STLC60134S 查看數據表（PDF） - STMicroelectronics
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STLC60134S Datasheet PDF : 22 Pages
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STLC60134S
RX PATH
Speech filter
An external bi-directional LC filter for up and
downstream POTS service splits the speech sig-
nal from the ADSL signal to the POTS circuits on
ATU-C.
The ADSL analog front end integrated circuit
does not contain any circuitry for the POTS serv-
ice but it guarantees that bandwidth is not dis-
turbed by spurious signals from the ADSL-spec-
trum.
Channel Filters
The external analog circuits provide partial echo
cancellation by an analog filtering of the receive
signal for both ATU-R (Reception of downstream
channel) and ATU-C (Reception of upstream
channel). This is feasible because the upstream
and the downstream data can be modulated on
separate carriers (FDM).
Line Noise Model
The power spectral density of the crosstalk noise
sources as described in ANSI document is given
in the figure below (no HDB3 interferer signals).
Also given in dotted line, is the noise model used
in this document to specify the sensivity require-
ments which are stronger than the original ones.
Figure 6. Crosstalk PSD.
dBm/Hz
-100
-110
-120
-130
-140
D98TL359
79.5 138 250
795
kHz
Signal to Noise Performance
RX- PATH SENSITIVITY AT MAXIMUM GAIN
The RX path sensitivity at the maximal RX-AGC
of the ATU-R receiver is defined at -140dBm/Hz
(for 100Ω ref) on the line. This figure corresponds
to the equivalent input noise of 31nVHz-1/2 seen
on the line.
The sensitivity at the maximal RX - gain of the
ATU-C receiver is defined at -130dBm/Hz (for
100Ω ref) on the line. The figure corresponds to
the equivalent input noise of 100nVHz-1/2 seen
on the line.
Both noise figures include the noise of the hybrid.
It is the equivalent average thermal noise over
the frequency band of interest. The maximum
noise density within the pass band can exceed
the average value as follows:
ATU-R RX path (max AGC setting):
<100nVHz-1/2 @ 138kHz
<31nVHz-1/2 for 250kHz < f
ATU-C RX path (max AGC setting):
<100nVHz-1/2 for 34.5kHz < f <138kHz
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:
ATU-R RX path (min AGC setting):
<500nVHz-1/2 @ 138kHz < f
ATU-C RX path (min AGC setting):
<1.5µVHz-1/2 @ 34.5kHz < f < 138kHz
These noise specifications correspond with 10bit
resolution of the complete RX-path.
Table 4. RX Common-mode Voltage
Description
Common mode signal VCM
at RXIN1 and RXIN2:
Value/Unit
1.6V < VCM <1.7V
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 se-
lection 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.
Table 5. AGC Characteristics.
Description
Input referred noise
(max. gain)
Max. input level
Max. output level
Gain range
Gain and step accuracy
Value/Unit
20nVHz-1/2
1Vpd
1Vpd
0 to 31dB with step = 1dB
± 0.3dB
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)
attenuation.
- Anti alias filter (60dB rejection @ image freq.)
7/22
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