A8499: High-Voltage Step-Down Regulator


DISCONTINUED: These parts are discontinued.  Samples are no longer available. For new customers or new applications, please contact Allegro. Date of status change: June 2, 2015.

Recommended Substitutions: For existing customer transition, and for new customers or new applications, refer to the A4447SLJTR-T.

The A8499 is a step-down regulator that will handle a wide input of operating voltage ranges. It is a fixed off-time current-mode-controlled buck regulator. The regulator requires an external clamping diode, inductor and filter capacitor. The off time is determined by an external resistor.

It will operate in both continuous and discontinuous modes. An internal blanking circuit will be used to filter out transients due to the reverse recovery of the external clamp diode. Typical blanking time is 200 nS.

The output voltage is adjustable from 1.2 V to 24 V based on a resistor divider and the 1.2 V 3 percent reference.

Applications include:

  • Applications with 8 to 50 V input voltage range needing buck regulator for 1.5 A output current
  • Consumer equipment power
  • Uninterruptible power supplies (lead acid battery charger)
  • Automotive: 9 to 16 V input, with higher voltage protection
  • 12 V lighter-powered applications (portable DVD, etc.)
  • Point of Sale (POS) applications
  • Industrial applications with 24 V or 36 V bus


Top Features

  • 8-50 V input range
  • Integrated DMOS switch
  • Flat efficiency curve across output current
  • 1.5 A output in standard SOIC-8 package
  • Low shutdown current
  • Low cost

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A8499SLJTR-T 8-lead SOIC -20°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 A8499 is supplied in a low-profile 8-lead SOIC with exposed pad (package LJ).

LJ SOIC with exposed pad 8 pin

Design Support Tools

Reference Design and PCB Gerber Files

Evaluation Board for A8499 is available upon request. Please contact your local representative.

Demo Board Documentation

Allegro MicroSystems, LLC provides Gerber files for reference only. Any material, information, or instructions are provided AS IS without warranty of any kind. It is the responsibility of the User(s) to optimize any Printed Circuit Board (PCB) layout, as well as the selection of any components, for the specific application of the User(s).