UC384XA-BW Current Mode PWM Controller
(UC3842A-BW/43A-BW/44A-BW/45A-BW)
DESCRIPTION
PIN
CONNECTION
The UC3842A-BW/43A-BW/44A-BW/45A-BW are fixed frequency current mode PWM
controller. They are specially designed for OFF−Line and DC to DC converter applications
with a minimal external components. Internally implemented circuits include a trimmed
oscillator for precise duty cycle control, a temperature compensated reference, high gain
error amplifier, current sensing comparator, and a high current totempole output ideally
suited for driving a power MOSFET. Protection circuitry includes built undervoltage lockout
and current limiting.
The UC3842A-BW and UC3844A-BW have UVLO thresholds of 16 V (on) and 10 V (off). The
corresponding thresholds for the UC3843A-BW/45A-BW are 8.4V (on) and
7.6V (off).
The UC3842A-BW and UC3843A-BW can operate within 100% duty cycle. The UC3844A-BW
and UC3845A-BW can operate within 50% duty cycle.
The UC384XA-BW has Start-Up Current 0.17mA (typ).
The UC384XA-BW are revised UC384XAM and differ by higher Unity Gain bandwidth of Error Amplifier.
FEATURES
•
•
•
•
Low Start-Up and Operating Current
High Current Totem Pole Output
Undervoltage Lockout With Hysteresis
Operating Frequency Up To 500KHz
BLOCK DIAGRAM
(toggle flip flop used only in UC3844, UC3845)
Absolute Maximum Ratings
Characteristic
Symbol
Value
Unit
Supply Voltage (low impedance
source)
VCC
30
V
Output Current
IO
VI
A
V
±1
−0.3 to 5.5
10
Input Voltage (Analog Inputs pins 2,3)
Error Amp Output Sink Current
Power Dissipation (TA=250C)
Storage Temperature Range
Lead Temperature (soldering 5 sec.)
ISINK (E.A)
PO
mA
W
oC
oC
1
Tstg
TL
-65 to150
260
1