1
2
3
4
5
6
7
8
GROUND
OUTPUT
V
CC
V
REF
R /C
T T
I
SENSE
V
FB
COMP
JG PACKAGE
(TOP VIEW)
11
A/B
V
cc
7 12
5 9
GROUND
4
7
R
T
/C
T
2
3
V
FB
1
1COMP
3
5
CURRENT
SENSE
34 V
2.50 V
OSC
UVLO
S/R
5 V
REF
VREF
Good
Logic
Internal
BIAS
Error
Amp
2R
R
1 V
CURRENT
SENSE
COMPARATOR
PWM
LATCH
S
R
T
8
14
V
REF
5 V
50 mA
7
V
C
106
OUTPUT
85
POWER
GROUND
Note 1: A = DIL−8 Pin Number. B = SO−14 and CFP−14 Pin Number.
UC1843-SP
www.ti.com
SLUS981 –MARCH 2010
QML CLASS V, CURRENT-MODE PWM CONTROLLER
Check for Samples: UC1843-SP
1
FEATURES
• QML-V Qualified, SMD 5962-86704
• Rad-Tolerant: 50 kRad (Si) TID (ELDRS Free)
(1)
• Controlled Baseline
• Optimized For Off-line and DC-to-DC
Converters
• Low Start-Up Current (<1 mA)
• Automatic Feed Forward Compensation
• Pulse-by-Pulse Current Limiting
• Enhanced Load Response Characteristics
• Under-Voltage Lockout With Hysteresis
• Double Pulse Suppression
• High Current Totem Pole Output
• Internally Trimmed Bandgap Reference
• 500-kHz Operation
• Low R
O
Error Amp
xxx
(1) Radiation tolerance is a typical value based upon initial device
qualification with dose rate = 10 mrad/sec. Radiation Lot
Acceptance Testing is available - contact factory for details.
DESCRIPTION
The UC1843 family of control devices provides the necessary features to implement off-line or dc-to-dc fixed
frequency current mode control schemes with a minimal external parts count. Internally implemented circuits
include under-voltage lockout featuring start up current less than 1 mA, a precision reference trimmed for
accuracy at the error amp input, logic to insure latched operation, a PWM comparator which also provides
current limit control, and a totem pole output stage designed to source or sink high peak current. The output
stage, suitable for driving N-Channel MOSFETs, is low in the off state. The under-voltage lockout threshold is
8.4 V and maximum duty cycle range is around 100%.
BLOCK DIAGRAM
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Copyright © 2010, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.