UTC UC3842A / 3843A LINEAR INTEGRATED CIRCUIT
CURRENT MODE PWM CONTROL
CIRCUITS
DESCRIPTION
The UTC UC3842A/3843A provide the necessary functions
to implement off-line or DC to DC fixed frequency current
mode , controlled switching circuits with a minimal external
part count
SOP-8
FEATURES
*Low external part count.
*Low start up current
( Typical 0.12mA )
*Automatic feed forward compensation
*Pulse-by-Pulse current limiting
*Under-voltage lockout with hysteresis
*Double pulse Suppression
*High current totem pole output to drive MOSFET directly
*Internally trimmed band gap reference
*500kHz operation
DIP-8
BLOCK DIAGRAM
7
Vcc
Vref
8
Internal
Bias
1/2Vref
5V REF
S/R
5
GND
Vref
Good
Logic
1/3Vref
U.V.L.O
CURRENT
SENSE
COMPARATOR
R
PWM
LATCH
S
7
Vcc
VFB
COMP
2
1
ERROR
AMPLIFIER
1V
6
OUTPUT
CURRENT SENSE
3
RT/CT
4
OSCILLATOR
5
GND
ABSOLUTE MAXIMUM RATINGS
(Ta=25°C)
PARAMETER
Supply Voltage(Low Impedance Source)
Supply Voltage(Icc<30mA)
Output Current ( Peak )
Output Energy(capacity Load)
Analog Inputs(pin 2,3)
Error Amplifier Output Sink Current
Power Dissipation
Lead Temperature( Soldering 10 Sec )
SYMBOL
V
CC
Vcc
Io
V
I(ANA)
I
SINK(EA)
PD DIP-8
SOP-8
Tlead
VALUE
30
Self Limiting
+-1
5
-0.3 ~ +6.3
10
at T
amb
<=25°C 1.0
at T
amb
<=25°C 0.5
300
UNIT
V
V
A
µJ
V
mA
W
W
°C
UTC
UNISONIC TECHNOLOGIES CO., LTD.
1
QW-R103-002,A
UTC-IC [ UNISONIC TECHNOLOGIES ]
