S-8821 datasheet(8/19 Pages) SII

Part #	S-8821

Description	VOLTAGE REGULATION STEP-UP CHARGE PUMP DC-DC CONVERTER

PDF	19 Pages

Scroll/Zoom	100%

Manufacturer	SII [Seiko Instruments Inc]

Direct Link	http://www.sii.co.jp

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8 / 19 page

VOLTAGE REGULATION STEP-UP CHARGE PUMP DC-DC CONVERTER

S-8821 Series

Rev.3.1_00

Seiko Instruments Inc.

Operation

1. Basic operation

Figure 6 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 step-up 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 6

S-8821 Datasheet(PDF) 8 Page - Seiko Instruments Inc