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I am currently working on DSADC in TC37 microcontroller. Here in the user manual, the following info is mentioned regarding passband frequency.

"Related to hardware characteristic for passband frequency ≤ 10 kHz the FIR1 has to be used with a decimation rate of 1:1." [Source: AURIXTC3XX_um_part2_v2.0 (1) (1).pdf (Page : 1366)]

Is the above passband frequency referring to input analog signal's frequency? Also it is mentioned to use FIR1 filter for passband frequency ≤ 10 kHz. Does anyone the reason for the need to enable FIR1 filter here?

Solved! Go to Solution.

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Hi @Bala , Please find the following feedback:

- “Passband frequency” means the user expected passband frequency of the analog input frequency. It is not the direct analog input frequency. Frequency components outside the selected passband frequency are expected to be filtered out.

- With both FIR0 and FIR1 enabled, user will have the optimal SNR.

- UM mentioned for passband ≤ 10kHz, FIR1 decimation rate should be 1:1. This information is obsolete. The main purpose to offer decimation flexibility for FIR1 (it can be 2:1 or 1:1) is, to have the
__same__passband frequency with__different__output rates. Please see below summary (fd is the DSADC filter output rate). From this table, we can see that, if FIR1 decimation rate 2:1 is chosen, then the OSR is doubled i.e. fd is halved. The fPB = halved fd/3, which is equal to fd/6.

Best Regards,

Meet.

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Hi @Bala , Yes correct,"passband frequency" in UM is the passband frequency of DSADC analog input signal. For the second query I need to check further internally, I will let you know once I find something.

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Hi @Bala , Please find the following feedback:

- “Passband frequency” means the user expected passband frequency of the analog input frequency. It is not the direct analog input frequency. Frequency components outside the selected passband frequency are expected to be filtered out.

- With both FIR0 and FIR1 enabled, user will have the optimal SNR.

- UM mentioned for passband ≤ 10kHz, FIR1 decimation rate should be 1:1. This information is obsolete. The main purpose to offer decimation flexibility for FIR1 (it can be 2:1 or 1:1) is, to have the
__same__passband frequency with__different__output rates. Please see below summary (fd is the DSADC filter output rate). From this table, we can see that, if FIR1 decimation rate 2:1 is chosen, then the OSR is doubled i.e. fd is halved. The fPB = halved fd/3, which is equal to fd/6.

Best Regards,

Meet.