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Original question:

ADC12DJ5200RF: ADC Overrange Detection Clarification

ADC12DJ5200RF: Overrange configuration not saving

Juan Montero
Prodigy 20 points
Part Number: ADC12DJ5200RF
Other Parts Discussed in Thread: ADC08DJ5200RF

Tool/software:

Hi,

We've been using the ADC08DJ5200RF successfully for a while and recently decided to implement an automatic gain adjustment mechanism which uses ORA0 and ORA1 (we're operating in single channel mode). We are setting OVR_CFG during initialisation and following the recommended step order in the datasheet. We're setting the register to 0x0F to enable overrange detection and select maximum pulse duration for the overrange outputs.

The issue we're having is it seems like the OVR_CFG register is not holding the value that we're programming into it. Before initially setting it, it seems to have a value of 0x81, and after attempting to write to it, we're reading a value of 0x03. Is there any particular requirement that must be met before this register is set? As mentioned, we're following the exact steps according to the data sheet:

1. Power-up or reset the device.
2. Apply a stable device CLK signal at the desired frequency.
3. Perform a software reset by toggling SOFT_RESET to 1. Wait at least 1 μs before continuing.
4. Program JESD_EN = 0 to stop the JESD204C state machine and allow setting changes.
5. Program CAL_EN = 0 to stop the calibration state machine and allow setting changes.
6. Program the desired JMODE.
7. Program the desired KM1 value. KM1 = K–1.
8. Program SYNC_SEL as needed. Choose SYNCSE or timestamp differential inputs.
9. Configure device calibration settings as desired. Select foreground or background calibration modes and
offset calibration as needed.
10. Program CAL_EN = 1 to enable the calibration state machine.
11. Enable overrange via OVR_EN and adjust settings if desired.

Adc_SetReg(OVR_CFG, 0x0F);

12. Program JESD_EN = 1 to re-start the JESD204C state machine and allow the link to restart.
13. The JESD204C interface operates in response to the applied SYNC signal from the receiver.
14. Program CAL_SOFT_TRIG = 0.
15. Program CAL_SOFT_TRIG = 1 to initiate a calibration.

Before the value is set:

Setting the register and reading it back:

Thanks in advance,

Juan

  • 0
    Prodigy 20 points

    Update: I'm now noticing that quite a few of the registers are returning values other than what we're trying to program into them:

    This is a snapshot taken after the initialisation routine has been executed, and we've attempted to set JMODE to 5, JESD_EN to 1 and CAL_EN to 1. Any ideas? I have a suspicion that I'm not retrieving the values correctly, because this is old code that has had the ADC functioning correctly for a while.

    Thanks

  • 0
    Prodigy 20 points

    Update 2: I realised I put the wrong part number on the title. I'm working with ADC08DJ5200RF

  • 0 in reply to Juan Montero
    TI__Expert 6150 points

    Hello,

    Juan apologies for the delay. Are you able to read the chip type register and confirm it matches your the default value of 0x03 in the datasheet? My thought is that if you can program the part and getting it working the readback functionality might not be working on the adc or FPGA. 

    best,

    Eric 

  • 0 in reply to Eric Kleckner
    Prodigy 20 points

    Hey Eric. Thanks for the reply and apologies for the late reply myself. Yeah, this is one of the ones I tried reading back after I started suspecting the values I was getting back. CHIP_TYPE is returning a 0x03, so I'm currently debugging the SPI interface.

    Thanks,

    Juan