Analog Devices Expands Range of Constant On-Time, Synchronous Buck Controllers

Analog Devices 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).

ADP1870 and ADP1871 Synchronous Buck Regulators -- Features and Benefits

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. Other features and benefits include:

* Constant on-time architecture for improved transient response
* Valley-detect current sense for improved noise immunity - no additional current resistor required
* Power saving mode (ADP1871 only) for improved efficiency at light load
* 0.6-V reference voltage with ±1.0 percent accuracy allows devices to be used in low-voltage, high-accuracy, point-of-load applications
* Precision-enable ensures precise turn-on with internal soft-start

The introduction of the ADP1870 and ADP1871 devices marks ADI’s continued expansion of the switching controller and regulator product lines following recent announcements of the ADP1872/3 constant on-time, synchronous buck controllers and the ADP1877 fixed frequency, dual buck controller.