UC3842B, UC3843B,
UC2842B, UC2843B,
NCV3843BV
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
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 (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.
SOIC−14
D SUFFIX
CASE 751A
14
1
SOIC−8
D1 SUFFIX
8
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).
CASE 751
1
PIN CONNECTIONS
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
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
ref
NC
Voltage Feedback
NC
NC
• Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
• Pb−Free Packages are Available
V
V
CC
C
Current Sense
NC
Output
GND
V
7(12)
CC
8
R /C
T
Power Ground
T
V
V
CC
ref
5.0V
Reference
(Top View)
Undervoltage
Lockout
8(14)
R
R
V
ref
V
C
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 17 of this data sheet.
Undervoltage
Lockout
7(11)
R /C
T
Output
T
Oscillator
6(10)
4(7)
Latching
PWM
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 19 of this data sheet.
Power
Ground
5(8)
Voltage
Feedback
Input
+
−
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 SOIC−14 package.
Figure 1. Simplified Block Diagram
©
Semiconductor Components Industries, LLC, 2007
1
Publication Order Number:
February, 2007 − Rev. 9
UC3842B/D