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.