R1245x SERIES
1.2A, 30V Step Down DC/DC converter
NO.EA-269-130322
1
OUTLINE
The R1245x series are CMOS-based Step-down DC/DC converter with internal N-channel high side Tr. The
ON resistance of the built-in high-side transistor is 0.35Ω and the R1245 can provide the maximum 1.2A output
current. Each of the ICs consists of an oscillator, a PWM control circuit, a voltage reference unit, an error
amplifier, a phase compensation circuit, a slope compensation circuit, a soft-start circuit, protection circuits, an
internal voltage regulator, and a switch for bootstrap circuit. The ICs can make up a step-down DC/DC converter
with an inductor, resistors, a diode, and capacitors.
The R1245x series are current mode operating type DC/DC converters without an external current sense
resistor, and realizes fast response and high efficiency. As an output capacitor, a ceramic type capacitor can be
used with the R1245X series. The options of the internal oscillator frequency are preset at 330kHz for version A
and B, 500kHz for version C and D, 1000kHz for version E and F, 2400kHz for version G and H.
As for protection, an Lx peak current limit circuit cycle by cycle, a thermal shutdown function and an under
voltage lockout (UVLO) function are built in. Furthermore, there are two types for short protection, for A/C/E/G
version, a latch protection function which makes the output latch off if the output voltage keeps lower than the set
output voltage for a certain time after detecting current limit is built in, for B/D/F/H version, a fold-back protection
function which changes the oscillator frequency slower after detecting short circuit or equivalent.
As for the packages of the R1245 series, HSOP-8E, DFN(PLP)2020-8, SOT23-6W are available.
FEATURES
● Operating Voltage ················································ 4.5V~30V
● Internal N-channel MOSFET Driver························· RON=0.35Ω Typ.
● Adjustable output voltage with external resistor ······ 0.8V or more
● Feedback voltage and tolerance ····························· 0.8V±1.0%
● Peak current limit ····················································· Typ. 2.0A
● UVLO function released voltage······························ Typ. 4.0V
● Operating frequency ················································ 330kHz (A/B version), 500kHz (C/D version),
1000kHz (E/F version), 2400kHz (G/H version)
● Fold-back protected frequency ································ 170kHz (B/D version), 250kHz (F version),
400kHz (H version)
● Latch protection delay time······································ Typ. 4ms for A/C/E/G version
● Ceramic capacitors recommended for input and output.
● Stand-by current ······················································ Typ. 0μA
● Packages ································································· SOT-23-6W, DFN(PLP)2020-8, HSOP-8E
APPLICATIONS
● Power source for digital home appliance such as digital TV, DVD players.
● Power source for 5V PSU or 2-cell or more Li-ion battery powered communication equipment, cameras,
video instruments such as VCRs, camcorders.
● Power source for high voltage battery-powered equipment.
● Power source for office equipment such as printers and fax machines.
R1245x
2
BLOCK DIAGRAMS
*1
Version Oscillator frequency Short protection type
A 330kHz Latch
B 330kHz Fold-back
C 500kHz Latch
D 500kHz Fold-back
E 1000kHz Latch
F 1000kHz Fold-back
G 2400kHz Latch
H 2400kHz Fold-back
FB
CE
-
+
Os cil lator
*1
BST
Regulator 5V
R
SD
SETPULSE
MAXDUTY
Current Slope
Circui
t
Reference
Soft Start
Circuit(1ms)
-
+
UVLO
0.8V
Regulator
Thermal Shutdown
Peak Current
Limit Circuit
Lx
VIN
GND
Limit Latch
Circuit (4ms)
Shutdown
*1
R1245x
3
SELECTION GUIDE
In the R1245x Series, the package, type of short protection (Latch or Fold back), and the oscillator frequency
can be selected with the user’s request.
Product code Package Quantity per reel Pb free Halogen free
R1245S003∗-E2-FE HSOP-8E 1,000 Yes Yes
R1245K003∗-TR DFN(PLP)2020-8 5,000 Yes Yes
R1245N001∗-TR-FE SOT-23-6W 3,000 Yes Yes
∗: Designation of the oscillator frequency and the protection function option.
Symbol Oscillator
frequency
Latch
protection
Fold back
protection
A 330kHz 9
B 330kHz 9
C 500kHz 9
D 500kHz 9
E 1000kHz 9
F 1000kHz 9
G 2400kHz 9
H 2400kHz 9
R1245x
4
PIN CONFIGURATION
• DFN(PLP)2020-8
Top View Bottom View
8 7 6 5 5 6 7 8
1 2 3 4 4 3 2 1
• HSOP-8E • SOT-23-6W
Top View Bottom View
8 7 6 5 5 6 7 8
1 2 3 4 4 3 2 1
Top View
6 5 4
1 2 3
*Connect the backside heat radiation tub to GND or same as GND level (recommendation). The tub is connected
to the GND pin.
PIN DESCRIPTION
z R1245S(HSOP-8E)
Pin No. Symbol Description
1 LX LX Switching Pin
2 VIN Power Supply Pin
3 CE Chip Enable Pin (Active with ”H”)
4 TEST TEST pin (must be open for user side.)
5 GND Ground Pin
6 FB Feedback Pin
7 NC No connection
8 BST Bootstrap Pin
*Connect the backside heat radiation tub to GND or same as GND level (recommendation). The tub is connected
to the GND pin.
R1245x
5
z R1245K (DFN(PLP)2020-8)
Pin No. Symbol Description
1 LX LX Switching Pin
2 VIN Power Supply Pin
3 VIN Power Supply Pin
4 CE Chip Enable Pin (Active with ”H” )
5 GND Ground Pin
6 FB Feedback Pin
7 TEST Test Pin ( must be open for user side.)
8 BST Bootstrap Pin
*Connect the backside heat radiation tub to GND or same as GND level (recommendation). The tub is connected
to the GND pin.
z R1245N (SOT23-6W)
Pin No. Symbol Description
1 BST Bootstrap Pin
2 GND Ground Pin
3 FB Feedback Pin
4 CE Chip Enable Pin (Active with ”H” )
5 VIN Power Supply Pin
6 LX LX Switching Pin
ABSOLUTE MAXMUM RATINGS
(GND=0V)
Symbol Item Rating Unit
VIN Input Voltage -0.3 to 32.0 V
VBST BST Pin Voltage VLX-0.3 to VLX+6.0 V
VLX LX Pin Voltage -0.3 to VIN+0.3 V
VCE CE Pin Input Voltage -0.3 to VIN+0.3 V
VCE CE Pin input Voltage -0.3 to VIN+0.3 V
VFB Feedback Pin Voltage -0.3 to 6.0 V
HSOP-8E
Standard Land Pattern*
2900
DFN(PLP)2020-8
Standard Land Pattern*
880
PD Power Dissipation
SOT-23-6W
Standard Land Pattern*
430
mW
Ta Operating Temperature Range -40 to 105 ºC
Tstg Storage Temperature Range -55 to 125 ºC
*For Power Dissipation, refer to the PACKAGE INFORMATION on the web site.
ABSOLUTE MAXIMUM RATINGS
Electronic and mechanical stress momentarily exceeded absolute maximum ratings may cause the permanent
damages and may degrade the lifetime 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.
R1245x
6
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, VIN= 12V, Ta=25ºC)
Symbol Item Conditions MIN. TYP. MAX. Unit
VIN Operating Input Voltage 4.5 30 V
IIN VIN Consumption Current VIN=30V, VFB=1.0V 0.5 1.0 mA
VUVLO1 UVLO Detect Voltage Specified VIN falling
edge 3.6 VUVLO2
-0.2
VUVLO2
-0.1 V
VUVLO2 UVLO Released Voltage Specified rising edge 3.8 4.0 4.2 V
VFB VFB Voltage Tolerance 0.792 0.800 0.808 V
∆VFB/∆T VFB Voltage Temperature Coefficient -40ºC ≤ Ta ≤ 105ºC ±100 ppm/ºC
Version A/B 300 330 360
Version C/D 450 500 550
Version E/F 900 1000 1100
fosc Oscillator Frequency
Version G/H 2200 2400 2600
kHz
Version B/D 170
Version F 250
kHz
fFLB Fold back Frequency VFB<0.56V
Version H 400
Version A/B/C/D 92
Version E/F 88
Maxduty Oscillator Maximum. Duty Cycle
Version G/H 76
%
tSS Soft-start Time VFB=0.72V 1 ms
tDLY Delay Time for Latch Protection Version A/C/E/G 4 ms
RLXH LX High Side Switch ON Resistance VBST-VLX=4.5V 0.35 Ω
ILXHOFF LX High Side Switch Leakage Current VIN=30V, VCE=0V 0 5 μA
ILIMLXH LX High Side Switch Limited Current VBST-VLX=4.5V 1.5 2.0 2.7 A
VCEL CE “L” Input Voltage VIN=30V 0.3 V
VCEH CE “H” Input Voltage VIN=30V 1.6 V
IFB VFB Input Current VIN=30.0V, VFB=1.0V -1.0 1.0 μA
ICEL CE “L” Input Current VIN=30V, VCE=0V -1.0 1.0 μA
ICEH CE “H” Input Current VIN=30V, VCE=30V -1.0 1.0 μA
TTSD Thermal Shutdown Detect
Temperature Hysteresis 30ºC 160 ºC
Istandby Standby Current VIN=30V 0 5 μA
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.
R1245x
7
TYPICAL APPLICATION
R1245x00xA/B 330kHz VOUT=1.2V VIN=24V
R1
6kΩ
R2
12kΩ
VIN
24V
CIN
10µF
CSPD
470pF
CBST
0.47µF
L 10µH
COUT
47µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
R1
6kΩ
R2
12kΩ
VIN
24V
CIN
10µF
CSPD
470pF
CBST
0.47µF
L 10µH
COUT
47µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
R1245x00xC/D 500kHz VOUT=3.3V VIN=24V
R1
3.75kΩ
R2
1.2kΩ
VIN
24V
CIN
10µF
CSPD
1000pF
CBST
0.47µF
L 10µH
COUT
22µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
R1
3.75kΩ
R2
1.2kΩ
VIN
24V
CIN
10µF
CSPD
1000pF
CBST
0.47µF
L 10µH
COUT
22µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
*TEST pin must be open.
R1245x
8
R1245x00xE/F 1000kHz VOUT=3.3V VIN=12V
R1
3.75kΩ
R2
1.2kΩ
VIN
12V
CIN
4.7µF
CSPD
470pF
CBST
0.47µF
L 4.7µH
COUT
10µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
R1
3.75kΩ
R2
1.2kΩ
VIN
12V
CIN
4.7µF
CSPD
470pF
CBST
0.47µF
L 4.7µH
COUT
10µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
R1245x00xG/H 2400kHz VOUT=5.0V VIN=12V
R1
6.3kΩ
R2
1.2kΩ
VIN
12V
CIN
2.2µF
CSPD
470pF
CBST
0.47µF
L 2.2µH
COUT
4.7µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
R1
6.3kΩ
R2
1.2kΩ
VIN
12V
CIN
2.2µF
CSPD
470pF
CBST
0.47µF
L 2.2µH
COUT
4.7µF
RCE
10kΩ
(recommended)
VIN
FB
TEST
GND
BST
Lx
CE
“H”active
D
*TEST pin must be open.
TECHNICAL NOTES
*External components must be connected as close as possible to the ICs and make wiring as short as possible.
Especially, the capacitor connected in between VIN pin and GND pin must be wiring the shortest. If their
impedance is high, internal voltage of the IC may shift by the switching current, and the operating may be
unstable. Make the power supply and GND lines sufficient. In the wiring of the power supply, GND, LX, VOUT and
the inductor, large current by switching may flow. To avoid the bad influence, the wiring between the resistance,
“Rup” for setting the output voltage and loading, and the wiring between the inductor and loading must be
separated.
*The ceramic capacitors have low ESR (Equivalent Series Resistance) and recommended for the ICs. The
recommendation of CIN capacitor between VIN and GND is 10μF or more for A/B/C/D version, 4.7μF or more for
E/F version, and 2.2μF or more for G/H version. Verify the bias dependence and the temperature characteristics
of the ceramic capacitors. Recommendation conditions are written based on the case which the
recommendation parts are used with the R1245.
*The R1245 series are designed with the recommendation inductance value and ceramic capacitor value and
phase compensation has been made. If the inductance value is large, due to the lack of current sensing amount
of the current mode, unstable operation may result. On the contrary, if the inductance value is small, the current
sensing amount may increase too much, low frequency oscillation may occur when the on duty ratio is beyond
R1245x
9
50%. Not only that, if the inductance value is small, according to the increase of the load current, the peak
current of the switching may increase, as a result, the current may reach the current limit value and the current
limit may work.
*As for the diode, use the Schottky diode with small capacitance between terminals. The reference characteristic
of the capacitance between terminals is around 100pF or less at 10V. If the capacitance between terminals is
large, excess switching current may flow and the operation of the IC may be unstable. If the capacitance
between terminals of the Scottky diode is beyond 100pF at 10V or unknown, verify the load regulation, line
regulation, and the load transient response.
*Output voltage can be set by adjustment of the values of R1 and R2. The equation of setting the output voltage
is VOUT=VFB × (R1+R2)/R2. If the values of R1 and R2 are large, the impedance of FB pin increases, and pickup
the noise may result. The recommendation value range of R2 is approximately between 1.0kΩ to 16kΩ. If the
operation may be unstable, reduce the impedance of FB pin.
*For the CE pin, as an ESD protection element, a diode to VIN pin is formed internal of the IC. If CE pin voltage
may become higher than VIN pin voltage, to prevent flowing large current from CE pin to VIN pin, connect 10kΩ or
more resistor between CE and VIN pin.
*Connect the backside heat radiation tub of the DFN(PLP)2020-9/HSOP-8E to the GND. As for multi-layered
boards, to make better power dissipation, putting some thermal vias on the thermal pad in the land pattern and
radiation of the heat to another layer is effective.
*After the soft-start operation, the latch function is enabled for version A/C/E/G. The latch protection starts the
internal counter when the internal current limit protection circuit detects the current limit. When the internal
counter counts up to the latch timer limit, typically 4ms, the output is latched off. To reset the latch function, make
the CE pin “L”, or make VIN pin voltage lower than UVLO detector threshold. Then in the case that the output
voltage or FB voltage becomes setting voltage within the latch timer preset time, counter is initialized. If the slew
rate of the power supply is too slow and after the soft-start time, the output voltage does not reach the set output
voltage even if the latch timer preset time is over, the latch function may work unexpectedly.
*After the soft-start operation, fold back protection function is enabled for version B/D/F/H. The fold back function
will limit the oscillator frequency if the FB pin voltage becomes lower than typically 0.56V. For B/D version, the
oscillator frequency will be reduced typically into 170kHz, for F version, into 250kHz, for H version, into 400kHz.
If the slew rate of the power supply is too slow, and even after the soft-start time, the output voltage is still less
than 70% of the set output voltage, or FB pin voltage is less than typically 0.56V, then this function may work
unexpectedly.
The performance of power circuit using this IC largely depends on external components. Selection of external
components is very important, especially, do not exceed each rating value (voltage/current/power).
R1245x
10
Recommended values for each output voltage
R1245x00xA/B: 330kHz
VOUT (V) 0.8 to
1.2
1.2 to
2.5
2.5 to
5.0 5.0 ≤
R1(RUP) (kΩ) =(VOUT / 0.8-1) × R2
R2(RBOT) (kΩ) 16 12 1.20 1.20
CSPD (pF) open 470 2200 1000
COUT (μF) 47 47 22 22
L(μH) 4.7 10 15 33
R1245x00xC/D：500kHz
VOUT (V) 0.8 to
1.2
1.2 to
1.5
1.5 to
2.0
2.0 to
5.0
5.0 to
12.0 12.0 ≤
R1(RUP) (kΩ) =(VOUT / 0.8-1) × R2
R2(RBOT) (kΩ) 16 16 16 1.2 1.2 1.2
CSPD (pF) open 100 100 1000 1000 470
COUT (μF) 100 100 22 22 22 22
L(μH) 4.7 4.7 10 10 15 15
R1245x00xE/F：1000kHz
VOUT (V) 0.8 to
1.0
1.0 to
1.2
1.2 to
1.5
1.5 to
2.5
2.5 to
5.0 5.0 ≤
R1(RUP) (kΩ) =(VOUT / 0.8-1) × R2
R2(RBOT) (kΩ) 16 16 16 16 1.2 1.2
CSPD (pF) open 100 100 100 470 470
COUT (μF) 100 100 47 22 10 10
L(μH) 2.2 2.2 2.2 2.2 4.7 10
R1245x00xG/H：2400kHz
VOUT (V) 1.2 to
1.8
1.8 to
2.5
2.5 to
5.0 5.0 ≤
R1(RUP) (kΩ) =(VOUT / 0.8-1) × R2
R2(RBOT) (kΩ) 16 12 1.2 1.2
CSPD (pF) 100 100 470 470
COUT (μF) 10 10 4.7 4.7
L(μH) 1.0 1.5 2.2 4.7
R1245x
11
*Divider resisters values and possible setting range of input /output
Input Voltage range [V]
VOUT
[V]
R1(RUP)
[kΩ]
R2(RBOT)
[kΩ] Ver.AB Ver.CD Ver.EF Ver.GH
0 open
0.8
0 16
4.5 to 20 4.5 to
13.5 4.5 to 7 -
1 4 16
4.5 to
25.5 4.5 to 17 4.5 to 8.5 -
8 16
1.2
6 12
4.5 to 30 4.5 to 20 4.5 to 10 -
10.5 12
1.5
14 16
4.5 to 30 4.5 to 25 4.5 to
12.5
4.5 to
5.5
20 16
1.8
15 12
4.5 to 30 4.5 to 30 4.5 to 15 4.5 to
6.5
24 16
2
1.8 1.2
4.5 to 30 4.5 to 30 4.5 to 17 4.5 to 7
34 16
25.5 12
2.5
2.55 1.2
4.5 to 30 4.5 to 30 4.5 to 21 4.5 to 9
3.3 3.75 1.2
4.5 to 30 4.5 to 30 4.5 to
27.5
4.5 to
12
5 6.3 1.2
5.5 to 30 5.5 to 30 6 to 30 7 to 17
6 7.8 1.2
6.5 to 30 6.5 to 30 7 to 30 8 to 20
9 12.3 1.2
10 to 30 10 to 30 11 to 30 12 to 30
12 16.8 1.2
13 to 30 13 to 30 14 to 30 16 to 30
15 21.3 1.2
16.5 to 30 16.5 to 30 17 to 30 20 to 30
24 34.8 1.2 26.5 to 30 26.5 to 30 27.5 to 30 30
R1245x
12
Recommended external Components examples (Considering all the range)
Symbol Characteristics Value Parts Name MFR
CIN 50V/X5R 10μF UMK325BJ106MM-T TAIYO YUDEN
50V/X7R
4.7μF GRM31CR71H475KA12L MURATA
50V/X7R
2.2μF GRM31CR71H225KA88L MURATA
COUT 50V/X5R 10μF UMK325BJ106MM-T TAIYO YUDEN
50V/X7R 10μF KTS500B106M55N0T00 Nippon Chemi-Con
25V/X7R 10μF GRM31CR71E106K MURATA
10V/X7R 22μF GRM31CR71A226M MURATA
GRM32EB31C476KE15
GRM32ER71A476KE15
MURATA
MURATA
16V B
10V/X7R
47μF
47μF
NOTE: The value of COUT depends on the setting
output voltage.
CBST 16V/X7R 0.47μF EMK212B7474KD-T TAIYO YUDEN
L 1.8A 10μH SLF6045T-100M1R6-3PF TDK
1.65A 4.7μH SLF7045T-4R7M2R0-PF TDK
1.7A 4.7μH NR4018T-4R7M2R0-PF TDK
2.4A 4.7μH NR6020T4R7M TAIYO YUDEN
1.9A 10μH NR6028T100M TAIYO YUDEN
2.3A 15μH NR6045T150M TAIYO YUDEN
1.9A 22μH NR6045T220M TAIYO YUDEN
1.9A 33μH NR8040T330M TAIYO YUDEN
1.7A 2.2μH VLCF4020T-2R2N1R7 TDK
1.65A 2.2μH NR4012T2R2M TAIYO YUDEN
1.8A 1.5μH NR3015T1R5N TAIYO YUDEN
1.8A 1.0μH NR4010T1R0N TAIYO YUDEN
D 30V/1.5A 0.42V MA22D28 Panasonic
30V/2.0A 0.37V CMS06 TOSHIBA
40V/2.0A 0.55V CMS11 TOSHIBA
40V/2.0A 0.43V MA24D60 Panasonic
15V/2.0A 0.32V SBS010M SANYO
RCE
An UP DIODE is formed between the CE pin and the VIN pin as an ESD protection element.
If the CE pin may become higher than the voltage of the VIN pin, connect the 10kohm resistance between the
CE pin and VIN pin, to prevent a large current from flowing into the VIN pin from the CE pin.
R1245x
13
Operation of the Buck Converter and the Output Current
The DC/DC converter charges energy in the inductor when the switch turns on, and discharges the energy from
the inductor when the switch turns off and controls with less energy loss, so that a lower output voltage than the
input voltage is obtained. Refer to the following figures.
<Basic Circuit> <Current through the inductor>
Switch L
Diode
VIN
i1
VOUT
COUT
i2
GND
T=1/fosc
ton toff
topen
ILmin
ILmax
IL
Step 1: The switch turns on and current IL (=i1) flows, and energy is charged into COUT. At this moment, IL
increases from ILmin (=0) to reach ILmax in proportion to the on-time period (ton) of the switch.
Step 2: When the switch turns off, the diode turns on in order to maintain IL at ILmax, and current IL (=i2)
flows.
Step 3: IL (=i2) decreases gradually and reaches IL=ILmin=0 after a time period of topen, and the diode
turns off. This case is called as discontinuous mode. If the output current becomes large, next switching
cycle starts before IL becomes 0 and the diode turns off. In this case, IL value increases from ILmin (>0),
and this case is called continuous mode.
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.
Output Current and Selection of External Components
The relation between the output current and external components is as follows:
When the switch of LX turns on:
(Wherein, the peak to peak value of the ripple current is described as IRP, the ON resistance of the switch is
described as RONH, and the diode forward voltage as VF, and the DC resistance of the inductor is described as
RL, and on time of the switch is described as ton)
VIN = VOUT + (RONH + RL) × IOUT + L × IRP / ton ································································ Equation 1
When the switch turns off (the diode turns on) as toff:
L × IRP / toff = VF + VOUT + RL × IOUT ··············································································· Equation 2
Put Equation 2 to Equation 1 and solve for ON duty of the switch, ton / ( toff + ton) = DON,
DON = (VOUT + VF + RL × IOUT)/(VIN + VF - RONH × IOUT) ···················································· Equation 3
R1245x
14
Ripple Current is as follows:
IRP = (VIN − VOUT − RONH × IOUT − RL × IOUT) × DON / fosc / L ············································· Equation 4
wherein, peak current that flows through L, and the peak current ILmax is as follows:
ILmax = IOUT + IRP / 2······································································································ Equation 5
As for the valley current ILmin,
ILmin = IOUT - IRP / 2 ······································································································· Equation 6
If ILmin<0, the step-down DC/DC converter operation becomes current discontinuous mode.
Therefore the current condition of the current discontinuous mode, the next formula is true.
IOUT < IRP / 2 ·················································································································· Equation 7
Consider ILmax and ILmin, conditions of input and output and select external components.
*The above explanation is based on the calculation in an ideal case in continuous mode.
R1245x
15
Ripple Current and Lx current limit
The ripple current of the inductor may change according to the various reasons. In the R1245x series, as an
Lx current limit, Lx peak current limit is used. Therefore the upper limit of the inductor current is fixed.
The peak current limit is not the average current of the inductor (output current). If the ripple current is large,
peak current becomes also large. The characteristic is used for the fold back current limit of version B/D/F/H.
In other words, the peak current limit is maintained and the switching frequency is reduced, as a result, the
average current of the inductor is reduced. To release this condition, at 170kHz for version B/D, at 250kHz
for version F, at 400kHz for version H must not be beyond the peak current limit. In the fig.1, the sequence of
the Lx current limit function is described.
Fig.1 LX Limit function sequence
Latch protection function for version A/C/E/G
The latch function works after detecting current limit and if the output voltage becomes low for a certain time,
the output is latched off. Refer to the TECHNICAL NOTES.
Fold back protection function for version B/D/F/H
If FB voltage becomes lower than approximately 0.56V, the fold back protection function limits the oscillator
frequency to typically 170kHz for version B/D, typically 250kHz fir version F, typically 400kHz for version H.
By reducing frequency, the ripple current increases. The R1245x has the peak current limit function,
therefore as in the equation 8, the Lx average current decreases by the increase of the ripple current.
IOUT =ILmax + IRP / 2 Equation 8
If FB voltage becomes less than 0.56V, the oscillator frequency is reduced. At heavy load, if the R1245x
becomes into the fold back protection mode, the situation may not be released by increase the ripple current.
In terms of other notes on this protection function, refer to the TECHNICAL NOTES.
R1245x
16
MAXIMUM OUTPUT CURRENT
The output current of the R1245x is limit by the power dissipation PD of the package and the maximum
specification 1.2A. The loss of the IC includes the switching loss, and it is difficult to estimate. To estimate the
maximum output, using the efficiency data is one method.
By using the efficiency data, the loss including the external components can be calculated with the equation,
(100/efficiency(%)-1)x(VOUT(V)xIOUT(V)). From this equation, by reducing the loss of external components, the
loss of the IC can be estimated. The main loss of the external components is composed by the rectifier diode
and DCR of the inductor. Supposed that the forward voltage of the diode is described as VF, the loss of the
diode can be described as follows:
(VIN(V)-RON(Ω)xIOUT(A)-VOUT(V)-VF(V)))/VIN(V)xVF(V)xIOUT(A)
The loss by the DCR of the inductor can be calculated by the formula DCR(Ω)xIOUT
2(A).
Thus,
The loss of the IC = (100 / efficiency(%) -1) x (VOUT(V) x IOUT(A) - (VIN(V) - RON(Ω) x IOUT(A) - VOUT(V) -VF(V)) /
VIN(V) x VF(V) xIOUT(A) - DCR(Ω) x IOUT
2(A)
The efficiency of the R1245 at Ta=25°C, VIN=12V, VOUT=3.3V, IOUT=600mA is approximately 89.5% for version
A/B(Oscillator frequency 330kHz). Supposed that the On resistance of the internal driver is 0.35Ω, the DCR of
the inductor is 65mΩ, the VF of the rectifier diode is 0.3V and applied to the formula above,
The loss of the IC = (100% / 89.5% - 1) x (3.3V x 0.6A) - (12V - 0.35Ω x 0.6A - 3.3V - 0.3V) / 12V x 0.3V x 0.6A
- 0.065Ωx0.62A=86mW
The power dissipation PD of the package is specified at Ta=25°C based on the Tjmax=125°C. Thus the thermal
resistance of the package θja=(Tjmax(°C)-Ta(°C))/PD(W), therefore the thermal resistance of the each
available package is as follows:
HSOP-8E: (125°C-25°C)/2.9W=34.5°C/W
DFN(PLP)2020-8: (125°C-25°C)/0.88W=114°C/W
SOT-23-6W: (125°C-25°C)/0.43W=233°C/W
Due to the loss of the IC is 86mW for this example, therefore Tj increase of the each package is as follows:
HSOP-8E: 34.5°C/Wx86mW=2.96°C
DFN(PLP)2020-8: 114°C/Wx86mW=9.80°C
SOT-23-6W: 233°C/Wx86mW=20.0°C
For all the packages, even if the ambient temperature is at 105°C, Tj can be suppressed less than 125°C. By
the increase of the temperature, on resistance and switching loss increases, therefore, temperature margin is
not enough, measure the efficiency at the actual maximum temperature and recalculation is necessary.
At the same condition, if the preset frequency is 2400kHz, the efficiency will be down to approximately 81%.
The result of the loss calculation is 310mW, therefore the Tj increase of each package is,
HSOP-8E: 34.5°C/Wx310mW=11°C
DFN(PLP)2020-8: 114°C/Wx310mW=35°C
SOT-23-6W: 233°C/Wx310mW=72°C
HSOP-8E can be used at the ambient temperature 105°C, DFN(PLP)2020-8 can be used at the ambient
temperature up to 90°C, SOT-23-6W can be used at the ambient temperature up to 53°C. Note that the result
is different by the frequency.
R1245x
17
The next graphs are the output current and estimated ambient temperature limit.
Maximum output current
VIN=12V , VOUT=3.3V , fosc=330kHz
0
200
400
600
800
1000
1200
1400
-50 0 50 100 150
Ta[°C]
IOUT[mA]
SOT-23-6 W
DFN2020-8
HSOP-8E
-40°C 105°C
VIN=12V , VOUT=3.3V , fosc=2400kHz
0
200
400
600
800
1000
1200
1400
-50 0 50 100 150
Ta[°C]
IOU T [mA]
SOT-23-6 W
DFN2020-8
HSOP-8E
-40°C 105°C
R1245x
18
INTERNAL EQUIVALENT CIRCUIT FOR EACH PIN
<BST pin> <Lx pin>
<FB pin> <CE pin>
<TEST pin>
Regulator
TEST
VIN
CE
Regulator
FB
BST
LX
Regulator
VIN
LX
R1245x
19
TYPICAL CHARACTERISTICS
1) FB voltage vs. Temperature 2)Driver On resistance vs. Temperature
R1245x00xx
　　　　　　　　　　　　　　　　(V
IN
=12V)
0.792
0.794
0.796
0.798
0.8
0.802
0.804
0.806
0.808
-50 -25 0 25 50 75 100 125
T
a
(℃)
FB Voltage (V)
R1245x00xx
　　　　　　　　　　　　　　　(V
IN
=12V)
200
250
300
350
400
450
500
-50 -25 0 25 50 75 100 125
T
a
(℃)
Driver On Resistance
(ｍΩ)
3) Oscillator frequency vs. Temperature
R1245x00xA/R1245x00xB
　　　　　　　　　　　　　　　　(V
IN
=12V)
300
310
320
330
340
350
360
-50 -25 0 25 50 75 100 125
T
a
(℃)
Frequency (kHz)
R1245x00xC/R1245x00xD
　　　　　　　　　　　　　　　　(VIN=12V)
450
475
500
525
550
-50 -25 0 25 50 75 100 125
Ta (℃)
Frequency (kHz)
R1245x00xE/R1245x00xF
　　　　　　　　　　　　　　　　(VIN=12V)
900
950
1000
1050
1100
-50-25 0 25 50 75100125
Ta (℃)
Frequency (kHz)
R1245x00xG/R1245x00xH
　　　　　　　　　　　　　　　　(VIN=12V)
2160
2240
2320
2400
2480
2560
2640
-50 -25 0 25 50 75 100 125
Ta (℃)
Frequency (kHz)
R1245x
20
4) Maximum duty cycle vs. Temperature
R1245x00xA/R1245x00xB
　　　　　　　　　　　　　　　(VIN=12V)
92
93
94
95
96
97
98
99
-50 -25 0 25 50 75 100 125
Ta (℃)
Maxduty (%
)
R1245x00xC/R1245x00xD
　　　　　　　　　　　　　　　(VIN=12V)
92
93
94
95
96
97
98
99
-50 -25 0 25 50 75 100 125
Ta (℃)
Maxduty (%
)
R1245x00xE/R1245x00xF
　　　　　　　　　　　　　　　(VIN=12V)
89
90
91
92
93
94
95
96
-50 -25 0 25 50 75 100 125
Ta (℃)
Maxduty (%
)
R1245x00xG/R1245x00xH
　　　　　　　　　　　　　　　(VIN=12V)
79
80
81
82
83
84
85
86
-50 -25 0 25 50 75 100 125
Ta (℃)
Maxduty (%
)
R1245x
21
5) Fold back frequency vs. Temperature
R1245x00xB
　　　　　　　　　　　　　　　　(VIN=12V)
80
100
120
140
160
180
200
220
240
-50 -25 0 25 50 75 100 125
Ta (℃)
Fold back Frequency
(kHz)
R1245x00xD
　　　　　　　　　　　　　　　　(VIN=12V)
80
100
120
140
160
180
200
220
240
-50 -25 0 25 50 75 100 125
Ta (℃)
Fold back Frequency
(kHz)
R1245x00xF
　　　　　　　　　　　　　　　　(VIN=12V)
120
170
220
270
320
370
420
-50 -25 0 25 50 75 100 125
Ta (℃)
Fold back Frequency
(kHz)
R1245x00xH
　　　　　　　　　　　　　　　　(VIN=12V)
120
220
320
420
520
620
720
-50 -25 0 25 50 75 100 125
Ta (℃)
Fold back Frequency
(kHz)
6) High side switch current limit vs. Temperature
R1245x00xx
　　　　　　　　　　　　　　　(VIN=12V)
1.5
1.7
1.9
2.1
2.3
2.5
2.7
-50 -25 0 25 50 75 100 125
Ta (℃)
LX Current Limit (A)
R1245x
22
7) UVLO detector threshold vs. Temperature 8) UVLO released voltage vs. Temperature
R1245x00xx
3.6
3.7
3.8
3.9
4
4.1
-50-250255075100125
Ta (℃)
UVLO
Detector Threshold (V)
R1245x00xx
3.8
3.9
4
4.1
4.2
-50-250255075100125
Ta (℃)
UVLO
Released Voltage (V)
9) Soft-start time vs. Temperature 10) Timer latch delay vs. Temperature
R1245x00xx
　　　　　　　　　　　　　　　　(VIN=12V)
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
-50 -25 0 25 50 75 100 125
Ta (℃)
Soft Start Time (ms)
R1245x00xx
　　　　　　　　　　　　　　　　(VIN=6V)
1
2
3
4
5
6
-50 -25 0 25 50 75 100 125
Ta (℃)
Delay Time For Latch
Protection (ms)
11) CE “H” Input voltage vs. Temperature 12) CE “L” Input voltage vs. Temperature
R1245x00xx
　　　　　　　　　　　　　　　　(VIN=12V)
0.5
1
1.5
2
2.5
-50 -25 0 25 50 75 100 125
Ta (℃)
CE "H" Voltage (V)
R1245x00xx
　　　　　　　　　　　　　　　　(V
IN
=12V)
0.5
1
1.5
2
2.5
-50 -25 0 25 50 75 100 125
T
a
(℃)
CE "L" Voltage (V)
R1245x
23
13) Soft-start waveform
R1245x00xA/R1245x00xB
VOUT=3.3V , VIN=12V , IOUT=0mA , Ta=25°C
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
200µs/div
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
200µs/div
R1245x00xA/R1245x00xB
VOUT=3.3V , VIN=12V , IOUT=600mA , Ta=25°C
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
200µs/div
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
200µs/div
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
V
CE
(5V/div)
I
LX
(200mA/div)
V
OUT
(1V/div)
V
LX
(10V/div)
14) Switching operation waveform
R1245x00xA/R1245x00xB
VOUT=3.3V , VIN=12V , IOUT=0mA , Ta=25°C
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
2µs/div
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
2µs/div
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
R1245x00xA/R1245x00xB
VOUT=3.3V , VIN=12V , IOUT=600mA , Ta=25°C
I
LX
(200mA/div)
V
OUT
(AC)
(20mV/div)
V
LX
(5V/div)
2µs/div
I
LX
(200mA/div)
V
OUT
(AC)
(20mV/div)
V
LX
(5V/div)
I
LX
(200mA/div)
V
OUT
(AC)
(20mV/div)
V
LX
(5V/div)
2µs/div
I
LX
(200mA/div)
V
OUT
(AC)
(20mV/div)
V
LX
(5V/div)
R1245x00xG/R1245x00xH
VOUT=3.3V , VIN=12V , IOUT=20mA , Ta=25°C
R1245x00xG/R1245x00xH
VOUT=3.3V , VIN=12V , IOUT=600mA , Ta=25°C
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
200ns/div
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
200ns/div
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
200ns/div
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
ILX
(200mA/div)
VOUT (AC)
(20mV/div)
VLX
(5V/div)
200ns/div
R1245x
24
15) Loaf transient response waveform
R1245x00xA/R1245x00xB
VOUT=0.8V , VIN=12V , IOUT=600⇔1200mA , Ta=25°C
V
OUT
(100mV/div)
I
OUT
(500mA/div)
100µs/div
V
OUT
(100mV/div)
I
OUT
(500mA/div)
100µs/div
R1245x00XA/R1245x00xB
VOUT=3.3V , VIN=12V , IOUT=600⇔1200mA , Ta=25°C
VOUT
(200mV/div)
IOUT
(500mA/div)
100µs/div
VOUT
(200mV/div)
IOUT
(500mA/div)
100µs/div
R1245x00xG/R1245x00xH
VOUT=1.5V , VIN=4.5V , IOUT=600⇔1200mA , Ta=25°C
R1245x00xG/R1245x00xH
VOUT=3.3V , VIN=12V , IOUT=600⇔1200mA , Ta=25°C
VOUT
( 100mV /div )
IOUT
( 500mA /div )
50us/div
VOUT
( 100mV /div )
IOUT
( 500mA /div )
50us/div 50us/div
VOUT
( 100mV /div )
IOUT
( 500mA /div )
50us/div
VOUT
( 100mV /div )
IOUT
( 500mA /div )
R1245x
25
16) Limit latch operation waveform 17) Released waveform from limit latch
R1245x00xA
VOUT=3.3V , VIN=12V , ROUT=5.5Ω→0.05Ω, Ta=25°C
R1245x00xA
VOUT=3.3V , VIN=12V , ROUT=5.5Ω→0.05Ω→5.5Ω
, Ta=25°C
18) Fold back operation waveform 19) Released waveform from fold back
R1245x00xB
VOUT=3.3V , VIN=12V , ROUT=5.5Ω→0.05Ω
Ta=25°C
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
20µs/div
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
20µs/div
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
R1245x00xB
VOUT=3.3V , VIN=12V , ROUT=5.5Ω→0.05Ω→5.5Ω
Ta=25°C
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
20µs/div
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
20µs/div
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
20) Switching waveform at fold back operation
R1245x00xB
VOUT=3.3V , VIN=12V , ROUT=0.05Ω, Ta=25°C
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
2µs/div
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
2µs/div
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
V
OUT
(2V/div)
V
LX
(10V/div)
I
LX
(1A/div)
VOUT
(2V/div)
VLX
(10V/div)
ILX
(1A/div)
1ms/div
VOUT
(2V/div)
VLX
(10V/div)
ILX
(1A/div)
VOUT
(2V/div)
VLX
(10V/div)
ILX
(1A/div)
1ms/div
VOUT
(2V/div)
VLX
(10V/div)
ILX
(1A/div)
1ms/div
VOUT
(2V/div)
VLX
(10V/div)
ILX
(1A/div)
1ms/div
R1245x
26
21) Output current vs. Efficiency (Version A/B)
R1245x00xA/R1245x00xB
VOUT=0.8V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 4.5V
VIN = 6.0V
VIN = 18V
R1245x00xA/R1245x00xB
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 4 .5 V
VIN = 1 2 V
VIN = 2 4 V
R1245x00xA/R1245x00xB
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 1 2 V
VIN = 2 4 V
VIN = 3 0 V
R1245x00xA/R1245x00xB
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 1 8 V
VIN = 2 4 V
VIN = 3 0 V
R1245x00xA/R1245x00xB
V
OUT
=15V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 2 4 V
VIN = 3 0 V
R1245x00xA/R1245x00xB
V
OUT
=24V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN =3 0 V
R1245x
27
22) Output Current vs. Efficiency (Version C/D)
R1245x00xC/R1245x00xD
V
OUT
=0.8V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 4.5V
VIN = 6.0V
VIN = 12V
R1245x00xC/R1245x00xD
V
OUT
=3.3V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 4.5V
VIN = 1 2V
VIN = 2 4V
R1245x00xC/R1245x00xD
V
OUT
=5.0V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 1 2 V
VIN = 2 4 V
VIN = 3 0 V
R1245x00xC/R1245x00xD
V
OUT
=12V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 1 8 V
VIN = 2 4 V
VIN = 3 0 V
R1245x00xC/R1245x00xD
V
OUT
=15V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 2 4 V
VIN = 3 0 V
R1245x00xC/R1245x00xD
V
OUT
=24V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 3 0 V
R1245x
28
23) Output current vs. Efficiency (Version E/F)
R1245x00xE/R1245x00xF
V
OUT
=0.8V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 4.5V
VIN = 6.0V
R1245x00xE/R1245x00xF
V
OUT
=3.3V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 4.5V
VIN = 12 V
VIN = 24 V
R1245x00xE/R1245x00xF
V
OUT
=5.0V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 12V
VIN = 24V
VIN = 30V
R1245x00xE/R1245x00xF
V
OUT
=12V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 24V
VIN = 30V
R1245x00xE/R1245x00xF
V
OUT
=15V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 2 4 V
VIN = 3 0 V
R1245x00xE/R1245x00xF
V
OUT
=24V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 30V
R1245x
29
24) Output current vs. Efficiency (Version G/H)
R1245x00xG/R1245x00xH
V
OUT
=1.5V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 4.5V
R1245x00xG/R1245x00xH
V
OUT
=3.3V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 6 V
VIN = 1 0 V
VIN = 1 2 V
R1245x00xG/R1245x00xH
V
OUT
=5.0V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 8.0V
VIN = 12V
R1245x00xG/R1245x00xH
V
OUT
=12V
　　　　　　　　　　　　　　　　(Ta=25℃)
0
20
40
60
80
100
0.01 0.1 1 10 100 1000 10000
I
OUT
(mA)
Efficiency (%)
VIN = 24V
VIN = 30V
R1245x
30
25) Output current vs Output voltage (Version A/B)
R1245x00xA/R1245x00xB
V
OUT
=0.8V
　　　　　　　　　　　　　　　 　　　(Ta=25℃)
0.792
0.794
0.796
0.798
0.800
0.802
0.804
0.806
0.808
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage(V)
VIN =4 .5 V VIN =6 .0 V
VIN =1 8 V
R1245x00xA/R1245x00xB
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.25
3.26
3.27
3.28
3.29
3.30
3.31
3.32
3.33
0 200 400 600 800 1000 1200
IOUT
(mA)
Output Voltage (V)
VIN = 4.5 V VIN = 12 V
VIN = 24 V
R1245x00xA/R1245x00xB
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 12V VIN = 2 4V
VIN = 30V
R1245x00xA/R1245x00xB
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.90
12.00
12.10
12.20
12.30
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 18V VIN = 24V
VIN = 30V
R1245x00xA/R1245x00xB
V
OUT
=15V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
14.80
15.00
15.20
15.40
15.60
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 2 4V
VIN = 3 0V
R1245x00xA/R1245x00xB
V
OUT
=24V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
23.90
24.10
24.30
24.50
24.70
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 30V
R1245x
31
26) Output current vs. Output voltage (Version C/D)
R1245x00xC/R1245x00xD
V
OUT
=0.8V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0.792
0.794
0.796
0.798
0.800
0.802
0.804
0.806
0.808
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 4.5V VIN = 6.0V
VIN = 12V
R1245x00xC/R1245x00xD
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.25
3.26
3.27
3.28
3.29
3.30
3.31
3.32
3.33
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 4.5V VIN = 12V
VIN = 24V
R1245x00xC/R1245x00xD
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 1 2 V VIN = 2 4 V
VIN = 3 0 V
R1245x00xC/R1245x00xD
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.80
11.90
12.00
12.10
12.20
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 18 V VIN = 24 V
VIN = 30 V
R1245x00xC/R1245x00xD
V
OUT
=15V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
14.60
14.80
15.00
15.20
15.40
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 24V
VIN = 30V
R1245x00xC/R1245x00xD
V
OUT
=24V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
23.60
23.80
24.00
24.20
24.40
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 30V
R1245x
32
27) Output current vs. Output voltage (Version E/F)
R1245x00xE/R1245x00xF
V
OUT
=0.8V
　　　　　　　　　　　　　　　 　　　(Ta=25℃)
0.792
0.794
0.796
0.798
0.800
0.802
0.804
0.806
0.808
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage(V)
VIN = 4.5V
R1245x00xE/R1245x00xF
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.25
3.26
3.27
3.28
3.29
3.30
3.31
3.32
3.33
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 4.5V VIN = 12V
VIN = 24V
R1245x00xE/R1245x00xF
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 12 V VIN = 24V
VIN = 30 V
R1245x00xE/R1245x00xF
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.80
11.90
12.00
12.10
12.20
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 2 4 V VIN = 3 0 V
R1245x00xE/R1245x00xF
V
OUT
=15V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
14.80
15.00
15.20
15.40
15.60
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 2 4V
VIN = 3 0V
R1245x00xE/R1245x00xF
V
OUT
=24V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
23.60
23.80
24.00
24.20
24.40
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 3 0 V
R1245x
33
28) Output current vs. Output voltage (Version G/H)
R1245x00xG/R1245x00xH
V
OUT
=1.5V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
1.485
1.490
1.495
1.500
1.505
1.510
1.515
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 4.5V
R1245x00xG/R1245x00xH
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.25
3.26
3.27
3.28
3.29
3.30
3.31
3.32
3.33
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 6 V VIN = 1 0V
VIN = 1 2 V
R1245x00xG/R1245x00xH
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 8.0V VIN = 12V
R1245x00xG/R1245x00xH
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.80
11.90
12.00
12.10
12.20
0 200 400 600 800 1000 1200
I
OUT
(mA)
Output Voltage (V)
VIN = 2 4 V VIN = 30V
R1245x
34
29) Input voltage vs. Output voltage (Version A/B)
R1245x00xA/R1245x00xB
V
OUT
=0.8V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0.792
0.794
0.796
0.798
0.800
0.802
0.804
0.806
0.808
4 6 8 1012141618
V
IN
(V)
Output Voltage (V)
IOUT=1mA IOUT=100mA
IOUT=500mA IOUT=1200m
A
R1245x00xA/R1245x00xB
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.27
3.28
3.29
3.30
3.31
3.32
3.33
4 8 12 16 20 24 28
V
IN
(V)
Output Voltage (V)
IOUT=1mA IOUT=10mA
IOUT=100mA IOUT=1200m
A
R1245x00xA/R1245x00xB
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
4 6 8 1012141618202224262830
V
IN
(V)
Output Voltage (V)
IOUT=1mA IOUT=100mA
IOUT=500mA IOUT=1200m
A
R1245x00xA/R1245x00xB
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.95
12.00
12.05
12.10
12.15
12.20
12 14 16 18 20 22 24 26 28 30
V
IN
(V)
Output Voltage (V)
IOUT=100mA IOUT=500mA
IOUT=1200mA
R1245x00xA/R1245x00xB
V
OUT
=15V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
14.90
15.00
15.10
15.20
15.30
14 16 18 20 22 24 26 28 30
V
IN
(V)
Output Voltage (V)
IOUT=100mA IOUT=500mA
IOUT=1200mA
R1245x00xA/R1245x00xB
V
OUT
=24V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
23.80
23.90
24.00
24.10
24.20
24 25 26 27 28 29 30
V
IN
(V)
Output Voltage (V)
IOUT=100mA IOUT=500mA
IOUT=1200mA
R1245x
35
30) Input voltage vs. Output voltage (Version C/D)
R1245x00xC/R1245x00xD
V
OUT
=0.8V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0.79
0.79
0.80
0.80
0.80
0.80
0.80
0.81
0.81
4.5 6 7.5 9 10.5 12 13.5
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xC/R1245x00xD
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.27
3.28
3.29
3.30
3.31
3.32
3.33
4 8 12 16 20 24 28
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xC/R1245x00xD
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
4 6 8 1012141618202224262830
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xC/R1245x00xD
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.80
11.90
12.00
12.10
12.20
12 14 16 18 20 22 24 26 28 30
V
IN
(V)
Output Voltage (V)
100mA 500mA
1200mA
R1245x00xC/R1245x00xD
V
OUT
=15V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
14.60
14.70
14.80
14.90
15.00
15.10
15.20
15.30
15.40
14 16 18 20 22 24 26 28 30
V
IN
(V)
Output Voltage (V)
100mA 500mA
1200mA
R1245x00xC/R1245x00xD
V
OUT
=24V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
23.80
23.90
24.00
24.10
24.20
24 25 26 27 28 29 30
V
IN
(V)
Output Voltage (V)
100mA 500mA
1200mA
R1245x
36
31) Input voltage vs. Output voltage (Version E/F)
R1245x00xE/R1245x00xF
V
OUT
=0.8V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
0.792
0.794
0.796
0.798
0.800
0.802
0.804
0.806
0.808
4.5 5 5.5 6 6.5
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xE/R1245x00xF
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.27
3.28
3.29
3.30
3.31
3.32
3.33
4 8 12 16 20 24 28
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xE/R1245x00xF
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
5 1015202530
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xE/R1245x00xF
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.80
11.90
12.00
12.10
12.20
12 14 16 18 20 22 24 26 28 30
V
IN
(V)
Output Voltage (V)
100mA 500mA
1200mA
R1245x00xE/R1245x00xF
V
OUT
=15V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
14.60
14.80
15.00
15.20
15.40
16 18 20 22 24 26 28 30
V
IN
(V)
Output Voltage (V)
100mA 500mA
1200mA
R1245x00xE/R1245x00xF
V
OUT
=24V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
23.60
23.80
24.00
24.20
24.40
26 27 28 29 30
V
IN
(V)
Output Voltage (V)
100mA 500mA
1200mA
R1245x
37
32) Input voltage vs. Output voltage (Version G/H)
R1245x00xG/R1245x00xH
V
OUT
=1.5V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
1.485
1.490
1.495
1.500
1.505
1.510
1.515
4.5 4.7 4.9 5.1 5.3 5.5
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xG/R1245x00xH
V
OUT
=3.3V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
3.27
3.28
3.29
3.30
3.31
3.32
3.33
4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xG/R1245x00xH
V
OUT
=5.0V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
4.95
4.97
4.99
5.01
5.03
5.05
6 8 10 12 14 16 18
V
IN
(V)
Output Voltage (V)
1mA 100mA
500mA 1200mA
R1245x00xG/R1245x00xH
V
OUT
=12V
　　　　　　　　　　　　　　　　　　(Ta=25℃)
11.80
11.90
12.00
12.10
12.20
14 16 18 20 22 24 26 28 30
V
IN
(V)
Output Voltage (V)
100mA 500mA
1200mA
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.