Order this document by UC3842A/D
HIGH PERFORMANCE
CURRENT MODE
CONTROLLERS
The UC3842A, UC3843A series of high performance fixed frequency
current mode controllers are specifically designed for off–line and dc–to–dc
converter applications offering the designer a cost effective solution with
minimal external components. These integrated circuits feature a trimmed
oscillator for precise duty cycle control, a temperature compensated
reference, high gain error amplifier, current sensing comparator, and a high
current totem pole output ideally suited for driving a power MOSFET.
Also included are protective features consisting of input and reference
undervoltage lockouts each with hysteresis, cycle–by–cycle current limiting,
programmable output deadtime, and a latch for single pulse metering.
These devices are available in an 8–pin dual–in–line plastic package as
well as the 14–pin plastic surface mount (SO–14). The SO–14 package has
separate power and ground pins for the totem pole output stage.
N SUFFIX
PLASTIC PACKAGE
CASE 626
8
1
D SUFFIX
PLASTIC PACKAGE
14
CASE 751A
The UCX842A has UYLO thresholds of 16 V (on) and 10 V (off), ideally
suited for off–line converters. The UCX843A is tailored for lower voltage
applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).
1
(SO–14)
• Trimmed Oscillator Discharge Current for Precise Duty Cycle Control
• Current Mode Operation to 500 kHz
PIN CONNECTIONS
• Automatic Feed Forward Compensation
Compensation
Voltage Feedback
Current Sense
1
2
8
7
V
ref
• Latching PWM for Cycle–By–Cycle Current Limiting
• Internally Trimmed Reference with Undervoltage Lockout
• High Current Totem Pole Output
• Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
V
CC
3
4
6
5
Output
Gnd
R
/C
T
T
(Top View)
• Direct Interface with Motorola SENSEFET Products
1
14
13
Compensation
NC
V
ref
2
NC
3
4
12
11
Voltage Feedback
NC
V
V
CC
C
5
6
10
9
Current Sense
NC
Output
Gnd
Simplified Block Diagram
R
/C
7
8
Power Ground
T
T
V
7(12)
CC
(Top View)
V
V
CC
ref
5.0V
Reference
Undervoltage
Lockout
ORDERING INFORMATION
Operating
8(14)
R
R
V
ref
V
C
Undervoltage
Lockout
Temperature Range
Device
Package
SO–14
SO–14
Plastic
Plastic
SO–14
SO–14
Plastic
Plastic
7(11)
UC3842AD
UC3843AD
UC3842AN
UC3843AN
UC2842AD
UC2843AD
UC2842AN
UC2843AN
R
C
T
Output
T
Oscillator
6(10)
4(7)
Latching
PWM
T
= 0° to +70°C
A
Power
Ground
5(8)
Voltage
Feedback
Input
+
–
2(3)
Error
Amplifier
Current
Sense
Input
Output
Compensation
1(1)
3(5)
T
= – 25° to +85°C
A
Gnd
5(9)
Pin numbers in parenthesis are for the D suffix SO–14 package.
Motorola, Inc. 1996
Rev 1
1
MOTOROLA ANALOG IC DEVICE DATA