RICOH RH5RH312B-T2, RH5RH313B-T1, RH5RH313B-T2, RH5RH321A-T1, RH5RH321A-T2 Datasheet

PWM STEP-UP DC/DC CONVERTER

RH5RH××1A/××2B/××3B SERIES

APPLICATION MANUAL

NO.EA-023-0006

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

↑↑ ↑

ab 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

115

222

3—4

—33

——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)

(mark side)

12

3

5

(mark side)

12

4

3

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.

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

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

8V

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)

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

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

4.875 5.000 5.125 V

8V

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

8V

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=VOUT–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

8V

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

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

2.925 3.000 3.075 V

8V

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 30 50 µA

To be measured at OUT pin

25µA

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

V

OUT

–0.4

V

VOUT≥1.5V 0.4 V

0.8V≤VOUT<1.5V

V

OUT

–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