UC1832/3
UC2832/3
UC3832/3
Precision Low Dropout Linear Controllers
FEATURES
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Precision 1% Reference
Over-Current Sense Threshold
Accurate to 5%
Programmable Duty-Ratio
Over-Current Protection
4.5V to 36V Operation
100mA Output Drive, Source or
Sink
Under-Voltage Lockout
DESCRIPTION
The UC1832 and UC1833 series of precision linear regulators include all the
control functions required in the design of very low dropout linear regulators.
Additionally, they feature an innovative duty-ratio current limiting technique
which provides peak load capability while limiting the average power dissipa-
tion of the external pass transistor during fault conditions. When the load cur-
rent reaches an accurately programmed threshold, a gated-astable timer is
enabled, which switches the regulator’s pass device off and on at an externally
programmable duty-ratio. During the on-time of the pass element, the output
current is limited to a value slightly higher than the trip threshold of the duty-ra-
tio timer. The constant-current-limit is programmable on the UCx832 to allow
higher peak current during the on-time of the pass device. With duty-ratio con-
trol, high initial load demands and short circuit protection may both be accom-
modated without extra heat sinking or foldback current limiting. Additionally, if
the timer pin is grounded, the duty-ratio timer is disabled, and the IC operates
in constant-voltage/constant-current regulating mode.
These IC’s include a 2 Volt (±1%) reference, error amplifier, UVLO, and a high
current driver that has both source and sink outputs, allowing the use of either
NPN or PNP external pass transistors. Safe operation is assured by the inclu-
sion of under-voltage lockout (UVLO) and thermal shutdown.
The UC1833 family includes the basic functions of this design in a low-cost, 8-
pin mini-dip package, while the UC1832 series provides added versatility with
the availability of 14 pins. Packaging options include plastic (N suffix), or ce-
ramic (J suffix). Specified operating temperature ranges are: commercial (0°C
to 70°C), order UC3832/3 (N or J); industrial (–25°C to 85°C), order UC2832/3
(N or J); and military (–55°C to 125°C), order UC1832/3J. Surface mount
packaging is also available.
Additional Features of the UC1832
series:
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Adjustable Current Limit to
Current Sense Ratio
Separate +V
IN
terminal
Programmable Driver Current
Limit
Access to V
REF
and E/A(+)
Logic-Level Disable Input
BLOCK DIAGRAMS
UDG-92040
6/94
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