BD3951F

Technical Note

4/9

www.rohm.com

2009.07 - Rev.A

© 2009 ROHM Co., Ltd. All rights reserved.

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Block Diagram, Application Circuit, Pin Description

PIN

External

Component

Value

Vcc

Capacitor :Cin

0.33μF～

10mF

OUT

Capacitor :Co

3.3μF～

2200μF

CT

Capacitor :Cct

0.01μF～10μF

SIN

Resistor :R1,R2

0Ω～100kΩ

RADJ

Resistor :R3,R4

0Ω～100kΩ

・

ESR range of the output capacitor Co is 0 (ceramic capacitor) to 100Ω.

・

VCC must be more than 5V under the condition SIN is used for VCC voltage drop detection.

Ex. Vcc=5.8V detection, Since 1.26V＊(R1+R2)/R1=5.8V,

R1=10kΩ,R2=36kΩ

・

Reset detection voltage must be more than 4V under the condition RADJ is used for OUT voltage drop detection.

Ex. OUT=4.5V detection, Since 1.26V＊(R3+R4)/R3=4.5V,

R3=10kΩ,R4=26kΩ

RESET function can be discarded while RADJ terminal pulls up to OUT terminal, which in case RES terminal output “H”.

Battery detection function can be discarded while SIN terminal pulls up to OUT terminal, which in case SOUT terminal output

“H”. 0～47KΩ pull up resistors are recommended in both condition.

Set application board test is necessary to select the

right pull up resistor value.

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Terminal Description

Pin. No

Pin Name

Function

1

Vcc

Battery power supply

2

SIN

Battery voltage detection input terminal. Must be connected to OUT terminal while this

function is not employed.

3

RADJ

RESET voltage adjustment terminal. Connect to GND in case internal detect voltage is

employed

4

CT

RESET delay time control terminal

5

GND

IC GND terminal

6

RES

RESET output terminal. Built in 20KΩ pull up.

7

SOUT

Battery voltage detection output terminal. Built in 20KΩ pull up.

8

OUT

5.0V output terminal

OUT SOUT RES GND

Vcc

SIN RADJ CT

Fig.13

Fig.14

Vref

OUT

GND

CT

RES

PreReg

SOUT

SIN

20kΩ

20kΩ

VCC

RADJ

VCC

1

2

3

4

5

6

7

8

0.33μF

3.3μF

0.1μF

R2:36kΩ

R1:10kΩ

Vcc

OUT

(8PIN)

3.3μF

RADJ

(3PIN)