application
INFO
available
UCC15701/2
UCC25701/2
UCC35701/2
Advanced Voltage Mode Pulse Width Modulator
FEATURES
•
700kHz Operation
•
Integrated Oscillator/ Voltage Feed
Forward Compensation
•
Accurate Duty Cycle Limit
•
Accurate Volt-second Clamp
•
Optocoupler Interface
•
Fault Counting Shutdown
•
Fault Latch off or Automatic Shutdown
•
Soft Stop Optimized for Synchronous
Rectification
•
1A Peak Gate Drive Output
•
130µA Start-up Current
•
750µA Operating Current
DESCRIPTION
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.
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 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.
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
IN
SUPPLY
R1
R2
6
R3
7
VREF
R4
9
R5
C
S
14
C
F
1
C3
R
F
R8
8
FB
GND
13
R11
C5
12
VREF
PGND
5
COUNT
SS
11
VSCLAMP
SYNC
OUT
ILIM
4
C
T
10
CT
RT
UCC35701
VFF
VDD
3
R6
R7
C6 V
OUT
C1
R8
R10
2
C2
RCS
C4
RGND
V
IN
RETURN
V
OUT
R13
R12
C6
C7
R14
R15
UDG-98005-1
SLUS293A - JANUARY 2000
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