Dear Specialists,
My customer is evaluating TSC2046E.
Even though the touch panel is not pressed, the Lo signal of \ PENIRQ is output, and then the controller continues to be interrupted.
I'd be grateful if you could advise.
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When I checked the waveform, the X + terminal dropped to about 1.5V after data acquisition (DOUT) on the controller side.
In the standby state (\ CS is Hi), the \ PENIRQ signal becomes Lo, so interrupts are repeatedly applied to the controller side.
After that, the voltage of the X + terminal gradually rises, and the \ PENIRQ signal becomes Hi.
Could you please see the waveform below.
This is a waveform without interrupt.
The schematic is listed below
---background
When the touch panel is changed, depending on the touch panel, the Lo signal of \ PENIRQ when the touch panel is not pressed does not appear.
When the capacitance between touch panels increases, the Lo signal of \ PENIRQ tends to continue to be output.
As described in the reference material (SBAA155A), even if the capacitors (circuit diagram: C5, C6) of the X + and Y + terminals are removed, the Lo signal of \ PENIRQ will continue to be output and the X + terminal will drop to about 0V. It takes time to return to the Hi signal of \ PENIRQ.
What is the reason why PENIRQ becomes L even though the touch panel is not pressed?
---quesiton and request
Could you please let us know why the phenomen happen and what is the measures.
Our guess is as follows.
The amount and time of the X + voltage drop, the voltage rise time from there, and PENIRQ are linked.
It seems that the X + voltage changes at the timing of enabling PENIRQ after the Idle state before the LSB output of DOUT shown in Fig. 9 of the data sheet.
Is it correct?
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I appreciate your great help in advance.
Best regards,
Shinichi