5

FUNCTIONAL DESCRIPTION

Clock Generator Circuit

As the SCI7654 has a built-in clock generator circuit, it requires no external source at all. The clock rate changes

depending on the FC pin signal level, and the Low Output or High Output mode can be selected. This allows

a frequency selection according to the current capacitance and load current when the booster output impedance

changes depending on the clock rate and external booster capacitance.

Voltage Converter Circuit

quadruple, triple or double. Four converter circuits are required for quadruple boosting, three converts are

required for triple boosting, and dual converters are required for double boosting.

Voltage step-up diagram (during -5V input)

Reference Voltage Circuit

The SCI7654 has a built-in reference voltage circuit for the voltage regulator. The temperature coefficient of

reference voltage can be changed using pins TC1 and TC2, and a voltage having one of four types of temperature

(0V)

(-5V)

-10V

-15V

-20V

10V

15V

20V

double boosting

triple boosting

quadruple boosting

TC1

TC2

Temperature Coefficient, CT (%/˚C)

Mode

Min.

Typ.

Max.

Min.

Typ.

Max.

CT0

-1.55

-1.5

-1.45

-0.07

-0.04

0

CT1

H

-1.70

-1.5

-1.30

-0.25

-0.15

-0.07

CT2

H

-1.90

-1.5

-1.10

-0.45

-0.35

-0.20

CT3

L

L

-2.15

-1.5

-0.85

-0.75

-0.55

-0.30

FC pin

Mode

Clock Rate

Current Consumption

Output Ripple

Low Output

4.0 kHz (Typ.)

High Output

16.0 kHz (Typ.)