S-8821 데이터 시트보기 (PDF) - Unspecified
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S-8821 Datasheet PDF : 24 Pages
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Rev.5.1_03
VOLTAGE REGULATION BOOST CHARGE PUMP DC-DC CONVERTER
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
CIN=4.7 F
SW1
C
CPUMP=0.10 F
C
SW2
SW3
SW4
Switch
control
circuit
Soft start
circuit
PFM control
oscillator
circuit
(1.0 MHz)
Rs
+
Rf
-
ON/OFF
circuit
Reference
voltage
VOUT
COUT=10 F
ON/OFF
GND
Figure 7
9
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