PC POWER SUPPLY SUPERVISORS
The UTC S3525 is specially designed for switching power supply
system. it provides protection circuits, power good output (PGO)
indicator, fault protection output (FPOB) and a PSONB control.
The protection circuits include over voltage protection (OVP),
under voltage protection (UVP) and over current protection (OCP)
monitoring for system voltages and currents.
When 3.3V, 5V or 12V voltage is decreasing to 2.68V, 4.3V and
9.9V respectively, the under voltage protection (UVP) function will be
enabled. FPOB will be set to high to turn off the PWM controller IC.
Toggling the PSONB from low to high will reset the fault protection latch.
The voltage difference across external current shunt is used for
OCP functions. An external resistor can be used to adjust protection threshold.
The power supply is turned on after 38mS delay time when
PSONB signal is set from high to low. To turn off power supply,
PSONB signal is set from low to high with the delay time 38mS. The
PGI circuitry provides a power-down warning signal for PGO. When
PGI input is lower than the internal 1.20V reference voltage, PGO signal is pulled low.
* OVP/UVP monitors 3.3V, 5V, 12V input voltage level.
* OCP monitors IS33, IS5, IS12 input current sense.
* Fault protection output (FPOB) with Open Drain Output stage.
* Power good output (PGO) with Open Drain Output stage.
* 38ms de-bounce time for PSONB input signal.
* 300ms time delay from PGI to PGO.
* 2.4ms time delay for PSONB to turn off FPOB.