S8821 datasheet(9/24 Pages) SII

부품명	S8821

상세설명	VOLTAGE REGULATION BOOST CHARGE PUMP DC-DC CONVERTER

PDF	24 Pages

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제조업체	SII [Seiko Instruments Inc]

홈페이지	http://www.sii.co.jp

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9 / 24 page

VOLTAGE REGULATION BOOST CHARGE PUMP DC-DC CONVERTER

Rev.5.1_02

S-8821 Series



Operation

1. Basic operation

Figure 7 shows the block diagram of the S-8821 Series.

The S-8821 series controls the output voltage by using the pulse frequency modulation (PFM) method.

The SW1 to SW4 switching transistors are switched ON/OFF with the clock generated by the internal

oscillator circuit, and operates the boost charge pump.

The output voltage is fed back and the voltage split by feedback resistances Rs and Rf and reference

voltage (Vref) are compared by a comparator. This comparator signal is used to modulate the oscillation

pulse frequency in order to keep the output voltage constant.

VIN

Switch

control

circuit

SW1

SW2

SW3

SW4

−

CPUMP=0.10

μF

Soft start

circuit

ON/OFF

circuit

ON/OFF

PFM control

oscillator

circuit

(1.0 MHz)

Reference

voltage

VOUT

GND

COUT=10

μF

CIN=4.7

μF

Figure 7

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