UC3843A High Performance
Current Mode Controller
The UC3843A series of high performance
fixed frequency current mode controllers are
specifically designed for off–line and dc–to–dc
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–by–cycle current limiting,
programmable output deadtime, and a latch for single
pulse metering.
This device is available in an 8–pin dual–in–
line plastic package as well as the 14–pin plastic sur-
face mount (SO–14). The SO–14 package has sepa-
rate power and ground pins for the totem pole output
stage.
The UCX843A is tailored for lower voltage
applications having UVLO thresholds of 8.5 V (on)
and 7.6 V (off).
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–By–Cycle 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–14 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°C, T
high
= +70°C.
4. This parameter is measured at the latch trip point with V
FB
= 0V.
5. Comparator gain is defined as: A
V
∆V
Output Compensation
∆V
Current Sense Input
4-18
FCI [ FIRST COMPONENTS INTERNATIONAL ]
