UC3842B, UC3843B,
UC2842B, UC2843B
High Performance
Current Mode Controllers
The UC3842B, UC3843B series are high performance fixed
frequency current mode controllers. They 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.
http://onsemi.com
PDIP–8
N SUFFIX
CASE 626
8
1
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 and surface
mount (SO–8) 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.
SO–8
D1 SUFFIX
CASE 751
8
1
SO–14
The UCX842B has UVLO thresholds of 16 V (on) and 10 V (off),
ideally suited for off–line converters. The UCX843B is tailored for
lower voltage applications having UVLO thresholds of 8.5 V (on) and
7.6 V (off).
D SUFFIX
CASE 751A
14
1
• Trimmed Oscillator for Precise Frequency Control
• Oscillator Frequency Guaranteed at 250 kHz
• 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
PIN CONNECTIONS
1
2
3
4
8
7
6
5
Compensation
Voltage Feedback
Current Sense
R /C
V
V
ref
CC
Output
Gnd
T
T
(Top View)
Compensation
1
2
3
4
5
6
7
14
13
12
11
10
9
V
ref
• Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
NC
Voltage Feedback
NC
NC
V
CC
V
C
V
7(12)
CC
Current Sense
NC
Output
Gnd
V
V
CC
ref
5.0V
Reference
8
Undervoltage
Lockout
R /C
T
Power Ground
T
8(14)
R
R
(Top View)
V
ref
V
C
Undervoltage
Lockout
7(11)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 16 of this data sheet.
R /C
T
Output
T
Oscillator
6(10)
4(7)
Latching
PWM
Power
Ground
5(8)
Voltage
Feedback
Input
+
-
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 17 of this data sheet.
2(3)
Output
Compensation
Error
Amplifier
Current
Sense
Input
3(5)
1(1)
Gnd 5(9)
Pin numbers in parenthesis are for the D suffix SO-14 package.
Figure 1. Simplified Block Diagram
Semiconductor Components Industries, LLC, 2001
1
Publication Order Number:
April, 2001 – Rev. 2
UC3842B/D