QF1DA512-DK Quickfilter Technologies LLC, QF1DA512-DK Datasheet - Page 17

• Manufacturer Part Number: QF1DA512-DK
• Description: KIT DEV FOR QF1DA512
• Manufacturer: Quickfilter Technologies LLC
• Series: SavFIRe™r

Specifications of QF1DA512-DK

• Main Purpose: Filters, Digital Filter Design
• Embedded: Yes, ASIC
• Utilized Ic / Part: QF1Da512
• Primary Attributes: 1 512 Tap FIR Filter, 12 ~ 24 Bit
• Secondary Attributes: Quickfilter Software Design Tool GUI, Works from 10 ~ 500ksps ADC Data Rates
• For Use With: WM2582 - EVALDI EARBUDS TYPE Y686-1006 - BOARD MSP-MOJO + EXPANSION HEADR
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 686-1010

Refer to the diagram below. This feature can be useful for noise reduction and possibly increasing bit resolution of the input data
stream. To select filtering of the down sampled data, DEC_AVG_EN, bit 0 of the FCONFIG register (address 05h) is enabled.
Channel Duplication
Channel duplication is a special feature in I2S mode (DECIMATE must also be set to 00h). Duplication uses the standard left-right
channel framing to create 2 channels of either right or left data. Using 2 QF1Da512s, the first device will both filter the specified
channel and duplicate (unaltered) the same channel‟s input data to the opposite channel‟s frame on dSDO. The second device will be
programmed to filter the unaltered data channel (and the previously filtered data will be passed to dSDO). For example, if the first
device is in Duplication mode, left-channel active and functions as a low pass filter, then the output of the first device will be Left-
lowpass/Left-raw-data (channel-1/channel-2). The second device is in Standard mode, right-channel active and functions as a high
pass filter, then the output of the second device will be Left-lowpass/Left-highpass.
9
Modes of Operation
The QF1Da512 filter can implement a symmetric 512-tap FIR filter or a 256-tap asymmetric FIR filter, which is used to define the
precise filtering characteristics desired. The filter coefficients are 32 bits wide. The filtering provided by the software may be of the
following types: low-pass, notched low-pass, high-pass, band-pass, dual band-pass, band-stop, and dual band-stop. Currently available
filter algorithms include Parks-McClellan and Windowed Sync. User defined filters can also be implemented.
The QF1Da512 can be loaded with up to 256 filter coefficients. To implement a non-folded (asymmetric) filter the FIR_FOLD bit in the
FCONFIG register (05h) should be set to 0, allowing a filter of up to 256 taps. A folded (symmetric) filter of up to 512 taps can be
implemented if FIR_FOLD is set to 1.
Note: For a folded filter, if the number of coefficients (N) is even, a filter of 2N taps will be realized. If N is odd, a filter of 2N-1 taps will
result.
The Quickfilter software allows the user to enter the filter characteristics required and see the predicted performance in terms of
frequency and impulse response. Once the desired performance has been attained, the configuration can be downloaded to the
QF1Da512, and the actual filter performance verified, by using the development kit. The development board can be fed with a white
noise source (or other source as desired by the user) and the software can display an FFT of the QF1Da512‟s filter response.
FIR Latency
The delay introduced by the Qf1Da512 is dependent on the number of taps of the filter and the data rate of the samples coming into the
FIR filter. The delay is calculated by the following equation:
Rev A8 January 7, 2009
FIR FILTER
Standard Mode
Duplication Mode
Filtered Channel: FIR Delay = (# taps – 1)/2 * 1/f
Bypassed Channel: Delay = 0
Filtered Channel: FIR Delay = (# taps – 1)/2 * 1/f
Replicated Channel: FIR Delay = 3/f
Input data word
Figure 10: Averaging /Down-sampler Block Diagram
EXAMPLE: N = DECIMATE register = 5
Outdt = (indt1 + indt2 + indt3 + indt4 + indt5) / 8
Can gain back up to nominal in FIR
accum
PRELIMINARY DATA SHEET
Div by next pwr of 2
s
right
shift
>= N
17
s
s
+ 8/f
+ 12/f
dds_avg_en
s
s
(N = 1-256)
sample/
hold
Output data word
www.quickfiltertech.com
QF1Da512