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ST75C530

SUPER INTEGRATED DEVICES WITH DSP, AFE & MEMORIES FORTELEPHONY, MODEM, FAX OVERINTERNET & POTS LINES

STMicroelectronics 

ST75C530 - ST75C540

V - FUNCTIONAL DESCRIPTION (continued)

V.4.3 - Crystal

The crystal frequency must be 44.2368MHz for

ST75C530 and 49.152MHz for ST75C540 with an

accuracy better that ±100 ppm. When using a third

harmonic crystal the schematic must be as follow :

see Figure 10.

The crystal features are :

- third harmonic,

- parallel, load capacitance = 10pF,

- æ 100ppm from 0oC to 70oC,

- RS < 50Ω,

- ATcut (example : SM55-10 MATEL).

Figure 10

ST75C540

73

72

EXTALL

XTALL

XTAL H3 **

C1

10pF

COG

C2

27pF

COG

L*

0.82µH (ST75C530)

0.68µH (ST75C540)

Cb

10nF

* Wire wound inductor recommanded (Example : SIGMA-SC30)

** Thrird harmonic (Example : MATEL-SM55-10)

XTAL H3 : 44.2368MHz (ST75C530)

49.152MHz (ST75C540)

V.4.4 - Typical Application Schematic

The Figure 11 is a block diagram designedto allow

transmission of fax signals up to +0dBm and sine

wave up to +6dBm on the telephone line. It allows

receptionof fax signals up to 0dBm and sine waves

up to +6dBm.Figure12 is a blockdiagramdesigned

to allow transmission of Modem signal up to -

10dBm and reception up to -10dBm. The OPAmps

are +12/0V powered. With this application sche-

matic the out of band transmit spectrum(from 4kHz

to 50kHz) is below -72dBm.

Figures 13 and 14 are examples of applicationsche-

maticswhich respectsgainvalue(respectivelyforfax

and voice application and for Modem application)

andthe minimum differentialloadonTxA1 andTxA2.

V.4.5 - Host Interface

The host interface is seen by the micro as a 128x8

RAM, with additional registers accessible through

an 8-bit address space. A selection Pin (INT/MOT)

allows to configurethe host bus for either INTEL or

MOTOROLA type control signals.

Figure 11

TxA1

TxA2

+8dB

600Ω

-1/2

1:1

Line

RxA

2.2nF

VCM

Figure 12

-10dB

TxA1

0dB

TxA2

600Ω

-1/2

1:1

Line

RxA

0dB

2.2nF

VCM

19/84

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