ST75951 datasheet(5/21 Pages) STMICROELECTRONICS

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4.2 - General Purpose Interrupt System (GPI)

The GPI will reflect any change of the GPIO’S

inputs or RING output when non-masked, so the

processor does not need to read the output control

word continuously. GPI level change tells the proc-

essor, one of the non-masked input pins level has

changed and he can read the control word. So

GPIO could extend the number of interrupt pins of

the processor.

5 - Ring

This pin is used for the Ring detect but also reports

the Line status, current limit.

6 - Digital Test Pin (TSTD1)

This pin is reserved for digital test purpose.

7 - Crystal (XTALIN , XTALOUT)

These pins must be tied to an external crystal or a

master clock generator (MCLK).

8 - Analog Interface (12 Pins)

8.1 - DAC and ADC Reference Voltage Output

(VREFP, VREFN )

These pins provide the positive and negative

reference Voltage used by the 16-bit converters.

The reference voltage, VREF, is the voltage difference

between the VREFP and VREFN outputs.

VREFP and VREFN should be externally decoupled

with respect to VCM.

8.2 - Common Mode Voltage Output (VCM)

This output pin is the common mode voltage

(AVDD - AGND)/2 . This output must be decoupled

with respect to GND.

8.3 - Common Mode Voltage Input (VCMP, VCMS)

These input pins are the common mode voltage for

internal circuitry. They have to be connected exter-

nally to VCM.

8.4 - Analog Transmit Output (D1 ,D2)

These pins are the output of the fully differential

converted analog signal, modulated at F0

(1MHz < F0 < 1.7MHz).

The digital data IN signal is converted in analog

signals (with (Sin X)/X compensation). Two ranges

of signal amplitude have to be considered ; modem

application with dynamic up to 2.5VPP with maxi-

mum performances SNDR = 83dB, voice applica-

tion with dynamic up to 3.2VPP differential

(SNDR = 75dB).

The transmit output stage can be programmed to

+2dB gain, 0db gain, 6dB or infinite attenuation.

8.5 - Analog Receive Inputs (D3, D4)

These pins are the differential analog inputs. These

analog inputs are presented to the F0 demodulator

and the sigma-delta modulator. The analog input

peak-to-peak differential signal range must be less

than 2.5 VPP. The gain of the receive stage is

programmable to 0dB or 6dB.

8.6. - Analog Test Pin (TSTA1, TSTA2)

These pins are reserved for analog test purpose.

8.7 Analog Auxiliary Receive Inputs (AUXIN)

This pin is the auxiliary analog input. This analog

input is presented to the analog modulator. The

analog input peak-to-peak signal range must be

less than 1.25 VPP. The gain of the receive stage

is 0dB.

PIN DESCRIPTION (continued)

ST75951

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