S1312 datasheet(21/47 Pages) SII

21 / 47 page

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

Rev.2.3_01

S-1312 Series

6. Overcurrent protection circuit

The S-1312 Series includes an overcurrent protection circuit having the characteristics shown in "1. Output voltage

vs. Output current (When load current increases) (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 pin and the

VSS pin. The current when the output pin is short-circuited (Ishort) is internally set at approx. 50 mA typ., and the

normal 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 load current so that,

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

dissipation of the package.

7. Thermal shutdown circuit

The S-1312 Series has a thermal shutdown circuit to protect the device from damage due to overheat. When the

junction temperature rises to 150

°C typ., the thermal shutdown circuit operates to stop regulating. When the junction

temperature drops to 120

°C typ., the thermal shutdown circuit is released to restart regulating.

Due to self-heating of the S-1312 Series, if the thermal shutdown circuit starts operating, it stops regulating so that the

output voltage drops. When regulation stops, the S-1312 Series does not itself generate heat and the IC's

temperature drops. When the temperature drops, the thermal shutdown circuit is released to restart regulating, thus

the S-1312 Series generates heat again. Repeating this procedure makes the waveform of the output voltage into a

pulse-like form. Stop or restart of regulation continues unless decreasing either or both of the input voltage and the

output current in order to reduce the internal power consumption, or decreasing the ambient temperature.

Table 14

Thermal Shutdown Circuit

VOUT Pin Voltage

Operate: 150

°C typ.*1

VSS level

Release: 120

°C typ.*1

Set value

*1. Junction temperature

S1312 Datasheet(PDF) 21 Page - Seiko Instruments Inc