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AN4003

PC POWER SUPPLY DESIGN WITH KA3511

Fairchild Semiconductor 

Pin

No. Name

Function

1 VCC Supply voltage. Operating range is 14V~30V. VCC =20V, Ta=25°C at test.

2 COMP Error amplifier output. It is connected to non-inverting input of pulse width

modulator comparator.

3 E/A(-) Error amplifier inverting input. Its reference voltage is always 1.25V.

4 E/A(+) Error amplifier non-inverting input feedback voltage.This pin may be used to

sense power supply output voltage.

5 TREM Remote on/off delay. Ton/Toff=8ms/24ms (Typ.) with C=0.1µF. Its high/low

threshold voltage is 1.8V/0.6V.

6 REM Remote on/off input. It is TTL operation and its threshold voltage is 1.4V. Voltage

at this pin can reach normal 4.6V, with absolutely maximum voltage, 5.25V. If

REM = “Low”, PWM = “Low”. That means the main SMPS is operational. When

REM = “High”, then PWM = “High” and the main SMPS is turned-off.

7

RT Oscillation frequency setting R. (Test Condition RT=10kΩ)

8

CT Oscillation frequency setting C. (Test Condition CT=0.01µF)

9 DET Under-voltage detect pin. Its threshold voltage is 1.25V Typ.

10 TPG PG delay. Td=250ms (Typ) with CPG=2.2µF. The high/low threshold voltage are

1.8V/0.6V and the voltage of Pin10 is clamped at 2.9V for noise margin.

11 PG Power good output signal. PG = “High” means that the power is “Good” for

operation and PG = “Low” means “Power fail”.

12 Vref Precision voltage reference trimmed to 2%. (Typical Value = 5.03V)

13 V3.3 Over voltage protection for output 3.3V. (Typical Value = 4.1V)

14 V5 Over voltage protection for output 5V. (Typical Value = 6.2V)

15 V12 Over voltage protection for output 12V. (Typical Value = 14.2V)

16 PT This is prepared for an extra OVP input or another protection signal. (Typical

Value = 1.25V)

17 TUVP Timing pin for under voltage protection blank-out time. Its threshold voltage is

1.8V and clamped at 2.9V after full charging. Target of delay time is 250ms and

it is realized through external (C=2.2µF).

18 GND Signal ground.

19 DTC Deadtime control input. The dead-time control comparator has an effective

120mV input offset which limits the minimum output dead time. Dead time may

be imposed on the output by setting the dead time control input to a fixed

voltage, ranging between 0V to 3.3V.

20 C2 Output drive pin for push-pull operation.

21 E Power ground.

22 C1 Output drive pin for push-pull operation.

Rev C, November 1999

4

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