback input for LED current 15 BOOT 16 SW Switched output terminal - PAD Exposed pad for enhanced thermal dissipation; connect to GND 14 CSH PAD Name Name 15 BOOT EN/PWM 3 Number Number 16 SW VIN 1 TON 2 Terminal List Table for A6214 (LK Package) DR 6 11 FAULT GND 7 10 FPWM FULL 8 9 RANGE Function Logic input for Enable and PWM dimming Dimming Ratio control. In stand-alone mode: connect to resistor divider network from VCC to set the dimming PWM duty cycle DMOS gate driver bootstrap terminal Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver FUNCTIONAL BLOCK DIAGRAMS VIN (4.5 to 55 V) CIN VIN RON TON GND EN/PWM VOUT EN/PWM VIN CBIAS ADIM VIN CBOOT On-Time Select On-Time VCC BOOT VCC SW Duty Cycle Control RSENSE D1 GND VOUT LED+ CSH Enable LDO L1 CSL VREF Radj CLED GND Internal 5 V ADIM iLED Reference A6214 Radj is optional. It can be used to fine-adjust the LED current in case the desired value of R SENSE is not available. Figure 3: Simplified Functional Block Diagram for A6214 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver VIN (4.5 to 55 V) VIN VOUT RON CIN TON On-Time Select VIN VCC EN/PWM CBOOT Buck Converter Duty Cycle Control On-Time LDO Internal 5 V bias LED Current EN/PWM VOUT LED+ CSH CSL CLED Radj Enable GND DR R2 FPWM RFPWM ADIM RSENSE D1 GND VCC R1 L1 SW Differential Amp Up to 10 mA external load CBIAS VIN Gate Driver GND BOOT VCC ADIM RANGE Internal PWM Duty Cycle Generator OSC FULL VCC FAULT (200 Hz to 1 kHz) VREF (0 to 200 mV) iLED Reference FAULT FAULT Mode A6216 Figure 4: Simplified Functional Block Diagram for A6216 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver ELECTRICAL CHARACTERISTICS: Valid at VIN = 12 V, VOUT = 6 V, TA = -40C to 125C, typical values at TA = 25C, unless otherwise noted Characteristics Symbol Input Supply Voltage VIN Undervoltage Lockout Threshold VIN Undervoltage Lockout Hysteresis VUVLO IIN IINSD Buck Switch Current Limit Threshold ISWLIM Buck Switch On-Resistance R BOOT Undervoltage Lockout Threshold BOOT Undervoltage Lockout Hysteresis VIN increasing DS(on) VBOOTUV Max. Unit - 55 V - 4.3 V 150 300 mV VCSH - VCSL = 0.5 V, EN = VIH, RON = 402 k - 5 - mA EN = VIL - 1 10 A 2.5 3.25 4 A - 0.25 0.4 3.1 3.4 3.7 V - 750 - mV - 75 100 ns VBOOT = VIN + 4.3 V, TA = 25C, ISW = 0.5 A VBOOT to VSW increasing Switching Minimum Off-Time tOFFmin VCSH - VCSL = 0 V Switching Minimum On-Time tONmin VCSH - VCSL = 0.3 V tON Typ. 4.5 - VBOTUVHYS VBOOT to VSW decreasing Selected On-Time Min. - VUVLO_HYS VIN decreasing VIN Pin Supply Current VIN Pin Shutdown Current Test Conditions VIN - 75 100 ns 800 1000 1200 ns VCSH - VCSL decreasing, SW turns on, ADIM tied to VCC 194 200 206 mV 2.65 - 50 V RON = 402 k REGULATION COMPARATOR AND ERROR AMPLIFIER Load Current Sense Regulation Threshold at 100% 1 VCSREG Output Current Sense Common Mode Voltage (measured at CSL pin) VOUT VIN = 55 V, fSW = 500 kHz, iLED = 0.5 A CSH Input Sense Current ICSH VCSH - VCSL = 0.2 V - -190 - A CSL Input Sense Current ICSL VCSH - VCSL = 0.2 V 50 75 100 A VCC 0 mA < ICC < 5 mA, VIN > 6 V INTERNAL LINEAR REGULATOR VCC Regulated Output VCC Current Limit 2 VCC Dropout Voltage iVCCLIM VLDO 4.85 5 5.15 V VCC 4.75 V 10 20 - mA Measure VIN - VCC. VIN = 5 V, iVCC = 9 mA - 0.15 0.35 V ENABLE/PWM INPUT Logic High Voltage VIH VEN increasing 1.8 - - V Logic Low Voltage VIL VEN decreasing - - 0.4 V RENPD VEN = 5 V - 100 - k tPWML Measured while EN = low, during dimming control, and internal references are powered-on (exceeding tPWML results in shutdown) 10 17 - ms External RFPWM = 30 k from FPWM pin to GND 180 200 220 Hz - - 0.8 V EN Pin Pull-down Resistance Maximum PWM Dimming Off-Time INTERNAL PWM DIMMING (A6216 ONLY) Internal PWM Dimming Frequency fPWM FULL, RANGE Pins Input Low Voltage VIL FULL, RANGE Pins Input High Voltage VIH Internal PWM Duty Cycle 2 - - V DPWM5(L) VDR driven by resistor divider from VCC, VCC / VDR = 9.72, fPWM = 200 Hz, RANGE = low 4.75 5 5.25 % DPWM5(H) VDR driven by resistor divider from VCC, VCC / VDR = 29.2, fPWM = 200 Hz, RANGE = high 4.5 5 5.5 % DPWM90(H) VDR driven by resistor divider from VCC, VCC / VDR = 1.62, fPWM = 200 Hz, RANGE = high 87 90 93 % Continued on the next page... Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver ELECTRICAL CHARACTERISTICS (continued): Valid at VIN = 12 V, VOUT = 6 V, TA = -40C to 125C, typical values at TA = 25C, unless otherwise noted Characteristics Symbol Test Conditions Min. Typ. Max. Unit 2.1 - - V - 100 - mV 38.4 40 41.4 mV ANALOG DIMMING INPUT Input Voltage for 100% LED Current VADIMH Regulation Threshold at 50% Analog Dimming VCSREG50 VADIM = 1 V Regulaton Threshold at 20% Analog Dimming VCSREG20 VADIM = 0.4 V FAULT Pull-Down Voltage VFAULT(PD) Fault condition asserted, pull-up current = 1 mA - - 0.4 V FAULT Pin Leakage Current VFAULT(LKG) Fault condition cleared, pull-up to 5 V - - 1 A VCSH - VCSL = VCSREG FAULT PIN (A6216 ONLY) TIMERS Cool Down Timer for Fault Retry tRETRY - 1 - ms Delay Timer for Reporting LED Open Fault tOPEN - 50 - s Thermal Shutdown Threshold 3 TSD 150 165 180 C Thermal Shutdown Hysteresis TSDHYS - 25 - C THERMAL SHUTDOWN In test mode, a ramp signal is applied across CSH and CSL pins to determine the CS regulation threshold voltage. In actual application, the average CS voltage is regulated at VCSREG regardless of ripple voltage. 2 The internal linear regulator is capable of supplying up to 10 mA to external devices. 3 Determined by design and characterization. Not production tested. 1 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver CHARACTERISTIC PERFORMANCE Average LED Current vs. PWM Duty Cycle Normalized LED Current vs ADIM Voltage 1 (VIN = 12 V, VOUT = 6 V, iLED = 1 A, TA = 25C) 100% Normalize LED Current Normalized LED Current (%) 80% 60% Measured Current 40% (RTON = 442 k, load = 2x LED at 1.5 A, fPWM = 200 Hz) 0.1 0.01 VIN = 24 V, L = 47 H Target VIN = 12 V, L = 22 H 20% VIN = 12 V, L = 47 H Ideal 0.001 0% 0 0.4 0.8 1.2 ADIM Voltage (V) 1.6 2 0.1 2.4 Internal PWM Duty Cycle vs DR Pin Voltage Frequency of Internal PWM vs. FPWM Resistance (VIN = 12 V, VOUT = 6 V, VDR = 1.7 V, TA = 25C) 100 90 1600 80 1400 Measured for RANGE=H 60 Target for RANGE=H 1200 fPWM (Hz) 70 Measured for RANGE=L 1000 800 Calculated 600 Measured Target for RANGE=L 40 100 Figure 6: PWM Dimming Performance - Duty cycle down to ~0.1% (1000:1) can be achieved with higher VIN or lower inductance. (VIN = 12 V, VOUT = 6 V, RTON = 300 k, fPWM = 300 Hz, TA = 25C) Duty Cycle (%) 10 PWM Duty Cycle (%) Figure 5: Analog Dimming Performance - LED current can be reduced linearly down to 10% using the ADIM pin voltage. 50 1 30 400 20 200 10 0 0 0 0 0.4 0.8 1.2 1.6 2 VDR (V) 2.4 2.8 3.2 3.6 4 Figure 7: Internal PWM Dimming Operation (A6216 only) - Duty cycle is controlled by the voltage at DR pin. 10 RFPWM (k) 20 30 Figure 8: Internal PWM Dimming Frequency (A6216 only) as a function of FPWM Resistance Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver CHARACTERISTIC PERFORMANCE (continued) CH1 = VPWM (5 V/div) CH2 = VSW (5 V/div) CH3 = VOUT (5 V/div) CH4 = iLED (500 mA/div) Time Scale= 500 s/div Figure 9: Startup for PWM Dimming operation - RTON = 442 k, L = 22 H, VIN = 12 V, Output = 2x LED at 1.5 A, PWM = 1 kHz 50%. Note that there is a ~150 s delay for the first PWM = H pulse, but none for subsequent pulses. CH1 = VPWM (5 V/div) CH2 = VSW (5 V/div) CH3 = VOUT (5 V/div) CH4 = iLED (500 mA/div) Time Scale= 5 s/div Figure 10: PWM Dimming with on-time of just 10 s - RTON = 442 k, L = 22 H, VIN = 12 V, Output = 2x LED at 1 A. Note that the LED current takes ~5s to ramp up to its steady-state value. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver FUNCTIONAL DESCRIPTION The A6214 is a buck regulator designed for driving a high-current LED string. It utilizes average current mode control to maintain constant LED current and consistent brightness. The LED current level is easily programmable by selection of an external sense resistor, with a value determined as follows: RSENSE = VCSREG / iLED fSW = 1 / [ k x (RTON + RINT )] where k = 0.00434, with fSW in MHz, tON in s, and RON and RINT (internal resistance, 20 k) in k. 2200 2000 If necessary, a resistor can be inserted in series with the CSL pin to fine-tune the LED current, as shown below: 1800 1600 1400 fSW (kHz) where VCSREG = VCSH - VCSL = 0.2 V typical. 1200 iCSH iLED CSH VCSREG tON = k x (RTON + RINT ) x ( VOUT / VIN ) CSL iCSL Radj RSENSE + VSENSE - - + iCSL x Radj VCSREG = iLED x RSENSE + iCSL x Radj Therefore iLED = (VCSREG - iCSL x Radj) / RSENSE Figure 11: How To Fine-Tune LED Current Using Radj For example, with a desired LED current of 1.4 A, the required RSENSE = 0.2 V / 1.4 A = 0.143 . But the closest power resistor available is 0.13 . Therefore, the difference is Radj x iCSL = 0.2 V - 1.4 A x 0.13 = 0.018 V where iCSL = 75 A typical Radj = 0.018 V / 75 A = 240 The LED current is further modulated by the ADIM (Analog Dimming) pin voltage. This feature can be used for LED brightness calibration, or for thermal foldback protection. See Analog Dimming section for details. Switching Frequency The A6214 operates in fixed on-time mode during switching. The on-time (and hence switching frequency) is programmed using an external resistor connected between the VIN and TON pins, as given by the following equation: 1000 800 600 400 200 0 0 100 200 300 400 500 600 700 800 900 1000 RTON (k) Figure 12: Switching Frequency vs. TON resistance ENABLE AND DIMMING The IC is activated when a logic high signal is applied to the EN (enable) pin. The buck converter ramps up the LED current to a target level set by RSENSE. When the EN pin is forced from high to low, the buck converter is turned off, but the IC remains in standby mode for up to 10 ms. If EN goes high again within this period, the LED current is turned on immediately. Active dimming of the LED is achieved by sending a PWM (pulse-width modulation) signal to the EN pin. The resulting LED brightness is proportional to the duty cycle (tON / Period) of the PWM signal. A practical range for PWM dimming frequency is between 100 Hz (Period = 10 ms) and 2 kHz. If EN is low for more than 17 ms, the IC enters shutdown mode to reduce power consumption. The next high signal on EN will initialize a full startup sequence, which includes a startup delay of approximately 150 s. This startup delay is not present during PWM operation. The EN pin is high-voltage tolerant and can be directly connected to a power supply. However, if EN is higher than the VIN voltage at any time, a series resistor (1-10 k) is required to limit the current flowing into the EN pin. This series resistor is not necessary if EN is driven from a logic input. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver PWM DIMMING RATIO The brightness of the LED string can be reduced by adjusting the PWM duty cycle at the EN pin as follows: Dimming ratio = PWM on-time / PWM period For example, by selecting a PWM period of 5 ms (200 Hz PWM frequency) and a PWM on-time of 5 s, a dimming ratio of 0.1% can be achieved. This is sometimes referred to as "1000:1 dimming." In an actual application, the minimum dimming ratio is determined by various system parameters, including: VIN , VOUT , inductance, LED current, switching frequency, and PWM frequency. As a general guideline, the minimum PWM on-time should be kept at 5 s or longer. A shorter PWM on-time is acceptable under more favorable operating conditions, such as higher VIN and lower inductance. INTERNAL PWM DIMMING (A6216 ONLY) In addition to external PWM dimming through EN pin, the A6216 is able to generate an internal PWM dimming signal in stand-alone mode. Frequency of the internal PWM signal can be set by connecting a resistor between FPWM pin and GND, as given by the following equation: fPWM = c / (RFPWM + RINT) where c = 6400, with fPWM in Hz, and RFPWM and RINT (internal resistance, 0.5 k) in k. This frequency can be between 200 Hz and 1 kHz when RANGE is High, or 200 Hz and 500 Hz when RANGE is Low. Duty cycle of PWM signal is linearly proportion to the voltage at DR (Dimming Ratio) pin. This is illustrated by the following chart: Internal PWM Duty Cycle To disable internal PWM generation, tie DR pin to VCC pin. (Do NOT leave DR pin floating or connected to GND.) The FPWM pin can be either left open, or tied to VCC. Note that at any time during stand-alone PWM dimming mode, if EN pin goes low, the LED is turned off immediately. This is illustrated in figure below. Internal PWM External PWM (EN pin) LED Current Figure 14: LED Current when Both Internal and External PWM Dimming Signals are Applied ANALOG DIMMING In addition to PWM dimming, the A6214/16 also provides an analog dimming feature. When VADIM is over 2 V, the LED current is at 100% level (as defined by the SENSE resistor). When VADIM is below 2 V, the LED current decreases linearly down to 20% at VADIM = 0.4 V. This is shown in the following figure: 200 mV 6 mV (100%) VCSREG RANGE = High 100% 100 mV 90% ADIM pin voltage 40 mV 0 RANGE = Low 33% 30% 0.4 V DR pin voltage (V) 5% 0% 0V are with VCC = 5 V. For better accuracy, derive the DR pin voltage using a resistor divider connected between VCC and GND. A practical range of internal PWM duty cycle when RANGE = High is between 5% (VDR = 0.17 V) and 90% (VDR = 3.08 V). To improve accuracy at low duty cycles between 5% and 30%, set RANGE to Low. If DR pin is above 3.4 V, duty cycle stays at around 99% if RANGE = High, 33% if Low. 0.17 0.514 3.08 3.43 ~4 5 Figure 13: Variation of PWM Duty Cycle with respect to DR Pin Voltage It should be noted that the internal PWM duty cycle depends on the ratio between VCC and VDR. The voltages shown in the chart 1V 2V Figure 15: ADIM Pin Voltage Controls SENSE Reference Voltage (hence LED current) It is possible to pull ADIM pin below 0.4 V to achieve lower than 20% analog dimming. However, the linearity may suffer if the LED ripple current become too large compared to the average current. For example, if the LED ripple current is 100 mA, then the average current can only be dimmed down to 100 mA linearly. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver ADIM pin can be used in conjunction with PWM dimming to provide wider LED dimming range over 1000:1. In addition, the IC can provide thermal foldback protection by using an external NTC (negative temperature coefficient) thermistor, as shown below: VIN MOS CIN VCC RS NTC R1 ADIM RP VSW VIN t 0 -VD iL iRIPPLE where D is the duty cycle, and VD is the forward drop of the diode D1 (typically under 0.5 V for Schottky diode). t During SW on-time: iRIPPLE = (VIN - VOUT) / L x tON = (VIN - VOUT) / L x t x D where D = tON / t. During SW off-time: iRIPPLE = (VOUT + VD) / L x tOFF = (VOUT + VD) / L x t x (1 - D) RSC VOUT GND If analog dimming is not required, the ADIM pin must be connected to VCC pin. (Do NOT leave ADIM pin floating or connected to GND.) D = tON / (tON + tOFF ) iL D Figure 16: Using an External NTC Thermistor to Implement Thermal Foldback OUTPUT VOLTAGE AND DUTY CYCLE The figure below provides simplified equations for approximating output voltage. The output voltage of a buck converter is approximately given as: VOUT = VIN x D - VD x (1 - D ) VIN x D, if VD << VIN L SW tON tOFF Period, t Figure 17: Simplified Waveforms for a Buck Converter Simplified equation for output voltage: VOUT = VIN x D - VD x (1 - D) If VD << VIN, then VOUT = VIN x D approximately. More precisely: VOUT = (VIN - iAVG x RDS(on)) x D - VD x (1 - D) - iAVG x (DCR + RSC) where DCR is ther internal resistance of inductor and RSC is the sense resistance. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 13 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver MINIMUM AND MAXIMUM OUTPUT VOLTAGES For a given input voltage, the maximum output voltage depends on the switching frequency and minimum tOFF . For example, if tOFF(min) = 150 ns and fSW = 2 MHz, then the maximum duty cycle is 80%. So for a 12.5 V input, the maximum output is approximately 10 V (based on the simplified equation of VOUT = VIN x D). This means up to 3 LEDs can be operated in series, assuming Vf = 3.2 V or less for each LED. The minimum output voltage depends on minimum tON and switching frequency. For example, if the minimum tON = 100 ns and fSW = 1 MHz, then the minimum duty cycle is 10%. That means with VIN = 24 V, the theoretical minimum VOUT is just 2.4 V. However, the internal current sense amplifier is designed to operate down to VOUT = 2.65 V. Therefore the output voltage should not go lower than 2.65 V, or else the current accuracy will suffer. To a lesser degree, the output voltage is also affected by other factors such as LED current, on-resistance of the high-side switch, DCR of the inductor, and forward drop of the low-side diode. As a general rule, switching at lower frequencies allows a wider range of VOUT , and hence more flexible LED configurations. 24 22 20 18 VOUT (V) 16 14 VOUT(max) (V) 12 VOUT(min) (V) If the LED string is completely shorted (VOUT = 0 V), LED current regulation will become impossible. The output current will increase until it trips SW overcurrent protection. The IC then shuts down and retries after approximately 1 ms cooldown period. THERMAL BUDGETING The A6214 is capable of supplying a 2 A current through its high-side switch. However, depending on the duty cycle, the conduction loss in the high-side switch may cause the package to overheat. Therefore care must be taken to ensure the total power loss of package is within budget. For example, if the maximum temperature rise allowed is T = 50C at the device case surface, then the maximum power dissipation of the IC is 1.4 W. Assuming the maximum RDS(on) = 0.4 and a duty cycle of 85%, then the maximum LED current is limited to 2 A approximately. At a lower duty cycle, the LED current can be higher. FAULT HANDLING The A6214 is designed to handle the following faults: * Pin-to-ground short * Pin-to-neighboring pin short * Pin open * External component open or short * Output short to GND The waveform in the figure below illustrates how the A6214 responds in the case in which the current sense resistor or the CSH and CSL pins are shorted together. Note that the SW pin overcurrent protection is tripped at around 3.5 A, and the part shuts down immediately. The part then goes through startup retry after approximately 1 ms of cooldown period. 10 8 6 4 2 0 0 0.2 0.4 0.6 0.8 1 1.2 Frequency (MHz) 1.4 1.6 1.8 2 Figure 18: Minimum and Maximum Output Voltage vs. Switching Freqency (VIN = 24 V, minimum tON and tOFF of 100 ns) If the required output voltage is lower than that permitted by the minimum tON , the controller will automatically extend the tOFF , in order to maintain the correct duty cycle. This means that the switching frequency will drop lower when necessary, in order to keep the LED current in regulation. CH1 = VPWM (5 V/div) CH2 = VSW (5 V/div) CH3 = VOUT (5 V/div) CH4 = iLED (1 A/div) Time Scale = 200 s/div Figure 19: In case of sense resistor short fault - Output current rises until it trips SW OCP at ~3.5 A. The IC shuts off and retries after ~1 ms cooldown period. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver As another example, the waveform in figure below shows the fault case where external diode D1 is missing or open. As LED current builds up, a larger-than-normal negative voltage is developed at the SW node during off-time. This voltage trips the missing detection function of the IC. The IC then shuts down immediately, and waits for a cooldown period before retry. CH1 = VFAULT (5 V/div) CH2 = VSW (5 V/div) CH3 = VOUT (5 V/div) CH4 = iLED (1 A/div) Time Scale = 1 s/div Figure 20: In case of missing low-side diode - SW voltage fall below -2 V and trips Missing-Diode fault. FAULT pin (A6216 only) is pulled Low immediately. The IC shuts off and retries after cooldown period. COMPONENT SELECTIONS The inductor is often the most critical component in a buck converter. Follow the procedure below to derive the correct parameters for the inductor: 1. Determine the saturation current of the inductor. This can be done by simply adding 20% to the average LED current: iSAT iLED x 1.2. 2. Determine the ripple current amplitude (peak-to-peak value). As a general rule, ripple current should be kept between 10% and 30% of the average LED current: 0.1 < iRIPPLE(pk-pk) / iLED < 0.3. 3. Calculate the inductance based on the following equations: L = (VIN - VOUT ) x D x t / iRIPPLE , and D = (VOUT + VD ) / ( VIN + VD ) , where D is the duty cycle, t is the period 1/ fSW , and VD is the forward voltage drop of the Schottky diode D1. OUTPUT FILTER CAPACITOR The A6214 is designed to operate in current regulation mode. Therefore it does not require a large output capacitor to stabilize the output voltage. This results in lower cost and smaller PCB area. In fact, having a large output capacitor is not recommended. In most applications, however, it is beneficial to add a small filter capacitor (around 0.1 F) across the LED string. This cap serves as a filter to eliminate switching spikes seen by the LED string. This is very important in reducing EMI noises, and may also help in ESD testing. ADDITIONAL NOTES ON RIPPLE CURRENT * For consistent switching frequency, it is recommended to choose the inductor and switching frequency to ensure the inductor ripple current percentage is at least 10% over normal operating voltage range (ripple current is lowest at lowest VIN). If ripple current is less than 10%, the switching frequency may jitter due to insufficient ripple voltage across CSH and CSL pins. However, the average LED current is still regulated. * For best accuracy in LED current regulation, a low current ripple of less than 20% is required. * There is no hard limit on the highest ripple current percentage allowed. A 40% ripple current is still acceptable, as long as both the inductor and LEDs can handle the peak current (average current x 1.2 in this case). However, higher ripple current % affects the accuracy of LED current, and limits the minimum current that can be regulated when using ADIM. * In general, allowing a higher ripple current percentage enables lower-inductance inductors to be used, which results in smaller size and lower cost. * If lower ripple current is required for the LED string, one solution is to add a small capacitor (such as 1 to 2.2 F) across the LED string from LED+ to GND. In this case, the inductor ripple current remains high while the LED ripple current is greatly reduced. * The effectiveness of this filter capacitor depends on many factors, such as: switching frequency, inductors used, PCB layout, LED voltage and current, and so forth. * The addition of this capacitor introduces a longer delay in LED current during PWM dimming operation. Therefore the accuracy of average LED current is reduced at short PWM on-time. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 15 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver INDUCTOR SELECTION CHART The chart in figure below summarizes the relationship between LED current, switching frequency, and inductor value. Based on this chart: assuming LED current = 1 A and L = 22 H, then minimum fSW = 0.7 MHz in order to keep the ripple current at 20% or lower. (Note: VOUT = VIN / 2 is the worst case for ripple current). If the switching frequency is lower, then a larger inductance must be used to meet the same ripple current requirement. 2.0 Switching Frequency (MHz) 1.8 1.6 1.4 1.2 L = 10 H 1.0 L = 15 H 0.8 L = 22 H 0.6 L = 33 H 0.4 L = 47 H 0.2 0.0 0 0.5 1 LED Current (A) 1.5 2 Figure 21: Relation between minimum switching frequency and LED current, given different inductance used (VIN = 12 V, VOUT = 6 V, ripple current = 20%) Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 16 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver Effects of Output Capacitor on LED Ripple Current VIN VIN L1 RSENSE D1 L1 iRIPPLE LED+ iRIPPLE RSENSE D1 LED+ iRIPPLE GND Without output capacitor: The same inductor ripple current flows through sense resistor and LED string. GND With a small capacitor across LED string: Ripple current through LED string is reducted, while ripple voltage across RSENSE remains high. Figure 22: Using an Output Filter Capacitor to Reduce Ripple Current in LED String Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 17 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver APPLICATION CIRCUIT DIAGRAMS VIN (20 to 55 V) C1 33 F 63 V C2 4.7 F 100 V GND L1 47 H 2 A 1 R1 2 442 k EN/PWM A6214 VIN BOOT TON 3 SW CSH EN 4 CSL ADIM 5 GND VCC C5 1 F 10 C4 9 0.1 F RSENSE 0.15 D1 60 V 2A 8 LED+ Radj 7 71.5 6 LED String (~15 V) C3 0.1 F 100 V GND iLED = (VCSREG - iCSL x Radj) / RSENSE = (0.2 - 0.000007 x 71.5) / 0.15 = 1.3 A Suggested Components Symbol Part Number Manufacturer C1 HHXA630ARA330MHA0G United Chemi-Con C2 C3225X7S2A475M200AB TDK C3 CGA4J2X7R2A104M125AA TDK L1 CDRH105RNP-470NC Sumida D1 10MQ060NTRPBF Vishay RSENSE RL1632R-R150-F Susumu Figure 23: Application Circuit Example for A6214 (for driving 15 V LED at 1.3 A, fSW = 500 kHz) VIN (4.5 to 55 V) CIN External PWM dimming signal 1 RON GND 442 k EN/PWM 2 3 4 VCC R1 RS RP CBIAS 1 F 5 6 7 NTC 8 VIN A6216 TON SW BOOT CBOOT 0.1 F 15 14 EN/PWM CSH ADIM CSL VCC GND FAULT GND FPWM RANGE iLED = 1 A before foldback RSENSE 0.2 D1 60 V 2A LED+ 13 12 DR FULL L1 47 H 2 A 16 VCC 11 10 k 10 9 CLED 0.1 F GND FAULT VCC Thermal Foldback using NTC Figure 24: Application Circuit Example for A6216 (with External PWM and Thermal Foldback) Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 18 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver APPLICATION CIRCUIT DIAGRAMS (continued) VIN VIN A6214/6 A6214/6 L1 SW LED+ RCS1 iLED1 GND RCS2 SW iLED2 D1 D2 CLED GND CLED CSH CSL L2 CSH LED- CSL Figure 25: Using two (or more) A6214/16 in parallel to drive the same LED string. Total LED current is the sum of currents from each driver. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 19 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver APPLICATION CIRCUIT DIAGRAMS (continued) PROTECTION FROM OUTPUT LC-RESONANCE During normal operation, if the LED load becomes disconnected (due to a bad connector, for example), the output capacitor CLED will be charged up to VOUT = VIN. Later, when the LED load is reconnected, higher voltage stored in CLED will create a huge current spike through the load. Normally this does not create any problems, since the current spike will decay within a few microseconds. However, if the LED load is connected through long cables, the parasitic inductance LK in the cable will form an LC-resonant circuit with CLED. If the resonant circuit is underdamped, VOUT may oscillate and becomes negative. This could subject CSH and CSL pins to negative spike voltage exceeding their Absolute Maximum Ratings. Therefore the following precautions are recommended to avoid output oscillation: * Use shortest possible LED cables to reduce LK. * Use lower capacitance for CLED to reduce stored energy (EC = 0.5 x CLED x VIN2). * Critically damp the output LC-resonant circuit, as shown in Figure 26. The drawback is additional power loss during PWM dimming operation (since C1 is charged and discharged through R1 during each PWM cycle). In case the output LC resonance cannot be eliminated (due to long LED cables, for example), consider adding a Schottky barrier diode (SBD) in parallel with CLED, as shown in Figure 28. The SBD clamps the negative spike of the LC resonance, so CSH and CSL pins are protected. This is the most effective protection with minimal side effects. CLED initially charged to VOUT = 50 V when load is open In critically-damped circuit, VOUT stays positive In underdamped circuit, VOUT goes negative Time/s Figure 27: Simulation Results Showing Difference in VOUT Between Underdamped and Critically-Damped Circuits L1 L1 CSH RSENSE CSL VOUT Total parasitic inductance of cable S1 LK 0.4 H VLED CSH RSENSE CSL VOUT S1 Total parasitic inductance of cable LK ic = 0 A R1 1 C1 0.22 F Add R1 and C1 to critically damp the LC-resonant circuit ESR 10 m CLED 0.1 F ic = 50 V Large current spike when S1 is closed ROUT 1 Total resistance of output path GND Figure 26: Countermeasure to Prevent VOUT Oscillation During Output Intermittent Open/Short Fault CLED VLED Add D2 to clamp the negative voltage of LC-resonant circuit D2 (60 V 1 A) GND Figure 28: Using Schottky Diode to Clamp the Negative spike from Output LC-Resonance Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 20 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver SYSTEM FAILURE DETECTION AND PROTECTION VIN C1, C2 = open or short 1 GND R1 = open or short 2 EN/PWM 3 4 C5 = open or short 5 VIN A6214 SW BOOT TON EN CSH ADIM CSL GND VCC 10 9 C4 open or short L1 = open or short RSENSE open or short D1 = open or short 8 LED+ 7 6 LED string open or short to GND C3 open or short GND SYSTEM-LEVEL FAILURE MODES Protected against open/short fault for all external components, including: * LED string * Sense resistor * Inductor * Diode * Input/output caps, etc. IC-LEVEL FAILURE MODES Protected against: * Any pin open * Any pin shorted to GND * Adjacent pin-to-pin short Figure 29: Showing Various Possible Fault Cases in an Application Circuit System Failure Mode Table (partial) Symptom Observed FAULT flag (A6216) asserted? A6214/16 Response Inductor shorted Dim light from LED Yes Current spike trips SW secondary OCP and turns off switching. Retries after 1 ms. Sense resistor open No light from LED Yes High differential sense voltage causes IC to shut off switching. Retries after 1 ms. Failure Mode Sense resistor shorted Dim light from LED Yes Increases SW current, which eventually trips SW secondary OCP fault. Retries after 1 ms. Diode open Dim light from LED Yes Detects missing diode fault and shuts off switching. Retries after 1 ms. Diode shorted No light from LED Yes Trips SW secondary OCP and turns off switching. Retries after 1 ms. LED string open No light from LED Yes* Continue to switch at maximum tON (Since this fault cannot be distinguished from VIN too low for LED forward drop) LED string shorted to GND, or Output cap shorted No light from LED Yes* IC unable to regulate LED current at VOUT = 0 V. SW current increases and trips OCP. IC shuts down and retries after 1 ms. LED string partially shorted Some LEDs are not on NO Normal operation (since IC has no way to know how many LED is supposed to be in series). Continued on the next page... Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 21 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver System Failure Mode Table (partial) (continued) Symptom Observed FAULT flag (A6216) asserted? Normal light from LED NO Normal operation (since IC only monitors inductor current). Boot cap open Dim light from LED Yes* IC attempts to switch but can't fully turn on SW. Short current spikes through LED string. Boot cap shorted No light from LED Yes* IC detects undervoltage fault across Boot cap and will not start switching. TON resistor open Dim light from LED Yes SW turns on and hits secondary current limit, then shuts down. Retries after 1 ms. NO Operates at maximum switching frequency (minimum tON and tOFF). May hit thermal limit. Failure Mode Output cap open TON resistor shorted Dim light from LED A6214/16 Response Note (*) * In case of LED current not in regulation, FAULT flag is asserted after approximately 50 s timeout delay. * For PWM dimming operation with on-time < 50 s, FAULT flag is asserted if LED current fails to reach regulation after 16 PWM = H pulses. * For PWM dimming operation with on-time > 50 s, FAULT flag is only asserted when PWM = H. However, if the fault persists for 16 consecutive PWM cycles, FAULT flag will be pulled Low and then it stays Low until the fault is cleared. CH1 = VPWM (5 V/div) CH2 = VFAULT (5 V/div) CH3 = VOUT (5 V/div) CH4 = iLED (500 mA/div) Time Scale = 5 ms/div Figure 30: VIN too low for LED regulation. PWM = 500 Hz 2% (40 s). FAULT = L after 16 PWM pulses. CH1 = VPWM (5 V/div) CH2 = VFAULT (5 V/div) CH3 = VOUT (5 V/div) CH4 = iLED (500 mA/div) Time Scale = 5 ms/div Figure 31: VIN too low for LED regulation. PWM = 500 Hz 20% (400 s). FAULT toggles each time PWM = H, but stays Low after 16 PWM pulses. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 22 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver PACKAGE OUTLINE DRAWINGS For Reference Only - Not for Tooling Use NOT TO SCALE Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown 4.90 +0.08 -0.10 0.55 3.30 0.25 8 0 10 1.75 0.25 0.19 B 2.41 0.25 3.91 +0.08 -0.10 1.00 10 2.41 6.00 0.20 5.60 A 0.685 0.20 1 2 Branded Face 1 0.25 BSC 3.30 SEATING PLANE 10X 0.10 C 1.55 0.10 C 0.40 0.30 SEATING PLANE 1.00 BSC 0.10 0.05 2 GAUGE PLANE C PCB Layout Reference View A Terminal #1 mark area B Exposed thermal pad (bottom surface) C Reference land pattern layout; all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) Package LK, 10-Pin SOICN with Exposed Thermal Pad Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 23 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver For Reference Only - Not for Tooling Use (Reference MO-153 ABT) Dimensions in millimeters. NOT TO SCALE Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown 0.65 0.45 8 0 5.00 0.10 16 16 0.20 0.09 1.70 B 3 NOM 4.40 0.10 3.00 6.40 0.20 A 6.10 0.60 0.15 1.00 REF 1 2 3 NOM 1 0.25 BSC 2 Branded Face 3.00 SEATING PLANE C 16X 0.10 SEATING PLANE C 0.30 0.19 GAUGE PLANE C PCB Layout Reference View 1.20 MAX 0.65 BSC NNNNNNN YYWW LLLL 0.15 0.00 A Terminal #1 mark area B Exposed thermal pad (bottom surface); dimensions may vary with device C Reference land pattern layout (reference IPC7351 SOP65P640X110-17M); All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) D 1 D Standard Branding Reference View N = Device part number = Supplier emblem Y = Last two digits of year of manufacture W = Week of manufacture L = Characters 5-8 of lot number Branding scale and appearance at supplier discretion Package LP, 16-Pin TSSOP with Exposed Thermal Pad Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 24 A6214 and A6216 Automotive-Grade, Constant-Current 2 A PWM Dimmable Buck Regulator LED Driver Revision History Number Date Description - September 23, 2015 Initial release 1 March 17, 2016 Added Load Current Sense Regulation Threshold footnote (page 7-8); updated Additional Notes on Ripple Current (page 15). 2 April 6, 2016 Added Parallel Operation figure (page 19) and SBD Protection figure (page 20); updated Protection from Output LC-Resonance (page 19); corrected LK package drawing dimension (page 23). 3 June 17, 2016 4 November 1, 2016 Updated k value (page 11). Updated Functional Description (page 11); added Table of Contents. Copyright (c)2016, Allegro MicroSystems, LLC Allegro MicroSystems, LLC reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro's products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro's product can reasonably be expected to cause bodily harm. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 25