A8670: Fixed Frequency, 2 A Synchronous Buck Regulator With Fault Warnings and Power OK


These parts are discontinued.  Samples are no longer available. For new customers or new applications, please contact Allegro. Date of status change: December 2, 2013.

The A8670 is a synchronous buck converter capable of delivering up to 2 A. The A8670 utilizes valley current mode control, allowing very short on-times to be achieved. This makes it ideal for applications that require very low output voltages relative to the input voltage, combined with high switching frequencies. Valley current mode control inherently provides improved transient response over traditional switcher schemes, through the use of a voltage feed forward loop and frequency modulation during large signal load changes.

The A8670 includes a comprehensive set of diagnostic flags, allowing the host platform to react to a myriad of different conditions. A fault output indicates when either the temperature is becoming unusually high, or a single point failure has occurred; for example, the switching node (LX) shorted to ground, or the timing resistor going open-circuit. A Power OK (POK) output is also provided after a fixed delay, to indicate when the output voltage is within regulation. The A8670 is a rugged solution, offering protection against input undervoltages, output overvoltages, overtemperature, output overloads, short circuits, current source overloads and any single point failures.

The A8670 is extremely flexible, with external loop compensation, on-time select (switching frequency), programmable soft-start, and current limit. The selectable pulse-by-pulse current limit avoids the requirement to oversize the inductor to cope with large fault currents. The switching frequency can be chosen, between 200 kHz and 1 MHz.

Applications include:

  • Servers
  • Point of load supplies
  • Network and telecom
  • Storage

The device package (ES) is a 20-contact, 4 mm × 4 mm, 0.75 mm nominal overall height QFN with exposed thermal pad. The package is lead (Pb) free, with 100% matte tin leadframe plating.

Top Features

  • High efficiency integrated FETs optimized for lower duty cycle voltage conversion: 180 mΩ high side, 40 mΩ low side
  • Adjustable output voltage, down to 0.6 V
  • Extremely short minimum controllable on-time; example: allows 12 V conversion to 0.6 V at >1 MHz
  • Reference accuracy of ±1% throughout temperature range
  • FAULT and Power OK pins for operating and protection modes:
    • Normal operation
    • VFB low or high
    • Overcurrent
    • UVLO
    • Thermal warning prior to TSD
    • Thermal shutdown (TSD)
    • LX–GND short protection
    • Timing resistor open circuit protection
  • Adjustable switching frequency and current limit to optimize efficiency and external component sizing
  • Externally adjustable soft-start time
  • Shutdown supply current only 1 µA
  • Pre-bias start-up capability
  • Input voltage range: from 7 to 16 V

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A8670EESTR-T 20-lead QFN -40°C to 85°C Yes View Data Discontinued Contact your
local sales rep
Distributor Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.


The device package (ES) is a 20-contact, 4 mm × 4 mm, 0.75 mm nominal overall height QFN with exposed thermal pad. The package is lead (Pb) free, with 100% matte tin leadframe plating.

ES QFN 20-lead