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OPT3101: About offset calibration

Kevin_wang
Prodigy 230 points
Part Number: OPT3101

Hi TI:

I encountered the following problems in the calibration process

  • When the offset calibration, such as the need to super - HDR mode of four groups of current value, whether to phase four groups of calibration current, and the four offset value written to the corresponding register, so whether we need four groups in the offset correction current measurement process meet the AMP > 10000？
  • In offset correction under the condition of four groups of current (choose only one group for correction of current measurement of AMP > 10000), in this case, when running in super - HDR mode and under a certain distance measurement, when the current group will lead to larger distance migration, there is no accurate calibration result in?So does the switching of current cause a large deviation in distance?

Look forward to your reply！

Best,

Kevin_Wang

  • 0
    TI__Mastermind 25855 points
    Hi Kevin,

    1) You are asking if phase offset calibration is required for all 4 current settings, correct? Yes, you will need correction on all 4.

    2) You are asking if you were to use the same calibration for all current settings (instead of a different calibration of each setting) would this have a large impact on distance error, correct? Yes, it would cause a large deviation. The forward current will change the voltage drop across the LED which changes the capacitance of the LED. This change in capacitance will change the RC constant of the circuit and result in a phase shift. If this phase shift is not calibrated for there will be a deviation in distance.

    Best,

    Alex
  • 0 in reply to Alex Bhandari-Young
    Prodigy 230 points
    Hi Alex:
    What I want to ask is in the process of phaseoffset calibration, when the four current values are calibrated, can the calibration calculation be carried out at the same distance? And do all four cases satisfy the condition of AMP>10000?
    Best,
    Kevin
  • 0 in reply to Kevin_wang
    TI__Mastermind 25855 points

    Hi Kevin,

    This depends on the current settings that you choose and the optics used. Likely multiple targets will be needed because you usually choose the super HDR currents to allow the device to function at a large range of distances/reflectivity.

    There are a couple options

    1) If you are willing to compromise on accuracy a bit you can decrease the amplitude requirement of 10k slightly without much impact on performance. On the EVM we calibrate phase offset at 2 distances total for the 4 currents. This means the larger of the two currents will be 24k and the lower one will read ~7k. Thus only 2 distances are needed instead of 4.

    2) If you are able to vary the target reflectivity then distance need not change.

    3) Or you can choose different distances such that amplitude is always 10k or greater for best results.

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 230 points

    Hi Alex:

    I want to know what the reference values of the Iphase and Qphase of xtalk correction are, because our EVM is broken!

    Thank you!

    Best!

    Kevin

  • 0 in reply to Kevin_wang
    TI__Mastermind 25855 points
    Hi Kevin,

    Sorry, I do not understand. Is this question related to our above discussion? I did not realize your EVM was broken. If this is a new question could you please create a new thread and provide some background? If not, could you please explain how this relates to our above discussion and give some more details so I can understand your problem?

    Best,

    Alex