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What is UC3844D?

This electronic component, produced by the manufacturer "ON Semiconductor", performs the same function as "HIGH PERFORMANCE CURRENT MODE CONTROLLERS".


UC3844D Datasheet PDF - ON Semiconductor

Part Number UC3844D
Description HIGH PERFORMANCE CURRENT MODE CONTROLLERS
Manufacturers ON Semiconductor 
Logo ON Semiconductor Logo 


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UC3844, UC3845, UC2844,
UC2845
High Performance
Current Mode Controllers
The UC3844, UC3845 series are high performance fixed frequency
current mode controllers. They are specifically designed for OffLine
and DCtoDC 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, cyclebycycle
current limiting, a latch for single pulse metering, and a flipflop which
blanks the output off every other oscillator cycle, allowing output dead
times to be programmed for 50% to 70%.
These devices are available in an 8pin dualinline plastic package
as well as the 14pin plastic surface mount (SOIC14). The SOIC14
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 offline converters. The UCX845 is tailored for
lower voltage applications having UVLO thresholds of 8.5 V (on) and
7.6 V (off).
Features
www.DataSheet4U.com
Current Mode Operation to 500 kHz Output Switching Frequency
Output Deadtime Adjustable from 50% to 70%
Automatic Feed Forward Compensation
Latching PWM for CycleByCycle 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 ON Semiconductor SENSEFETt Products
PbFree Packages are Available
VCC 7(12)
Vref
8(14)
RTCT
4(7)
Voltage
Feedback
2(3)
1(1)
Output
Comp.
R
5.0V
Reference
VCC
Undervoltage
Lockout
R
Vref
Undervoltage
Lockout
Oscillator
+
Error
Amplifier
Flip
Flop
&
Latching
PWM
GND 5(9)
Pin numbers in parenthesis are for the D suffix SOIC14 package.
Figure 1. Simplified Block Diagram
VC
7(11)
Output
6(10)
PWR GND
5(8)
Current
Sense
3(5)
© Semiconductor Components Industries, LLC, 2006
July, 2006 Rev. 7
1
http://onsemi.com
8
1
14
1
8
1
PDIP8
N SUFFIX
CASE 626
SOIC14
D SUFFIX
CASE 751A
SOIC8
D1 SUFFIX
CASE 751A
PIN CONNECTIONS
Compensation 1
Voltage Feedback 2
Current Sense 3
RT/CT 4
8 Vref
7 VCC
6 Output
5 GND
(Top View)
Compensation 1
NC 2
Voltage Feedback 3
NC 4
Current Sense 5
NC 6
RT/CT 7
14 Vref
13 NC
12 VCC
11 VC
10 Output
9 GND
8 Power Ground
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 14 of this data sheet.
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page page 14 of this data sheet.
Publication Order Number:
UC3844/D

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UC3844D equivalent
UC3844, UC3845, UC2844, UC2845
0
−4.0
−8.0
−12
−16
−20
−24
0
VCC = 15 V
TA = 125°C
TA = −55°C
TA = 25°C
20 40 60 80 100
Iref, REFERENCE SOURCE CURRENT (mA)
Figure 8. Reference Voltage Change
versus Source Current
120
110
VCC = 15 V
RL 0.1 W
90
70
50
−55 −25
0
25 50 75 100 125
TA, AMBIENT TEMPERATURE (°C)
Figure 9. Reference Short Circuit Current
versus Temperature
VCC = 15 V
IO = 1.0 mA to 20 mA
TA = 25°C
VCC = 12 V to 25 V
TA = 25°C
2.0 ms/DIV
Figure 10. Reference Load Regulation
2.0 ms/DIV
Figure 11. Reference Line Regulation
0
VCC
Source Saturation
(Load to Ground)
VCC = 15 V
80 ms Pulsed Load
−1.0 TA = 25°C
120 Hz Rate
−2.0
TA = −55°C
3.0
TA = −55°C
2.0
TA = 25°C
1.0
0
0
Sink Saturation
(Load to VCC)
GN
D
200 400 600
IO, OUTPUT LOAD CURRENT (mA)
800
Figure 12. Output Saturation Voltage
versus Load Current
90%
10%
VCC = 15 V
CL = 1.0 nF
TA = 25°C
50 ns/DIV
Figure 13. Output Waveform
http://onsemi.com
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Part Details

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