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

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PWM STEP-UP DC/DC CONVERTER

RH5RH××1A/××2B/××3B SERIES

APPLICATION MANUAL

NO.EA-023-0006

PWM STEP-UP DC/DC CONVERTER

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 reference 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 newly 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 oscillator 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 provided 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 supply 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.

FEATURES

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)

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 equipment.

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

1

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

RH5RH

BLOCK DIAGRAM

Lx

VLX limiter

Slow start

Vref

 

 

OUT

 

 

 

Vss

Buffer

Phase Comp.

 

 

 

 

 

LxSW

 

 

 

PWM control

 

EXT

 

+

 

OSC

Error Amp.

 

 

 

 

Chip Enable

 

 

CE

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

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 :

 

RH5RH×××× ×× Part Number

 

} }

}

 

 

 

 

 

 

a

b

c

 

 

 

 

 

 

 

Code

 

 

 

 

Description

 

 

 

a

 

Setting Output Voltage (VOUT):

 

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 :

 

 

Ex.

SOT-89

: T1, T2

c

 

 

SOT-89-5

: T1, T2

 

 

(refer to Taping Specifications)

 

 

“T1” is prescribed as a standard.

 

 

 

 

 

 

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.

2

RH5RH

PIN CONFIGURATION

SOT-89

SOT-89-5

 

 

5

4

 

(mark side)

 

 

(mark side)

 

1

2

3

1

2

3

PIN DESCRIPTION

 

Pin No.

 

 

 

 

 

 

 

 

Symbol

Description

××1B

××2B

××3B

 

 

 

 

 

 

 

 

 

 

 

1

1

5

VSS

Ground Pin

 

 

 

 

 

 

 

2

2

2

OUT

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

 

 

 

 

 

 

 

3

4

 

Lx

Switching Pin (Nch Open Drain)

 

 

 

 

 

 

 

3

3

EXT

External Tr. Drive Pin (CMOS Output)

 

 

 

 

 

 

 

1

 

Chip Enable Pin (Active Low)

 

CE

 

 

 

 

 

 

 

 

3

RH5RH

ABSOLUTE MAXIMUM RATINGS

 

 

Vss=0V

 

 

 

 

 

 

 

 

 

Symbol

 

 

Item

 

Rating

Unit

Note

 

 

 

 

 

 

 

 

 

 

VOUT

Output Pin Voltage

 

+12

V

 

 

 

 

 

 

 

 

 

 

 

VLX

Lx Pin Voltage

 

+12

V

Note1

 

 

 

 

 

 

 

 

 

 

VEXT

EXT Pin Voltage

 

– 0.3 to VOUT+0.3

V

Note2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCE

CE Pin Voltage

 

–0.3 to VOUT+0.3

V

Note3

 

 

 

 

 

 

 

 

 

 

ILX

Lx Pin Output Current

 

250

mA

Note1

 

 

 

 

 

 

 

 

 

 

IEXT

EXT Pin Current

 

±50

mA

Note2

 

 

 

 

 

 

 

 

 

 

PD

Power Dissipation

 

500

mW

 

 

 

 

 

 

 

 

 

 

 

Topt

Operating Temperature Range

 

–30 to +80

˚C

 

 

 

 

 

 

 

 

 

 

 

Tstg

Storage Temperature Range

 

–55 to +125

˚C

 

 

 

 

 

 

 

 

 

 

 

Tsolder

Lead Temperature(Soldering)

 

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.

ABSOLUTE MAXIMUM RATINGS

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

ELECTRICAL CHARACTERISTICS

 

 

 

 

 

 

 

• RH5RH301A

 

 

 

 

 

 

VOUT=3.0V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Symbol

 

Item

Conditions

MIN.

TYP.

MAX.

Unit

 

Note

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

Output Voltage

 

2.925

3.000

3.075

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIN

 

Input Voltage

 

 

 

8

V

 

 

 

 

 

 

 

IOUT=1mA,VIN : 02V

 

 

 

 

 

 

 

 

Vstart

 

Start-up Voltage

 

0.8

0.9

V

 

 

 

 

 

 

 

IOUT=1mA,VIN : 20V

 

 

 

 

 

 

 

 

Vhold

 

Hold-on Voltage

0.7

 

 

V

 

 

 

 

 

 

 

To be measured at OUT Pin

 

 

 

 

 

 

 

 

IDD1

 

Supply Current 1

 

15

25

µA

 

 

 

 

 

(excluding Switching Current)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To be measured at OUT Pin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IDD2

 

Supply Current 2

(excluding Switching Current)

 

2

5

µA

 

 

 

 

 

 

 

VIN=3.5V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ILX

 

Lx Switching Current

VLX=0.4V

60

 

 

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ILXleak

 

Lx Leakage Current

VLX=6V,VIN=3.5V

 

 

0.5

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fosc

 

Oscillator Frequency

 

40

50

60

kHz

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maxdty

 

Oscillator Maximum Duty

on (VLX “L” ) side

70

80

90

%

 

 

 

 

 

Cycle

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

η

 

Efficiency

 

70

85

 

%

 

 

 

 

 

 

 

Time required for the rising

 

 

 

 

 

 

 

 

tstart

 

Soft-Start Time

0.5

2.0

 

ms

 

Note1

 

 

 

of VOUT up to 3V.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VLXlim

 

VLX Voltage Limit

Lx Switch ON

0.65

0.8

1.0

V

 

Note2

 

 

 

 

 

 

 

 

 

 

 

 

 

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)VIN is applied.

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

(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) ILX 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.

5

RH5RH

 

 

 

 

 

 

 

 

 

 

• RH5RH501A

 

 

 

 

 

 

VOUT=5.0V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Symbol

 

Item

Conditions

MIN.

TYP.

MAX.

Unit

 

Note

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

Output Voltage

 

4.875

5.000

5.125

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIN

 

Input Voltage

 

 

 

8

V

 

 

 

 

 

 

 

Iout=1mA,Vin:02V

 

 

 

 

 

 

 

 

Vstart

 

Start-up Voltage

 

0.8

0.9

V

 

 

 

 

 

 

 

Iout=1mA,Vin:20V

 

 

 

 

 

 

 

 

Vhold

 

Hold-on Voltage

0.7

 

 

V

 

 

 

 

 

 

 

To be measured at OUT Pin

 

 

 

 

 

 

 

 

IDD1

 

Supply Current 1

 

30

45

µA

 

 

 

 

 

(excluding Switching Current)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To be measured at OUT Pin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IDD2

 

Supply Current 2

(excluding Switching Current)

 

2

5

µA

 

 

 

 

 

 

 

VIN=5.5V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ILX

 

Lx Switching Current

VLX=0.4V

80

 

 

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ILXleak

 

Lx Leakage Current

VLX=6V,VIN=5.5V

 

 

0.5

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fosc

 

Oscillator Frequency

 

40

50

60

kHz

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maxdty

 

Oscillator Maximum Duty

on (VLX “L” ) side

70

80

90

%

 

 

 

 

 

Cycle

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

η

 

Efficiency

 

70

85

 

%

 

 

 

 

 

 

 

Time required for the rising

 

 

 

 

 

 

 

 

tstart

 

Soft-Start Time

0.5

2.0

 

ms

 

Note1

 

 

 

of VOUT up to 5V.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Lx Switch ON

0.65

0.8

1.0

V

 

Note2

 

 

VLXlim

 

VLX Voltage Limit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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)VIN is applied.

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

(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) ILX 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

• RH5RH302B

 

 

 

 

 

 

VOUT=3.0V

 

 

 

 

 

 

 

 

 

 

 

Symbol

 

Item

Conditions

MIN.

TYP.

MAX.

Unit

 

Note

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

Output Voltage

 

2.925

3.000

3.075

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIN

 

Input Voltage

 

 

 

8

V

 

 

 

 

 

 

EXT no load,VOUT :02V

 

 

 

 

 

 

 

Vstart

 

Oscillator Start-up Voltage

 

0.7

0.8

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IDD1

 

Supply Current 1

EXT no load,VOUT=2.88V

 

30

50

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IDD2

 

Supply Current 2

EXT no load,VOUT=3.5V

 

2

5

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IEXTH

 

EXT “H” Output Current

VEXT=VOUT–0.4V

 

 

–1.5

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IEXTL

 

EXT “L” Output Current

VEXT=0.4V

1.5

 

 

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fosc

 

Oscillator Frequency

 

80

100

120

kHz

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maxdty

 

Oscillator Maximum Duty

VEXT “H” side

70

80

90

%

 

 

 

 

Cycle

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time required for the rising

 

 

 

 

 

 

 

tstart

 

Soft-Start Time

0.5

2.0

 

ms

 

Note1

 

 

 

 

of VOUT up to 3V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

Symbol

Item

Conditions

MIN.

TYP.

MAX.

Unit

Note

 

 

 

 

 

 

 

 

VOUT

Output Voltage

 

4.875

5.000

5.125

V

 

 

 

 

 

 

 

 

 

VIN

Input Voltage

 

 

 

8

V

 

 

 

EXT no load,VOUT :02V

 

 

 

 

 

Vstart

Oscillator Start-up Voltage

 

0.7

0.8

V

 

 

 

 

 

 

 

 

 

IDD1

Supply Current 1

EXT no load,VOUT=4.8V

 

60

90

µA

 

 

 

 

 

 

 

 

 

IDD2

Supply Current 2

EXT no load,VOUT=5.5V

 

2

5

µA

 

 

 

 

 

 

 

 

 

IEXTH

EXT “H” Output Current

VEXT=VOUT–0.4V

 

 

–2

mA

 

 

 

 

 

 

 

 

 

IEXTL

EXT “L” Output Current

VEXT=0.4V

2

 

 

mA

 

 

 

 

 

 

 

 

 

fosc

Oscillator Frequency

 

80

100

120

kHz

 

 

 

 

 

 

 

 

 

Maxdty

Oscillator Maximum Duty

VEXT “H” side

70

80

90

%

 

Cycle

 

 

 

 

 

 

 

 

 

 

 

 

Time required for the rising

 

 

 

 

 

tstart

Soft-Start Time

0.5

2.0

 

ms

Note1

of VOUT up to 5V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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)

7

RH5RH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

• RH5RH303B

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT=3.0V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Symbol

 

 

 

 

 

Item

Conditions

MIN.

TYP.

MAX.

Unit

 

Note

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

Output Voltage

 

 

 

 

 

2.925

3.000

3.075

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIN

 

Input Voltage

 

 

 

 

 

 

 

8

V

 

 

 

 

 

 

 

 

 

 

 

IOUT=1mA,VIN : 02V

 

 

 

 

 

 

 

 

Vstart

 

Start-up Voltage

 

0.8

0.9

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vhold

 

Hold-on Voltage

IOUT=1mA,VIN : 20V

0.7

 

 

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

η

 

Efficiency

 

 

 

 

 

70

85

 

%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IDD1

 

Supply Current 1

To be measured at OUT pin

 

30

50

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IDD2

 

Supply Current 2

To be measured at OUT pin

 

2

5

µA

 

 

 

 

 

VIN=3.5V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VLX=0.4V

60

 

 

mA

 

 

 

 

ILX

 

Lx Switching Current

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ILXleak

 

Lx Leakage Current

VLX=6V,VIN=3.5V

 

 

0.5

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IEXTH

 

EXT “H” Output Current

VEXT=VOUT–0.4V

 

 

–1.5

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IEXTL

 

EXT “L” Output Current

VEXT=0.4V

1.5

 

 

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT1.5V

VOUT–0.4

 

 

V

 

 

 

 

VCEH1

 

CE “H” Level 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT1.5V

 

 

0.4

V

 

 

 

 

VCEL1

 

CE “L” Level 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.8VVOUT<1.5V

VOUT–0.1

 

 

V

 

 

 

 

VCEH2

 

CE “H” Level 2

 

 

 

 

 

 

 

 

 

 

 

 

 

0.8VVOUT<1.5V

 

 

0.1

V

 

 

 

 

VCEL2

 

 

 

 

“L” Level 2

 

 

 

 

 

 

 

 

CE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.5

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ICEH

 

CE “H” Input Current

 

 

CE=3V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

–0.5

 

 

µA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ICEL

 

CE “L” Input Current

 

 

 

 

 

 

 

 

 

 

CE=0V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fosc

 

Oscillator Frequency

 

 

 

 

 

80

100

120

kHz

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maxdty

 

Oscillator Maximum Duty

on (VLX “L” )side

70

80

90

%

 

 

 

 

 

Cycle

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

tstart

 

Soft-Start Time

Time required for the rising

0.5

2.0

 

ms

 

Note1

 

 

 

of VOUT up to 3V.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VLXlim

 

VLX Voltage Limit

Lx Switch ON

0.65

0.8

1.0

V

 

Note2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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)VIN is applied.

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

(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) ILX 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.

8

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