S-1155 Datasheet, PDF (15/28 Pages) Seiko Instruments Inc – HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR

Rev.1.1_00
HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR
S-1155 Series
5. Thermal shutdown circuit
The S-1155 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-1155 Series, if the thermal shutdown circuit starts operating, it stops regulating so that
the output voltage drops. When regulation stops, the S-1155 does not itself generate heat so that the IC’s
temperature drops. When the temperature drops, the thermal shutdown circuit is released to restart regulating, thus
this IC generates heat again. Repeating this procedure makes waveform of the output voltage pulse-like form.
Stop/Restart of regulation continues unless decreasing either/both of the input voltage and the output voltage in
order to reduce the internal current consumption, or decreasing the ambient temperature.
Table 7
Thermal Shutdown Circuit
Operation : 150°C (Typ.)^*1
Release : 120°C (Typ.)^*1
*1. Junction temperature
VOUT Pin Voltage
V_SS level
Set value
6. Rush current control circuit
The S-1155 Series has a rush current control circuit to control the rush current generated during power-on or when
the ON/OFF pin is ON. This circuit limits the rush current (400 mA, Typ.) immediately after power-on or from the
ON/OFF pin is ON until the specified time (100 µs min.) which is set internally.
Caution
The junction temperature drops to 120°C (Typ.) by the operation of thermal shutdown circuit,
after stopping regulation, the circuit is released to restart regulation; in this case, note that the
period to limit rush current may become shorter (10 µs min.).
Seiko Instruments Inc.
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