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  ON Semiconductor Electronic Components Datasheet  

UC2844 Datasheet

(UC2844 / UC2845) High Performance Current Mode Controllers

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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
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


  ON Semiconductor Electronic Components Datasheet  

UC2844 Datasheet

(UC2844 / UC2845) High Performance Current Mode Controllers

No Preview Available !

UC3844, UC3845, UC2844, UC2845
MAXIMUM RATINGS
Rating
Symbol
Value
Unit
Total Power Supply and Zener Current
Output Current, Source or Sink (Note 1)
Output Energy (Capacitive Load per Cycle)
(ICC + IZ) 30 mA
IO 1.0 A
W 5.0 mJ
Current Sense and Voltage Feedback Inputs
Error Amp Output Sink Current
Power Dissipation and Thermal Characteristics
D Suffix, Plastic Package, Case 751A
Maximum Power Dissipation @ TA = 25°C
Thermal Resistance JunctiontoAir
N Suffix, Plastic Package, Case 626
Maximum Power Dissipation @ TA = 25°C
Thermal Resistance JunctiontoAir
Operating Junction Temperature
Operating Ambient Temperature
UC3844, UC3845
UC2844, UC2845
Vin
IO
PD
RqJA
PD
RqJA
TJ
TA
0.3 to + 5.5
10
862
145
1.25
100
+ 150
0 to + 70
25 to + 85
V
mA
mW
°C/W
W
°C/W
°C
°C
Storage Temperature Range
Tstg
65 to + 150
°C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. Maximum Package power dissipation limits must be observed.
ELECTRICAL CHARACTERISTICS (VCC = 15 V, (Note 2), RT = 10 k, CT = 3.3 nF, TA = Tlow to Thigh (Note 3), unless otherwise noted.)
UC284X
UC384X
Characteristics
Symbol Min Typ Max Min Typ Max Unit
REFERENCE SECTION
Reference Output Voltage (IO = 1.0 mA, TJ = 25°C)
Vref 4.95 5.0 5.05 4.9 5.0 5.1
Line Regulation (VCC = 12 V to 25 V)
Regline
2.0 20
2.0 20
Load Regulation (IO = 1.0 mA to 20 mA)
Regload
3.0 25
3.0 25
Temperature Stability
TS
0.2
0.2
Total Output Variation over Line, Load, Temperature Vref 4.9 5.1 4.82 5.18
Output Noise Voltage (f = 10 Hz to kHz, TJ = 25°C)
Vn
50
50
Long Term Stability (TA = 125°C for 1000 Hours)
S
5.0
5.0
Output Short Circuit Current
ISC 30 85 180 30 85 180
OSCILLATOR SECTION
Frequency
TJ = 25°C
TA = Tlow to Thigh
fosc 47 52 57 47 52 57
46 60 46 60
Frequency Change with Voltage (VCC = 12 V to 25 V) Dfosc/DV
0.2 1.0
0.2 1.0
Frequency Change with Temperature
TA = Tlow to Thigh
Dfosc/DT
5.0
5.0
Oscillator Voltage Swing (PeaktoPeak)
Vosc
1.6
1.6
Discharge Current (Vosc = 2.0 V, TJ = 25°C)
Idischg
10.8
10.8
ERROR AMPLIFIER SECTION
Voltage Feedback Input (VO = 2.5 V)
VFB 2.45 2.5 2.55 2.42 2.5 2.58
Input Bias Current (VFB = 2.7 V)
IIB − −0.1 1.0 − −0.1 2.0
Open Loop Voltage Gain (VO = 2.0 V to 4.0 V)
AVOL 65 90 65 90
2. Adjust VCC above the Startup threshold before setting to 15 V.
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
Tlow = 0°C for UC3844, UC3845
25°C for UC2844, UC2845
Thigh = +70°C for UC3844, UC3845
+85°C for UC2844, UC2845
V
mV
mV
mV/°C
V
mV
mV
mA
kHz
%
%
V
mA
V
mA
dB
http://onsemi.com
2


Part Number UC2844
Description (UC2844 / UC2845) High Performance Current Mode Controllers
Maker ON Semiconductor
Total Page 16 Pages
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