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www.fairchildsemi.com KA3505 PC SMPS Supervisory IC Features · · · · · · · · · · · · · 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 0.1µF external capacitor. 16-DIP 1 Rev. 1.0.1 ©2002 Fairchild Semicond