ST70134 datasheet(8/22 Pages) STMICROELECTRONICS

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ST70134A

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RX-PATH NOISE AT MINIMUM GAIN

At the minimum AGC the total average thermal

noise of the analog RX-path at the ADC input

should be lower than the ADC quantisation noise.

The maximum noise density within the pass band

can exceed the average value as follows:

RX path (min AGC setting) <500nVHz-1/2 @

138kHz < f

These noise specifications correspond to 10bit

resolution of the complete RX-path.

AGC of RX Path

The AGC gain in the RX-path is controlled through

a 5-bits digital code.

Four inputs are provided for RX input and the

selection is made with the RXMUX bits of the

CTRLIN interface.

This can be used to make lower gain paths in

case of high input signal.

RX Filters

The combination of the external filter (an LC lad-

der filter typically) with the integrated lowpass fil-

ter must provide:

– Echo reduction to improve dynamic range.

– DMT sidelobe and out of band (anti-aliasing) at-

tenuation.

– Anti alias filter (60dB rejection @ image frequency).

RX Filters

The integrated filter have the following character-

istics:

Table 3 : RX Common-mode Voltage

Description

Value/Unit

Common mode signal VCM

at RXIN1 and RXIN2:

1.6V < VCM <1.7V

Table 4 : AGC Characteristics

Description

Value/Unit

Input referred noise(max. gain) 31nVHz-1/2

Max. input level

1Vpd

Max. output level

1Vpd

Gain range

0 to 31dB with

step = 1dB

Gain and step accuracy

± 0.3dB

Table 5 : Integrated HC Filter Characteristics

Description

Value / Unit

Maximum input level

1Vpd

Maximum output level

1Vpd

Type

3rd order butterworth

Frequency band

1.104MHz (0% setting, see below)

Frequency tuning

-43.75% -> +0%

Max. in-band ripple

1dB

Matlab Model

Default cut off frequency @ -3dB

Actual cut off @ -3dB

HC Freq. selection register

[B, A] = butter (3, w0, 's')

F0 = 1560KHz

w0 = 2 * pi * F0/((20 + n)/16)

n = -4,..,3 see (AFE settings,Table 19)

Table 6 : Phase Characteristic

Description

Value / Unit

Total RX filter group delay

< 50

µs @ 138kHz < f < 1.104MHz

Total RX filter group delay distortion

< 15

µs @ 138kHz < f < 1.104MHz

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