UC3842A High Performance
Current Mode Controller
The UC3842A series of high performance
fixed frequency current mode controllers are
specifically designed for off鈥搇ine and dc鈥搕o鈥揹c
converter applications offering the designer a cost
effective solution with minimal external components.
This integrated circuit features a trimmed oscillator
for precise duty cycle control, 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鈥揵y鈥揷ycle current limiting,
programmable output deadtime, and a latch for single
pulse metering.
This device is available in an 8鈥損in dual鈥搃n鈥?/div>
line plastic package as well as the 14鈥損in plastic surface
mount (SO鈥?4). The SO鈥?4 package has separate
power and ground pins for the totem pole output
stage.
The UC3842A has UVLO thresholds of
16V(on) and 10V(off), ideally suited for off鈥搇ine
converters.
Trimmed Oscillator Discharge Current for Precise Duty
CD SUFFIX
Cycle Control
PLASTIC PACKAGE
Current Mode Operation to 500 kHz
8 DIP
Automatic Feed Forward Compensation
Latching PWM for Cycle鈥揃y鈥揅ycle Current Limiting
D8 SUFFIX
Internally Trimmed Reference with Undervoltage Lockout
PLASTIC PACKAGE
High Current Totem Pole Output
8 SOP
Undervoltage Lockout with Hysteresis
Low Startup and Operating Current
l
l
l
l
l
l
l
l
CS SUFFIX
PLASTIC PACKAGE
SOP-14
SIMPLIFIED BLOCK DIAGRAM
PIN CONNECTIONS
Pin numbers adjacent to terminals are for the D suffix 8-DIP package.
Pin numbers in parenthesis are for the S suffix SOP鈥?4 package.
NOTES:
1. Maximum Package power dissipation limits must be observed.
2. Adjust V
CC
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
T
low
= 0擄C, T
high
= +70擄C.
4. This parameter is measured at the latch trip point with V
FB
= 0V.
5. Comparator gain is defined as: A
V
鈭哣
Output Compensation
鈭哣
Current Sense Input
4-12
1
2
3
4
5
6
