APW7061
Functional Pin Description
VCC (Pin 1)
COMP (Pin 3)
This pin provides a supply voltage to the device, When This pin is the output of the error amplifier. Add an
VCC is risingabove the threshold 4.2V, the device is external resistor and capacitor network to provide
turned on, and conversely, when VCC drops below the loop compensation for the PWM converter (see
the falling threshold, the device is turned off. A 1uF Application Information).
decoupling capacitor to GND is recommended.
Pull this pin below 0.4V will shutdown the controller,
FB (Pin 2)
forcing the UGATE and LGATE signals to be 0V. A
soft start cycle will be initiated upon the release of
this pin.
FB pin is the inverting input of the error amplifier, and
it receives the feedback voltage from an external
resistive divider across the output (VOUT). The output PHASE (Pin 5)
voltage is determined by:
A resistor (ROCSET) is connected between this pin and
the drain of the low-side MOSFET will determine the
over current limit. An internally generated 250uA
æ
ö
÷
÷
ø
ROUT
RGND
ç
VOUT = 0.8V ´ 1+
ç
è
where ROUT is the resistor connected from VOUT to FB, current source will flow through this resistor, creating
and RGND is the resistor connected from FB to GND.
a voltage drop. This voltage will be compared with the
voltage across the low-side MOSFET. The threshold
of the over current limit is therefore given by :
When theFB voltage is under 50% VREF, it will cause
the under voltage protection, and shutdown the device.
Remove the condition and restart the VCC voltage,
250 mA ´ R OCSET
ILIMIT
=
R DS(ON)
will enable again the device.
GND (Pin 4)
An over current condition will cycle the soft start
function until the over current condition is removed.
Because of the comparator delay time, so theon time
of the low-side MOSFET must be longer than 800ns
Signal ground for the IC.
UGATE (Pin 6)
This pin provides gate drive for the high-side MOSFET.
BOOT (Pin 7)
to have the over current protection work.
This pin provides the supply voltage to the high side
MOSFET driver. For driving logic level N-channel
MOSEFT, a bootstrap circuit can be use to create a
suitable driver’s supply.
LGATE (Pin 8)
This pin provides the gate drive signal for the low side
MOSFET.
Copyright ã ANPECElectronicsCorp.
5
www.anpec.com.tw
Rev. A.7 - Nov., 2005
ANPEC [ ANPEC ELECTRONICS COROPRATION ]
