RS5RJ5817B 查看數據表（PDF） - RICOH Co.,Ltd.

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RS5RJ5817B

VFM STEP-UP DC/DC CONVERTER WITH VOLTAGE REGULATOR AND DETECTOR

RICOH Co.,Ltd. 

RS5RJ

OPERATION

VIN

100µH

LX

8

VDD

6

100µF

OSC

VFM

LX Tr

–

+

Vref1

Pch Tr

VOUT

5

+

–

Vref2

22µF

1

VSS

VOUT

1µF

FIG. A Diagram of RS5RJ including external circuits

1. VDD Output Voltage

VDD output voltage is shown in Fig. B.

(1) In the case of VIN–Vf≥VDD0:

In Area B, LxTr is maintained in an OFF state, so that VIN–Vf (V) is output as it is from VDD pin without

step-up operation.

(2) In the case of VIN–Vf <VDD0:

In Area A, this IC functions as Step-up DC/DC converter. The step-up operation will now be explained

with reference to FIG. A. The step-up operation is an operation for regulating the VDD output voltage by

comparing Vref1 and the VDD output voltage by error amplifier circuits and subjecting LxTr to on-time con-

trol by VFM circuits (i.e., by controlling the step-up operation).

2. VOUT Output Voltage

A constant voltage is output from VOUT pin, with above-mentioned the VDD output voltage being subjected to a

step-down operation by a linear regulator. This step-down operation will now be explained with reference to FIG. A.

The step-down operation is an operation for regulating the VDD output voltage by Pch Tr by comparing Vref2 and

the VDD output voltage.

VIN

VDD0

VOUT0

Vf

: Input Voltage

: VDD Set Voltage

: VOUT Set Voltage

: ON Voltage of Diode

Area A

VDD0

VDD Area B

VOUT0

VOUT

VDD0+Vf

1.2V

10V

Input Voltage (V)

FIG. B Output Voltage vs. Input Voltage characteristic

8

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