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
UC3844, UC3845, UC2844, UC2845
MAXIMUM RATINGS
Rating Symbol Value Unit
Total Power Supply and Zener Current (I + I ) 30 mA
CC Z
Output Current, Source or Sink (Note 1) I 1.0 A
O
Output Energy (Capacitive Load per Cycle) W 5.0 J
Current Sense and Voltage Feedback Inputs V 0.3 to + 5.5 V
in
Error Amp Output Sink Current I 10 mA
O
Power Dissipation and Thermal Characteristics
D Suffix, Plastic Package, Case 751A
Maximum Power Dissipation @ T = 25C P 862 mW
A D
Thermal Resistance JunctiontoAir R 145 C/W
JA
N Suffix, Plastic Package, Case 626
Maximum Power Dissipation @ T = 25C P 1.25 W
A
D
Thermal Resistance JunctiontoAir R 100 C/W
JA
Operating Junction Temperature T + 150 C
J
Operating Ambient Temperature T C
A
UC3844, UC3845 0 to + 70
UC2844, UC2845 25 to + 85
Storage Temperature Range T 65 to + 150 C
stg
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 (V = 15 V, (Note 2), R = 10 k, C = 3.3 nF, T = T to T (Note 3), unless otherwise noted.)
CC T T A low high
UC284X UC384X
Characteristics Symbol Min Typ Max Min Typ Max Unit
REFERENCE SECTION
Reference Output Voltage (I = 1.0 mA, T = 25C) V 4.95 5.0 5.05 4.9 5.0 5.1 V
O J ref
Line Regulation (V = 12 V to 25 V) Reg 2.0 20 2.0 20 mV
CC line
Load Regulation (I = 1.0 mA to 20 mA) Reg 3.0 25 3.0 25 mV
O load
Temperature Stability T 0.2 0.2 mV/C
S
Total Output Variation over Line, Load, Temperature V 4.9 5.1 4.82 5.18 V
ref
Output Noise Voltage (f = 10 Hz to kHz, T = 25C) V 50 50 V
J n
Long Term Stability (T = 125C for 1000 Hours) S 5.0 5.0 mV
A
Output Short Circuit Current I 30 85 180 30 85 180 mA
SC
OSCILLATOR SECTION
Frequency f kHz
osc
47 52 57 47 52 57
T = 25C
J
46 60 46 60
T = T to T
A low high
Frequency Change with Voltage (V = 12 V to 25 V) f 0.2 1.0 0.2 1.0 %
CC osc/ V
Frequency Change with Temperature f 5.0 5.0 %
osc/ T
T = T to T
A low high
Oscillator Voltage Swing (PeaktoPeak) V 1.6 1.6 V
osc
Discharge Current (V = 2.0 V, T = 25C) I 10.8 10.8 mA
osc J dischg
ERROR AMPLIFIER SECTION
Voltage Feedback Input (V = 2.5 V) V 2.45 2.5 2.55 2.42 2.5 2.58 V
O FB
Input Bias Current (V = 2.7 V) I 0.1 1.0 0.1 2.0 A
FB IB
Open Loop Voltage Gain (V = 2.0 V to 4.0 V) A 65 90 65 90 dB
O VOL
2. Adjust V above the Startup threshold before setting to 15 V.
CC
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
T =0C for UC3844, UC3845 T = +70C for UC3844, UC3845
low high
25C for UC2844, UC2845 +85C for UC2844, UC2845