application
INFO
UCC15701/2
UCC25701/2
UCC35701/2
available
Advanced Voltage Mode Pulse Width Modulator
FEATURES
DESCRIPTION
700kHz Operation
The UCC35701/UCC35702 family of pulse width modulators is intended for
isolated switching power supplies using primary side control. They can be
used for both off-line applications and DC/DC converter designs such as in
a distributed power system architecture or as a telecom power source.
Integrated Oscillator/ Voltage Feed
Forward Compensation
Accurate Duty Cycle Limit
Accurate Volt-second Clamp
Optocoupler Interface
The devices feature low startup current, allowing for efficient off-line start-
ing, yet have sufficient output drive to switch power MOSFETs in excess of
500kHz.
Voltage feed forward compensation is operational over a 5:1 input range
and provides fast and accurate response to input voltage changes over a
4:1 range. An accurate volt-second clamp and maximum duty cycle limit
are also featured.
Fault Counting Shutdown
Fault Latch off or Automatic Shutdown
Soft Stop Optimized for Synchronous
Rectification
Fault protection is provided by pulse by pulse current limiting as well as the
ability to latch off after a programmable number of repetitive faults has oc-
curred.
1A Peak Gate Drive Output
130mA Start-up Current
750mA Operating Current
Two UVLO options are offered. UCC35701 family has turn-on and turn-off
thresholds of 13V/9V and UCC35702 family has thresholds of 9.6V/8.8V.
The UCC35701/2 and the UCC25701/2 are offered in the 14 pin SOIC (D),
14 pin PDIP (N) or in 14 pin TSSOP (PW) packages. The UCC15701/2 is
offered in the 14 pin CDIP (J) package.
TYPICAL APPLICATION DIAGRAM
V
SUPPLY
IN
R1
R6
R2
R7
VFF
6
VDD
3
R3
7
RT
VREF
UCC35701
CT
V
C6
OUT
10 CT
C4
C1
R4
9
VSCLAMP
R8
C2
OUT
ILIM
4
2
R5
11 SYNC
14 SS
R10
CS
CF
RCS
1
COUNT
C3
R
F
12 VREF
PGND
GND
5
V RETURN
IN
R8
RGND
8
FB
13
R11
V
OUT
C5
R13
C7
R12
C6
R14
R15
UDG-98005-1
SLUS293C - JANUARY 2000 - REVISED JUNE 2005