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AFE58JD18: Seeking guidance on time varying TGC via digital control

Matthew Zimmerman
Prodigy 20 points
Part Number: AFE58JD18
Other Parts Discussed in Thread: AFE5816

There is a nice guide regarding using time varying TGC with an analog control. However, I'm wondering if there is any guidance available for implementing time varying TGC with digital control. Specifically, I'd like to use the DIG_TGC_ATTENUATION registers (or something similar). I don't want to use an external DAC connected to the analog VCAT inputs. 

Is this even possible?

  • 0
    TI__Expert 6040 points

    Thanks Matt for looking at the AFE58JD18!  as you can see , Dig-TGC_attenuation is a coarse gain control with a 6dB step. This is usually not suitable for real ultrasound TGC compenstation. the reason we put the DTGC in the AFE is for some appliciatons who only needs fixed gain.  Then DTGC can serve that purpose. 

    if you really need the digital TGC, you can look into AFE5816 device.  AFE5816 only has digital TGC.  

    Thanks!

  • 0 in reply to Xiaochen (Sean)Xu
    Prodigy 20 points

    I understand the coarse gain control with 6dB step. However, assuming that is ok, do you have any guidance on making that change during acquisition? My understanding is that setting would be sent via SPI. Is there a stable latency from spi command to TGC change?

  • 0 in reply to Matthew Zimmerman
    TI__Expert 6040 points

    SPI control to DTGC gain switch is immediate. not much delay. you may need to consider the glitch during transition. at 6dB step, glitch/overshoot should be visible. 

    Thanks!