LIN D
O C
#:
1840
UC184xA/284xA/384xA
C
URRENT
M
ODE
PWM C
ONTROLLER
T
H E
I
N F I N I T E
P
O W E R
O F
I
N N O VA T I O N
P
R O D U C T I O N
D
A T A
S
H E E T
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 compo-
nents. 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 program-
mable oscillator to set frequency and
maximum duty cycle. The under-
voltage 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.
K E Y F E AT U R E S
s
LOW START-UP CURRENT.
(0.5mA max.)
s
TRIMMED OSCILLATOR DISCHARGE
CURRENT.
(See Product Highlight)
p
OPTIMIZED FOR OFF-LINE AND DC-TO-DC
CONVERTERS.
p
AUTOMATIC FEED FORWARD
COMPENSATION.
p
PULSE-BY-PULSE CURRENT LIMITING.
p
ENHANCED LOAD RESPONSE
CHARACTERISTICS.
p
UNDER-VOLTAGE LOCKOUT WITH
HYSTERESIS.
p
DOUBLE PULSE SUPPRESSION.
p
HIGH-CURRENT TOTEM POLE OUTPUT.
p
INTERNALLY TRIMMED BANDGAP
REFERENCE.
p
500KHz OPERATION.
p
LOW R
O
ERROR AMPLIFIER.
PRODUCT HIGHLIGHT
C
OMPARISON
OF
UC384
X
A
VS
.
SG384
X
D
ISCHARGE
C
URRENT
A P P L I C AT I O N S
SG384x
Max. Limit
UC384xA
SG384x
Min. Limit
T
A
=25°C
s
ECONOMICAL OFF-LINE FLYBACK OR
FORWARD CONVERTERS.
s
DC-DC BUCK OR BOOST CONVERTERS.
s
LOW COST DC MOTOR CONTROL.
A
V A I L A B L E
O
P T I O N S
Part #
UCx842A
UCx843A
7.5
7.8
8.3
Mean
8.8
9.3
Start-Up Hysteresis Max. Duty
Voltage
Cycle
16V
8.4V
16V
8.4V
6V
0.8V
6V
0.8V
<100%
<100%
<50%
<50%
−3σ
+3σ
UCx844A
UCx845A
Discharge Current Distribution - mA
PA C K A G E O R D E R I N F O R M AT I O N
T
A
(°C)
0 to 70
-40 to 85
-55 to 125
M
Plastic DIP
8-pin
UC384xAM
UC284xAM
—
DM
Plastic SOIC
8-pin
UC384xADM
UC284xADM
—
D
Plastic SOIC
14-pin
UC384xAD
UC284xAD
—
Y
Ceramic DIP
8-pin
—
UC284xAY
UC184xAY
Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (i.e. UC3842ADMT)
F O R F U R T H E R I N F O R M AT I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1
Copyright © 1995
Rev. 1.2 12/95
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841
1
MICROSEMI [ MICROSEMI CORPORATION ]
