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.
