Part Datasheet Search > Voltage Regulators > ON Semiconductor > UC3845BVDR2 Datasheet PDF > UC3845BVDR2 Datasheet Pages 1/19
UC3845BVDR2 Datasheet - ON Semiconductor
| Manufacturer: | ON Semiconductor |
| Category: | Voltage Regulators |
| Case Package: | SOIC-14 |
| Description: | Current Mode PWM Controller 1A 500kHz 14Pin SOIC N T/R |
| Pictures: |
UC3845BVDR2Datasheet PDF
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© Semiconductor Components Industries, LLC, 2008
September, 2008 − Rev. 9
1 Publication Order Number:
UC3844B/D
UC3844B, UC3845B,
UC2844B, UC2845B
High Performance
Current Mode Controllers
The UC3844B, UC3845B 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 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 from 50% to 70%.
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 UCX844B has UVLO thresholds of 16 V (on) and 10 V (off),
ideally suited for off−line converters. The UCX845B is tailored for
lower voltage applications having UVLO thresholds of 8.5 V (on) and
7.6 V (off).
Features
• Trimmed Oscillator for Precise Frequency Control
• Oscillator Frequency Guaranteed at 250 kHz
• 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
• Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
• Pb−Free Packages are Available
Pin numbers in parenthesis are for the D suffix SOIC-14 package.
Output
V
C
R
T
/C
T
V
ref
V
CC
Undervoltage
Lockout
GND
5.0V
Reference
V
ref
Undervoltage
Lockout
Latching
PWM
Oscillator
Error
Amplifier
5(9)
3(5)
5(8)
6(10)
7(11)
Power
Ground
Current
Sense Input
1(1)
2(3)
4(7)
8(14)
Output/
Compensation
Voltage
Feedback
Input
V
CC
7(12)
R
R
Figure 1. Simplified Block Diagram
14
SOIC−14
D SUFFIX
CASE 751A
1
See detailed ordering and shipping information in the package
dimensions section on page 15 of this data sheet.
ORDERING INFORMATION
See general marking information in the device marking
section on page 16 of this data sheet.
DEVICE MARKING INFORMATION
1
8
PDIP−8
N SUFFIX
CASE 626
PIN CONNECTIONS
Compensation
NC
Voltage Feedback
NC
Current Sense
NC
R
T
/C
T
Compensation
Voltage Feedback
Current Sense
R
T
/C
T
V
ref
V
ref
NC
V
CC
V
C
Output
GND
Power Ground
V
CC
Output
GN
D
(Top View)
8
7
6
5
1
2
3
4
1
2
3
4
14
13
12
11
5
6
7
10
9
8
(Top View)
SOIC−8
D1 SUFFIX
CASE 751
1
8
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