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