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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)

Tx Characteristics

Symbol

Parameter

Gtx Transmit Gain

Ntx

Mmic

VLpeak

Dtx

Transmit noise

Microphone mute

Transmit softclipping

level on TxA1-TxA2

Transmit distortion

Test Conditions

_MIKGAIN=7FFF,_TXGAIN=7FFF, AGC disabled

VMIC2 = -21dBV

VMIC2 = -9dBV

2kΩ between MIC2 and GND

VMIC2 = -21dBV

_MIKGAIN=7FFF,_TXGAIN=7FFF, AGC disabled

see Figure 3, VMIC2 = -9dBV

_MIKGAIN=7FFF,_TXGAIN=7FFF, AGC disabled

see Figure 3, VMIC2 = -9dBV

Min.

Typ.

18

8

-73

60

2.5

Max.

2

Unit

dB

dB

dBmp

dB

Vpp

%

Rx Characteristics

Symbol

Grx

Nrx

Mrx

Dtx

Parameter

Receive Gain

Receive noise

Mute

Receive distortion

(SPK2 output)

Test Conditions

Min.

_SPKGAIN=7FFF , AGC disabled, VRXA = -16 dBV

VRXA = dBV

_SPKGAIN=7FFF , AGC Disabled, VRXA = -16dBV

Typ.

6

-79

60

Max.

2

Unit

dB

dBmp

dB

%

AGC

The line current information is coming from the

D.A.A. on DP_RING pin (frequencycoded informa-

tion using by example a TS555 general purpose

timer). The AGC has a 6dB depth . Theattenuation

table can be loaded to comply with each country

regulation. The default table has the following val-

ues. The value of the AGC gain is applied to both

Tx and Rx path (see Table 1).

The address of the table is given in the register

@_TABLE.

The table length is 53. The AGC is enabled using

CONF or MODC command (see paragraph ”VII -

COMMAND SET DESCRIPTION”.

Once the AGC is running, it is possible to freeze the

AGC gain with the register AGC_FRZ.

Softclipping

The softclipping introduces a 12dB gain and has a

18dB depth.

The softclipping value is half digital range

(4000 Hex) (see Figure 5).

Table 1 : AGC Gain versus Period Information

Period (ms) <9 10 10.8 11.6 14.5 13.3

Table Index <13 13 14 15 16 17

Gain (dB)

0 0.7 1.5 2.2 3 3.4

Figure 5 : Softclipping Static Gain

Tx Softclipping and Distortion

(mVRMS)

104

VTxA1-TxA2 (VRMS)

Distortion

D (%)

12

10

103

8

6

102

4

2

0

10

102

103

VMICX (mVRMS)

14.1 15.5 16.6 17.5 18.3 19.1 20 >20

18 19 20 21 22 23 24 >24

4 4.5 4.8 5.1 5.4 5.6 5.8 6

16/84

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