1 Features
1• Input Voltage Range of 2.8 V to 5.5 V
• 0.8-V Reference Voltage
• Precision Enable
• No Compensation Required
• Constant Frequency Across Input Range
• Low Quiescent Current of 400 μA
• Internal Soft-Start
• Short Circuit Protection
• 6-Pin WSON Package and 8-Pin VSSOP Package

2 Applications
• Simple-to-Design, High-Efficiency, Step-Down
Switching Regulators
• FPGAs, DSPs, and ASIC Power Supplies
• Set-Top Boxes
• Cable Modems
• Printers
• Digital Video Recorders
• Servers
• Graphic Cards

3 Description
The LM1771 device is an efficient synchronous buck
switching controller with a precision enable requiring no external compensation. The constant ON-time
control scheme provides a simple design free of
compensation components, allowing minimal
component count and board space. The precision enable pin allows flexibility in sequencing multiple
rails and setting UVLO. The LM1771 also
incorporates a unique input feedforward to maintain a
constant frequency independent of the input voltage.
The LM1771 is optimized for a low-voltage input range of 2.8 V to 5.5 V and can provide an adjustable
output as low as 0.8 V. Driving an external high-side
PFET and low-side NFET, it can provide efficiencies
as high as 95%.
Three versions of the LM1771 are available
depending on the switching frequency desired for the
application. Nominal switching frequencies are in the
range of 100 kHz to 1000 kHz.