HSP50214BVI Intersil, HSP50214BVI Datasheet - Page 25

• Manufacturer Part Number: HSP50214BVI
• Manufacturer: Intersil

Specifications of HSP50214BVI

• Lead Free Status / RoHS Status: Not Compliant

These gain error values are scaled by the programmable
AGC loop gains to adjust the data path gain.
The maximum slew rate is ~1.5dB per output sample. See
Equation 18.
In order to fully evaluate the dynamic range of the PDC,
Table 9B is provided, which details the bit weighting from the
input to the AGC Multiplier.
Re-Sampler/Halfband Filter
The re-sampler is an NCO controlled polyphase filter that
allows the output sample rate to have a non-integer
relationship to the input sample rate. The filter engine can be
viewed conceptually as a fixed interpolation filter, followed by
an NCO controlled decimator.
The prototype polyphase filter has 192 taps designed at 32
times the input sample rate. Each of the 32 phases has 6
filter taps (6)(32) = 192. The stopband attenuation of the
prototype filter is greater than 60dB, as shown in Figure 24.
The signal to total image power ratio is approximately 55dB,
due to the aliasing of the interpolation images. The filter is
capable of decimation factors from 1 to 4. If the output is at
least 2x the baud rate, the 32 interpolation phases yield an
effective sample rate of 64x the baud rate or approximately
1.5%, (1/64), maximum timing error.
Following the Re-sampler are two interpolation halfband
filters. The halfband filters allow the user to up-sample by 2
or 4 to recover time resolution lost by decimating.
Interpolating by 2 or 4 gives 1/4 or 1/8 baud time resolution
(assuming 2x baud at the re-sampler output). The halfband
filters use the same coefficients as HB3 and HB5 from the
Halfband Filters Section. If one halfband is used, the 23-tap
filter is chosen. If two are used, the 23-tap filter runs first
There is a 65dB limitation in SNR using the Re-Sampler Filter. When only the Interpolation FIRs are used, the full SNR range is passed.
FIGURE 24A. POLYPHASE RESAMPLER FILTER BROADBAND
-100
-120
-20
-40
-60
-80
0
1
2
FREQUENCY RESPONSE
3
4
FREQUENCY (RELATIVE TO f
5
6
25
7
8
9
10 11 12 13 14 15 16
S
)
HSP50214B
FIGURE 24.
followed by the 15-tap filter operating at twice the first
halfband’s rate. The 23-tap filter requires 7 multiplies, and
the 15-tap filter requires 5 multiplies to complete a filter
calculation.
Using the interpolation halfband filters allows for reduction in
the FIR filter sample rate. This optimizes the use of the
programmable FIR filter by allowing the FIR output sample
rate to be closer to the Nyquist rate of the desired bandwidth.
Optimizing the FIR filter performance provides better use of
the programmable FIR taps. Table 10 details the maximum
clocking rates for the possible resampling and interpolation
halfband filter configurations of this section of the PDC.
Control Word 16, Bits 2-0 identify the filter configuration.
Control Word 16, Bit 3 is used to bypass the polyphase re-
sampler filter.
For proper data output from the interpolation filters, the data
ready signal must account for the interpolation process.
Figure 25 illustrates the insertion of additional data ready
pulses to provide sufficient pulses for the new output sample
rate. The Re-sampler Output Pulse Delay parameter is set in
Control Word 16, Bits 4-11. These bits set the delay between
the output samples when interpolation is utilized. Program
this distance between pulses using
A value of at least 5 is required to have sufficient time to
update the Output Buffer Register. (Writing 5 samples
requires 5 clock cycles) A value of at least 16 is required for
proper serial output from the part. (Conversion from 16-bit
parallel to serial). The value is programmed in numbers of
PROCCLK’s.
N
FIGURE 24B. POLYPHASE RESAMPLER FILTER PASS BAND
=
-10
-20
-30
-40
-50
-60
-70
-80
10
0
[
(
0
f
PROCCLK
FREQUENCY RESPONSE
/f
OUT
FREQUENCY (RELATIVE TO f
) 1 ]
–
S
)
May 1, 2007
(EQ. 20)
FN4450.4