The LM2677 series of regulators are monolithic integrated circuits which provide all of
the active functions for a step-down (buck) switching regulator capable of driving up to 5-A loads
with excellent line and load regulation characteristics. High efficiency (>90%) is obtained
through the use of a low on-resistance DMOS power switch. The series consists of fixed output
voltages of 3.3-V, 5-V, and 12-V and an adjustable output version.
The SIMPLE SWITCHER® concept provides
for a complete design using a minimum number of external components. The switching clock frequency
can be provided by an internal fixed frequency oscillator
(260 kHz) or from an externally provided clock in the range of 280 kHz to 400 kHz, which
allows the use of physically smaller-sized components. A family of standard inductors for use with
the LM2677 are available from several manufacturers to greatly simplify the design process. The
external Sync clock provides direct and precise control of the output ripple frequency for
consistent filtering or frequency spectrum positioning.
The LM2677 series also has built-in thermal shutdown, current-limiting, and an ON/OFF
control input that can power down the regulator to a low
50-µA quiescent-current standby condition. The output voltage is ensured to a ±2%