LM3485 Datasheet | National Semiconductor

Description The LM3485 is a high efficiency PFET switching regulator controller that a system designer can use to quickly and easily develop a small, low cost, switching buck regulator for a wide range of applications. The use of a hysteretic control scheme provides for simple design without any control loop stability concerns using a wide variety of external ponents. The PFET architecture also allows for low ponent count as well as ultra-low dropout operation. Another benefit is high efficiency operation at light loads without an increase in output ripple. Current limit protection circuit is provided by measuring the voltage across the PFET’s RDSON thus eliminating a costly sense resistor. The current limit can be adjusted allowing for designs at various output currents and costs. n n n n n n n n 4.5V to 35V wide input range 1.242V to VIN adjustable output range High Efficiency 93% ± 1.3% ( ± 2% over temp) internal reference 100% duty cycle Maximum operating frequency > 1MHz Current limit protection MSOP-8 Applications n n n n n n n n Set-Top Box DSL/Cable Modem PC/IA Auto PC TFT Monitor Battery Powered Portable Applications Distributed Power Systems Always On Power Features n Easy to use control methodology n No control loop pensation required Typical Application Circuit © 2002 National Semiconductor Corporation DS200346 .national. Connection Diagram Top View 8 Lead Plastic MSOP-8 NS package Number MUA08A Package Marking and Ordering Information Order Number LM3485MM LM3485MMX Package Type MSOP-8 MSOP-8 Package Marking S29B S29B Supplied As: 1000 units on Tape and Reel 3500 units on Tape and Reel Pin Description Pin Name ISENSE GND NC FB ADJ Pin Number 1 2 3 4 5 Description The current sense input pin. This pin should be connected to Drain node of the external PFET. Signal ground. No connection. The feedback input. Connect the FB to a resistor voltage divider between the output and GND for an adjustable output voltage....