5.1-V Preference Regulator VIN 15 2 VREF 13 VC SYNC 10 UVLO Lockout F/F Q RT 9 Q CT 8 C/S- 3 COMP + - #3 + C/S+ 4 11 A OUT T OOO SR UC1846 Output Stage UC1847 Output Inverted Q S 0.5 V 14 B OUT + 0.5 mA NI 5 12 GND + E/A - INV 6 1 + - COMP 7 350 mV 6 kX Current Limit Adjust 16 Shutdown fig 2 The first current-mode PWM controller UC1846: the part has gone through several revisions at TI. The last revision was in July 2010. (Figure courtesy of TI.) FB 2 1.5 V Overcurrent SQ VCC OK COMP 1 CS 3 Leading Edge Blanking REF/2 R 4V Voltage Reference REF OK 0.5 V Logic Power Oscillator SQ SQ 7 VCC 6 OUT R PWM 13.5 V Latch R Full-Cycle Soft Start UCC # 801 UCC # 804 UCC # 805 Only TQ J=4 ma 1V 5 GND 8 4 REF RC UDG92009-3 fig 3 Unitrode's UCC3800 series was the first PWM controller family to implement the biCMOS process. (Figure courtesy of TI.) 12 IEEE PowEr ElEctronIcs MagazInE z September 2014