UC2844B Просмотр технического описания (PDF) - Motorola => Freescale
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UC2844B Datasheet PDF : 16 Pages
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Order this document by UC3844B/D
UC3844B, 45B
UC2844B, 45B
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–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
from 50% to 70%.
These devices are available in an 8–pin dual–in–line and surface mount
(SO–8) 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 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).
• 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
Simplified Block Diagram
VCC 7(12)
HIGH PERFORMANCE
CURRENT MODE
CONTROLLERS
N SUFFIX
PLASTIC PACKAGE
CASE 626
D1 SUFFIX
PLASTIC PACKAGE
CASE 751
(SO–8)
8
1
8
1
D SUFFIX
PLASTIC PACKAGE
CASE 751A
(SO–14)
14
1
PIN CONNECTIONS
Compensation 1
Voltage Feedback 2
Current Sense 3
8 Vref
7 VCC
6 Output
RT/CT 4
5 Gnd
(Top View)
Compensation 1
NC 2
14 Vref
13 NC
Voltage Feedback 3
NC 4
Current Sense 5
12 VCC
11 VC
10 Output
NC 6
RT/CT 7
9 Gnd
8 Power Ground
(Top View)
Vref
8(14)
5.0V
Reference
R
Vref
R
Undervoltage
Lockout
VCC
Undervoltage
Lockout
RT/CT
4(7)
Voltage
Feedback
Input
2(3)
Output/
Compensation
1(1)
Oscillator
Error
Amplifier
Latching
PWM
Gnd 5(9)
Pin numbers in parenthesis are for the D suffix SO–14 package.
MOTOROLA ANALOG IC DEVICE DATA
VC
7(11)
Output
6(10)
Power
Ground
5(8)
Current
Sense Input
3(5)
ORDERING INFORMATION
Device
Operating
Temperature Range
Package
UC384XBD
SO–14
UC384XBD1
UC384XBN
TA = 0° to + 70°C
SO–8
Plastic
UC284XBD
UC284XBD1
TA = – 25° to + 85°C
SO–14
SO–8
UC284XBN
Plastic
UC384XBVD
SO–14
UC384XBVD1 TA = – 40° to +105°C SO–8
UC384XBVN
Plastic
X indicates either a 4 or 5 to define specific device
part numbers.
© Motorola, Inc. 1996
Rev 1
1
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