PEF22827EL-V11 Lantiq, PEF22827EL-V11 Datasheet - Page 74

• Manufacturer Part Number: PEF22827EL-V11
• Manufacturer: Lantiq

Specifications of PEF22827EL-V11

• Lead Free Status / RoHS Status: Supplier Unconfirmed

5
The Analog Block of the PEF 22827 provides a filterless VDSL AFE (Analog Front
End)
management commands. The AFE is connected to the External Adaptive Hybrid, which
eliminates the requirement for transmission and receive filters.
The filterless AFE satisfies diverse requirements:
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5.1
The Infineon filterless AFE differs from a classical AFE. A classical AFE includes
predefined fixed filters and a hybrid, which attenuate the echo noise to a minimum in
order not to limit the SNR. Generally, echo noise has two sources:
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A classical AFE includes the following elements:
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1)
Preliminary Data Sheet
It may be necessary to add additional external components to ensure best performance under any line
conditions. Refer to the reference design guidelines.
Support for different band-plans
Support for different PSDs with a single chip-set
Support for different line throughputs
Echo signal in the transmission bands. This portion of the echo is attenuated by the
hybrid and by the receive filter.
Echo side-lobes, out-of-transmission-band (in-receive-band), generated by the non-
linearity of the line-driver and analog circuitry. This portion of the echo is attenuated
by the transmission filter and by the hybrid.
Analog chip: Mainly converts analog signals to digital, and digital to analog. The chip
includes ADC and DAC blocks.
Internal Line driver: Drives the transmit signal according to specific PSD masks.
Transmit and receive filters: Defined according to the band plan. Their main purpose
is to overcome echo noise in the DSL modem. Echo noise is an inherent element in
any DSL modem. Echo noise decreases the SNR (Signal to Noise Ratio) and thus
limits the overall performance of a modem. Receive and transmit filters are passive
and pre-defined. Such filters can not be used in regions that support a different band
plan.
Hybrid: Converts a single-pair loop into dual-pair circuitry, and vise versa. The hybrid
should be perfectly matched to the line to avoid reflections of the transmission signal
into the receive path (echo signal). Passive hybrids are matched to a pre-defined line
impedance. However, line impedance varies from region to region, and within a
region, due to bridge taps. Consequently, matching is not perfect and permits the
presence of echo noise.
1)
, which is programmable under system control and modifiable through
Functional Description – Analog Block
Classical AFE
74
Functional Description – Analog Block
Rev. 1.1, 2005-01-30
VDSL6100i
PEF 22827