application
INFO
available
UC1825
UC2825
UC3825
High Speed PWM Controller
FEATURES
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Compatible with Voltage or Current Mode
Topologies
DESCRIPTION
The UC1825 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
Practical Operation Switching Frequencies
and logic circuitry while maximizing bandwidth and slew rate of the
to 1MHz
error amplifier. This controller is designed for use in either cur-
50ns Propagation Delay to Output
rent-mode or voltage mode systems with the capability for input volt-
age feed-forward.
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
Wide Bandwidth Error Amplifier
which will double as a maximum duty cycle clamp. The logic is fully
Fully Latched Logic with Double Pulse
latched to provide jitter free operation and prohibit multiple pulses at
Suppression
an output. An under-voltage lockout section with 800mV of hysteresis
assures low start up current. During under-voltage lockout, the out-
Pulse-by-Pulse Current Limiting
puts are high impedance.
Soft Start / Max. Duty Cycle Control
These devices feature totem pole outputs designed to source and
sink high peak currents from capacitive loads, such as the gate of a
Under-Voltage Lockout with Hysteresis
power MOSFET. The on state is designed as a high level.
Low Start Up Current (1.1mA)
BLOCK DIAGRAM
UDG-92030-2
SLUS235A - MARCH 1997 - REVISED MARCH 2004
TI [ TEXAS INSTRUMENTS ]
