¡El MIC38C4x are fixed-frequency, high performance, current-mode PWM controllers. Microchip’s BiCMOS devices are pin compatible with 384x bipolar devices, but feature several improvements. Undervoltage lockout circuitry allows the ‘42 and ‘44 versions to start up at 14.5V and operate down to 9V, and the ‘43 and ‘45 versions start at 8.4V with operation down to 7.6V. All versions operate up to 20V. When compared to bipolar 384x devices operating from a 15V supply, start-up current has been reduced to 50 μA typical and operating current has been reduced to 4.0 mA typical. Decreased output rise and fall times drive larger MOSFETs, and rail-to-rail output capability increases efficiency, especially at lower supply voltages. ¡El MIC38C4x also features a trimmed oscillator discharge current and bandgap reference. ¡El MIC38C4x denotes 8-pin plastic DIP, SOIC, and MSOP packages. MIC38C4x-1 denotes 14-pin plastic DIP and SOIC packages. 8-pin devices feature small size, while 14-pin devices separate the analog and power connections for improved performance and power dissipation. For fast rise and fall times and higher output drive, refer to the MIC38HC4x.