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Original question:

OPT3101: OPT3101 photo diode input circuit description and spice model

OPT3101: Interference of several devices

Stefan L
Prodigy 40 points
Part Number: OPT3101

Tool/software:

Hello,

in the linked thread is described, that more than one OPT3101 can work in the same area without disturbing each other, because of the IQ demodulation technique.

OPT3101: OPT3101 photo diode input circuit description and spice model - Sensors forum - Sensors - TI E2E support forums

Unfortunately, we can not confirm that.
Our devices are similar to the OPT3101EVM. The configuration is done with the help of the Configurator Tool in Super HDR mode.

If device #1 is directed onto a second device, #2 is strongly disturbed by the other device.

This can clearly be observed by switching of the LED currents.

Is there a special configuration to optimize this behaviour?

Thanks.

  • 0
    TI__Prodigy 600 points

    Stefan

    Device #1 or #2, I believe you meant different module with separate OPT3101. 

    Are you trying to integrate two OPT3101 devices to cover different field of view on the same module?  Or are you using two separate devices and pointing to the same object and see wrong distance result? How close are these two parts?

    Thank you.

    Wenjuan

  • 0 in reply to Wenjuan Fan
    Prodigy 40 points

    Hello Wenjuan,

    Thank you for your response.

    We are using two seperate devices.
    Two scenarios are possible:
    1) Both devices point to the same object, so that the emitter light spots overlap.

    2) One device points dirctly into the optic of the second device.

  • +1 in reply to Stefan L
    TI__Prodigy 600 points

    Stefan,

    OPT3101 is using phase difference between the emitted and reflected light to calculate distance. The emitted light is modulated at high frequency (10MHz), two devices won't interfere each other. 

    In the two scenarios, the concern would be saturating the photodiode. OPT3101 has ambient cancellation that lets it function under certain levels of IR light such as in sunlight. If the diodes are not saturated and OPT3101 is able to cancel, then it will function. 

    You mentioned you observed switching of the LED currents when pointing one to another. If the diodes are not saturated, can you try to verify the distance output? The IR light from another OPT3101 will show as "ambient" value. 

    Best regards,

    Wenjuan

  • +1 in reply to Wenjuan Fan
    TI__Prodigy 600 points

    Stefan,

    OPT3101 is using on-chip oscillator. The oscillator frequency of the two OPT3101 can never be the same due to process variations. Their phase is also not locked. So only the signal from the same AFE which is frequency / phase locked will be processed. Other AFE signal which is not frequency / phase locked will be rejected. So the interference should be negligible. 

    However, the signal from the second AFE will occupy the dynamic range of the 1st AFE and vice versa. So there is a chance that one AFE could cause saturation of the other AFE depending on the reflected light coming back. 

    Hope it helps. 

    I will close the tiket and if any other questionsn please open a new one. 

    Thank you.

    Wenjuan