HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR

S-1155 Series

Seiko Instruments Inc.

14

3. Shutdown pin (ON/OFF pin)

This pin starts and stops the regulator.

When the ON/OFF pin is set to the shutdown 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 between the VOUT and VSS pin.

Note that the current consumption increases when a voltage of 0.3 V to 1.0 V is applied to the ON/OFF pin.

The ON/OFF pin is configured as shown in Figure 12. Since the ON/OFF pin is neither pulled down nor pulled up

internally, do not use it in the floating state.

When not using the ON/OFF pin, connect it to the VSS pin in the product A type, and connect it to the VIN pin in B

type.

Table 6

Logic Type

ON/OFF Pin

Internal Circuits VOUT Pin Voltage Current Consumption

A

“L”: Power on

Operate

Set value

A

“H”: Power off

Stop

B

“L”: Power off

Stop

B

“H”: Power on

Operate

Set value

VSS

ON/OFF

VIN

Figure 12

4. Overcurrent protection circuit

The S-1155 Series has an overcurrent protection circuit having the characteristics shown in (1) Output Voltage vs.

Output Current (When load current is increased) (Ta = 25

°C) in “ Characteristics (Typical Data)”, in order to

protect the output transistor against an excessive output current and short circuiting between the VOUT and VSS

initial value is restored for the output voltage, if releasing a short circuit once.

Caution

This overcurrent protection circuit does not work as for thermal protection. If this IC long keeps

short circuiting inside, pay attention to the conditions of input voltage and the load current so

that, under the usage conditions including short circuit, the loss of the IC will not exceed power

dissipation of the package.