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−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
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 (SOIC−8) plastic package as well as the 14−pin plastic surface
mount (SOIC−14). The SOIC−14 package has separate power and
ground pins for the totem pole output stage.
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).
1
SOIC−14
D SUFFIX
CASE 751A
14
1
SOIC−8
D1 SUFFIX
CASE 751
8
1
Features
• 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
V
V
ref
CC
Output
GND
R /C
T
T
(Top View)
Compensation
1
2
3
4
5
6
7
14
13
12
11
10
9
V
• Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
ref
NC
Voltage Feedback
NC
NC
V
V
CC
• This is a Pb−Free and Halide−Free Device
C
V
CC
7(12)
Current Sense
NC
Output
V
V
GND
CC
ref
5.0V
Reference
Undervoltage
Lockout
8
R /C
T
Power Ground
T
8(14)
R
R
(Top View)
V
ref
V
C
Undervoltage
Lockout
7(11)
ORDERING INFORMATION
R /C
T
Output
T
Oscillator
See detailed ordering and shipping information in the package
dimensions section on page 17 of this data sheet.
6(10)
4(7)
Latching
PWM
Power
Ground
5(8)
Voltage
Feedback
Input
2(3)
Output
Compensation
+
-
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 19 of this data sheet.
Error
Amplifier
Current
Sense
Input
3(5)
1(1)
GND 5(9)
Pin numbers in parenthesis are for the D suffix SOIC−14 package.
Figure 1. Simplified Block Diagram
© Semiconductor Components Industries, LLC, 2013
1
Publication Order Number:
September, 2013 − Rev. 17
UC3842B/D