OPT3001-Q1: Sensor seems stopped working or not available on I2C while performing Radio Immunity test

sevender sharma

Part Number: OPT3001-Q1
Other Parts Discussed in Thread: OPT3001

Tool/software:

We are using OPT3001IDNPRQ1 in our system to adjust the display backlight on the basis of Ambient light. We are performing EMC (radio immunity) test and we are facing issue with light sensor data.

Is there any data which can show that OPT3001-Q1 is quite immune to the external field applied? Please suggest what we can do to improve the immunity performance.

Thanks

8 months ago

0 Joseph Scherphorn 8 months ago

TI__Expert 4710 points

Hello Sevender,

We are looking into this, If you could provide a schematic for your current use case that may be helpful.

Thank you,

Joseph Scherphorn

0 sevender sharma 8 months ago in reply to Joseph Scherphorn

Prodigy 90 points

Hi Joseph,

Thank you for your reply.

Please see the snap.

0 Bruce McKenney 8 months ago

Guru 100365 points

The I2C (as a bus) is highly susceptible to noise, (mostly) because of the passive high. Noise can result in bus malfunctions or (more insidious) false data bits.

Noise effects can be mitigated somewhat with (a) shielding (b) stronger pullups (c) redundant reads (voting) (d) in extreme cases: bus recovery (the 9-clock SDA trick and/or power/reset control over the target).

This is independent of the the device being used, though there are some few I2C devices that employ a checksum/CRC on the packets.

0 Joseph Scherphorn 8 months ago in reply to sevender sharma

TI__Expert 4710 points

I agree with Bruce and would advise the addition of pull-up resistors on the I2C lines. Typically, I include these in my original design and consider it a general best practice

0 sevender sharma 8 months ago in reply to Bruce McKenney

Prodigy 90 points

Hi Bruce,

We are using 4.7K resistor for pull-up. In your opinion what value we should try (you must be having some previous experience)?

0 Joseph Scherphorn 8 months ago in reply to sevender sharma

TI__Expert 4710 points

Hello Sevender,

Were you previously using these pullups (and simply not pictured on schematic sent) or are you now implementing them after this conversation? 4.7K should be fine, typical application information on data sheet for OPT3001 advises 10K ohm pullups but in practice we often use 4.7k as well. Your choice is sufficient.

Thank you,

Joseph Scherphorn

0 sevender sharma 8 months ago in reply to Joseph Scherphorn

Prodigy 90 points

Hi Joseph,

Yes, we were using these resistors from initial state. In the schematics shared, we are using one external connector to connect to master boards. In master board we are using I2C pullups (4.7K).

0 Bruce McKenney 7 months ago in reply to sevender sharma

Guru 100365 points

I think we ended up with 2K. But we also did all the other things I mentioned.

It's probably useful to get some idea (via a scope) just how bad things are before setting off on a distraction. Amplitudes from Radiated Susceptibility are presumably lower than what we see. (And maybe it's not the bus after all.)

I posted mainly so people don't forget the hazard from the bus itself. I've gained a new appreciation for the resiliency (brute force) of good ol' RS-232 (:-)).

[Edit: Minor clarification]

0 sevender sharma 7 months ago in reply to Bruce McKenney

Prodigy 90 points

Hi Bruce/Joseph

Thank you for your support here. We tried by reducing the pullup resistors to 1k but issues still exists. Now we are trying to shield the connection cable.

We can not probe the signal in the Radio chamber while testing.

The thing I was seeking from your side that is this kind of issues you had faced earlier and what all can be the reasons. from the discussion it seems the IC seems pretty immune, only external circuitry we are doubting.

Thanks again for your support.

0 Joseph Scherphorn 7 months ago in reply to sevender sharma

TI__Expert 4710 points

Hello Sevender,

I'm looking into this and working to connect you with resources better versed in EMI issues. I appreciate your patience and look forward to providing you with solutions.

Thank you,

Josph Scherphorn

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OPT3001-Q1: Sensor seems stopped working or not available on I2C while performing Radio Immunity test