PS257 is designed for monitoring a switching power supply (S.P.S.), especially for desktop
ATX system. It protects the S.P.S. and PC from over voltage, under voltage, over current, short
circuit and over temperature status. It monitors dual +12V, 5V, 3.3V and -12V DC supply channels.
PS257 also provides a FAN drive module with two control modes - "step control mode" and
"OP-amp control mode". It adjusts the FAN speed according to the sensed temperature and
generates "over-temperature protection" when the temperature is too high.
It monitors the power-good-input signal (PGI) from SPS and generates power-good-output
signal (PGO) to motherboard. Therefore it enables/disables protection according to the SPS status
and provides a reliable power supply environment.
z Over-Voltage/Under-Voltage Protection (OVP & UVP) and lock out
It monitors 3.3V, 5V, -12V and dual +12V. FPO/ goes to high and latch-up when one of these
supply voltages exceeds their normal operation voltage range.
z Over Current Protection (OCP) and lock out
It monitors 3.3V, 5V and dual +12V. FPO/ goes to high and latch-up when one of these supply
currents exceeds their normal operation current range.
z PGO (Power Good Output) signal generation-
It generates PGO to motherboard according to the power status.
z Over Temperature Protection (OTP) and lock out.
z FAN drive control with two modes: "step control mode" and "OPamp control mode"
z Wide power supply range (3.8V~16V)
z Fault-protection output with open drain output stage
z LED lighting-up when error occurs or remote-off
z Built-in delay/debounce for the following important timing features:
¾ 300mS power good output delay when remote-on
¾ 75ms delay for UV/OC protection when AC-on
¾ 38mS PSON/ control de-bounce
4-Channel Secondary Monitoring IC Version： PRE.005
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