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UC3844 Datasheet(PDF) 1 Page - ON Semiconductor

Part No. UC3844
Description  HIGH PERFORMANCE CURRENT MODE CONTROLLERS
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Maker  ONSEMI [ON Semiconductor]
Homepage  http://www.onsemi.com
Logo ONSEMI - ON Semiconductor

UC3844 Datasheet(HTML) 1 Page - ON Semiconductor

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Device
Operating
Temperature Range
Package
UC3844, 45
UC2844, 45
HIGH PERFORMANCE
CURRENT MODE
CONTROLLERS
ORDERING INFORMATION
UC3844D
UC3845D
TA = 0° to +70°C
TA = – 25° to +85°C
SO–14
SO–14
PIN CONNECTIONS
Order this document by UC3844/D
D SUFFIX
PLASTIC PACKAGE
CASE 751A
(SO–14)
N SUFFIX
PLASTIC PACKAGE
CASE 626
1
8
1
14
(Top View)
Vref
(Top View)
Compensation
Voltage Feedback
Current Sense
RT/CT
Vref
VCC
Output
Gnd
1
2
3
45
6
7
8
Compensation
NC
Voltage Feedback
NC
Current Sense
NC
RT/CT
NC
VCC
VC
Output
Gnd
Power Ground
1
2
3
4
5
6
7
9
8
10
11
12
13
14
UC3844N
UC3845N
Plastic
Plastic
UC2844D
UC2845D
SO–14
SO–14
UC2844N
UC2845N
Plastic
Plastic
1
MOTOROLA ANALOG IC DEVICE DATA
High Performance
Current Mode Controllers
The UC3844, UC3845 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
an oscillator, 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,
a latch for single pulse metering, and a flip–flop which blanks the output off
every other oscillator cycle, allowing output deadtimes to be programmed for
50% to 70%.
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 UCX844 has UVLO thresholds of 16 V (on) and 10 V (off), ideally
suited for off–line converters. The UCX845 is tailored for lower voltage
applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).
Current Mode Operation to 500 kHz Output Switching Frequency
Output Deadtime Adjustable from 50% to 70%
Automatic Feed Forward Compensation
Latching PWM for Cycle–By–Cycle Current Limiting
Internally Trimmed Reference with Undervoltage Lockout
High Current Totem Pole Output
Input Undervoltage Lockout with Hysteresis
Low Startup and Operating Current
Direct Interface with Motorola SENSEFET Products
Simplified Block Diagram
5.0V
Reference
Flip
Flop
&
Latching
PWM
VCC
Undervoltage
Lockout
Oscillator
Error
Amplifier
7(12)
VC
7(11)
Output
6(10)
PWR GND
5(8)
3(5)
Current
Sense
Vref
8(14)
4(7)
2(3)
1(1)
Gnd
5(9)
RTCT
Voltage
Feedback
R
R
+
Vref
Undervoltage
Lockout
Output
Comp.
Pin numbers in parenthesis are for the D suffix SO–14 package.
VCC
© Motorola, Inc. 1996
Rev 1


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