UC1824
UC2824
UC3824
High Speed PWM Controller
FEATURES
DESCRIPTION
•
Complementary Outputs
The UC1824 family of PWM control ICs is optimized for high fre-
quency switched mode power supply applications. Particular care
was given to minimizing propagation delays through the comparators
and logic circuitry while maximizing bandwidth and slew rate of the
error amplifier. This controller is designed for use in either current-
mode or voltage mode systems with the capability for input voltage
feed-forward.
•
Practical Operation Switching Frequencies
to 1MHz
•
•
50ns Propagation Delay to Output
High Current Dual Totem Pole Outputs
(1.5A Peak)
Protection circuitry includes a current limit comparator with a 1V
threshold, a TTL compatible shutdown port, and a soft start pin which
will double as a maximum duty cycle clamp. The logic is fully latched
to provide jitter free operation and prohibit multiple pulses at an out-
put. An under-voltage lockout section with 800mV of hysteresis as-
sures low start up current. During under-voltage lockout, the outputs
are high impedance.
•
•
Wide Bandwidth Error Amplifier
Fully Latched Logic with Double Pulse
Suppression
•
•
•
•
•
Pulse-by-Pulse Current Limiting
Soft Start / Max. Duty Cycle Control
Under-Voltage Lockout with Hysteresis
Low Start Up Current (1.1 mA)
These devices feature totem pole outputs designed to source and
sink high peak currents from capacitive loads, such as the gate of a
power MOSFET. The on state is designed as a high level.
±
Trimmed Bandgap Reference (5.1V 1%)
BLOCK DIAGRAM
UDG-92034-1
3/97