UC1825_13 Datasheet, PDF (1/19 Pages) Texas Instruments – High Speed PWM Controller

High Speed PWM Controller
application
INFO
available
UC1825
UC2825
UC3825
FEATURES
• Compatible with Voltage or Current Mode
Topologies
• Practical Operation Switching Frequencies
to 1MHz
• 50ns Propagation Delay to Output
• High Current Dual Totem Pole Outputs
(1.5A Peak)
• 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 (1.1mA)
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
and logic circuitry while maximizing bandwidth and slew rate of the
error amplifier. This controller is designed for use in either cur-
rent-mode or voltage mode systems with the capability for input volt-
age feed-forward.
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 output. An under-voltage lockout section with 800mV of hysteresis
assures low start up current. During under-voltage lockout, the out-
puts are high impedance.
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.
BLOCK DIAGRAM
SLUS235A - MARCH 1997 - REVISED MARCH 2004
UDG-92030-2