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IPAC-X

PSB/PSF 21150

Description of Functional Blocks

Data Sheet

2003-01-30

Protection Circuit for Transmitter

Figure 32

External Circuitry for Transmitter

Figure 32 illustrates the secondary protection circuit recommended for the transmitter.

The external resistors (5 ... 10

W) are required in order to adjust the output voltage to the

pulse mask on the one hand and in order to meet the output impedance of minimum 20

(transmission of a binary zero according to ITU-T I.430) on the other hand.

Two mutually reversed diode paths protect the device against positive or negative

overvoltages on both lines.

An ideal protection circuit should limit the voltage at the SX pins from – 0.4 V to VDD

+ 0.4 V. With the circuit In Figure 32 the pin voltage range is increased from – 0.7 V to

VDD + 1.4 V. The resulting forward voltage of 1.4 V will prevent the protection circuit from

becoming active if the 96 kHz test signal is applied while no supply voltage is present.

Protection Circuit for Receiver

Figure 33 illustrates the external circuitry used in combination with a symmetrical

receiver. Protection of symmetrical receivers is rather simple.

SX1

5 ... 10

Ohm

5 ...10

Ohm

Vdd

S Bus

1:1

21150_23

SX2

IPAC-X Datasheet(PDF) 63 Page - Infineon Technologies AG