Table 12. AGC of TX Path (from filter output to TXP and TXN).

Output noise

25mVHz

-1/2

Input level (nominal)

1Vpd

Output level nominal, full-scale

1.5Vpd

Maximum Output Load

> 500

Ω; <10pF

AGC range:

-15dB...dB

AGC step:

1dB

Gain and step accuracy

±0.3dB

Minimum code (0000) stands for AGC = -15dB and maximum (1111 - MSB left) for AGC = 0dB (See Tx

setting, Table22).

TX Pre-driver Capability

The pre-driver drives an external line power amplifier which transmits the required power to the line.

Table 13. TX Pre-driver

TX drive level to the external line driver for max. AGC setting

1.5 Vpdif

External line driver input impedance:

resistive

capacitive

> 500

Ω

< 30pF

Pre-driver characteristics:

closed loop gain:

-15dB...0dB with step = 1dB

ooutput impedance:

output offset voltage (0dB)

< 10mV

input noise voltage (0dB)

< 20nVHz

Ω

< 50nVHz

<138k

Ω

output common mode voltage:

1.6V < Vcm < 1.7V

TX Filter

The TX filters act not only to suppress the DMT sidebands but also as smoothing filters on the D/A con-

vertor’s output to suppress the image spectrum. For this reason they must be realized in a continuous

time approach.

ATU-R TX Filter

The purpose of this filter is to remove out-of-band noise of the ATU-R TX path echoed to the ATU-R RX

path. In order to meet the transmitter spectral response, an additional filtering must be (digitally) per-

formed. The integrated filter has the following characteristics:

Table 14. Integrated SC Filter Characteristics

Description

Value/Unit

Input referred noise

100nVHz

-1/2

Max. input level

1Vpd

Max. output level

1Vpd

Type

4th order chebytchef

Frequency band

138kHz (0% setting see below)

Frequency tuning

-25% -> +25%

Max. in-band ripple

1dB

Matlab Model

Default cut-off frequency @ -3dB

Actual cut-off @ -3dB

SC Freq. selection register

[B,A] = cheby1 (4,0.5,W0,’s’) {ripple = 0.5}

F0 = 151.8kHz

W0 = 2*pi*F0/((17+n)/16)

n = -4,..,3

see (AFE settings, Table 22)

STLC60134S

10/22