SUPER-SMALL PACKAGE 2-CIRCUIT HIGH RIPPLE-REJECTION LOW CURRENT CONSUMPTION LOW DROPOUT CMOS VOLTAGE REGULATOR

S-1721 Series

Seiko Instruments Inc.

22

3. ON/OFF pin 1 and 2

These pins start and stop the regulator.

When the ON/OFF pin is set to the power-off level, the entire internal circuit stops operating, and the built-in P-

channel MOS FET output transistor between the VIN and VOUT pin is turned off, in order to reduce the current

k

Ω which is placed between the VOUT and VSS pin. Note that the current consumption increases when a voltage of

0.3 V to 1.2 V (@Ta = 25

°C) is applied to the ON/OFF pin.

The ON/OFF pin is configured as shown in Figures 24 and 25. In the S-1721 Series A, B C, and D types, the

ON/OFF pin is internally pulled up to VIN or pulled down to VSS when in the floating status, so the VOUT pin is set

In the S-1721 Series E, F, G and H types, do not use S-1721 Series in the floating status because the ON/OFF pin

is not internally pulled up or pulled down.

When not using the ON/OFF pin in the S-1721 Series E, F, G, and H types, connect the ON/OFF pin to the VIN pin

in the E, F (1ch only), and G (2ch only) types. In the F (2ch only), G (1ch only) and H types, connect the ON/OFF pin

to the VSS pin.

Table

11

Logic Type

ON/OFF Pin

Internal

Circuits

VOUT Pin Voltage

Current

Consumption

A

1ch “H”: Power on

2ch “H”: Power on

Operate

Operate

Set value

Set value

B

1ch “H”: Power on

2ch “L”: Power on

Operate

Operate

Set value

Set value

C

1ch “L”: Power on

2ch “H”: Power on

Operate

Operate

Set value

Set value

D

1ch “L”: Power on

2ch “L”: Power on

Operate

Operate

Set value

Set value

E

1ch “L”: Power off

2ch “L”: Power off

Stop

Stop

F

1ch “L”: Power off

2ch “H”: Power off

Stop

Stop

G

1ch “H”: Power off

2ch “L”: Power off

Stop

Stop

H

1ch “H”: Power off

2ch “H”: Power off

Stop

Stop

(1)

S-1721 Series A, B, C, D Types

(2)

S-1721 Series E, F, G, H Types

VSS

VIN

ON/OFF

B (2ch), C (1ch), D types

A, B (1ch), C (2ch) type

VSS

VIN

ON/OFF

Figure

24

Figure

25