Datasheet

4
UCC15701/2
UCC25701/2
UCC35701/2
PIN DESCRIPTIONS
VDD: Power supply pin. A shunt regulator limits supply
voltage to 14V typical at 10mA shunt current.
PGND: Power Ground. Ground return for output driver
and currents.
GND: Analog Ground. Ground return for all other circuits.
This pin must be connected directly to PGND on the
board.
OUT: Gate drive output. Output resistance is 10W maxi
-
mum.
VFF: Voltage feedforward pin. This pin connects to the
power supply input voltage through a resistive divider
and provides feedforward compensation over a 0.8V to
3.2V range. A voltage greater than 4.0V or less than
0.6V on this pin initiates a soft stop cycle.
RT: The voltage on this pin mirrors VFF over a 0.8V to
3.2V range. A resistor to ground sets the ramp capacitor
charge current. The resistor value should be between
20k and 200k.
CT: A capacitor to ground provides the oscillator/
feedforward sawtooth waveform. Charge current is 2 ·
I
RT
, resulting in a CT slope proportional to the input volt
-
age. The ramp voltage range is GND to V
RT
.
Period and oscillator frequency is given by:
T
VC
I
tRC
RT T
RT
DIS CH T T
=
·
·
+»··
2
05.
F
RT CT
»
·
2
8FB
9VS C LAMP
10CT
3VDD
5.0V
REF
SS
2ILIM
1COUNT
14
13
GND
4OUT
5PGND
12 VREF
0.7V
13/9V (35701)
9.6/8.8V (35702)
SSDONE
7RT
6VF F
11 S YNC
4.5V
4V
V
REF
0.6V
0.2V
CURRENT FAULT
CURRENT LIMIT
V
REF
0.6V
4V
2*I
RT
0.2V
3m A
I
25*I
RUN
I
I
RT
PEAK
VALLEY
SHUTDOWN
LATC H
FAULT
LATC H
0.2V
VDD
HIGH LINE
LO W LINE
PWM
SQ
R
D
S
Q
R
D
1.5R
+
R
RQ
S
D
RQ
S
D
SSDONE
PWM
DQ
R
DETAILED BLOCK DIAGRAM
UDG-98004