LM25085A Datasheet | National Semiconductor

LM25085A 42V Constant On-Time PFET Buck Switching Controller .. March 16, 2009 42V Constant On-Time PFET Buck Switching Controller with 0.9V Reference General Description The LM25085A is a functional variant of the LM25085 COT PFET Buck Switching Controller. The functional differences of the LM25085A are: The feedback reference voltage is 0.9V, the forced off-time after current limit detection is longer, and the soft-start time is shorter (1.8 ms). The LM25085A is a high efficiency PFET switching regulator controller that can be used to quickly and easily develop a small, efficient buck regulator for a wide range of applications. This high voltage controller contains a PFET gate driver and a high voltage bias regulator which operates over a wide 4.5V to 42V input range. The constant on-time regulation principle requires no loop pensation, simplifies circuit implementation, and results in ultra-fast load transient response. The operating frequency remains nearly constant with line and load variations due to the inverse relationship between the input voltage and the on-time. The PFET architecture allows 100% duty cycle operation for a low dropout voltage. Either the RDS(ON) of the PFET or an external sense resistor can be used to sense current for over-current detection. Features - Wide 4.5V to 42V input voltage range - Adjustable current limit using RDS(ON) or a current sense - - - - - - - - - - resistor Programmable switching frequency to 1MHz No loop pensation required Ultra-Fast transient response Nearly constant operating frequency with line and load variations Adjustable output voltage from 0.9V Precision ±2% feedback reference Capable of 100% duty cycle operation Internal soft-start timer Integrated high voltage bias regulator Thermal shutdown Package - MSOP-8EP - MSOP-8 - LLP-8 (3 mm x 3 mm) Typical Application, Basic Step Down Controller © 2009 National Semiconductor Corporation .national. LM25...