XRT8000 datasheet(21/24 Pages) EXAR

21 / 24 page

XRT8000

Rev. 1.11

SYNC

8 kHz

FIN

XRT8000

CLK1

CLK2

T1, T1/8

E1, E1/8

8 kHz

Figure 11. Slave Reverse Mode (Cont’d)

Output

Freq.

kHz

1544

193

2048

256

Board Layout Considerations

The CLK1 and CLK 2 outputs are surrounded with supply

pins (GND(514),Vcc(712). It is recommended to

decouple these supplies with a 0.1uF very close to the

pins. The positive supply (7,12,15) and ground pins

(4,5,14) can all be connected to the Digital Supply and

Ground.

The internal VCO has its proper supply’s pins (GND 9,

Vcc 10) these supply pins have to be decoupled by a

0.1uF capacitor and should be connected to an Analog

Supply if possible. If there is no Analog Supply, then

connect these pins as close as possible to the supply

source.

If the layout is done with separate layers for the supplies,

cut an island under the XTT8000 such that no current

flows under the circuit. It has been observed that coupling

can occur because heavy digital currents are flowing

under the locations of the XRT8000.

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