TSC2007: PENREQ output oscillates

Daisuke Higa

Part Number: TSC2007

Tool/software:

Hi support team all.

My customer is currently continuing the evaluation, but has encountered two problems.

Q1
The issue is that the PENREQ output oscillates, as shown in the attached image. I don't know why this is happening.
We are hoping it will be H or L, but it's not happening.
Could you please advise on how to solve this problem?

100ms/div

Q2
Even if it doesn't oscillate as shown in the image below, something like chattering occurs when the waveform rises or falls.
This chattering occurs when the touch panel is touched, so I've taken measures by connecting an RC LPF to the PENREQ output, but I haven't been able to completely avoid it.
Could you please advise on how to solve this problem?

Best regards,

2 months ago

0 Daveon Douglas 2 months ago

TI__Mastermind 27330 points

Hi DH,

Q1. This could happen if the touchscreen lines (X/Y) are floating or noisy. TSC2007 can falsely detect rapid toggling on these lines. Adding a series resistor can help suppress ringing on these lines and you can use many of the application notes linked on the webpage as reference schematics.

Q2. I think the RC LPF was a good idea, you could increase the time constant to further dampen edge chatter. Lastly check the touchscreen itself as this could also be contributing to the noise.

0 Daisuke Higa 2 months ago in reply to Daveon Douglas

Genius 4360 points

Hi Douglas-san

Thank you for your answering.

Where should I add the series resistor?

And which circuit document should I refer to?

The circuit you attached is almost identical to my customer's, but they are having trouble.

+1 Daveon Douglas 2 months ago in reply to Daisuke Higa

TI__Mastermind 27330 points

You would add the series resistor directly on each X(+/-)/Y(+/-) lines as shown between the panel and device. Adjust from 100Ohm to 300Ohm to see if this reduces any noise on the line

0 Daisuke Higa 2 months ago in reply to Daveon Douglas

Genius 4360 points

Hi Douglas-san

Thanks you updating.

I understood.

0 Daisuke Higa 2 months ago in reply to Daveon Douglas

Genius 4360 points

Hi Douglas-san

Thanks your updating.

I understood.

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TSC2007: PENREQ output oscillates