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ADS1293: Some question about "BW" definition in datasheet...

Peter Tseng
Mastermind 6170 points
Part Number: ADS1293

Dears,

My customer have some questions about the bandwidth in datasheet.

1. in the table 8, there mentioned BW, what is its definition?

for example, while BW is 160, it menas

a. signal only can pass from 0~160Hz

b. signal only can pass from 0.05~160Hz

c. signal only can pass from 0.5~160Hz, or 

d. others, please explain it

2. based on above question, if customer want to design for 0~150Hz LPF, how did they need to do?

Thanks.

  • 0
    TI__Guru 66256 points

    Hello Peter,

    Thanks for your interest in our ADS1293!

    The bandwidth listed in Table 8 is the signal bandwidth at the output of the digital filter for the PACE and ECG channels. This bandwidth depends on the decimation ratio and output data rate. Typically, this spec indicates the -3dB point of the digital filter response.

    If you look back at Figure 18, you see that the digital filter is comprised of three stages, each a sinc5 filter with a different decimation ratio. The PACE channels come from the output of Stage 2, while the ECG channels come from the output of Stage 3. The filter response will look different depending on where the output is taken from, but all will start with unity-gain (0 dB) at DC and then roll-off to -3 dB at the specified signal bandwidth in Table 8.

    Is the customer interested in signals only from 0Hz to 150Hz? I would still think that a 160Hz bandwidth in the digital filter will be sufficient - remember that the filter response will begin to roll-off before the -3dB point, so in reality, you want the filter cutoff to exist beyond your signal bandwidth of interest. Otherwise, if they want the -3dB point to occur exactly at 150Hz, you could scale the input clock frequency. The acceptable input clock frequency range is from 3.7MHz to 4.5MHz. Please see Section 8.3.19 on page 28 for more details on the clocking options for the ADS1293.

    Best Regards,