Tool/software:
Hi!
My audio decoder (player chip with inbuilt HP amp) provides the amplifier output with a buffered ground reference (DC bias on the L and R outputs, along with a matching CBUF). The level is at around 1.2V.
Looking at the datasheet (including the Absolute Maximum values), I don't see a reason why I couldn't use the TS3A227E with this codec by connecting the reference CBUF to AGND, provided that the chip is set to FM mode (disconnecting the Depletion FETs) before the codec is powered up (and hence, avoid driving the biased L and R signals into the system GND through headphones during connection):
- 1.2V is within the range defined by Absolute Maximum Values for AGND
- I can reference the microphone bias to the analog GND (I don't actually need the microphone, but would like the button detection capabilities of the chip)
- Button detection ADC measurement seems to be differential according to the datasheet
- No lines will exceed the stated limits of the chip
- Detection seems to only perform differential measurements that shouldn't depend on system GND, as described here: https://e2e.ti.com/support/switches-multiplexers-group/switches-multiplexers/f/switches-multiplexers-forum/1009226/faq-how-do-the-autonomous-audio-accessory-detection-configuration-switch-ic-s-from-ti-ts3a225e-ts3a226ae-and-ts3a227e-detect-audio-accessory-type
- Also, I can provide system GND to AGND for the duration of detection
Questions:
1. Is there some assumption in the detection algorithm that I've missed, that would preclude button detection or even basic operation in this state?
... yeah, that's the main question, I don't see any others.
