AN-D18

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
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