APW7074 datasheet(6/20 Pages) ANPEC

6 / 20 page

Rev. A.2 - Feb., 2006

APW7074

www.anpec.com.tw

Function Pin Descriptions

VCC (Pin14)

Power supply input pin. Connect a nominal 12V power

supply to this pin. The power-on reset function

monitors the input voltage by this pin. It is recommended

that a decoupling capacitor (1 to 10uF) be connected

to GND for noise decoupling.

PVCC (Pin13)

This pin provides a supply voltage for the lower gate

drive, connect this pin to VCC pin in normal use.

BOOT (Pin10)

This pin provides the bootstrap voltage to the upper

gate driver for driving the N-channel MOSFET.

PHASE (Pin8)

This pin is the return path for the upper gate driver.

Connect this pin to the upper MOSFET source. This

pin is also used to monitor the voltage drop across the

MOSFET for over-current protection.

GND (Pin7)

This pin is the signal ground pin. Connect the GND pin

to a good ground plane.

PGND (Pin11)

This pin is the power ground pin for the lower gate

driver. It should be tied to GND pin on the board.

COMP (Pin4)

This pin is the output of PWM error amplifier. It is used

to set the compensation components.

FB (Pin5)

This pin is the inverting input of the PWM error amplifier.

It is used to set the output voltage and the compensation

components. This pin is also monitored for under-

voltage protection; if the FB voltage is under 50% of

reference voltage, the device will be shut down.

UGATE (Pin9)

This pin is the gate driver for the upper MOSFET of

PWM output.

LGATE (Pin12)

This pin is the gate driver for the lower MOSFET of

PWM output.

SS (Pin3)

Connect a capacitor to GND and a 10uA current source

charges this capacitor to set the soft-start time.

OCSET (Pin2)

This pin serves two functions: a shutdown control and

the setting of over current limit threshold. Pulling this

pin below 1.3V will shutdown the controller, forcing

the UGATE and LGATE signals to be low.

A resistor (Rocset) connected between this pin and

the drain of the high side MOSFET will determine the

over current limit. An internal 200uA current source

will flow through this resistor, creating a voltage drop,

which will be compared with the voltage across the

high side MOSFET. The threshold of the over current

limit is therefore given by:

(

)

DS(ON)

OCSET

PEAK

200uA

EN (Pin6)

Pull this pin above 1.3V to enable the device and pull

this pin below 1.2V to disable the device. In shutdown,

the SS is discharged and the UGATE and LGATE pins

are held low. Note that don’t leave this pin open.

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