AN-D27

Supertex inc.
AN-D27
Application Note
DMOS Devices
For Telecommunications
Supertex DMOS transistors provide rugged and efficient solutions for various functions for telecommunication applications. Their combined features of high breakdown voltage,
low threshold voltage, low on-resistance, and low input capacitance are the basis for their design-ins. High breakdown
voltage is required to withstand ring voltages, AC line power
crossing, and the residuals of lightning surges. Low threshold voltage and low on-resistance ensure handset specifications are met under long loop conditions: far away from the
central office. Low input capacitance allows for fast switching speeds while minimizing bias current.
Supertex high voltage low threshold DMOS transistors are
available in N-channel and P-channel versions. Both enhancement-mode and depletion-mode are offered. Various
through hole and surface mount packages are available.
Electronic Hook Switch
Tip
TP2640N3
Ring
►►
►►
►►
►►
Telephone
Handset
Circuits
400V P-channel MOSFET
-2.0V maximum threshold voltage
Guaranteed 15Ω maximum on-resistance at VGS = -2.5V
Negligible susceptibility to transient turn-on
Doc.# DSAN-AN-D27
A040313
Supertex inc.
www.supertex.com
AN-D27
Pulse Dialing/Muting Function
Tip
Receiver
Microphone
TN2540N8
Ring
TN2540N8
Pulse
Dialer
IC
Mute
►► 400V N-channel MOSFET
►► 1.8V maximum threshold voltage
►► Maximum input capacitance of 125pF
Memory Power Supply
Tip
LND150N3
Ring
VDD
3.0MΩ
+
VZ
-
Memory
IC
IN4625
(5.1V)
►► 500V depletion mode MOSFET
►► 1.0µamp maximum quiescent current
►► 1.0mamp on demand output current
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)
Supertex inc.
©2013 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited.
Doc.# DSAN-AN-D27
A040313
2
1235 Bordeaux Drive, Sunnyvale, CA 94089
Tel: 408-222-8888
www.supertex.com
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