S1212B Datasheet, PDF (16/58 Pages) Seiko Instruments Inc – HIGH-WITHSTAND VOLTAGE LOW CURRENT CONSUMPTION LOW DROPOUT CMOS VOLTAGE REGULATOR

HIGH-WITHSTAND VOLTAGE LOW CURRENT CONSUMPTION LOW DROPOUT CMOS VOLTAGE REGULATOR
S-1212B/D Series
Rev.3.0_00
5. Thermal shutdown circuit
The S-1212B/D Series has a built-in thermal shutdown circuit to limit overheating. When the junction temperature
increases to 165°C typ., the thermal shutdown circuit becomes the detection status, and the regulating is stopped.
When the junction temperature decreases to 140°C typ., the thermal shutdown circuit becomes the release status,
and the regulator is restarted.
If the thermal shutdown circuit becomes the detection status due to self-heating, the regulating is stopped and V_OUT
decreases. For this reason, the self-heating is limited and the temperature of the IC decreases. The thermal
shutdown circuit becomes release status when the temperature of the IC decreases, and the regulating is restarted,
thus the self-heating is generated again. Repeating this procedure makes the waveform of V_OUT into a pulse-like
form. This phenomenon 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. Note that the product may
suffer physical damage such as deterioration if the above phenomenon occurs continuously.
Caution 1. When the heat radiation of the application is not in a good condition, the self-heating cannot be
limited immediately, and the IC may suffer physical damage. Perform thorough evaluation
including the temperature characteristics with an actual application to confirm no problems
happen.
2. If a large load current flows during the restart process of regulating after the thermal shutdown
circuit changes to the release status from the detection status, the thermal shutdown circuit
becomes the detection status again due to self-heating, and a problem may happen in the restart
of regulating. A large load current, for example, occurs when charging to the C_L whose
capacitance is large.
Perform thorough evaluation including the temperature characteristics with an actual application
to select C_L.
Table 15
Thermal Shutdown Circuit
Release: 140°C typ.^*1
Detection: 165°C typ.^*1
VOUT Pin Voltage
Constant value^*2
Pulled down to V_SS^*3
*1. Junction temperature
*2. The constant value is output due to the regulating based on the set output voltage value.
*3. The VOUT pin voltage is pulled down to V_SS due to the feedback resistors (R_s and R_f) and a load.
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