IPAC-X datasheet(62/270 Pages) INFINEON

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IPAC-X

PSB/PSF 21150

Description of Functional Blocks

Data Sheet

2003-01-30

3.3.7

S/T Interface Circuitry

For both the receive and transmit direction a 1:1 transformer is used to connect the

IPAC-X transceiver to the 4 wire S/T interface. Typical transformer characteristics can

be found in the chapter on electrical characteristics. The connections of the line

transformers is shown in Figure 31.

Figure 31

Connection of Line Transformers and Power Supply to the IPAC-X

For the transmit direction an external transformer is required to provide isolation and

pulse shape according to the ITU-T recommendations.

3.3.7.1

External Protection Circuitry

The ITU-T I.430 specification for both transmitter and receiver impedances in TEs results

in a conflict with respect to external S-protection circuitry requirements:

– To avoid destruction or malfunction of the S-device it is desirable to drain off even

small overvoltages reliably.

– To meet the 96 kHz impedance test specified for transmitters and receivers (for TEs

only, ITU-T I.430 sections 8.5.1.2a and

8.6.1.1) the protection circuit must be

dimensioned such that voltages below 1.2 V (ITU-T I.430 amplitude) x transformer

ratio are not affected.

This requirement results from the fact that this test is also to be performed with no supply

voltage being connected to the TE. Therefore the second reference point for

overvoltages VDD, is tied to GND. Then, if the amplitude of the 96 kHz test signal is

greater than the combined forward voltages of the diodes, a current exceeding the

specified one may pass the protection circuit.

The following recommendations aim at achieving the highest possible device protection

against overvoltages while still fulfilling the 96 kHz impedance tests.

21150_05

IPAC-X

Protection

Circuit

Protection

Circuit

1:1

Transmit

Pair

Receive

Pair

SX1

SX2

SR1

SR2

GND

VDD

VSS

3.3 V

10 µF

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