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PC Power Supply Output Monitor Circuitry
Few External Components
Over Voltage Protection for 3.3V/5V/12V Output
Under Voltage Protection for 3.3V/5V/12V Output With
Delay Time
Over Current Protection for 3.3V/5V/12V Output With
Delay Time
Fault Protection Output With Open Collector Output
Power Supply on/off Delay Time Control (PSON)
Power Good Signal Generator With Hysteresis
Open Collector PG Output
300ms Power Good Delay
Current Sense Setting Function With RI
Latch Function Controlled by PSON and Protection Input
16-Pin Dual In-line Package
Description
The KA3505 is complete output supervisory circuitry
intended for use in the secondary side of the switched mode
power supply. It provides all the functions necessary to
monitor and control the output of the power supply system.
Power good signal generator, Remote on and off control,
some precision protection features against over-voltage,
under-voltage and over-current are implemented. It directly
senses all the output rails for OVP and UVP without any
external dividers. As for output control, Power Good Output
(PGO) and Fault Protection Output (FPO) are also included.
Utilizing a minimum number of external components, the
KA3505 offers a simple and cost effective solution, greatly
reducing PCB board space for power supply system.
OCP (Over Current Protection)
It has precision OCP functions for +3.3V, +5V, +12V
outputs. The block is made up of three comparators with
current source setting function. Two inputs of each OCP
comparator are connected to both sides of output inductor that
is located in the secondary output of SMPS.
FPO (Fault Protection Output)
Fault Protection Output indicates the fault condition as
protection signal. When fault state occurs, the main power is
to be turned-off and the PGO signal goes LOW.
NORMAL = "LOW", FAULT = "HIGH"
OVP (Over Voltage Protection)
It has OVP functions for +3.3V, +5V, +12V outputs. The
circuit is made up of a comparator with three detecting inputs.
PGO (Power Good Output)
Power Good Signal Generator is to monitor the voltage level
of power supply for safe operation of a microprocessor
having some delay time at turn-on. The delay time is
programmed by a timing capacitor connected to TPG pin of
KA3505. The power good output should be low state before
the output voltage is out of regulation at turn-off.
NORMAL = "HIGH", FAULT = "LOW"
UVP (Under Voltage Protection)
It also has UVP functions for +3.3V, +5V, +12V outputs. The
block is made up of a comparator with three detecting inputs.
Remote ON/OFF
Remote on/off section is used to control SMPS externally.
If a high signal is supplied to the remote on/off input, FPO
signal becomes a high state and all secondary outputs are
grounded. The remote on/off signal is transferred with some
on-delay and off-delay time of 8ms, 24ms respectively with
0.1碌F external capacitor.
16-DIP
1
Rev. 1.0.1
漏2002 Fairchild Semiconductor Corporation
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