LM1770

LM1770 Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation November 2005 LM1770 Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation General 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 compensation components, allowing minimal component 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 100kHz to 1000kHz. Features n n n n n n n n Input voltage range of 2.8V to 5.5V 0.8V reference voltage No compensation 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 20166201 © 2005 National Semiconductor Corporation DS201662 www.national.com LM1770 Connection Diagram Top View ...