Ricoh RH5RH12B, RH5RH1A, RH5RH13B User Manual

ELECTRONIC DEVICES DIVISION

PWM STEP-UP DC/DC CONVERTER

RH5RH××1A/××2B/××3B SERIES

APPLICATION MANUAL

NO.EA-023-9803

NOTICE

1. The products and the product specifications described in this application manual 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. This application manual 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 application manual 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, computer 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 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, fire-containment 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 application manual.

8. Please contact Ricoh sales representatives should you have any questions or comments concerning the prod­ucts or the technical information.

June 1995

OUTLINE

......................................................................................................

1

FEATURES

....................................................................................................

1

APPLICATIONS

.............................................................................................

1

BLOCK DIAGRAM

.........................................................................................

2

SELECTION GUIDE

.......................................................................................

2

PIN CONFIGURATION

...................................................................................

3

PIN DESCRIPTION

........................................................................................

3

ABSOLUTE MAXIMUM RATINGS

...................................................................

4

ELECTRICAL CHARACTERITICS

...................................................................

5

OPERATION OF STEP-UP DC/DC CONVERTER

...........................................

10

TYPICAL CHARACTERISTICS

......................................................................

13

1) Output Voltage vs. Output Current

.......................................................................

13

2) Efficiency vs. Output Current

.............................................................................

14

3) Supply Current (No Load) vs. Input Voltage

..............................................................

15

4) Output Current vs. Ripple Voltage

........................................................................

15

5) Start-up/Hold-on Voltage vs. Output Current (Topt=25˚C)

...............................................

16

6) Output Voltage vs. Temperature

.........................................................................

17

7) Start-up Voltage vs. Temperature

........................................................................

18

8) Hold-on Voltage vs. Temperature

........................................................................

18

9) Supply Current 1 vs. Temperature

.......................................................................

18

10) Supply Current 2 vs. Temperature

.......................................................................

18

11) Lx Switching Current vs. Temperature

...................................................................

18

12) Lx Leakage Current vs. Temperature

....................................................................

18

13) Oscillator Frequency vs. Temperature

....................................................................

19

14) Oscillator Duty Cycle vs. Temperature

...................................................................

19

15) Vlx Voltage Limit vs. Temperature

........................................................................

20

16) EXT “H” Output Current vs. Temperature

................................................................

20

17) EXT “L” Output Current vs. Temperature

.................................................................

20

18) Load Transient Response

................................................................................

21

19) Distribution of Output Voltage

............................................................................

22

20) Distribution of Oscillator Frequency

......................................................................

22

RH5RH SERIES

APPLICATION MANUAL

CONTENTS

TYPICAL APPLICATIONS

............................................................................

23

• RH5RH××1A

.................................................................................................

23

• RH5RH××2B

..................................................................................................

23

• RH5RH××3B

..................................................................................................

24

• CE pin Drive Circuit

............................................................................................

22

APPLICATION CIRCUITS

.............................................................................

26

• 12V Step-up Circuit

............................................................................................

26

• Step-down Circuit

..............................................................................................

26

• Step-up/Step-down Circuit with Flyback

.......................................................................

27

PACKAGE DIMENSIONS

..............................................................................

28

TAPING SPECIFICATIONS

...........................................................................

28

PWM STEP-UP DC/DC CONVERTER

1

RH5RH

××

1A/

××

2B/

××

3B SERIES

OUTLINE

The RH5RH××1A/××2B/××3B Series are PWM Step-up DC/DC converter ICs by CMOS process.

The RH5RH

××1A IC consists of an oscillator, a PWM control circuit, a driver transistor (Lx switch), a refer-

ence voltage unit, an error amplifier, a phase compensation circuit, resistors for voltage detection, a soft-start cir­cuit, and an Lx switch protection circuit. A low ripple, high efficiency step-up DC/DC converter can be constructed
of this RH5RH

××1A IC with only three external components, that is, an inductor, a diode and a capacitor.

These RH5RH

××1A/××2B/××3B ICs can achieve ultra-low supply current (no load) –TYP. 15µA –by a new-

ly developed PWM control circuit, equivalent to the low supply current of a VFM (chopper) Step-up DC/DC con­verter.

Furthermore, these ICs can hold down the supply current to TYP. 2µA by stopping the operation of the oscil-

lator when the input voltage > (the output voltage set value + the dropout voltage by the diode and the inductor).

These RH5RH

××1A/××2B/××3B Series ICs are recommendable to the user who desires a low ripple PWM

DC/DC converter, but cannot adopt a conventional PWM DC/DC converter because of its too large supply current.

The RH5RH

××2B/××3B Series ICs use the same chip as that employed in the RH5RH××1A IC and are pro-

vided with a drive pin (EXT) for an external transistor. Because of the use of the drive pin (EXT), an external
transistor with a low saturation voltage can be used so that a large current can be caused to flow through the
inductor and accordingly a large output current can be obtained. Therefore, these RH5RH

××2B/××3B Series ICs

are recommendable to the user who need a current as large as several tens mA to several hundreds mA.

The RH5RH

××3B IC also includes an internal chip enable circuit so that it is possible to set the standby sup-

ply current at MAX. 0.5µA.

These RH5RH

××1A/××2B/××3B ICs are suitable for use with battery-powered instruments with low noise

and low supply current.

•

Small Number of External Components

..........

Only an inductor, a diode and a capacitor (RH5RH××1A)

•

Low Supply Current

...........................................

TYP. 15µA (RH5RH301A)

•

Low Ripple and Low Noise

•

Low Start-up Voltage (when the output current is 1mA)

..................

MAX. 0.9V

•

High Output Voltage Accuracy

..........................

±2.5%

•

High Efficiency

...................................................

TYP. 85%

•

Low Temperature-Drift Coefficient of Output Voltage

......................

TYP. ±50 ppm/˚C

•

Soft-Start

.............................................................

MIN. 500µs

•

Small Packages

...................................................

SOT-89 (RH5RH××1A, RH5RH××2B),
SOT-89-5 (RH5RH

××

3B)

FEATURES

APPLICATIONS

•

Power source for battery-powered equipment.

•

Power source for cameras, camcorders, VCRs, PDAs, electronic data banks,and hand-held communication
equipment.

•

Power source for instruments which require low noise and low supply current, such as hand-held audio equip-

ment.

•

Power source for appliances which require higher cell voltage than that of batteries used in the appliances.

2

RH5RH

×××× – ×× ← Part Number

↑ ↑ ↑

a b c

SELECTION GUIDE

In RH5RH Series, the output voltage, the driver, and the taping type for the ICs can be selected at the user's

request. The selection can be made by designating the part number as shown below :

For example, the product with Output Voltage 5.0V, the External Driver (the Oscillator Frequency 100kHz)

and Taping Type T1, is designated by Part Number RH5RH502B-T1.

Code Description

Setting Output Voltage (VOUT):

a

Stepwise setting with a step of 0.1V in the range of 2.7V to 7.5V is possible.

Designation of Driver:

1A: Internal Lx Tr. Driver (Oscillator Frequency 50kHz)

b 2B: External Tr. Driver (Oscillator Frequency 100kHz)

3B: Internal Tr./External Tr. (selectively available) (Oscillator Frequency 100kHz, with chip
enable function)

Designation of Taping Type :

c

Ex. SOT-89 :T1, T2

SOT-89-5 :T1, T2
(refer to Taping Specifications)
“T1” is prescribed as a standard.

RH5RH

BLOCK DIAGRAM

Lx

Vss

EXT

LxSW

CE

Error Amp.

OUT

V

LX limiter

Buffer

PWM control

OSC

Chip Enable

Slow start

Phase Comp.

Vref

+

–

Error Amp. (Error Amplifier) has a DC gain of 80dB, and Phase Comp. (Phase Compensation Circuit)
provides the frequency characteristics including the 1st pole (fp=0.25Hz) and the zero point (fz=2.5kHz).
Furthermore, another zero point (fz=1.0kHz) is also obtained by the resistors and a capacitor connected to
the OUT pin.

(Note) Lx Pin

............

only for RH5RH××1A and RH5RH××3B

EXT Pin

.........

only for RH5RH

××2B and RH5RH××3B

CE Pin

...........

only for RH5RH

××3B

}

}

}

3

•

SOT-89-5

PIN CONFIGURATION

•

SOT-89

PIN DESCRIPTION

Pin No.

××1B ××2B ××3B

1 1 5

2 2 2

3 — 4

— 3 3

— — 1

RH5RH

Symbol Description

VSS Ground Pin

OUT Step-up Output Pin, Power Supply (for device itself)

Lx Switching Pin (Nch Open Drain)

EXT External Tr. Drive Pin (CMOS Output)

CE Chip Enable Pin (Active Low)

5

4

(mark side)

1 2

(mark side)

3

1 2

3

4

RH5RH

ABSOLUTE MAXIMUM RATINGS

Symbol Item

VOUT Output Pin Voltage

VLX Lx Pin Voltage

VEXT EXT Pin Voltage

VCE CE Pin Voltage

ILX Lx Pin Output Current

IEXT EXT Pin Current

PD Power Dissipation

Topt Operating Temperature Range

Tstg Storage Temperature Range

Tsolder Lead Temperature(Soldering)

Rating Unit Note

+12 V

+12 V Note1

– 0.3 to VOUT+0.3 V Note2

–0.3 to VOUT+0.3 V Note3

250 mA Note1

±50 mA Note2

500 mW

–30 to +80 ˚C

–55 to +125 ˚C

260˚C,10s

(Note 1) Applicable to RH5RH××1A and RH5RH××3B. (Note 2) Applicable to RH5RH××2B and RH5RH××3B.
(Note 3) Applicable to RH5RH

××3B.

Vss=0V

Absolute Maximum ratings are threshold limit values that must not be exceeded even for an instant under any
conditions. Moreover, such values for any two items must not be reached simultaneously. Operation above
these absolute maximum ratings may cause degradation or permanent damage to the device. These are stress
ratings only and do not necessarily imply functional operation below these limits.

ABSOLUTE MAXIMUM RATINGS

5

ELECTRICAL CHARACTERISTICS

• RH5RH301A

Symbol Item

VOUT Output Voltage

VIN Input Voltage

Vstart Start-up Voltage

Vhold Hold-on Voltage

I

DD1 Supply Current 1

IDD2 Supply Current 2

ILX Lx Switching Current

ILXleak Lx Leakage Current

fosc Oscillator Frequency

Maxdty

Oscillator Maximum Duty
Cycle

η

Efficiency

tstart Soft-Start Time

VLXlim VLX Voltage Limit

Conditions MIN. TYP. MAX. Unit Note

2.925 3.000 3.075 V

8 V

IOUT=1mA,V

IN : 0→2V 0.8 0.9 V

IOUT=1mA,VIN : 2→0V 0.7 V

To be measured at OUT Pin

(excluding Switching Current)

15 25 µA

To be measured at OUT Pin

(excluding Switching Current) 2 5 µA

VIN=3.5V

VLX=0.4V 60 mA

VLX=6V,VIN=3.5V 0.5 µA

40 50 60 kHz

on (VLX “L” ) side 70 80 90 %

70 85 %

Time required for the rising

0.5 2.0 ms Note1

of VOUT up to 3V.

Lx Switch ON 0.65 0.8 1.0 V Note2

VOUT=3.0V

RH5RH

Unless otherwise provided, VIN=1.8V, VSS=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 1).

(Note 1) Soft-Start Circuit is operated in the following sequence :

(1) V

IN is applied.

(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of V

IN.

(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase

Compensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error
Amp.

(Note 2) I

LX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,

Lx Switch is turned OFF by an Lx Switch Protection Circuit.

6

RH5RH

• RH5RH501A

VOUT=5.0V

Unless otherwise provided, VIN=3V, Vss=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 1).

(Note 1) Soft-Start Circuit is operated in the following sequence :

(1) V

IN is applied.

(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of V

IN.

(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase

Compensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error
Amp.

(Note 2) I

LX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,

Lx Switch is turned OFF by an Lx Switch Protection Circuit.

Symbol Item

VOUT Output Voltage

VIN Input Voltage

Vstart Start-up Voltage

Vhold Hold-on Voltage

I

DD

1 Supply Current 1

IDD2 Supply Current 2

ILX Lx Switching Current

ILXleak Lx Leakage Current

fosc Oscillator Frequency

Maxdty

Oscillator Maximum Duty
Cycle

η

Efficiency

tstart Soft-Start Time

VLXlim VLX Voltage Limit

Conditions MIN. TYP. MAX. Unit Note

4.875 5.000 5.125 V

8 V

Iout=1mA,Vin:0→2V 0.8 0.9 V
Iout=1mA,Vin:2→0V 0.7 V

To be measured at OUT Pin

(excluding Switching Current)

30 45 µA

To be measured at OUT Pin

(excluding Switching Current) 2 5 µA

VIN=5.5V

VLX=0.4V 80 mA

VLX=6V,VIN=5.5V 0.5 µA

40 50 60 kHz

on (VLX “L” ) side 70 80 90 %

70 85 %

Time required for the rising

0.5

2.0

ms Note1

of VOUT up to 5V.

Lx Switch ON 0.65 0.8 1.0 V Note2

7

RH5RH

• RH5RH302B

Symbol Item

VOUT Output Voltage

VIN Input Voltage

Vstart Oscillator Start-up Voltage

IDD

1

Supply Current 1

IDD

2

Supply Current 2

IEXTH EXT “H” Output Current

IEXTL EXT “L” Output Current

fosc Oscillator Frequency

Maxdty

Oscillator Maximum Duty
Cycle

tstart Soft-Start Time

Conditions MIN. TYP. MAX. Unit Note

2.925 3.000 3.075 V

8 V

EXT no load,VOUT :0→2V 0.7 0.8 V

EXT no load,VOUT=2.88V 30 50 µA

EXT no load,VOUT=3.5V 2 5 µA

VEXT=V

OUT–0.4V –1.5 mA

VEXT=0.4V 1.5 mA

80 100 120 kHz

VEXT “H” side

70 80 90

%

Time required for the rising

0.5

2.0

ms Note1

of V

OUT up to 3V

VOUT=3.0V

Unless otherwise provided, VIN=1.8V, Vss=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 2).

• RH5RH502B

VOUT=5.0V

Unless otherwise provided, VIN=3V, Vss=0V, IOUT=10mA, Topt=25˚C and use External Circuit of Typical
Application (FIG. 2).

(Note 1) refer to page 5 (Note 1)

Symbol Item

VOUT Output Voltage

VIN Input Voltage

Vstart Oscillator Start-up Voltage

IDD

1

Supply Current 1

IDD

2

Supply Current 2

IEXTH EXT “H” Output Current

IEXTL EXT “L” Output Current

fosc Oscillator Frequency

Maxdty

Oscillator Maximum Duty
Cycle

t

start Soft-Start Time

Conditions MIN. TYP. MAX. Unit Note

4.875 5.000 5.125 V

8 V

EXT no load,VOUT :0→2V 0.7 0.8 V

EXT no load,VOUT=4.8V 60 90 µA

EXT no load,VOUT=5.5V 2 5 µA

VEXT=VOUT–0.4V –2 mA

VEXT=0.4V 2 mA

80 100 120 kHz

VEXT “H” side

70 80 90 %

Time required for the rising

0.5 2.0 ms Note1

of V

OUT up to 5V

8

• RH5RH303B

Symbol Item

V

OUT Output Voltage

VIN Input Voltage

Vstart Start-up Voltage

Vhold Hold-on Voltage

η

Efficiency

IDD1 Supply Current 1

IDD2 Supply Current 2

ILX Lx Switching Current

ILXleak Lx Leakage Current

IEXTH EXT “H” Output Current

IEXTL EXT “L” Output Current

VCEH1 CE “H” Level 1

VCEL1 CE “L” Level 1

VCEH2 CE “H” Level 2

VCEL2 CE “L” Level 2

ICEH CE “H” Input Current

ICEL CE “L” Input Current

fosc Oscillator Frequency

Maxdty

Oscillator Maximum Duty
Cycle

tstart Soft-Start Time

VLXlim VLX Voltage Limit

Conditions MIN. TYP. MAX. Unit Note

2.925 3.000 3.075 V

8 V

IOUT=1mA,V

IN : 0

→

2V 0.8 0.9 V

IOUT=1mA,VIN : 2→0V 0.7 V

70 85 %

To be measured at OUT pin 30 50 µA

To be measured at OUT pin

2 5 µA

VIN=3.5V

VLX=0.4V 60 mA

VLX=6V,VIN=3.5V 0.5 µA

VEXT=VOUT–0.4V –1.5 mA

VEXT=0.4V 1.5 mA
VOUT≥1.5V

VOUT–0.4

V

VOUT≥1.5V 0.4 V

0.8V≤VOUT<1.5V

VOUT–0.1

V

0.8V≤VOUT<1.5V 0.1 V

CE=3V 0.5 µA

CE=0V –0.5 µA

80 100 120 kHz

on (V

LX “L” )side 70 80 90 %

Time required for the rising

0.5 2.0 ms Note1

of VOUT up to 3V.

Lx Switch ON 0.65 0.8 1.0 V Note2

VOUT=3.0V

Unless otherwise provided, VIN=1.8V, VSS=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 3).

(Note 1) Soft-Start Circuit is operated in the following sequence :

(1) V

IN is applied.

(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of V

IN.

(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase Com

pensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error Amp.

(Note 2) I

LX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,

Lx Switch is turned OFF by an Lx Switch Protection Circuit.

RH5RH

9

• RH5RH503B

VOUT=5.0V

RH5RH

Unless otherwise provided, VIN=3V, VSS=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 3).

(Note 1) Soft-Start Circuit is operated in the following sequence :

(1) V

IN is applied.

(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of V

IN.

(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase Com
pensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error Amp.

(Note 2) I

LX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,

Lx Switch is turned OFF by an Lx Switch Protection Circuit.

Symbol Item

VOUT Output Voltage

VIN Input Voltage

Vstart Start-up Voltage

Vhold Hold-on Voltage

η

Efficiency

IDD1 Supply Current 1

IDD2 Supply Current 2

ILX Lx Switching Current

ILXleak Lx Leakage Current

IEXTH EXT “H” Output Current

IEXTL EXT “L” Output Current

VCEH1 CE “H” Level 1

VCEL1 CE “L” Level 1

VCEH2 CE “H” Level 2

VCEL2 CE “L” Level 2

ICEH CE “H” Input Current

ICEL CE “L” Input Current

fosc Oscillator Frequency

Maxdty

Oscillator Maximum Duty
Cycle

tstart Soft-Start Time

VLXlim VLX Voltage Limit

Conditions MIN. TYP. MAX. Unit Note

4.875 5.000 5.125 V

8 V

IOUT=1mA,VIN : 0→2V 0.8 0.9 V

IOUT=1mA,VIN : 2→0V 0.7 V

70 85 %

To be measured at OUT pin 60 90 µA

To be measured at OUT pin

2 5 µA

VIN=5.5V

V

LX=0.4V 80 mA

VLX=6V,VIN=5.5V 0.5 µA

VEXT=VOUT–0.4V –2.0 mA

VEXT=0.4V 2.0 mA

VOUT≥1.5V

VOUT–0.4

V

VOUT≥1.5V 0.4 V

0.8V≤VOUT<1.5V

VOUT–0.1

V

0.8V≤VOUT<1.5V 0.1 V

CE=5V 0.5 µA

CE=0V –0.5 µA

80 100 120 kHz

on (V

LX “L” )side 70 80 90 %

Time required for the rising

0.5 2.0 ms Note1

of VOUT up to 5V.

Lx Switch ON 0.65 0.8 1.0 V Note2

10

OPERATION OF STEP-UP DC/DC CONVERTER

Step-up DC/DC Converter charges energy in the inductor when Lx Transistor (LxTr) is on, and discharges the
energy with the addition of the energy from Input Power Source thereto, so that a higher output voltage than the
input voltage is obtained.

The operation will be explained with reference to the following diagrams :

< Current through L >< Basic Circuits >

RH5RH

i2

L

SD

I

OUT

VOUT

CLLx Tr

i1

V

IN

IL

ILmin

ILmax

topen

t

ton

toff

T=1/fosc

Step 1 : LxTr is turned ON and current IL (= i1 ) flows, so that energy is charged in L. At this moment, IL(=i1 ) is

increased from ILmin (= 0) to reach ILmax in proportion to the on-time period (ton) of LxTr.

Step 2 : When LxTr is turned OFF, Schottky diode (SD) is turned ON in order that L maintains IL at ILmax, so

that current IL (= i2) is released.

Step 3 : IL (=i2) is gradually decreased, and in the case of discontinuous mode, IL reaches ILmin (=0) after a time

period of topen, so that SD is turned OFF. However, in the case of a continuous mode which will be mentioned
later,the time period (toff) runs out before IL reaches ILmin (=0), so that LxTr is turned ON in the next
cycle, and SD is turned OFF. In this case, ILmin does not reach zero, and IL (=i1) increases from ILmin (> 0).

In the case of PWM control system, the output voltage is maintained constant by controlling the on-time peri­od (ton), with the oscillator frequency (fosc) being maintained constant.

•

Discontinuous Conduction Mode and Continuous Conduction Mode

In the above two diagrams, the maximum value (ILmax) and the minimum value (ILmin) of the current which
flows through the inductor are the same as those when LxTr is ON and also when LxTr is OFF.

The difference between ILmax and ILmin, which is represented by ∆I, is :

∆I=ILmax–ILmin=V

IN · ton/L=(VOUT–VIN) · topen/L

.........................................

Equation 1

wherein T=1/fosc=ton+toff

duty (%)=ton/T · 100=ton · fosc · 100
topen≤toff

In Equation 1, V

IN · ton/L and (VOUT–VIN) · topen/L are respectively show the change in the current at ON, and the

change in the current at OFF.

11

RH5RH

When the output current (IOUT) is relatively small, topen<toff as illustrated in the above diagram. In this case,
the energy charged in the inductor during the time period of ton is discharged in its entirely during the time peri­od of toff, so that ILmin becomes zero (ILmin=0). When I

OUT is gradually increased, topen eventually becomes

equal to toff (topen=toff), and when I

OUT is further increased. ILmin becomes larger than zero (ILmin >0). The

former mode is referred to as the discontinuous mode and the latter mode is referred to as the continuous mode.

In the continuous mode, when Equation 1 is solved for ton and the solution is tonc,

tonc =T · (1–V

IN/VOUT)

................................................................................................

Equation 2

When ton<tonc, the mode is the discontinuous mode, and when ton=tonc, the mode is the continuous mode.

•

Output Current in Discontinuous Mode

In the discontinuous mode, when LxTr is on, the energy P

ON charged in the inductor is provided by Equation 3

as follows :

P

ON=∫

0

ton

VIN · IL (t) dt =∫

0

ton

(VIN2· t/L) dt

=V

IN

2

· ton2/(2 · L)

.................................................................................................

Equation 3

In the case of the step-up DC/DC converter, the energy is also supplied from the input power source at the time

of OFF.

Thus, P

OFF=∫

0

topen

VIN · IL (t) dt =∫

0

topen

((VOUT–VIN) · t/L)dt

=V

IN · (VOUT–VIN) · topen

2

/(2 · L)

Here, topen=V

IN · ton/(VOUT–VIN) from Equation 1, and when this is substituted into the above equation.

=V

IN

3

· ton2/(2 · L · (V

OUT–VIN)

..........................................................................

Equation 4

Input power is (P

ON+POFF)/T. When this is converted in its entirely to the output.

P

IN=(PON+POFF)/T=VOUT · IOUT=POUT

.....................................................................

Equation 5

Equation 6 can be obtained as follows by solving Equation 5 for I

OUT by substituting Equations 3 and 4 into

Equation 5 :

I

OUT=VIN

2

· ton2/(2 · L · T · (VOUT–VIN))

.....................................................................

Equation 6

The peak current which flows through L · LxTr · SD is

ILmax=V

IN · ton/L

......................................................................................................

Equation 7

12

RH5RH

Therefore it is necessary that the setting of the input/output conditions and the selection of peripheral compo-

nents should be made with ILmax taken into consideration.

•

Output Current in Continuous Conduction Mode

When the operation enters into the continuous conduction mode by increasing the I

OUT, ILmin becomes equal

to Iconst (> 0), and this current always flows through the inductor. Therefore, V

IN · Iconst is added to PIN in

Equation 5.

Thus, P

IN=VIN · Iconst+(PON+POFF)/T=VOUT · IOUT=POUT

When the above Equation is solved for IOUT,

I

OUT=VIN

2

· tonc2/(2 · L · T · (VOUT–VIN))+VIN · Iconst/VOUT

............................................

Equation 8

The peak current which flows through L · LxTr · SD is

ILmax=V

IN · ton/L+Iconst

...................................................................................................

Equation 9

From Equations 6 and 9, the larger the value of L, the smaller the load current at which the operation enters
into the continuous mode, and the smaller the difference between ILmax and ILmin, and the smaller the value of
ILmax.

Therefore, when the load current is the same, the larger the value of L, the easier the selection of peripheral
components with a small allowable current becomes, and the smaller the ripple of the peripheral components can
be made. In this case, however, it must be noted from Equation 6 that I

OUT becomes small when the allowable cur-

rent of the inductor is small or when V

IN is so small that the operation cannot enter into the continuous mode.

The above explanation is directed to the calculation in an ideal case where there is no energy loss caused by the
resistance in the external components and LxSW. In an actual case, the maximum output current will be 50
to 80% of the above calculated maximum output current. In particular, care must be taken because V

IN is

decreased in an amount corresponding to the voltage drop caused by LxSW when IL is large or V

IN is low.

Furthermore, it is required that with respect to V

OUT, Vf of the diode (about 0.3V in the case of a Schottky type

diode) be taken into consideration.

HINTS

13

RH5RH

TYPICAL CHARACTERISTICS

1) Output Voltage vs. Output Current
RH5RH301A

L=120µH

V

IN=1.0V

1.5V

2.0V

0 20

40

60

3.1

3.0

2.9

2.8

2.7

2.6

2.5
Output Current I

OUT(mA)

Output Voltage VOUT(V)

L=270µH

1.5V

3.1

3.0

2.9

2.8

2.7

2.6

2.5
Output Current I

OUT(mA)

Output Voltage VOUT(V)

0

10 20 30

40

50 60

VIN=1.0V

2.0V

RH5RH501A

L=120µH

V

IN=

1.0V

Output Current I

OUT(mA)

Output Voltage VOUT(V)

3.0V

4.0V

0 50 100 150

4.0

4.2

4.4

4.6

4.8

5.0

5.2

2.0V

RH5RH302B

L=28µH

Output Current I

OUT(mA)

Output Voltage VOUT(V)

2.5V2.0V

1.5V

0 200 400 600

2.8

2.9

3.0

3.1

VIN=0.9V

RH5RH301A

RH5RH501A

L=270µH

V

IN=1.0V

Output Current I

OUT(mA)

Output Voltage VOUT(V)

2.0V

3.0V

4.0V

0

50 100 150

4.0

4.2

4.4

4.6

4.8

5.0

5.2

RH5RH502B

L=28µH

V

IN=1.5V

Output Current I

OUT(mA)

Output Voltage VOUT(V)

2.0V

3.0V

4.0V

0 500 1000

4.4

4.6

4.8

5.0

5.2

14

RH5RH

2) Efficiency vs. Output Current
RH5RH301A

L=120µH

V

IN=1.0V

1.5V

2.0V

0 10

20

30

90

80

70

60

50

40

Output Current I

OUT(mA)

Efficiency η (%)

L=270µH

1.5V

2.0V

0 10

20

30 40

90

100

80
70
60
50
40

Output Current I

OUT(mA)

Efficiency η (%)

VIN=1.0V

RH5RH501A

L=120µH

V

IN=1.0V

3.0V

4.0V

0 50

100

150

90

100

80
70
60

50
40

Output Current I

OUT(mA)

Efficiency η (%)

2.0V

RH5RH302B

L=28µH

V

IN=0.9V

2.0V

2.5V

0

200

400

600

80

100

60

40

20

0

Output Current I

OUT(mA)

Efficiency η (%)

1.5V

RH5RH301A

RH5RH501A

L=270µH

V

IN=

1.0V

3.0V

4.0V

2.0V

0 50

100

150

90

100

80
70

60
50
40

Output Current I

OUT(mA)

Efficiency η (%)

RH5RH502B

L=28µH

V

IN=1.5V

3.0V

4.0V

2.0V

0

500

1000

80

100

60

40

20

0

Output Current I

OUT(mA)

Efficiency η (%)

15

RH5RH

3) Supply Curret (No Load) vs. Input Voltage

4) Output Current vs.Ripple Voltage

RH5RH301A

L=120µH

1.0 1.2

1.4

1.6 1.8 2.0

50

60

70

40
30
20
10
0

Input Voltage V

IN(V)

Supply Current IIN (µA)

L=270µH

1.0 1.2

1.4

1.6 1.8 2.0

50

60

70

40
30

20
10
0

Input Voltage V

IN(V)

Supply Current IIN (µA)

RH5RH501A

L=120µH

1 2

3

4

200

150

100

50

0

Input Voltage V

IN(V)

Supply Current IIN (µA)

RH5RH301A

L=120µH

1

5

10

20 30 40

50

60

70

80

90 100

50

60

70

80

40
30
20
10

0

Output Current I

OUT(mA)

Ripple Voltage Vr (mV p-p)

VIN=0.9V

2.0V

3.0V

RH5RH301A

RH5RH501A

L=270µH

1 2

3

4

200

150

100

50

0

Input Voltage V

IN(V)

Supply Current IIN (µA)

RH5RH501A

L=120µH

1

5

10

20 30 40

50 60 70 80 90 100

50

60

70

80

90

100

40
30
20
10
0

Output Current I

OUT(mA)

Ripple Voltage Vr (mV p-p)

4.0V

3.0V

2.0V

VIN=0.9V

16

5) Start-up/Hold-on Voltage vs. Output Current (Topt=25˚C)

RH5RH

RH5RH301A

L=270µH

1

10

20 30

40 50 60 70 80

50

60

70

40
30
20
10
0

Output Current I

OUT(mA)

Ripple Voltage Vr (mV p-p)

2.0V

3.0V

VIN=0.9V

L=270µH

1

10

90

20 30 40 50

60 70 80

50

60

70

80

40
30

20
10
0

Output Current I

OUT(mA)

Ripple Voltage Vr (mV p-p)

2.0V

3.0V

4.0V

VIN=0.9V

RH5RH302B

L=28µH

1

50

100 150 200

50

60

70

40
30
20
10

0

Output Current I

OUT(mA)

Ripple Voltage Vr (mV p-p)

VIN=0.9V

2.0V

3.0V

RH5RH301A

L=120µH

0

10

20

30

1.0

1.2

1.4

0.8

0.6

0.4

0.2
0

Output Current I

OUT(mA)

Start-up/Hold-on Voltage Vstart/Vhold (V)

Vstart

Vhold

RH5RH501A

RH5RH502B

L=28µH

1

50

100 150

250

200

100

120

80
60
40
20
0

Output Current I

OUT(mA)

Ripple Voltage Vr (mV p-p)

VIN=0.9V

2.0V

3.0V

4.0V

RH5RH501A

L=120µH

0

10

20

30

1.0

1.2

1.4

1.6

0.8

0.6

0.4

0.2
0

Output Current I

OUT(mA)

Start-up/Hold-on Voltage Vstart/Vhold (V)

Vstart

Vhold

17

RH5RH

6) Output Voltage vs.Temperature

RH5RH302B

L=28µH

0 20

40 60 80 100

1.0

1.2

1.4

0.8

0.6

0.4

0.2
0

Output Current I

OUT(mA)

Start-up/Hold-on Voltage Vstart/Vhold (V)

Vstart

Vhold

L=28µH

1.0

1.2

1.4

0.8

0.6

0.4

0.2
0

0

20

40 60

80 100

Output Current I

OUT(mA)

Start-up/Hold-on Voltage Vstart/Vhold (V)

Vstart

Vhold

RH5RH301A

IOUT=10mA
V

IN=2V

L=120µH

–40

–20

0 20 40 60 80 100

3.1

3.0

3.2

2.9

2.8

2.7
Temperature Topt(˚C)

Output Voltage VOUT (V)

RH5RH302B

IOUT=10mA
V

IN=2V

L=28µH

3.1

3.2

3.0

2.9

2.8

2.7
–40

–20

0 20 40

60 80 100

Temperature Topt(˚C)

Output Voltage VOUT (V)

RH5RH502B

RH5RH501A

IOUT=10mA
V

IN=3V

L=120µH

–40

–20

0 20 40 60 80

100

5.1

5.2

5.0

4.9

4.8

4.7
Temperature Topt(˚C)

Output Voltage VOUT (V)

RH5RH502B

IOUT=10mA
V

IN=3V

L=28µH

–40

–20

0 20 40

60 80 100

Temperature Topt(˚C)

5.1

5.2

5.0

4.9

4.8

4.7

Output Voltage VOUT (V)

18

RH5RH

9) Supply Current 1 vs.Temperature

RH5RH501A

0.8

1.0

1.2

0.6

0.4

0.2
0

–20–40

0

20

40

60 80

Temperature Topt(˚C)

Start-up Voltage Vstart(V)

–40 –20 0

20

40 60 80

Temperature Topt(˚C)

0.8

1.0

0.6

0.4

0.2

0

Hold-on Voltage Vhold(V)

RH5RH501A

–40

–20

0 20 40 60 80

Temperature Topt(˚C)

80

100

60

40

20

0

Supply Current 1 IDD1(µA)

RH5RH501A

–40

–20

0 20 40 60 80

Temperature Topt(˚C)

100

125

150

75
50
25
0

Lx Switching Current ILX (mA)

RH5RH501A

RH5RH501A

–40

–20

0 20 40 60 80

Temperature Topt(˚C)

4

5

3

2

1

0

Supply Current 2 IDD2(µA)

RH5RH501A

–40

–20

0 20

40 60 80

Temperature Topt(˚C)

0.8

1.0

0.6

0.4

0.2

0

Lx Leakage Current ILXleak (µA)

7) Start-up Voltage vs. Temperature 8) Hold-on Voltage vs. Temperature

10) Supply Current 2 vs.Temperature

11) Lx Switching Current vs.Temperature

12) Lx Leakage Current vs.Temperature

19

RH5RH

13) Oscillator Frequency vs. Temperature

14) Oscillator Duty Cycle vs. Temperature

RH5RH301A

IOUT=10mA
V

IN=2V

L=120µH

Oscillator Frequency fosc(kHz)

50

60

70

80

90

100

40
30
20
10
0

–20 0

20

40

60

80

100–40

Temperature Topt(˚C)

IOUT=10mA
V

IN=3V

L=120µH

–40

–20

0

20 40 60 80 100

Temperature Topt(˚C)

Oscillator Frequency fosc(kHz)

50

60

70

80

90

100

40
30
20
10
0

RH5RH302B

IOUT=10mA
V

IN=2V

L=28µH

–40

–20

0 20 40 60 80

100

Temperature Topt(˚C)

Oscillator Frequency fosc(kHz)

60

80

100

120

140

40
20
0

RH5RH301A

IOUT=10mA
V

IN=2V

L=120µH

–40

–20

0 20 40

60 80

Temperature Topt(˚C)

Oscillator Duty Cycle Maxdty(%)

70

80

90

100

60

50

RH5RH501A

RH5RH502B

IOUT=10mA
V

IN=3V

L=28µH

–40

–20

0 20 40 60 80

100

Temperature Topt(˚C)

Oscillator Frequency fosc(kHz)

60

80

100

120

140

40
20
0

RH5RH501A

IOUT=10mA
V

IN=3V

L=120µH

–40

–20

0 20 40 60 80

Temperature Topt(˚C)

Oscillator Duty Cycle Maxdty(%)

70

80

90

100

60

50

20

RH5RH

15) VLX Voltage Limit vs. Temperature

RH5RH302B

IOUT=10mA
V

IN=2V

L=28µH

–40

–20

0 20 40 60 80

Temperature Topt(˚C)

Oscillator Duty Cycle Maxdty(%)

70

80

90

100

60

50

IOUT=10mA
V

IN=3V

L=28µH

–40

–20

0 20

40

60 80

Temperature Topt(˚C)

Oscillator Duty Cycle Maxdty(%)

70

80

90

100

60

50

RH5RH501A

–40

–20

0

20 40

60

80

Temperature Topt(˚C)

VLX Voltage Limit VLXlim(V)

0.4

0.6

0.8

1.0

1.2

0.2

0.0

RH5RH501A

–40

–20

0

20 40 60 80

Temperature Topt(˚C)

EXT "H" Output Current IEXTH(mA)

4

6

8

10

2

0

RH5RH502B

RH5RH501A

–40

–20

0 20 40

60 80

Temperature Topt(˚C)

EXT "L" Output Current IEXTL(mA)

4

6

8

10

2

0

16) EXT “H” Output Current vs. Temperature 17) EXT “L” Output Current vs. Temperature

21

RH5RH

18) Load Transient Response
RH5RH301A

IOUT=1mA-30mA
V

IN=2V

L=120µH

0

20

40 60

80

Time t(ms)

3.0

3.5

4.0

4.5

5.0

2.5

2.0

1.5

1.0

Output Voltage VOUT (V)

150

180

210

240

120
90
60

30

0

Output Current IOUT(mA)

Output VoltageOutput Voltage

Output Current

IOUT=1mA-30mA
V

IN=3V

L=120µH

0

20

40 60 80

Time t(ms)

5.0

5.5

6.0

6.5

7.0

4.5

4.0

3.5

3.0

Output Voltage VOUT (V)

150

180

210

240

120

90
60
30

0

Output Current IOUT(mA)

Output Voltage

Output Current

RH5RH302B

IOUT=1mA-30mA
V

IN=2V

L=28µH

0 20 40 60 80

Time t(ms)

3.0

3.5

4.0

4.5

5.0

2.5

2.0

1.5

1.0

Output Voltage VOUT (V)

150

180

210

240

120

90
60
30

0

Output Current IOUT(mA)

Output Voltage

Output Current

RH5RH501A

RH5RH502B

IOUT=1mA-30mA
V

IN=3V

L=28µH

0

20 40

60 80

Time t(ms)

5.0

5.5

6.0

6.5

7.0

4.5

4.0

3.5

3.0

Output Voltage VOUT (V)

150

180

210

240

120

90
60

30

0

Output Current IOUT(mA)

Output Voltage

Output Current

22

RH5RH

19) Distribution of Output Voltage

0 5 10 15 20 25 30 35

Distribution (%)

Output Voltage VOUT (V)

5.18~5.20

5.16~5.18

5.14~5.16

5.12~5.14

5.10~5.12

5.08~5.10

5.06~5.08

5.04~5.06

5.02~5.04

5.00~5.02

4.98~5.00

4.96~4.98

4.94~4.96

4.92~4.94

4.90~4.92

4.88~4.90

4.86~4.88

4.84~4.86

4.82~4.84

4.80~4.82

RH5RH501A

20) Distribution of Oscillator Frequency

0 5 10 15 20 25

Distribution (%)

Oscillator Frequency fosc (kHz)

59~60
58~59
57~58
56~57
55~56
54~55
53~54
52~53
51~52
50~51
49~50
48~49
47~48
46~47
45~46
44~45
43~44
42~43
41~42
40~41

RH5RH501A

23

RH5RH

TYPICAL APPLICATIONS

VIN

Inductor

Diode

Lx

OUT

Vss

V

OUT

+

Capacitor

Components Inductor (L) : 120µH (Sumida Electric Co., Ltd.)

Diode (D) : MA721 (Matsushita Electronics Corporation, Schottky Type)
Capacitor (C

L) : 22µF (Tantalum Type)

FIG. 1

VIN

Inductor

Diode

OUT

Vss

V

OUT

+

Capacitor

Cb

Rb

Tr

EXT

Components Inductor (L) : 28µH (Troidal Core)

Diode (D) : HRP22 (Hitachi, Schottky Type)
Capacitor (C

L

) : 100µF (Tantalum Type)

Transistor (Tr) : 2SD1628G
Base Resistor (Rb) : 300Ω
Base Capacitor (Cb) : 0.01µF

FIG. 2

• RH5RH

××2B

• RH5RH

××1A

24

RH5RH

VIN

Inductor

Diode

Lx

OUT

Vss

V

OUT

+

Capacitor

EXT
CE

NC

Components Inductor (L) : 120µH (Sumida Electric Co., Ltd.)

Diode (D) : MA721 (Matsushita Electronics Corporation, Schottky Type)
Capacitor (C

L) : 22µF (Tantalum Type)

FIG. 3

VIN

Inductor

Diode

Lx

OUT

Vss

V

OUT

+

Capacitor

Cb

Rb

Tr

EXT

CE

NC

Components Inductor (L) : 28µH (Troidal Core)

Diode (D) : HRP22 (Hitachi, Schottky Type)
Capacitor (C

L) : 100µF (Tantalum Type)

Transistor (Tr) : 2SD1628G
Base Resistor (Rb) : 300Ω
Base Capacitor (Cb) : 0.01µF

FIG. 4

• RH5RH××3B

25

VIN

Inductor

Diode

Lx

OUT

Vss

V

OUT

+

Capacitor

EXT
CE

NC

RH5RH××3B

Pull-up
resistor

Tr

CE

RH5RH

• CE pin Drive Circuit

FIG. 5

26

VIN

Inductor

Diode

OUT

Vss

V

OUT

+

Capacitor

EXT

ZD:6.8V

RH5RH502B

Tr

Cb

R

ZD

Rb

Starter Circuit

(Note) When the Output Current is small or the Output Voltage is unstable,use the Rzd for flowing the bias current through the Zener diode ZD.

FIG. 6

VIN

Inductor

Diode

OUT

Vss

V

OUT

+

Capacitor

RH5RH

××1A

Tr

PNP

Lx

Rb1

Rb2

Starter Circuit

(Note) When the LX pin Voltage is over the rating at the time PNP Tr is OFF,use a RH5RH××2B and drive the PNP Tr. by the external NPN Tr.

FIG. 7

APPLICATION CIRCUITS

• 12V Step-up Circuit

RH5RH

• Step-down Circuit

27

VIN

Trance1:1

Diode

OUT

Vss

V

OUT

+

Capacitor

Lx

RH5RH

××1A

Starter Circuit

(Note) Use a RH5RH××2B,depend on the Output Current.

FIG. 8

ZDST

RST

Tr

V

OUT side

V

OUT side

V

IN side

V

IN side

Starter Circuit

Starter Circuit

ZDst 2.5V≤/ZDst≤Designation of Output Voltage
Rst Input Bias Current of ZDst and Tr.

(several kΩ to several hundreds kΩ)

• Step-up/Step-down Circuit with Flyback

*

The Starter Circuit is necessary for all above circuits.

1.for Step-up Circuit.

2.for Step-down and Step-up/Step-down Circuit.

RH5RH

28

PACKAGE DIMENSIONS (Unit: mm)

TAPING SPECIFICATIONS (Unit: mm)

• SOT-89

• SOT-89-5

• SOT-89

• SOT-89-5

RH5RH

4.5±0.1

0.4±0.1

0.4±0.1

1.5±0.1

1.6±0.2

1.5±0.1

±0.1 ±0.1 ±0.1

1.5±0.1

2.5±0.1

0.4

MIN.

4.25MAX.

0.8

ø1.0

1 2

3

0.42 0.47 0.42

4.5±0.1

1.5±0.1

0.4±0.1

0.4±0.1

1.6±0.2

1.5±0.1

1.5±0.1

±0.1 ±0.1

±0.1

2.5±0.1

0.42±0.1

ø1.0

5

4

1 2

3

0.4

0.9

MIN.

+0.5

–0.3

4.5

0.42

0.47

0.42

User Direction of Feed.

T1

ø

T2

8.0±0.1

5.0

1.5

4.0±0.1

2.0±0.05

1.5±0.1

5.65±0.05

4.7

12±0.3

+0.1
–0

2.5MAX.

0.3±0.1

T 1

T 2

2.5MAX.

0.3±0.1

12±0.3

5.0

4.7

8.0±0.1

4.0±0.1

2.0±0.05

5.65±0.05

1.5±0.1

ø

1.5

+0.1
–0

User Direction of Feed.

29

RH5RH

When using these ICs, be sure to take care of the following points :

•

Set external components as close as possible to the IC and minimize the connection between the components

and the IC. In particular, when an external component is connected to OUT Pin, make minimum connection
with the capacitor.

•

Make sufficient grounding. A large current flows through Vss Pin by switching. When the impedance of the

Vss connection is high, the potential within the IC is varied by the switching current. This may result in
unstable operation of the IC.

•

Use capacitor with a capacity of 10µF or more, and with good high frequency characteristics such as tanta-

lum capacitor. We recommend the use of a capacitor with a resistance to the voltage being at least three
times the output set voltage. This is because there may be the case where a spike-shaped high voltage is gen­erated by the inductor when Lx transistor is turned OFF.

•

Take the utmost care when choosing a inductor. Namely, choose such an inductor that has sufficiently small

d.c. resistance and large allowable current, and hardly reaches magnetic saturation. When the inductance
value of the inductor is small, there may be the case where I

LX exceeds the absolute maximum ratings at the

maximum load. Use an inductor with an appropriate inductance.

•

Use a diode of a Schottky type with high switching speed, and also take care of the rated current.

•

These ICs are provided with a soft-start circuit. However, there may be the case where the overshoot of the

out put voltage takes place depending upon the peripheral circuits employed and the input/output condi­tions. In particular, when the input voltage is increased slowly, the occurrence of the overshoot of the output
voltage becomes conspicuous. Therefore in the case where the overshoot becomes a problem, take a counter­measure against this problem, for example, by clamping the output (OUT Pin) by use of a Zener diode.

•

The transient response characteristics corresponding to the variations in the input and output are set so as

to be slightly delayed by an internal phase compensation circuit in order to prevent the oscillation. because
of such setting of the transient response characteristics, take care of the occurrence of the overshoot and/or
undershoot of the output voltage.

•

The internal phase compensation circuit is designed with the avoidance of the problem of the occurrence of

the oscillation fully taken into consideration. However, there may be the case the oscillation takes place
depending upon the conditions for the attachment of external components. In particular, take the utmost
care when an inductor with a large inductance is used.

The performance of power source circuits using these ICs largely depends upon the peripheral circuits. Take the utmost care in the
selection of the peripheral circuits. In particular, design the peripheral circuits in such a manner that the values such as voltage, current
and power of each component, PCB patterns and the IC do not exceed their respective rated values.

APPLICATION HINTS

RICOH COMPANY, LTD.
ELECTRONIC DEVICES DIVISION

HEADQUARTERS

13-1, Himemuro-cho, Ikeda City, Osaka 563-8501, JAPAN
Phone [phone] Fax [phone]

YOKOHAMA OFFICE (International Sales)

3-2-3, Shin-Yokohama, Kohoku-ku, Yokohama City, Kanagawa 222-8530,
JAPAN
Phone [phone] Fax [phone]·1695

http://www.ricoh.co.jp/LSI/english/

RICOH CORPORATION
ELECTRONIC DEVICES DIVISION

SAN JOSE OFFICE

3001 Orchard Parkway, San Jose, CA 95134-2088, U.S.A.
Phone [phone] Fax [phone]