The IC limits peak voltage at its switching output to a level programmed by connecting an external Zener diode.
Supertex, Inc. has introduced HV9821, a clamped-mode, high-side buck converter IC for driving a low-voltage LED load at constant current programmable up to 50mA (or higher, as permitted by power dissipation, etc.). It is well suited for LED backlighting of push-buttons, switches and other automation control applications.
The IC limits peak voltage at its switching output to a level programmed by connecting an external Zener diode. This feature ensures a reasonable on-time of the switch, while minimizing the conduction power loss in HV9821. Power dissipation in the IC can be maintained below a chosen maximum level by selecting an adequate voltage clamp level VZ. HV9821 operates with fixed off-time, programmable externally with a resistor.
“HV9821 features programmable clamped-mode switching, which provides single LED operation from a high-voltage input with heat dissipation in the IC minimised,” states Alex Mednik, application engineering director at Supertex. “To accommodate that, HV9821 is packaged in a special 19-lead DFN, providing excellent thermal properties and high-voltage isolation.”
HV9821 is available in a lead(Pb)-free/RoHS compliant 19L (7×5) DFN package (HV9821K7-G). Samples are available from stock. Lead-time for production quantities is 4-6 weeks, ARO. Pricing is US$1.05, in 1K quantities.
