LM1770 Datasheet | National Semiconductor

Description The LM1770 is an efficient synchronous buck switching controller in a tiny SOT23 package. The constant on-time control scheme provides a simple design free of pensation ponents, allowing minimal ponent count and board space. It also incorporates a unique input feed-forward to maintain a constant frequency independent of the input voltage. The LM1770 is optimized for a low voltage input range of 2.8V to 5.5V and can provide an adjustable output as low as 0.8V. Driving an external high side PFET and low side NFET it can provide efficiencies as high as 95%. Three versions of the LM1770 are available depending on the switching frequency desired for the application. Nominal switching frequencies are in the range of 100k Hz to 1000k Hz. Features n n n n n n n n Input voltage range of 2.8V to 5.5V 0.8V reference voltage No pensation required Constant frequency across input range Low quiescent current of 400µA Internal soft-start Short circuit protection Tiny SOT-23 package Applications n Simple To Design, High Efficiency Step Down Switching Regulators n Set-Top Boxes n Cable Modems n Printers n Digital Video Recorders n Servers Typical Application Circuit © 2005 National Semiconductor Corporation DS201662 .national. Connection Diagram Top View SOT23-5 Package NS Package Number MA05B Ordering Information Order Number LM1770SMF LM1770SMFX LM1770TMF LM1770TMFX LM1770UMF LM1770UMFX Package Type SOT23-5 SOT23-5 SOT23-5 SOT23-5 SOT23-5 SOT23-5 NSC Package Drawing MF05A MF05A MF05A MF05A MF05A MF05A On-time 500ns 500ns 1000ns 1000ns 2000ns 2000ns Supplied As 1000 units Tape and Reel 3000 units Tape and Reel 1000 units Tape and Reel 3000 units Tape and Reel 1000 units Tape and Reel 3000 units Tape and Reel Pin Descriptions Pin # 1 2 3 4 5 Name VIN GND LG HG FB Function Input supply Ground NFET Gate Drive PFET Gate Drive Feedback Pin .national. Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are...