S8821 datasheet(12/24 Pages) SII

12 / 24 page

VOLTAGE REGULATION BOOST CHARGE PUMP DC-DC CONVERTER

S-8821 Series

Rev.5.1_02



External Capacitor Selection

1. Input and Output Capacitors (CIN, COUT)

The input capacitor (CIN) lowers the power supply impedance and averages the input current.

The CIN value is selected according to the impedance of the power supply that is used. Select a ceramic

capacitor with a small equivalent series resistance (ESR). Although this figure varies according to the

impedance of the power supply that is used as well as the load current value, it is generally in the range

of 4.7

μF to 10 μF.

For the output capacitor (COUT), select a ceramic capacitor with a small ESR for smoothing the ripple

voltage. A value of 10

μF is recommended for the capacitance value. Use of a capacitor with a

capacitance lower than 10

μF results in a larger ripple voltage. Conversely, use of a capacitor with a

capacitance greater than 10

μF results in the output voltage not being able to rise up to setting value

and the impossibility to obtain the desired output current.

2. Pump Capacitor (CPUMP)

The pump capacitor (CPUMP) is required for boosting the voltage. Select a ceramic capacitor with a small

ESR. A capacitance value of 0.10

μF is recommended. Use of a capacitor with a capacitance greater

than 0.10

μF results in a larger ripple voltage. Conversely, use of a capacitor with a capacitance lower

than 0.10

μF results in the output voltage not being able to raise up to setting value and the impossibility

to obtain the desired output current.

S8821 датащи(PDF) 12 Page - Seiko Instruments Inc