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
•
•
•
•
•
•
•
•
Current Mode Operation to 500 kHz
Automatic Feed Forward Compensation
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
Direct Interface with Motorola SENSEFET Products
PIN CONNECTIONS
Compensation 1
Voltage Feedback 2
Current Sense 3
RT/CT 4
(Top View)
8
7
6
5
Vref
VCC
Output
Gnd
Compensation
NC
Voltage Feedback
NC
Current Sense
1
2
3
4
5
6
7
(Top View)
14 Vref
13 NC
12 VCC
11 VC
10 Output
9
8
Gnd
Power Ground
Simplified Block Diagram
VCC
Vref
8(14)
R
R
RTCT
4(7)
Voltage
Feedback
Input
2(3)
Output
Compensation
1(1)
+
–
NC
RT/CT
7(12)
5.0V
Reference
Vref
Undervoltage
Lockout
Oscillator
Latching
PWM
Error
Amplifier
VCC
Undervoltage
Lockout
VC
7(11)
Output
6(10)
Power
Ground
5(8)
Current
Sense
3(5) Input
ORDERING INFORMATION
Device
UC3842AD
UC3843AD
UC3842AN
UC3843AN
UC2842AD
UC2843AD
UC2842AN
UC2843AN
©
Motorola, Inc. 1996
Operating
Temperature Range
Package
SO–14
TA = 0° to +70°C
SO–14
Plastic
Plastic
SO–14
Gnd
5(9)
TA = – 25° to +85°C
SO–14
Plastic
Plastic
Rev 1
Pin numbers in parenthesis are for the D suffix SO–14 package.
MOTOROLA ANALOG IC DEVICE DATA
1
MOTOROLA [ MOTOROLA, INC ]
