SI4770-77-A20 Datasheet, PDF (31/54 Pages) Silicon Laboratories – HIGH-PERFORMANCE CONSUMER ELECTRONICS

Si4770/77-A20
4.8. Channel Equalizer
The Si4770/77-A20 supports advanced FM multi-path
channel equalization. Multi-path interference results in
fading of the FM signal at the receiver. Frequency
selective fading causes different frequencies of an input
signal to be attenuated and phase shifted differently in a
channel. Frequency selective fading gives rise to
notches in the frequency response of the channel. The
Si4770/77-A20 channel equalizer performs blind
equalization utilizing proprietary constant modulus
algorithm (CMA) to restore the flat response of the
channel.
4.9. Digital ZIF I/Q Interface
(Si4777 Only)
The digital ZIF I/Q output can provide the down
converted channelized AM/FM signal at baseband to a
third-party processor for AM/FM HD radio processor for
IBOC signal processing. The Si4777 provide a 500 kHz
BW signal for FM IBOC signal processing and a 30 kHz
BW signal for AM IBOC signal processing. The ZIF I/Q
4-pin interface consists of two data serial lines
containing I and Q data, a bit clock, and a word frame
for each data sample. The interface operates in master
mode and supports five different data formats:
 I²S ZIF
 Left-Justified ZIF
 Right-Justified ZIF
 DSP ZIF
 DSP Left-Justified ZIF
4.9.1. ZIF I/Q Data Formats
In I²S format, by default, the MSB is captured on the
second rising edge of IQCLK following each IQFS
transition. The remaining bits of the word are sent in
order, down to the LSB.
In Left-Justified format, by default, the MSB is captured
on the first rising edge of IQCLK following each IQFS
transition. The remaining bits of the word are sent in
order, down to the LSB.
In Right-Justified format, by default, the LSB is captured
on the last rising edge of IQCLK in each valid IQFS
interval.
In DSP format, the IQFS becomes a pulse with a width
of 1 IQCLK period. There are two options in transferring
the digital baseband I/Q data in DSP format: the MSB of
I and Q data can be transferred on the first rising edge
of IQCLK following the IQFS pulse (left-justified DSP
format) or on the second rising edge.
In all data formats, depending on the word size, IQCLK
frequency, and sample rates, there may be unused
IQCLK cycles after the LSB of each word before the
next IQFS transition and MSB of the next word. In
addition, if preferred, the user can configure the MSB to
be captured on the falling edge of IQCLK via properties.
The number of baseband I/Q bits is configured for 16
bits.
Table 14. ZIF I/Q Interface Description
Pin
IOUT
QOUT
IQFS
IQCLK
Description
16-bit baseband I word
16-bit baseband Q word
Word frame sync for I and Q words
Bit clock for I and Q data
Rev. 0.9
31