S8880A Datasheet, PDF (6/30 Pages) Seiko Instruments Inc – ENERGY HARVESTING POWERED BY ULTRA-LOW POWER AND ULTRA-LOW VOLTAGE OPERATION BOOST CHARGE PUMP FOR STEP-UP DC-DC CONVERTER STARTUP

ENERGY HARVESTING POWERED BY ULTRA-LOW POWER AND ULTRA-LOW VOLTAGE OPERATION BOOST CHARGE PUMP FOR STEP-UP DC-DC CONVERTER STARTUP
S-8880A Series
Rev.1.0_01
 Operation
1. Basic operation
Figure 3 shows an internal block diagram to describe the basic operation.
(1) In the S-8880A Series, when a voltage is input to the VIN pin, the oscillation circuit starts operation, and the
CLK signal is output.
(2) The charge pump circuit is driven by the CLK signal to boost the voltage input to the VIN pin.
(3) The voltage boosted in the charge pump circuit is output from the CPOUT pin and is gradually charged to the
startup capacitor (C_CPOUT) connected to the CPOUT pin. Consquently, 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 "H" to "L". As a result, the discharge control switch (M1),
which was off, turns on.
(5) When M1 turns on, the boosted voltage charged to C_CPOUT is discharged from the OUT pin.
(6) When V_CPOUT decreases to the level of the discharge stop voltage (V_CPOUT2) as the result of the discharge, M1
turns off, and the discharge is stopped.
(7) When the VM pin voltage (V_VM) reaches or exceeds the power-off voltage (V_OFF), the output signal (EN−) of the
comparator (COMP2) changes from "L" to "H". As a result, the oscillation circuit stops operation and the
power-off status is entered.
(8) When V_VM does not reach or exceed V_OFF, the voltage input to the VIN pin is boosted in the charge pump
circuit and is recharged to C_CPOUT (Retun to the operation specified in (3)).
Caution When stopping the discharge to the OUT pin and recharging the startup capacitor (C_CPOUT), C_CPOUT
needs to be discharged until CPOUT pin voltage (V_CPOUT) decreases to discharge stop voltage
(V_CPOUT2) or lower. In this case, set the condition as follows:
Condition: OUT pin voltage (V_OUT) < V_CPOUT2
Charging operation
CPOUT
5
*1
VIN 4
*1
Charge pump circuit
CLK signal
Oscillation
circuit
EN−
C_CPOUT
Discharging
operation
COMP1
−
+
1 OUT
M1
*1
Detection
operation
V_REF
−
+
COMP2
3 VM
*1
2
VSS
*1. Parasitic diode
6
Figure 3