UC2825DWTR High Speed PWM Controller Circuit Board Chips integrated circuit components
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Detailed Product Description
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UC2825DWTR High Speed PWM Controller FEATURES (1)Compatible with Voltage or Current Mode Topologies (2)50ns Propagation Delay to Output
(3)Practical Operation Switching Frequencies to 1MHz (4)High Current Dual Totem Pole Outputs (1.5A Peak)
(5)Wide Bandwidth Error Amplifier (6)Fully Latched Logic with Double Pulse Suppression
(7)Pulse-by-Pulse Current Limiting (8)Soft Start / Max. Duty Cycle Control
(9)Under-Voltage Lockout with Hysteresis (10)Low Start Up Current (1.1mA) DESCRIPTION The UC1825 family of PWM control ICs is optimized for high
frequency 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. 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. Printed Circuit Board Layout Considerations High speed circuits demand careful attention to layout and
component placement. To assure proper performance of the UC1825
follow these rules: 1) Use a ground plane. 2) Damp or clamp
parasitic inductive kick energy from the gate of driven
MOSFETs. Do not allow the out-put pins to ring below ground. A
series gate resistor or a shunt 1 Amp Schottky diode at the
output pin will serve.
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