Order this document by UC3842A/D
UC3842A, 43A
UC2842A, 43A
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.
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).
• Trimmed Oscillator Discharge Current for Precise Duty Cycle Control
•
•
•
•
•
•
•
•
HIGH PERFORMANCE
CURRENT MODE
CONTROLLERS
N SUFFIX
PLASTIC PACKAGE
CASE 626
8
1
D SUFFIX
PLASTIC PACKAGE
CASE 751A
(SO–14)
14
1
PIN CONNECTIONS
Current Mode Operation to 500 kHz
Automatic Feed Forward Compensation
Compensation 1
7
VCC
6
Output
RT/CT 4
High Current Totem Pole Output
Vref
Current Sense 3
Internally Trimmed Reference with Undervoltage Lockout
8
Voltage Feedback 2
Latching PWM for Cycle–By–Cycle Current Limiting
5
Gnd
Undervoltage Lockout with Hysteresis
Low Startup and Operating Current
(Top View)
Direct Interface with Motorola SENSEFET Products
Compensation
1
14 Vref
NC
2
13 NC
Voltage Feedback
3
12 VCC
NC
4
11 VC
Current Sense
5
10 Output
NC
6
9
Gnd
RT/CT
7
8
Power Ground
Simplified Block Diagram
VCC
7(12)
(Top View)
Vref
5.0V
Reference
8(14)
R
Vref
Undervoltage
Lockout
R
RTCT
2(3)
Output
Compensation
1(1)
ORDERING INFORMATION
VC
Output
Latching
PWM
+
–
Error
Amplifier
6(10)
Power
Ground
5(8)
Current
Sense
3(5) Input
Gnd
Device
Operating
Temperature Range
5(9)
Pin numbers in parenthesis are for the D suffix SO–14 package.
SO–14
UC3842AD
UC3843AD
UC3842AN
TA = 0° to +70°C
SO–14
Plastic
UC3843AN
Plastic
UC2842AD
SO–14
UC2843AD
UC2842AN
TA = – 25° to +85°C
UC2843AN
© Motorola, Inc. 1996
MOTOROLA ANALOG IC DEVICE DATA
Package
7(11)
Oscillator
4(7)
Voltage
Feedback
Input
VCC
Undervoltage
Lockout
SO–14
Plastic
Plastic
Rev 1
1
