TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038E – JANUARY 1989 – REVISED DECEMBER 1999
D
D
D
D
D
D
D
D
D
D
D
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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
Undervoltage Lockout With Hysteresis
Double-Pulse Suppression
High-Current Totem-Pole Output
Internally Trimmed Bandgap Reference
500-kHz Operation
Error Amplifier With Low Output
Resistance
Designed to Be Interchangeable With
UC2842 and UC3842 Series
description
D PACKAGE
(TOP VIEW)
COMP
NC
VFB
NC
ISENSE
NC
RT/CT
1
14
2
13
3
12
4
11
5
10
6
9
7
8
REF
NC
VCC
VC
OUTPUT
GND
POWER GROUND
NC – No internal connection
D-8 OR P PACKAGE
(TOP VIEW)
COMP
VFB
ISENSE
RT/CT
1
8
2
7
3
6
4
5
REF
VCC
OUTPUT
GND
The TL284x and TL384x series of control
integrated circuits provide the features that are
necessary to implement off-line or dc-to-dc fixed-frequency current-mode control schemes with a minimum
number of external components. Some of the internally implemented circuits are an undervoltage lockout
(UVLO), featuring a start-up current of less than 1 mA, and a precision reference trimmed for accuracy at the
error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation
(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 when it is in the
off state.
Major differences between members of these series are the UVLO thresholds and maximum duty-cycle ranges.
Typical UVLO thresholds of 16 V (on) and 10 V (off) on the TLx842 and TLx844 devices make them ideally suited
to off-line applications. The corresponding typical thresholds for the TLx843 and TLx845 devices are 8.4 V (on)
and 7.6 V (off). The TLx842 and TLx843 devices can operate to duty cycles approaching 100%. A duty-cycle
range of 0 to 50% is obtained by the TLx844 and TLx845 by the addition of an internal toggle flip-flop, which
blanks the output off every other clock cycle.
The TL284x-series devices are characterized for operation from –40°C to 85°C. The TL384x-series devices are
characterized for operation from 0°C to 70°C.
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.
Copyright © 1999, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
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