AD9142 : Interpolation Configuration

Question

Hi, 
 We are using the AD9142 DAC and trying to bypass the interpolation block in some use cases, the block diagram in the datasheet shows the three 2x interpolation blocks and a bypass path for each. This suggests that it is possible to bypass the interpolation blocks and operate in 1x mode where no FIR are applied to the signal. However, the SPI Interpolation Control Register seems to specify only the 2x, 4x, x8 interpolation modes. 
 How can we configure the DAC to bypass the interpolation? 
 Thanks

JMMina · Accepted Answer

Hi LabResearch , 
 We've confirmed with one of the designers that 1x interpolation was not released for AD9142/A. If you need to bypass the interpolation filters for your application, there is the AD9139 which has 1x and 2x interpolation. It has a similar architecture to AD9142A and can run at the same max speed, with just a few differences (e.g. no course and fine modulation, no block for input signal power detection and protection, etc.) 
 The block diagram was originally illustrated that way because we sometimes allow for HB1 or HB2 to be used individually for 2x (so the switch around HB1 would make sense), however upon testing there were no power or speed savings by letting HB2 be the 2x mode filter option, so it was limited to HB1. We will line this up for datasheet revision. 
 Regards, 
 Marco)

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AD9142 : Interpolation Configuration