S-8821 Datasheet, PDF (9/19 Pages) Seiko Instruments Inc – VOLTAGE REGULATION STEP-UP CHARGE PUMP DC-DC CONVERTER

Rev.3.1_00
VOLTAGE REGULATION STEP-UP CHARGE PUMP DC-DC CONVERTER
S-8821 Series
2. Step-up Charge Pump
The step-up charge pump steps up the voltage by switching ON/OFF of the SW1 to SW4 switching
transistors.
First, in order to charge the pump capacitance (C_PUMP), set SW1 to OFF, SW2 to ON, SW3 to OFF, and
SW4 to ON (charge cycle). Following charging the electricity, in order to discharge the charged
electricity to the output capacitance (C_OUT), SW1 set the switches as to ON, SW2 to OFF, SW3 to ON,
and SW4 to OFF (discharge cycle).
The input voltage can be stepped up to a constant voltage value by repeating this charge cycle and
discharge cycle.
Figure 7 shows the charge cycle, and Figure 8 shows the discharge cycle.
SW2: ON
SW1: OFF
V_IN
Current flow
C_PUMP
0.10 μF
C_OUT
10 μF
SW 4: ON
SW 3: OFF
Figure 7
SW 2: OFF
SW1: ON
V_IN
C_PUMP
0.10 μF
SW4: OFF
Current flow
C_OUT
10 μF
SW3: ON
Figure 8
Seiko Instruments Inc.
9