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SP504CF

Application Note

Signal Processing Technologies 

SP504 - Overvoltage and ESD Protection Using Transzorbs

+5V

22µF

1N5819

22µF

28 31 25 27 26 30

C2+ C2- VCC VDD C1+ C1- 32

VSS

SP504CF

Drivers

TxD

14

22µF

DTR

13

RTS

16

15 14 13 12 11 10

TxC

15

ST

22

2 34 567

RL

17

ProTek Devices

SM16LC15C

LL

24

Receivers

RxD

1

RxC

20

CTS

80

DSR

15 14 13 12 11 10

78

DCD

ProTek Devices

SM16LC15C

19

RI

2 34 567

21

SCT

79

* - Please note that the ProTek transient

voltage suppressors should also be con-

nected to the other SP504 drivers and re-

ceivers in the same configuration as shown

above.

Although the SP504 is internally protected for ESD

and overvoltage, an external transient voltage sup-

pression circuit can be added to increase the level of

protection of the device. This may be desired for

greater ESD protection or clamping the input or out-

put voltages. The maximum driver output and re-

ceiver input voltages should not exceed ±15V.

The SP504 configuration above uses ProTek Devices'

SM16LC15C TVS devices to protect the receiver in-

puts and the driver outputs since these pins are di-

rectly exposed to the connector and the outside world.

The V of the TVS can be as low as 5V and high as

wm

15V to cover the RS-232 voltage levels. However,

the RS-232 3kΩ to 7kΩ input impedance will not

comply if the voltage levels exceed the clamping

voltage of the TVS.

ProTek Devices • Tempe, AZ. • 602-431-8101

SP504AN

SP504 Application Note

2

© Copyright 2000 Sipex Corporation

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