R1242S SERIES
30V Input 3A Buck DC/DC converter
NO.EA-191-130312
1
OUTLINE
The R1242S Series are CMOS-based 30V Input, 3A, Synchronous Rectified Step-down DC/DC Converters
with built-in Highside Switch. Each of these ICs contains Nch Highside Tr. (Typ. 0.1) and can supply maximum
3A output current. In order to reduce heat generation caused by energy loss, FET can be used as Lowside
switch. Lowside switch turns off when ICs shut down. Each of these ICs consists of the followings: an oscillator, a
PWM control circuit, a voltage reference unit, an error amplifier, a phase compensation circuit, a slope control
circuit, a soft-start circuit, protection circuits, an internal regulator, a switch, and so on. Also, each of these ICs
consists of the following external components: an inductor, resistors, an external FET, and capacitors.
The R1242S Series operates with Current Mode Topology, which does not require any sense resistor. As a
result, these ICs can achieve high speed and high efficiency. The oscillator frequencies for each version are set
as follows; adjustable between 330kHz to 1000kHz for versions A and B, 330kHz for versions C and D, 500kHz
for versions E and F, and 1000kHz for versions G and H.
Each of these ICs are equipped with the protection functions, such as Peak Current Limit function, Latch
function, Fold back function, Thermal-Shutdown function, and Undervoltage-Lockout (UVLO) function. Peak
Current Limit function restricts the maximum current into 4.5A. Latch function (comes with versions A, C, E, and
G) shuts off the output if current limit detection continues for a certain period of time. Fold back function (comes
with versions B, D, F, and H) reduces the initial oscillator frequencies into 1/4 when output is short-circuited.
FEATURES
• Operating Voltage ............................................................ 5V ~ 30V
• Supply Current ................................................................. Typ. 0.8mA (Set VOUT=1.0V@VIN=30V)
• Internal Nch MOSFET Driver (Ron=100mTyp.)
• External Nch MOSFET Drive Buffer for Synchronous Operation
• Adjustable Output Voltage with External Resistor ........... 0.8V ~ 15V
• Feed Back Voltage........................................................... 0.8V with 1.5% accuracy
• Output Current ................................................................. 3A
• Peak Current Limit Function ............................................ Typ. 4.5A
• UVLO Function
• Internal Soft Start Time .................................................... Typ. 0.5ms
• Maximum Duty Cycle .......................................................Typ. 88%
• UVLO Detector Threshold................................................ Typ. 3.6V
• Thermal Shutdown Function ............................................ Typ. 160°C, with 30°C hysteresis
• Operating Frequency .......................................................Version A/B adjustable from 330kHz to 1MHz
Version C/D 330kHz
Version E/F 500kHz
Version G/H 1000kHz
• Built-in Foldback Protection and its frequency................. 1/4 at fold condition: Ver.B
83kHz: Ver.D, 125kHz: Ver.F, 250kHz: Ver.H
• Short Protection Function for Internal Boost Regulator
• Short Protection delay time for Output Latch...................Typ. 5ms : Ver.A/C/E/G
• Ceramic Capacitor Compatible
• Stand-by Function: 0μA (Typ.), Max. 20μA (@VIN=30V, CE="L")
• Package ...........................................................................HSOP-8E
R1242S
2
APPLICATIONS
• Power source for digital home appliance
• Power source for hand-held communication equipment, cameras, video instruments such as VCRs,
camcorders.
• Power source for battery-powered equipment.
• Battery Charger
Block Diagram
∗1
Ver fosc Short Protection
A Adjustable Latch
B Adjustable Fold back
C 330kHz Latch
D 330kHz Fold back
E 500kHz Latch
F 500kHz Fold back
G 1000kHz Latch
H 1000kHz Fold back
R1242S
3
Selection Guide
In the R1242 Series, short-circuit protection functions and frequency types can be selected from the
followings; Short-circuit protection functions: Latch or Fold back; Frequency types: Adjustable or Fixed. Fixed
frequencies are selectable from 330kHz, 500kHz, or 1000kHz.
Product Name Package Quantity per Reel Pb Free Halogen Free
R1242S001∗-E2-FE HSOP-8E 1,000 pcs Yes Yes
∗ : Latch or Fold back, frequency can be selected at the user’s request
Code Frequency Latch Type protection Fold back Type protection
A Adjustable Yes No
B Adjustable No Yes
C 330kHz Yes No
D 330kHz No Yes
E 500kHz Yes No
F 500kHz No Yes
G 1000kHz Yes No
H 1000kHz No Yes
R1242S
4
PIN CONFIGURATIONS
●HSOP-8E
R1242
1 8
7
6
5
2
3
4
TOP VIEW
PIN DESCRIPTIONS
• R1242S001A/B
PIN No. Symbol Description
1 CE Chip Enable Pin (Active with “H”)
2 EXT Gete Drive Pin
3 BST Bootstrap Pin
4 VIN Power Supply Pin
5 LX LX Switching Pin
6 GND Ground Pin
7 FB Feedback Pin
8 RT Frequency Setting Pin
∗ Tab is GND level. (They are connected to the reverse side of this IC.)
∗ The tab must be connected to the GND.
• R1242S001C/D/E/F/G/H
PIN No. Symbol Description
1 CE Chip Enable Pin (Active with “H”)
2 EXT Gate Drive Pin
3 BST Bootstrap Pin
4 VIN Power Supply Pin
5 LX LX Switching Pin
6 GND Ground Pin
7 FB Feedback Pin
8 TEST TEST Pin. OPEN or connect to GND
∗ Tab is GND level. (They are connected to the reverse side of this IC.)
∗ The tab must be connected to the GND.
R1242S
5
Absolute Maximum Ratings
(GND=0V)
Symbol Item Rating Unit
VIN Input Voltage -0.3 ~ 32 V
VBST Boost Pin Voltage VLX - 0.3 ~ VLX + 6 V
VLX LX Pin Voltage -0.3 ~ VIN + 0.3 V
VCE CE Pin Input Voltage -0.3 ~ VIN + 0.3 V
VFB VFB Pin Voltage -0.3 ~ 6 V
VEXT EXT Pin Voltage -0.3 ~ 6 V
VRT RT Pin Voltage -0.3 ~ 6 V
PD Power Dissipation (HSOP-8E) ∗ 2.9
W
Ta Operating Temperature Range -40 ~ 85 ºC
Tstg Storage Temperature Range -55 ~ 125 ºC
∗) For Power Dissipation, please refer to PACKAGE INFORMATION.
ABSOLUTE MAXIMUM RATINGS
Electronic and mechanical stress momentarily exceeded absolute maximum ratings may cause the permanent
damages and may degrade the life time and safety for both device and system using the device in the field.
The functional operation at or over these absolute maximum ratings is not assured.
RECOMMENDED OPERATING CONDITIONS (ELECTRICAL CHARACTERISTICS)
All of electronic equipment should be designed that the mounted semiconductor devices operate within the
recommended operating conditions. The semiconductor devices cannot operate normally over the recommended
operating conditions, even if when they are used over such conditions by momentary electronic noise or surge. And the
semiconductor devices may receive serious damage when they continue to operate over the recommended operating
conditions.
R1242S
6
Electrical Characteristics
(Otherwise notified in Conditions, VIN= 12V, Ta=25ºC)
Symbol Item Conditions MIN. TYP. MAX. Unit
VIN Operating Input Voltage 5.0 30 V
IIN VIN Consumption Current VIN=30V, VFB=1.0V 0.45 0.80 1.20 mA
VUVLO1 UVLO Detect Voltage Falling VUVLO2
-0.5 VUVLO2
-0.3 V
VUVLO2 UVLO Released Voltage Rising 3.7 4.0 4.3 V
VFB VFB Voltage Tolerance 0.788 0.800 0.812 V
VFB/Ta VFB Voltage Temperature Coefficient -40ºC Ta 85ºC ±100 ppm/
ºC
RT=GND 900 1000 1100 kHz
RT=floating 290 330 375 kHz
Oscillator Frequency (Ver. A/B)
RT=120k 450 500 550 kHz
Oscillator Frequency (Ver. C/D) 300 330 370 kHz
Oscillator Frequency (Ver. E/F) 450 500 550 kHz
fosc
Oscillator Frequency (Ver. G/H) 900 1000 1100 kHz
VFB<0.56,RT=GND (Ver. B) 250 kHz
VFB <0.56 (Ver. D) 83 kHz
VFB <0.56 (Ver. F) 125 kHz
VFLB Fold back Frequency
VFB <0.56 (Ver. H) 250 kHz
Maxduty Max. Duty Cycle RT=120k (Ver. A/B)
VIN=9V (Ver. C/D) 82 88 95 %
tstart Soft Start Time 0.5 ms
tDLY Delay Time for Latch Protection (Ver. A/C/E/G) 5 ms
RLXH LX High Side Switch ON Resistance 0.1
ILXHOFF LX High Side Switch Leakage Current 0 20
μA
ILIMLXH LX High Side Switch Limited Current 4.5 A
VCEH CE “H” Input Voltage 1.7 V
VCEL CE “L” Input Voltage 0.4 V
IFB VFB Input Current -1.0 1.0
μA
ICEH CE “H” Input Current -1.0 1.0
μA
ICEL CE “L” Input Current -1.0 1.0
μA
TTSD Thermal Shutdown
Detect Temperature Hysteresis 30ºC 160 ºC
Istandby Standby Current VIN=30V, VCE=0V 0 20
μA
RRISE EXT “H” Switch On Resistance IEXT=-100mA 6 11
RFALL EXT “L” Switch On Resistance IEXT=100mA 0.5 1.5
VEXTLIM Detecting Voltage for Low
Side Switch Current Limit 36 55 76 mV
R1242S
7
Typical application
R1242S001A/B VOUT=1.8V 330kHz
FET
FB
GND
BST
Lx
CE
Cbst
R1
R2
L
Cspd
220pF
RT EXT
330kHz
Rspd
"H"active
(recommendation)
(Rt=Floating)
R1242S001C/D VOUT=1.2V 330kHz
FET
FB
GND
BST
Lx
CE
Cbst
R1
R2
L
Cspd
220pF
TEST EXT
Rspd
GND "H"active
Recommendation parts
CIN 10μF KTS500B106M55N0T00 (Nippon Chemi-Con)
COUT 22μF GRM31CR71A226M (Murata)
Cbst 0.1μF GRM21BB11H104KA01L (Murata)
L 4.7μH VLF10045T-4R7N6R1 (TDK)
FET TPC8031 (TOSHIBA)
15
16k
20k
5.1k
COUT
22μF × 2
CIN
10μF 0.1μF 4.7μH
VIN VIN
VOUT
VOUT
COUT
22
μ
F
×
2
0.1
μ
F
5.1k
VIN
VIN
CIN
10
μ
F
8k
16k
15
(recommendation)
1.2V
1.8V
4.7
μ
F
R1242S
8
R1242S001A/B VOUT=1.2V 500kHz
FB
GND
BST
LX
CE
Cbst
R1
R2
L
2.2uH
Cspd
470pF
RT EXT
1.2V
Rspd
FET
"H"active
(recommendation)
500kHz
Rbst
R1242S001E/F VOUT=1.2V 500kHz
FB
GND
BST
Lx
CE
Cbst
R1
R2
L
Cspd
470pF
TEST EXT
1.2V
Rspd
FET
"H"active
(recommendation)
Rbst
Recommendation parts
CIN 10μF KTS500B106M55N0T00 (Nippon Chemi-Con)
COUT 22μF GRM31CR71A226M (Murata)
Cbst 0.1μF GRM21BB11H104KA01L (Murata)
L 2.2μH RLF7030T-2R2M5R4 (TDK)
FET TPC8031 (TOSHIBA)
15
8k
VIN
VIN
16k
CIN
10
μ
F
VOUT
5.1k
15
0.1
μ
F
15
8k
16k
VIN VIN
CIN
10
μ
F
(Rt=120k)
COUT
22
μ
F × 2
VOUT
COUT
22
μ
F × 2
0.1
μ
F
15
5.1k
2.2
μ
H
2.2
μ
H
R1242S
9
R1242S001A/B VOUT=3.3V 1000kHz
FB
GND
BST
Lx
CE
Cbst
R1
R2
L
Cspd
100pF
RT EXT
3.3V
FET
"H"active
(recommendation)
1000kHz
(Rt=GND)
R1242S001G/H VOUT=3.3V 1000kHz
FB
GND
BST
Lx
CE
Cbst
R1
R2
L
Cspd
100pF
TEST EXT
GND
3.3V
FET
Rspd
"H"active
(recommendation)
Recommendation parts
CIN 10μF KTS500B106M55N0T00 (Nippon Chemi-Con)
COUT 10μF GRM31CR71E106K (Murata)
Cbst 0.1μF GRM21BB11H104KA01L (Murata)
L 4.7μH VLF10045T-4R7N6R1 (TDK)
FET SSM3K14T (TOSHIBA)
VIN VIN
VIN VIN
CIN
10
μ
F
CIN
10
μ
F 0.1
μ
F 4.7
μ
H
VOUT
VOUT
4.7
μ
H
0.1
μ
F
5.1k
5.1k
50k
16k
50k
16k
15Ω
COUT
COUT
10
μ
F
10μF
R1242S
10
Notes Concerning to External Parts
External components must be connected as close as possible to the ICs and their wiring must be short as
possible. Especially, the capacitor must be connected with the shortest distance between VIN and GND pins. If
the impedances of the power supply line and the GND line are high, the operation can be unstable due to the
switching current which fluctuates the electric potential of the inside the ICs. The impedances of power supply
line and GND line must be as low as possible. When designing their wirings, it is necessary to give careful
consideration to the large current flowing into the power supply, GND, Lx, VOUT and inductor. The wiring of output
voltage setting resistance (R1) and the wiring of inductor must be separated from load wiring.
The ceramic capacitors with low ESR (Equivalent Series Resistance) must be used for the ICs. The
recommended value for the CIN capacitor between VIN and GND is equal or more than 10μF.
The selections of inductor (L) and output capacitor (COUT) can be different according to the ICs’ oscillation
frequencies, output voltages and input voltages. Refer to “Recommended Value for Each Output Voltage” on the
next page and select the most suitable values at the conditions of use.
The internal phase compensation is built in the ICs; therefore, if the values selected are largely deviated from
the recommended values, the operation may result in unstable.
The over current protection circuit could be influenced by self-heating of the ICs and heat dissipation of the
PCB environment.
In order to prevent self-turning on, FET with smaller gate resistance and with smaller Cgd / Cgs
(capacities between gate drains and the capacities between gate sources) should be selected.
The output voltage (VOUT) can be calculated as VOUT = VFB × (R1+R2)/R2. The various voltage settings are
possible by changing the values of R1 and R2. However, R2 value must be equal or less than 16k.
Rspd prevents the deterioration in the regulation characteristics, which is caused by spike noise occurred in
VOUT. Spike noise is largely depending on the PCB layout. If the PCB board layout is optimized, there is no need
of Rspd; however, if the spike noise is a concern, Rspd with 15 or so should be used.
After the completion of soft start, latch function (for versions A, C, E, and G) starts to work. The internal
counter starts counting up when the over current protection circuit activates the limited current detection. When
the internal counter counts up to 5ms, which is typical latch timer period, latch function turns off the output. The
turned off output can be reset when CE pin is changed to “L”, and also VIN pin voltage is became less than 3.6V
(Typ.), which is UVLO detecting voltage. If the output voltage increases more than the setting voltage (FB pin
voltage is 0.8V (Typ.)) within the latch timer period, the counter restores the default. If the power-supply voltage’s
start-up is slow and the output voltage is not reached to the setting voltage within the latch timer period after the
soft start, the careful attention is required.
After the soft start, fold back function (for Version B, D, F, and H) starts to work. The fold back function limits
the oscillation frequencies into 1/4 when (FB pin voltage decreases to less than 0.56V (Typ.)). If the
power-supply voltage’s start-up is slow and the output voltage is not reached to the 70% of the setting voltage
even for a short period of time after the soft start, the careful attention is required.
The ICs are not supporting Nonsynchronous rectification using a diode as a rectifier.
The table on the next page shows the recommended values for setting frequency and setting output voltage.
R1242S
11
R1242Recommended Value for Each Output Voltage
330kHz
VOUT[V] 0.8 1.2 1.2 1.5 1.5 1.8 1.8 2.5 2.5 3.3 5 9 15
VIN_range[V] 5~14 ~12 9~30 5~10 10~30 5~15 12~30 5~15 12~30 5~30 7~30 15~30 20~30
L[μH] 2.2 10 4.7 10 4.7 15 4.7 15 10 15 15 15 15
COUT[μF] 100 22 44 22 44 22 44 22 22 22 22 22 22
Cspd[pF] - 470 470 220 220 470 220 220 220 220 220 220 220->100
R1[] - 8000 8000 14000 14000 20000 20000 34000 34000 50000 84000 164000 284000
R2[] - 16000 16000 16000 16000 16000 16000 16000 16000 16000 16000 16000 16000
500kHz
VOUT[V] 0.8 1.0 1.2 1.5 1.5 1.8 1.8 2.5 3.3 5 9 12 15
VIN_range[V] ~9 ~10 5~15 5~18 7~19 5~23 9~21 5~29 5~30 7~30 15~30 18~30 20~30
L[μH] 2.2 2.2 2.2 4.7 2.2 4.7 2.2 10 10 10 10 15 15
COUT[μF] 100 44 44 44 44 44 44 22 22 22 22 22 22
Cspd[pF] - 1000 470 220 220 220 220 220 220 220 220 470 220
R1[] - 4000 8000 14000 14000 20000 20000 34000 50000 84000 164000 28000 284000
R2[] - 16000 16000 16000 16000 16000 16000 16000 16000 16000 16000 2000 16000
1000kHz
VOUT[V] 0.8 1.2 1.5 1.8 2.5 3.3 5 5 9 15
VIN_range[V] 5~7 5~10 5~15 5~15 5~19 5~30 7~12 12~30 15~30 20~30
L[μH] 1.5 2.2 2.2 4.7 4.7 4.7 4.7 4.7 4.7 10
COUT[μF] 100 22 22 22 22 10 10 10 10 10
Cspd[pF] - 220 100 220 220 100 100 56 56 100
R1[] - 8000 14000 20000 34000 50000 84000 84000 164000 284000
R2[] - 16000 16000 16000 16000 16000 16000 16000 16000 16000
R1242S
12
R1242Recommendation parts
Symbol Condition Value Parts Name MFR
CIN 10μF/50V UMK325BJ106MM-T TAIYO YUDEN
10μF/50V KTS500B106M55N0T00 Nippon Chemi-Con
10μF/10V GRM31CR71A106K muRata
COUT VOUT>10V 10μF/50V KTS500B106M55N0T00 Nippon Chemi-Con
10V>VOUT>1.8V 10μF/25V GRM31CR71E106K muRata
VOUT<1.8V 22μF/10V GRM31CR71A226M muRata
(at the diode rectifier, the specified
condition only)
Cbst 0.1μF/50V GRM21BB11H104KA01L muRata
L 1.5μH±30%/4.0A 1.5μH SLF7055T-3PF-1R5N4R0 TDK
2.2μH±20%/5.4A 2.2μH RLF7030T-2R2M5R4 TDK
4.7μH±30%/6.1A 4.7μH VLF10045T-4R7N6R1 TDK
10μH±20%6.2A 10μH VLF12060T-100M6R2 TDK
15μH±20%5.0A 15μH VLF12060T-150M5R0 TDK
FET 30V/4A 57m SSM3K14T TOSHIBA
30V/13A 14.3m TPCC8003-H TOSHIBA
30V/11A 9.8m TPCP8005-H TOSHIBA
30V/11A 10.1m TPC8031-H TOSHIBA
RCE Up Diode is connected between CE pin and VIN pin as an ESD protection element.
If there is a possibility that the CE pin voltage becomes higher than the VIN pin voltage,
it is recommended to insert a 5k resistance or more in order to prevent the large current
flowing from CE pin into VIN pin.
R1242S
13
Technical Notes on the voltage between BST pin and LX pin
In the application of the "Bootstrap" Start switching regulator, the R1242 series, when the LX pin voltage becomes
equal or less than the BST voltage supply regulator, the BST voltage supply regulator charges the capacitor,
Cbst. By this function, even if the LX pin becomes "H", the high side switch composed of an Nch transistor can be
turned on.
Under the condition of PWM operation, the BST voltage supply regulator of the R1242, while the LX pin voltage
is "L", the voltage between BST pin and GND pin is controlled and maintained the level as of 5V, then regardless
of the voltage drop by the bootstrap switch, the BST voltage supply regulator can drive a high side switch and the
low side external MOSFET.
However, if either the maximum duty cycle limit or the low side switch current limit is detected, sampling of the
voltage between BST pin and LX pin is halted, and the output of the BST voltage supply regulator becomes
stacked at 5V as same as a conventional "Bootstrap" Start switching regulator. Depending on the external FET
gate capacitance, excessive voltage drop can be caused by bootstrap switching, and also switching failure can
be caused by insufficient electrical charge on Cbst. As a result, the desired voltage may not be obtained. Higher
frequency requires higher electrical charge. Special attention is required in case of using the device at 1000 kHz.
Events that may trigger such trouble are
(A) Detect of the current limit of low side switch at light load
(B) VOUT>VIN/2 and starting the circuit without using CE pin individually or CE pin and VIN are tied and
controlled at the same time.
(C) The voltage difference between the input and the output is small and usage at maximum duty cycle is
expected.
The countermeasure to avoid the trouble caused by the events above is to use an external diode, Dbst shown
in the figure below. The Dbst will charge CBST and prevents the abnormal switching. The supply voltage to Dbst
should be in the range from 4.5V to 6.0V and if the set output voltage of the R1242 is in the range from 4.5V to
6.0V, then the output voltage can be used directly as the supply voltage of Dbst. The voltage rating of the diode,
Dbst must be VIN or more, the forward current of Dbst must be 20mA or more. Other specifications of the Dbst
are not important.
Application Circuit example
FB
GND
BST
Lx
CE
Cbst
R1
R2
L
Cspd
RT EXT FET
"H"active
(recommendation)
1000kHz
(Rt=GND)
(
)Dbst
*if necessary
R1242S
14
Operating Frequency
In the application circuit of the R1242S001A/B, the 330kHz operation is selected by leaving Rt open.
Connecting a 200k to 0 resistor between Rt(pin 8) and ground can be used to set the switching frequency to
approximately 450kHz to 1000kHz. To calculate the Rt resistor, use the equation below:
*(Between 330kHz and 450kHz switching frequency can be also set by connecting the appropriate resistor
according to the next equation.)
Rt=120000/(2/(1000000/fosc-1)-1) []
The switching frequency vs. Rt value is shown in Figure 1 and Figure 2.
Figure 1: Linearscale
Figure 2: Logscale
R1242S
15
Operation of step-down DC/DC converter and Output Current
The DC/DC converter charges energy in the inductor when LX transistor is ON, and discharges the energy
from the inductor when LX transistor is OFF and controls with less energy loss, so that a lower output voltage
than the input voltage is obtained. The operation will be explained with reference to the following diagrams:
<Basic Circuit> <Current through L>
Hiside Tr L
Lowside FET
VIN
i1
VOU T
COUT
i2
GND
ILmax
ILmin
ton toff
T=1/fosc
IL
Iconst
t
⋅ Step1. Hiside Tr. Turns on and current IL (=i1) flows, and energy is charged into COUT. At this moment, IL
increases from ILmin to reach ILmax in proportion to the on-time period (ton) of Hiside Tr.
⋅ Step2. When Hiside Tr. Turns off, Synchronous rectifier Lowside FET turns on in order that L maintains IL at
ILmax, and current IL (=i2) flows.
⋅ Step3. IL decreases from ILmax to reach ILmin in proportion to the off-time period (toff) of Hiside Tr.
In the case of PWM control system, the output voltage is maintained by controlling the on-time period (ton), with
the oscillator frequency (fosc) being maintained constant.
The maximum value (ILmax) and the minimum value (ILmin) of the current flowing through the inductor are the
same as those when Hiside Tr. Turns on and off.
R1242S
16
Output Current and selection of External components
The relation between the output current and external components is as follows:
When Hiside Tr. Of LX is ON:
(Wherein, Ripple Current p-p value is described as IRP, ON resistance of Hiside Tr. And Lowside FET of LX are
respectively described as RONH and RONL, and the DC resistor of the inductor is described as RL.)
VIN = VOUT + (RONH + RL) × IOUT + L × IRP / ton .................................................................Equation 1
When Hiside Tr. Of Lx is “OFF” (Lowside FET is “ON”):
L × IRP / toff = RONL × IOUT + VOUT + RL × IOUT .................................................................Equation 2
Put Equation 2 to Equation 1 and solve for ON duty of Hiside Tr., DON = ton / (toff + ton),
DON = (VOUT + (RONL + RL) × IOUT)/( VIN + (RONL – RONH) × IOUT) .......................................Equation 3
Ripple Current is as follows:
IRP = (VIN – VOUT – RONH × IOUT – RL × IOUT) × DON / fosc / L..............................................Equation 4
wherein, peak current that flows through inductor, Hiside Tr, and Lowside FET is as follows:
ILmax = IOUT + IRP / 2 ......................................................................................................Equation 5
Consider ILmax, condition of input and output and select external components.
∗The above explanation is directed to the calculation in an ideal case in continuous mode.
R1242S
17
TYPICAL CHARACTERISTICS
1
)
FB Volta
g
e2
)
Oscillator Fre
q
uenc
y(
ver.A
,
B Rt=floatin
g)
3
)
Oscillator Fre
q
uenc
y(
ver.A
,
B Rt=GND
)
4
)
Oscillator Fre
q
uenc
y(
ver.A
,
B Rt=120kΩ
)
5
)
Oscillator Fre
q
uenc
y(
ver.C
,
D
)
6
Oscillator Fre
uenc
ver.E
F
(VIN=12V)
0.792
0.794
0.796
0.798
0.800
0.802
0.804
0.806
0.808
-40 -15 10 35 60 85
Ta(°C)
VFB(V)
(VIN=12V)
270
290
310
330
350
370
390
-40 -15 10 35 60 85
Ta(°C)
fosc(kHz)
(VIN=12V)
800
850
900
950
1000
1050
1100
1150
1200
-40 -15 10 35 60 85
Ta(°C)
fosc(kHz)
(VIN=12V)
400
450
500
550
600
-40 -15 10 35 60 85
Ta(°C)
fosc(kHz)
(VIN=12V)
400
450
500
550
600
-40 -15 10 35 60 85
Ta(°C)
fosc(kHz)
(VIN=12V)
270
290
310
330
350
370
390
-40 -15 10 35 60 85
Ta(°C)
fosc(kHz)
R1242S
18
7
)
Oscillator Fre
q
uenc
y(
ver.G
,
H
)
8
)
Fold-Back Fre
q
uenc
y(
ver.A
,
B Rt=GND
)
9
)
Fold-Back Fre
q
uenc
y(
ver.C
,
D
)
10
)
Fold-Back Fre
q
uenc
y(
ver.E
,
F
)
11
)
Fold-Back Fre
q
uenc
y(
ver.G
,
H
)
12
)
Maxdut
y(
ver.A
,
B Rt=floatin
g)
-4 -4 -4
(V
IN
=12V)
70.0
75.0
80.0
85.0
90.0
95.0
100.0
-40 -15 10 35 60 85
Ta(°C)
Maxduty(%)
(V
IN
=12V)
800
850
900
950
1000
1050
1100
1150
1200
-40 -15 10 35 60 85
Ta(°C)
fosc(kHz)
(V
IN
=12V)
150
200
250
300
350
-40 -15 10 35 60 85
Ta(°C)
f
FLD
(kHz)
(V
IN
=12V)
45
55
65
75
85
95
105
115
-40 -15 10 35 60 85
Ta(°C)
f
FLD
(kHz)
(V
IN
=12V)
80
90
100
110
120
130
140
150
160
-40 -15 10 35 60 85
Ta(°C)
f
FLD
(kHz)
(V
IN
=12V)
150
200
250
300
350
-40 -15 10 35 60 85
Ta(°C)
f
FLD
(kHz)
R1242S
19
13
)
Maxdut
y(
ver.C
,
D
)
14
)
Maxdut
y(
ver.G
,
H
)
15
)
Maxdut
y(
ver.A
,
B Rt=GND
)
16
)
Maxdut
y(
ver.C
,
D
)
17
)
Maxdut
y(
ver.G
,
H
)
(V
IN
=12V)
70.0
75.0
80.0
85.0
90.0
95.0
100.0
-40 -15 10 35 60 85
Ta(°C)
Maxduty(%)
(V
IN
=12V)
70.0
75.0
80.0
85.0
90.0
95.0
100.0
-40 -15 10 35 60 85
Ta(°C)
Maxduty(%)
(Ta=25℃)
50.0
60.0
70.0
80.0
90.0
100.0
5 1015202530
V
IN
[V]
Maxduty(%)
(Ta=25℃)
70.0
75.0
80.0
85.0
90.0
95.0
100.0
5 1015202530
V
IN
[V]
Maxduty(%)
(Ta=25℃)
70.0
75.0
80.0
85.0
90.0
95.0
100.0
5 1015202530
V
IN
[V]
Maxduty(%)
R1242S
20
18)Efficiency vs Load Current
fosc=330kHz
V
OUT
:0.8V V
OUT
:3.3V
V
OUT
:15V
fosc=500kHz
V
OUT
:0.8V V
OUT
:3.3V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin= 5 V
Vin= 9 V
Vin= 12 V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin= 24 V
Vin= 30 V
V
IN
=24V
V
IN
=30V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin= 5 V
Vin= 9 V
V
IN
=5V
V
IN
=9V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin= 5 V
Vin= 9 V
Vin= 12 V
Vin= 24 V
Vin= 30 V
V
IN
=5V
V
IN
=9V
V
IN
=12V
V
IN
=24V
V
IN
=30V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency[%]
Vin= 5 V
Vin= 9 V
Vin= 12 V
Vin= 24 V
Vin= 30 V
V
IN
=5V
V
IN
=9V
V
IN
=12V
V
IN
=24V
V
IN
=30V
V
IN
=5V
V
IN
=9V
V
IN
=12V
R1242S
21
V
OUT
:15V
fosc=1000kHz
V
OUT
:0.8V V
OUT
:3.3V
V
OUT
:15V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin= 24 V
Vin= 30 V
V
IN
=24
V
V
IN
=30
V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin= 5
V
V
IN
=5V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin= 5 V
Vin= 9 V
Vin= 12 V
V
IN
=5V
V
IN
=9V
V
IN
=12V
(Ta=25℃)
0
20
40
60
80
100
1 10 100 1000 10000
I
OUT
[mA]
Efficiency [%]
Vin=24V
Vin=30V
V
IN
=24V
V
IN
=30V
R1242S
22
19)Load Regulation
fosc=330kHz
V
OUT
:0.8V V
OUT
:3.3V
V
OUT
:15V
fosc=500kHz
V
OUT
:0.8V V
OUT
:3.3V
(Ta=25℃)
0.75
0.76
0.77
0.78
0.79
0.8
0.81
0.82
0.83
0.84
0.85
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 5 V
Vin= 9 V
Vin= 12 V
V
IN
=5V
V
IN
=9V
V
IN
=12V
(Ta=25℃)
14
14.2
14.4
14.6
14.8
15
15.2
15.4
15.6
15.8
16
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 24 V
Vin= 30 V
V
IN
=24V
V
IN
=30V
(Ta=25℃)
3.1
3.15
3.2
3.25
3.3
3.35
3.4
3.45
3.5
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 5 V
Vin= 9 V
Vin= 12 V
Vin= 24 V
Vin= 30 V
V
IN
=5V
V
IN
=9V
V
IN
=12V
V
IN
=24V
V
IN
=30V
(Ta=25℃)
0.75
0.76
0.77
0.78
0.79
0.8
0.81
0.82
0.83
0.84
0.85
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 5 V
Vin= 9 V
V
IN
=5V
V
IN
=9V
(Ta=25℃)
3.1
3.15
3.2
3.25
3.3
3.35
3.4
3.45
3.5
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 5 V
Vin= 9 V
Vin= 12 V
Vin= 24 V
Vin= 30 V
V
IN
=5V
V
IN
=9V
V
IN
=12V
V
IN
=24V
V
IN
=30V
R1242S
23
V
OUT
:15V
fosc=1000kHz
V
OUT
:0.8V V
OUT
:3.3V
V
OUT
:15V
(Ta=25℃)
14
14.2
14.4
14.6
14.8
15
15.2
15.4
15.6
15.8
16
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 24 V
Vin= 30 V
V
IN
=24V
V
IN
=30V
(Ta=25℃)
0.75
0.76
0.77
0.78
0.79
0.8
0.81
0.82
0.83
0.84
0.85
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 5
V
V
IN
=5V
(Ta=25℃)
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin= 5 V
Vin= 9 V
Vin= 12 V
V
IN
=5V
V
IN
=9V
V
IN
=12V
(Ta=25℃)
14
14.2
14.4
14.6
14.8
15
15.2
15.4
15.6
15.8
16
0 500 1000 1500 2000 2500 3000
I
OUT
[mA]
V
OUT
[V]
Vin=24V
Vin=30V
V
IN
=24V
V
IN
=30V
R1242S
24
20)Line Regulation
fosc=330kHz
V
OUT
:0.8V V
OUT
:3.3V
V
OUT
:15V
fosc=500kHz
V
OUT
:0.8V V
OUT
:3.3V
(Ta=25℃)
0.75
0.76
0.77
0.78
0.79
0.80
0.81
0.82
0.83
0.84
0.85
5 1015202530
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
(Ta=25℃)
3.10
3.15
3.20
3.25
3.30
3.35
3.40
3.45
3.50
5 1015202530
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
(Ta=25℃)
14.0
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
16.0
20 25 30
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
(Ta=25℃)
0.75
0.76
0.77
0.78
0.79
0.80
0.81
0.82
0.83
0.84
0.85
5678
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
(Ta=25℃)
3.10
3.15
3.20
3.25
3.30
3.35
3.40
3.45
3.50
5 1015202530
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
R1242S
25
V
OUT
:15V
f
osc=
1000kH
z
V
OUT
:0.8V V
OUT
:3.3V
V
OUT
:15V
(Ta=25℃)
14.0
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
16.0
20 25 30
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
(Ta=25℃)
14.0
14.2
14.4
14.6
14.8
15.0
15.2
15.4
15.6
15.8
16.0
20 25 30
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=2000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
(Ta=25℃)
0.75
0.76
0.77
0.78
0.79
0.80
0.81
0.82
0.83
0.84
0.85
5678
V
IN
[V]
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
(Ta=25℃)
3.10
3.15
3.20
3.25
3.30
3.35
3.40
3.45
3.50
5 1015202530
V
IN
(V)
V
OUT
[V]
Iout=1mA
Iout=100mA
Iout=500mA
Iout=1500mA
Iout=3000mA
I
OUT
=1mA
I
OUT
=100mA
I
OUT
=500mA
I
OUT
=1500mA
I
OUT
=3000mA
RICOHCOMPANY, LTD.
ElectronicDevicesCompany
http://www.ricoh.com/LSI/
For the conservation of the global environment, Ricoh is advancing the decrease of the negative environmental impact material.
After Apr. 1, 2006, we will ship out the lead free products only. Thus, all products that will be shipped from now on comply with RoHS Directive.
Basically after Apr. 1, 2012, we will ship out the Power Management ICs of the Halogen Free products only. (Ricoh Halogen Free products are
also Antimony Free.)
Halogen Free
RICOHCOMPANY,LTD.
ElectronicDevicesCompany
●Higashi-ShinagawaOffice(InternationalSales)
3-32-3,Higashi-Shinagawa,Shinagawa-ku,Tokyo140-8655,Japan
Phone:+81-3-5479-2857Fax:+81-3-5479-0502
RICOHEUROPE(NETHERLANDS)B.V.
●SemiconductorSupportCentre
NieuwKronenburgProf.W.H.Keesomlaan1,1183DJ,Amstelveen,TheNetherlands
P.O.Box114,1180ACAmstelveen
Phone:+31-20-5474-309Fax:+31-20-5474-791
RICOHELECTRONICDEVICESKOREACo.,Ltd.
11floor,Haesung1building,942,Daechidong,Gangnamgu,Seoul,Korea
Phone:+82-2-2135-5700Fax:+82-2-2135-5705
RICOHELECTRONICDEVICESSHANGHAICo.,Ltd.
Room403,No.2Building,690#BiBoRoad,PuDongNewdistrict,Shanghai201203,
People'sRepublicofChina
Phone:+86-21-5027-3200Fax:+86-21-5027-3299
RICOHCOMPANY,LTD.
ElectronicDevicesCompany
●Taipeioffice
Room109,10F-1,No.51,HengyangRd.,TaipeiCity,Taiwan(R.O.C.)
Phone:+886-2-2313-1621/1622Fax:+886-2-2313-1623
1.Theproductsandtheproductspecificationsdescribedinthisdocumentaresubjecttochangeor
discontinuationofproductionwithoutnoticeforreasons
suchasimprovement.Therefore,before
decidingtousetheproducts,pleaserefertoRicohsalesrepresentativesforthelatest
informationthereon.
2.Thematerialsinthisdocumentmaynotbecopiedorotherwisereproducedinwholeorinpart
withoutpriorwrittenconsentofRicoh.
3.Pleasebesuretotakeanynecessaryformalitiesunderrelevantlawsorregulationsbefore
exportingorotherwisetakingoutofyourcountrytheproductsorthetechnicalinformation
describedherein.
4.Thetechnicalinformationdescribedinthisdocumentshowstypicalcharacteristicsofand
exampleapplicationcircuitsfortheproducts.Thereleaseofsuchinformationisnottobe
construedasawarrantyoforagrantoflicenseunderRicoh'soranythirdparty'sintellectual
propertyrightsoranyotherrights.
5.
Theproductslistedinthisdocumentareintendedanddesignedforuseasgeneralelectronic
componentsinstandardapplications(officeequipment,telecommunicationequipment,
measuringinstruments,consumerelectronicproducts,amusementequipmentetc.).Those
customersintendingtouse
aproductinanapplicationrequiringextremequalityandreliability,
forexample,inahighlyspecificapplicationwherethefailureormisoperationoftheproduct
couldresultinhumaninjuryordeath(aircraft,spacevehicle,nuclearreactorcontrolsystem,
trafficcontrolsystem,automotiveand
transportationequipment,combustionequipment,safety
devices,lifesupportsystemetc.)shouldfirstcontactus.
6.Wearemakingourcontinuousefforttoimprovethequalityandreliabilityofourproducts,but
semiconductorproductsarelikelytofailwithcertainprobability.Inordertopreventanyinjuryto
personsordamagestopropertyresultingfromsuchfailure,customersshouldbecarefulenough
toincorporatesafetymeasuresintheirdesign,suchasredundancyfeature,firecontainment
featureandfail-safefeature.Wedonotassumeanyliability
orresponsibilityforanylossor
damagearisingfrommisuseorinappropriateuseoftheproducts.
7.Anti-radiationdesignisnotimplementedintheproductsdescribedinthisdocument.
8.
PleasecontactRicohsalesrepresentativesshouldyouhaveanyquestionsorcomments
concerningtheproductsorthetechnicalinformation.