Texas Instruments TS3A227E, Руководство пользователя

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Using the GUI
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5. Attach the external microphone between the SLEEVE and RING2 and match the microphone ground
to the location of the ground chosen in step 3.
6. Enable Key Press Detection and Raw Data .
7. Attach the key and the GUI now reports the detected resistance.
7.5 Power Off Noise Removal Evaluation
The depletion FETs of the TS3A227E provide a ground connection when the device is unpowered,
eliminating the humming noise phenomenon associated with previous-generation audio jack switches. The
EVM provides an easy means to evaluate this performance with the following procedure:
1. Remove both jumpers from J12. This floats the ground lines of the codec audio jack J10 and simulates
what the TS3A227E would be like without the depletion FETs.
2. Insert the speakers into jack J10.
3. Turn on the speakers and turn the volume up until a humming noise appears.
4. Turn off the speakers.
5. Remove the jumper from J2. This removes power from the TS3A227E.
6. Insert the speakers into the TS3A227E audio jack J4.
7. Turn on the speakers and turn the volume up and the humming noise is no longer present.
7.6 Slow Plug-In Issue
Any system which utilizes an audio jack must overcome the slow plug-in issue to deliver a positive
end-user experience. On the TS3A227E-EVM, the audio jack follows the guideline of having the detection
mechanism on the tip pin but the mechanical structure of the jack trips too early for a standard insertion.
This causes an incorrect detection because the RING2 pin is not making contact when the detection
algorithm runs, resulting in a false OMTP detection when a 4-pole standard or 3-pole is inserted.
To remove this issue, there are two immediate options:
• Increase the insertion de-bounce period to compensate for the mechanical shortcomings of the jack:
– This option can be tested with the TS3A227E-EVM and GUI. Increase the insertion de-bounce
incrementally and observe how the detection passes. At 150 ms de-bounce, the slow plug-in issue
is eliminated.
– Conversely, the de-bounce can be reduced to observe the effects of having a shorter de-bounce.
• Change the audio jack to a better mechanical structure:
– This is the best option, by choosing a jack with the detection mechanism further inside the jack it
would ensure that the headset is fully inserted and is entirely reliant on the de-bounce
TI recommends developers that use the TS3A227E utilize the EVM test points for the audio jack pins and
connect the EVM to the audio jack that is planned for implementation. This allows the system designer to
test how the TS3A227E and the audio jack perform together and makes changes as necessary.
18 TS3A227E EVM User's Guide SLVUAD9 – December 2014
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