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

S-882Z Series

10

Seiko Instruments Inc.

To reliably start up the step-up DC-DC converter, in the S-882Z Series, select the discharge start voltage value

converter to be started, its external parts, and the output load.

Generally, an output smoothing capacitor with a large capacitance value and an output load are connected to the

output pin of the step-up DC-DC converter. Therefore, to start up the step-up DC-DC converter thus connected, it

is necessary to select a large capacitance value for the startup capacitor.

As a reference, the following shows an example that a Schottky diode (SD1) is added between the output pin

(OUT) and the power supply pin (VDD) of the step-up DC-DC converter to be started up in the S-882Z Series

(refer to Figure 14). As a result, it is possible to start up the step-up DC-DC converter by the capacitor with a

small value.

VIN

VIN

OUT

VM

VSS

S-882Z Series

VSS

Step-up DC-DC converter

VDD

OUT

CPOUT

SD1

Figure 14 Connection Diagram (Reference)

performed is described below.

0.1

µF)

Capacitance value of power smoothing capacitor for step-up DC-DC converter (unit :

µF)

Consumption current value of step-up DC-DC converter (unit : mA)

Minimum operation voltage of step-up DC-DC converter (unit : V)

Step-up DC-DC converter startup time

≅ Soft start time (unit : ms)