Supertex inc. AN-D18 High Voltage Regulators and Linear Circuits Using DN25 Depletion-mode MOSFETs can be used either as “normally closed” switches or current sources. This note shows circuits, utilizing depletion mode devices, that will benefit many applications. The main performance features of the circuits Application Note and examples of applications are listed. For more applications information on depletion mode MOSFETs, refer to other LND1 and DN25 series application notes. High Voltage Protected Regulator Current Surge Protection DN2540N8 R DN2540N8 VIN 400V + - CKT VREG C VOUT = 3.0V C RX5RA30AX ►► Current limit up to 150mA ►► Back-to-back pair for bi-directional limiting Inrush limiting for lamps/motors/capacitive loads, instrumentation, telecommunication ►► ±400V transient protection ►► +5.0 to +400V operation ►► Typically 800nA quiescent current Telecommunication, automotive, fax machines, off-line control circuits SMPS Start-Up Solid State Relay P - V P V + R + VZ DN2540N3 0 DN2540N3 VIN R DN2540N3 5V + - DC - DC Converter 12V - ►► Normally on ►► ±400V blocking ►► Low CIN for fast switching ►► Off-line capability ►► Switchable to save power ►► Improves efficiency Telecommunication, instrumentation, fax machines, modems, data line diagnostics Switchmode power supply Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives an adequate “product liability indemnification insurance agreement.” Supertex inc. does not assume responsibility for use of devices described, and limits its liability to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http//www.supertex.com) ©2013 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited. Doc.# DSAN-AN-D18 A040313 Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com