Download

PDF Abstract Text:

560 Ohm

DT 95-1a

DESIGN TIP
Here is information on how our PVT412L microelectronic relay (MER) will save time and money while improving performance and reliability in FAX / Modem designs. Figure 1 is the schematic of a basic modem showing K1 mechanical relay. It is the equivalent of a hook-switch in the traditional telephone set and in this case, K1 is either an electromechanical relay (EMR) or a reed relay. Because such relays inherently cause contact bounce upon contact closure, R1, C1 debouncing circuitry
560 Ohm
DT 95-1a
International Rectifier · 233 Kansas Street, El Segundo, CA 90245 USA
0.005µF / 1kV
1:1 10 Ohm fusible Varistor To Telephone Company Network
6.8V OH
K1 Relay
10 Ohm
0.47µF / 250V 10K RI 10K +5V
Figure 1. Basic Modem Using Mechanical EMR
DT 95-1a
When the K1 electromechanical or reed relay is replaced with our PVT412L MER, as in Figure 2, the following cost and space savings are realized. · R1, C1 debouncing circuitry is no longer needed. Solid-state switching is bounce-free because there are no physical parts making and breaking the contact. · R2 and R3 fusible resistors are no longer required thanks to the internal active, current-limiting feature of the PVT412L. Even more important than the savings in space and cost, should one or both of the fusible
1:1 To Telephone Company Network
K1 Relay
+5V Varistor
0.47µF / 250V 10K RI 10K +5V
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105 http://www.irf.com / Data and specifications subject to change without notice. 2 / 26 / 2002
www.irf.com