P
RODUCTION
D
ATA
S
HEET
T
HE
I
NFINITE
P
OWER OF
I
NNOVATION
L
IN
F
INITY
M
ICROELECTRONICS
I
NC
.
11861
W
ESTERN
A
VENUE
,
G
ARDEN
G
ROVE
,
CA.
92841,
714-898-8121,
F
AX
:
714-893-2570
1
Copyright © 1995
Rev. 1.2a,2005-03-09
UC184xA / 284xA / 384xA
C
URRENT
M
ODE
PWM
C
ONTROLLER
DESCRIPTION
The UC184xA family of control ICs provides
all the necessary features to implement off-line
fixed-frequency, current-mode switching power
supplies with a minimum of external
components. The current mode architecture
demonstrates improved load regulation, pulse-
by-pulse current limiting and inherent protection
of the power supply output switch. The IC
includes: A bandgap reference trimmed to ±1%
accuracy, an error amplifier, a current sense
comparator with internal clamp to 1V, a high
current totem pole output stage for fast
switching of power MOSFET's, and an
externally programmable oscillator to set
frequency and maximum duty cycle. The
undervoltage lock-out is designed to operate with
250µA typ. start-up current, allowing an efficient
bootstrap supply voltage design. Available
options for this family of products, such as start-
up voltage hysteresis and duty cycle, are
summarized below in the Available Options
section. The UC184xA family of control ICs is
also available in 14-pin SOIC package which
makes the Power Output Stage Collector and
Ground pins available.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
C
OMPARISON
OF
UC384
X
A
VS
. SG384
X
D
ISCHARGE
C
URRENT
UC384xA
7.5 8.3 9.3
Mean
SG384x
Min. Limit
7.8
-3s
8.8
+3s
SG384x
Max. Limit
Discharge Current Distribution - mA
T
A
=25C
KEY FEATURES
LOW START-UP CURRENT.
(0.5mA max.)
TRIMMED OSCILLATOR
DISCHARGE CURRENT. (See
Product Highlight)
OPTIMIZED FOR OFF-LINE
AND DC-TO-DC
CONVERTERS.
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.
500KHz OPERATION.
LOW RO ERROR AMPLIFIER.
KEY FEATURES
ECONOMICAL OFF-LINE
FLYBACK OR FORWARD
CONVERTERS.
DC-DC BUCK OR BOOST
CONVERTERS.
LOW COST DC MOTOR
CONTROL.
Available Options
Part#
Start-Up
Voltage
Hysteresis
Max. Duty
Cycle
UCx842A 16V 6V <100%
UCx843A 8.4V 0.8V <100%
UCx844A 16V 6V <50%
UCx845A 8.4A 0.8V <50%
PACKAGE ORDER INFO
M
Plastic DIP
8-Pin
DM
Plastic SOIC
8-Pin
D
Plastic SOIC
14-Pin
Y
Ceramic DIP
8-Pin
T
A
(°C)
RoHS Compliant / Pb-free
Transition DC: 0503
RoHS Compliant / Pb-free Transition DC: 0440
0 to 70 UC384xAM UC384xADM UC384xAD -
-40 to +85 UC284xAM UC284xADm UC284xAD UC284xAY
-55 to 125 - - - UC184xAY
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. UC3842ADM-TR)