Constant On-Time, Synchronous Buck Controllers

Analog Devices, Inc. (ADI) introduced two current-mode, synchronous buck controllers that support input-power voltages ranging from 2.95 V to 20 V. The ADP1870 and ADP1871 synchronous buck controllers provide superior transient response through the use of a constant on-time, current-mode control system. The devices are suited to intermediate rail or point-of-load generation in consumer, industrial and instrumentation, and telecommunications and networking applications.

The new buck converters also offer enhanced performance at low duty cycles by using a valley current-mode control architecture. The ADP1870 and ADP1871 are available in three frequency options - 300 kHz, 600 kHz, and 1 MHz. Additionally, the ADP1871 offers a power-saving mode capable of pulse-skipping to maintain output regulation while improving system efficiency at light loads. Low-voltage biasing is supplied through a 5-V internal LDO (low-dropout oscillator). Both regulators feature an internally-fixed soft-start period to limit input in-rush current from the input supply during startup and to provide reverse current protection during soft-start for a pre-charged output.