S-882Z datasheet(8/24 Pages) SII

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ULTRA-LOW VOLTAGE OPERATION CHARGE PUMP IC FOR STEP-UP DC-DC CONVERTER STARTUP

S-882Z Series

Rev.1.2_00

Seiko Instruments Inc.

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 (CCPOUT) connected to the CPOUT pin and the voltage of the CPOUT pin gradually rises.

(4)

When the CPOUT pin voltage (VCPOUT) reaches or exceeds the discharge start voltage (VCPOUT1), 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 CCPOUT is discharged from the OUT pin.

(6)

When VCPOUT declines to the level of the discharge stop voltage (VCPOUT2) as the result of the discharge, M1

switches off, and the discharge is stopped.

(7)

When the VM pin voltage (VVM) reaches or exceeds the shutdown voltage (VOFF), 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 VVM does not reach VOFF or more, the stepped up electric power from the charge pump circuit is

recharged to CCPOUT. (Retun to the operation specified in (3).)

Caution When stopping the discharge to OUT pin and recharging a startup capacitor (CCPOUT), CCPOUT is

needed to be charged until CPOUT pin voltage (VCPOUT) is lowered less than discharge stop

voltage (VCPOUT2). In this case, set the condition as follows:

Condition: Out pin voltage (VOUT)<Discharge stop voltage (VCPOUT2)

Charge pump circuit

Oscillation

circuit

CLK signal

−

VREF

−

OUT

VIN

VSS

CPOUT

CCPOUT

Charging

Discharging

Detection

−

COMP1

COMP2

Figure 12 Operation Diagram

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