UCC25705

UCC25705, UCC25706, UCC35705, UCC35706 HIGH-SPEED VOLTAGE MODE PULSE WIDTH MODULATOR D Greater Than 4-MHz Operation D Integrated Oscillator / Voltage Feed Forward Compensation D >4:1 Input Voltage Range D 25-ns Current Limit Delay D Programmable Maximum Duty Cycle Clamp D Optocoupler Interface D 50-μA Start-Up Current D 4.2-mA Operating Current @ 1 MHz D Smallest Footprint of the 8-pin MSOP Package Minimizes Board Area and Height SLUS473B -- NOVEMBER 1999 -- REVISED OCTOBER 2010 D, OR P PACKAGE (TOP VIEW) DGK PACKAGE (TOP VIEW) ILIM FB VFF DISCH 1 2 3 4 1 ILIM 2 FB 3 VFF 4 DISCH VDD OUT GND RC 8 7 6 5 8 VDD 7 OUT 6 GND 5 RC description The UCC35705 and UCC35706 devices are 8-pin voltage mode primary side controllers with fast over-current protection. These devices are used as core high-speed building blocks in high performance isolated and non-isolated power converters. UCC35705/UCC35706 devices feature a high speed oscillator with integrated feed-forward compensation for improved converter performance. A typical current sense to output delay time of 25 ns provides fast response to overload conditions. The IC also provides an accurate programmable maximum duty cycle clamp for increased protection which can also be disabled for the oscillator to run at maximum possible duty cycle. Two UVLO options are offered. The UCC35705 with lower turn-on voltage is intended for dc-to-dc converters while the higher turn-on voltage and the wider UVLO range of the UCC35706 is bette...