UCC3807-2

Features:

·User Programmable Maximum PWM Duty Cycle
·100  A Startup Current
·Operation to 1MHz
·Internal Full Cycle Soft Start
·Internal Leading Edge Blanking of Current Sense Signal
·1A Totem Pole Output


Application

The circuit shown in Fig. 2 illustrates the use of the UCC3807 in a typical off-line application. The 100W, 200kHz, universal input forward converter produces a regulated 12VDC at 8 Amps. The programmable maximum duty cycle of the UCC3807 allows operation down to 80VRMS and up to 265VRMS with a simple RCD clamp to limit the MOSFET voltage and provide core reset. In this application the maximum duty cycle is set to about 65%. Another feature of the design is the use of a flyback winding on the output filter choke for both bootstrapping and voltage regulation. This method of loop closure eliminates the optocoupler and secondary side regulator, common to most off-line designs, while providing good line and load regulation.


Pinout




Specifications

Supply Voltage (I_DD 10mA). . . . . . . . . . . . . . . . . . . . . . . 13.5V
Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30mA
OUT Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1A
Analog Inputs (FB, CS) . . . . . . . . . . . . . 0.3V to (VDD + 0.3V)
Power Dissipation at T_A +25 (N or J packages) . . . . . . . . 1W
Power Dissipation at T_A +25 (D package) . . . . . . . . . . 0.65W
Storage Temperature . . . . . . . . . . . . . . . . . . . 65 to +150
Junction Temperature. . . . . . . . . . . . . . . . . . . 65 to +150
Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300
All currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages.


Description

The UCC3807 family of high speed, low power integrated circuits contains all of the control and drive circuitry required for off-line and DC-to-DC fixed frequency current mode switching power supplies with minimal external parts count.

These devices UCC3807 are similar to the UCC3800 family, but with the added feature of a user programmable maximum duty cycle. Oscillator frequency and maximum duty cycle are programmed with two resistors and a capacitor. The UCC3807 family also features internal full cycle soft start and internal leading edge blanking of the current sense input.

The UCC3807 family offers a variety of package options, temperature range options, and choice of critical voltage levels. The family has UVLO thresholds and hysteresis levels for off-line and battery powered systems. Thresholds are shown in the table below.

Part Number	Turn-on Threshold	Turn-off Threshold	Packages
UCCx807-1	7.2V	6.9V	J
UCCx807-2	12.5V	8.3V	N, D
UCCx807-3	4.3V	4.1V	N, D, PW