1FEATURES
2• 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
• 5-Pin SOT-23 Package

APPLICATIONS
• Simple To Design, High Efficiency Step Down
Switching Regulators
• Set-Top Boxes
• Cable Modems
• Printers
• Digital Video Recorders
• Servers

DESCRIPTION
The LM1770 is an efficient synchronous buck
switching controller in a tiny SOT-23 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.