Moteur de recherche de fiches techniques de composants électroniques |
|
AD7730LBRU-REEL Fiches technique(PDF) 27 Page - Analog Devices |
|
AD7730LBRU-REEL Fiches technique(HTML) 27 Page - Analog Devices |
27 / 53 page AD7730/AD7730L –27– Chop Mode With chop mode enabled on the AD7730, the signal processing chain is synchronously chopped at the analog input and at the output of the first stage filter. This means that for each output of the first stage filter to be computed, the full settling time of the filter has to elapse. This results in an output rate from the filter that is three times lower than for a given SF word than for nonchop mode. The output update and first notch of this first stage filter correspond and are determined by the relationship: Output Rate = f CLK IN 16 × 1 3 × SF where SF is the decimal equivalent of the data loaded to the SF bits of the Filter Register and fCLK IN is the master clock frequency. Second Stage Filter As stated earlier, the second stage filter has three distinct modes of operation which result in a different overall filter profile for the part. The modes of operation of the second stage filter are discussed in the following sections along with the different filter profiles which result. Normal FIR Operation The normal mode of operation of the second stage filter is as a 22-tap low-pass FIR filter. This second stage filter processes the output of the first stage filter and the net frequency response of the filter is simply a product of the filter response of both filters. The overall filter response of the AD7730 is guaranteed to have no overshoot. Figure 11 shows the full frequency response of the AD7730 when the second stage filter is set for normal FIR operation. This response is for chop mode enabled with the decimal equivalent of the word in the SF bits set to 512 and a master clock frequency of 4.9152 MHz. The response will scale proportionately with master clock frequency. The response is shown from dc to 100 Hz. The rejection at 50 Hz ±1 Hz and 60 Hz ± 1 Hz is better than 88 dB. The –3 dB frequency for the frequency response of the AD7730 with the second stage filter set for normal FIR operation and chop mode enabled is determined by the following relationship: f 3dB = 0.0395 × f CLK IN 16 × 1 3 × SF In this case, f3 dB = 7.9 Hz and the stopband, where the attenua- tion is greater than 64.5 dB, is determined by: f STOP = 0.14 × f CLK IN 16 × 1 3 × SF In this case, fSTOP = 28 Hz. FREQUENCY – Hz 0 –60 –100 090 10 20 30 40 50 60 70 80 –10 –50 –70 –90 –30 –40 –80 –20 –120 –110 100 Figure 11. Detailed Full Frequency Response of AD7730 (Second Stage Filter as Normal FIR, Chop Enabled) Figure 12 shows the frequency response for the same set of conditions as for Figure 11, but in this case the response is shown out to 600 Hz. This response shows that the attenuation of input frequencies close to 200 Hz and 400 Hz is significantly less than at other input frequencies. These “peaks” in the fre- quency response are a by-product of the chopping of the input. The plot of Figure 12 is the amplitude for different input fre- quencies. Note that because the output rate is 200 Hz for the conditions under which Figure 12 is plotted, if something ex- isted in the input frequency domain at 200 Hz, it would be aliased and appear in the output frequency domain at dc. FREQUENCY – Hz 0 –60 –100 0 450 50 100 150 200 250 300 350 400 –10 –50 –70 –90 –30 –40 –80 –20 –120 –110 500 550 600 Figure 12. Expanded Full Frequency Response of AD7730 (Second Stage Filter as Normal FIR, Chop Enabled) REV. B |
Numéro de pièce similaire - AD7730LBRU-REEL |
|
Description similaire - AD7730LBRU-REEL |
|
|
Lien URL |
Politique de confidentialité |
ALLDATASHEET.FR |
ALLDATASHEET vous a-t-il été utile ? [ DONATE ] |
À propos de Alldatasheet | Publicité | Contactez-nous | Politique de confidentialité | Echange de liens | Fabricants All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |