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AD7760 Pass-band Bandwidth

Question asked by vuquan91 on Apr 15, 2018
Latest reply on May 10, 2018 by vuquan91

I am currently using AD7760 to convert RF signals. The converted data is stored in FIFO and then read out by TI CCS. The setting for AD7760 is as in the above table (filter 3 is set as default filter by bit DL_FILT set to 0). Then I use FFT Graph function of CCS to verify the passband bandwidth. In case 1 (the value of Control Register 1 is set to 0x0018), the graph shows as in the following figure. The passband bandwidth seems to be correct as shown to be nearly 768kHz.

However, in case 2 (the value of Control Register 1 is set to 0x0009), the passband bandwidth is supposed to be 432kHz, but the graph shows something like this.

In both case, the value of Control Register 2 is set to 0x0002 as recommended in the datasheet. Does anyone get any idea about this?

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