circuit function www.diodes.com diodes incorporated has extended its family of mosfets tailored for voip communication equipment. the ZXMN20B28K and zxmn15a27k are avalanche rugged and designed for driving transformers in the dc-dc converter stage of subscriber line interface circuits (slic). these mosfets combined with a transformer allow a wide range of battery voltage (v bat ) to be efficiently converted in the slic. this eliminates high voltage external power supplies that are bulky and expensive. slics are the gateway for voip applications in the exchange and can be used for interfacing with a range of different end equipment including cable (emta), dsl modems (iad) and analog terminal adapters. as well as private branch exchanges including ip-pbx. voip enables a lower total cost of ownership whilst providing more services to the end-user. issue number | 001 21 october 2009 new product announcement mosfets optimised for voice over internet protocol (voip) for generating the v bat required for driving the ring and tip linefeed output of slics, an on-board dc-dc converter using mosfet-transformer is the most suitable. increased efficiency the mosfet and transformer dc-dc conversion has a greater power efficiency than the equivalent solution using a bipolar transistor (bjt) and inductor. typically the efficiency can be increased from 67% to 80%. low dc supply voltage (v dc ) the mosfet and transformer is the preferred solution for slics with low v dc . the diodes advantage the ZXMN20B28K and zxmn15a27k are n-channel mosfets designed to meet the stringent circuit requirements in the dc-dc conversion stage of slics. high breakdown voltage (v dss ) and pulse current (i dm ) with 200v and 150v v dss , then v bat exceeding 150v can be driven into multiple subscriber lines with lengths beyond 6km. also, with high i dm handling capabilities, the mosfets can drive the transformer to deliver the required ring and tip currents. avalanche rugged both mosfets have been designed to withstand the high pulse avalanche energy that will be induced by the transformer during switching transition. low gate charge (q g ) and input capacitance (c iss ) low q g and c iss means that both mosfets can be driven with minimal or no buffering. this simplifies the slic design and reduces component count and cost. the ZXMN20B28K is also capable of being driven at low logic level voltages. aec-q101, green and rohs compliant the ZXMN20B28K and zxmn15a27k are qualified to aec-q101 standard, are rohs compliant and contain no halogens or antimony compounds. ZXMN20B28K zxmn15a27k
www.diodes.com diodes mosfets for transformer based dc-dc converters mosfets optimised for voice over internet protocol (voip) issue number | 001 21 october 2009 new product announcement ZXMN20B28K zxmn15a27k r ds(on) max (m ? ) @ v gs part name pack v dss (v) p d (w) i d (a) i dm (a) 5v 6v 10v c iss typ (pf) q g typ (nc) @5v q g typ (nc) @10v e as uis (note 1) ZXMN20B28K to252-3l 200 10.2 2.3 17.3 780 - 750 358 8.1 12.9 yes (note 2) zxmn15a27k to252-3l 150 9.5 2.6 17.2 - - 650 169 - 6.6 yes (note 3) zxmn10a25k to252-3l 100 9.9 6.4 21.0 - 150 125 859 9.6 17.2 no zxmn10a08g sot223 100 3.9 2.9 11.0 - 300 250 405 4.2 7.7 no zxmn10a11k to252-3l 100 8.5 3.5 9.9 - 450 350 274 3.0 5.4 no zxmn10a11g sot223 100 3.9 2.4 7.9 - 450 350 274 3.0 5.4 no zxmn7a11k to252-3l 70 8.5 6.1 17.0 190 - 130 298 4.4 7.4 no zxmn7a11g sot223 70 3.9 3.8 10.0 190 - 130 298 4.4 7.4 no zxmn6a25n8 so-8 60 2.8 5.7 25.7 70 - 50 1063 11.0 20.4 no zxmn6a08g sot223 60 3.9 5.3 20.0 150 - 80 459 4.0 5.8 no zxmn6a08e6 sot23-6 60 1.7 3.5 16.0 150 - 80 459 4.0 5.8 no zxmn6a11g sot223 60 3.9 4.4 15.6 180 - 120 330 3.0 5.7 no notes: 1. single pulse avalanche energy (e as ) testing using an unclamped inductive switch (uis) test in production. 2. e as = 73mj with uis conditions of l = 4.83mh, i as = 5.5a, r g = 25 ? , v dd = 100v, starting t j = 25c. 3. e as = 55mj with uis conditions of l = 5.95mh, i as = 4.3a, r g = 25 ? , v dd = 100v, starting t j = 25c. slic controller dc-dc converter v bat linefeed circuitry v tr trip ring twisted pair line to phone v dc n-channel mosfet
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