FAN7680 Datasheet, PDF (1/16 Pages) Fairchild Semiconductor – PC Power Supply Outputs Monitoring IC

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FAN7680
PC Power Supply Outputs Monitoring IC
Features
• PC Power Supply Output Monitor Circuitry
• Few External Components
• Over Voltage Protection for 3.3V, 5V and 12V(Vcc)
Outputs
• Under Voltage Protection for 3.3V, 5V and 12V(Vcc)
Outputs with Delay Time
• Fault Protection Output with Open Drain Output
• Open Drain Power Good Output
• 300ms Power Good Delay
• 38ms PSON On/Off Debounce
• 73us Debounce
• 2.3ms PSON to FPO Turn Off Delay
• Latch Function Controlled by PSON and Protection
Inputs
Typical Application
• PC Power Supply
Description
The FAN7680 is a complete output supervisory circuitry
intended for use in the secondary side of a switched mode
power supply. It provides over voltage protection (OVP),
under voltage protection (UVP), fault protection output
(FPO), remote On/Off (PSON), latch, internal delay circuits
and power good signal generator to monitor and control the
output of the switching power supply system. As for output
control, power good output(PGO) and fault protection out-
put(FPO) are included. It directly senses all the output rails
for OVP and UVP without external dividers. The FAN7680
offers a simple and cost effective solution with minimum
number of external components and greatly reduces PCB
board space for power supply.
8-DIP
1
8-SOP
1
OVP
The FAN7680 has OVP functions for +3.3V, +5V,
+12V(Vcc) outputs. This block is made up of three compara-
tors with two inputs and resistor dividers. One input of a
comparator is connected to a reference voltage and another
input is connected to a resistor divider.
UVP
The FAN7680 also has UVP functions for +3.3V, +5V,
+12V(Vcc) outputs. This block is made up of three compara-
tors with two inputs and resistor dividers. One input of a
comparator is connected to a reference voltage and another
input is connected to a resistor divider.
PSON
The remote on/off(PSON) section is for controlling the
SMPS externally. When a high signal is applied to the PSON
input, the FPO signal becomes a high state and all secondary
outputs are grounded. The remote on/off signal is transferred
with some on/off debounce time.
FPO
The FPO(Fault Protection Output) is a signal which indicates
the system fault condition according to protection signals.
When a fault state is occured, the FPO signal becomes high
and the PGO signal becomes low and the main power is to be
turned off.
Normal State; "Low"
Fault State; "High"
PGO
The power good signal generator provides a signal according
to output voltage conditions of a power supply for safe oper-
ation of a secondary system. The power good output should
be low state before the output voltage is out of regulation at
turn-off of the input power switch.
Normal State ; "High"
Fault State ; "Low"
©2003 Fairchild Semiconductor Corporation
Rev. 1.0.0