S-882Z Datasheet, PDF (8/24 Pages) Seiko Instruments Inc – ULTRA-LOW VOLTAGE OPERATION CHARGE PUMP IC FOR STEP-UP DC-DC CONVERTER STARTUP

ULTRA-LOW VOLTAGE OPERATION CHARGE PUMP IC FOR STEP-UP DC-DC CONVERTER STARTUP
S-882Z Series
Rev.1.2_00
„ Operation
1. Basic Operation : IC with 2.0 V Discharge Start Voltage
(1) In the S-882Z Series, when power of 0.3 V or higher is input to the VIN pin, the oscillation circuit starts
operation with that power, and the CLK signal is output from the oscillation circuit.
(2) The charge pump circuit is driven by this CLK signal, and the power of the VIN pin is converted to the
stepped up electric power in the charge pump circuit.
(3) The stepped up electric power output from the charge pump circuit is gradually charged to the startup
capacitor (C_CPOUT) connected to the CPOUT pin and the voltage of the CPOUT pin gradually rises.
(4) When the CPOUT pin voltage (V_CPOUT) reaches or exceeds the discharge start voltage (V_CPOUT1), the output
signal of the comparator (COMP1) changes from high level to low. As a result, the discharge control switch
(M1), which was off, turns on.
(5) When M1 switches on, the step up electric power charged to C_CPOUT is discharged from the OUT pin.
(6) When V_CPOUT declines to the level of the discharge stop voltage (V_CPOUT2) as the result of the discharge, M1
switches off, and the discharge is stopped.
(7) When the VM pin voltage (V_VM) reaches or exceeds the shutdown voltage (V_OFF), the output signal (EN−) of
the comparator (COMP2) changes from low level to high. As a result, the oscillation circuit stops operation
and the shutdown state is entered.
(8) When V_VM does not reach V_OFF or more, the stepped up electric power from the charge pump circuit is
recharged to C_CPOUT. (Retun to the operation specified in (3).)
Caution
When stopping the discharge to OUT pin and recharging a startup capacitor (C_CPOUT), C_CPOUT is
needed to be charged until CPOUT pin voltage (V_CPOUT) is lowered less than discharge stop
voltage (V_CPOUT2). In this case, set the condition as follows:
Condition: Out pin voltage (V_OUT)<Discharge stop voltage (V_CPOUT2)
Charging
CPOUT
5
CCPOUT
Discharging
VIN 4
Charge pump circuit
CLK signal
Oscillation
circuit
EN−
2
VSS
COMP1
−
+
1 OUT
M1
Detection
VREF
−
+
COMP2
3 VM
Figure 12 Operation Diagram
8
Seiko Instruments Inc.