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TS5A63157 failures

Andrew Coad
Expert 1625 points
Other Parts Discussed in Thread: TS5A63157, TPD1E04U04

Hi,

I'm using the TS5A63157 in the first stage of a guitar amplifier to provide a -10dB attenuation option. I have had a couple of failures of the device - the nature of the failure is that it still passes the analog signal but looks like a 10K approx. impedance. The circuit diagram is below:

VCC5.5 is supplied from a TPS7A4901 LDO. VGND is VCC5.5/2. D3 is a 5V TVS bi-dir diode. VCC5.5 is switched on after the MCU detects a guitar is plugged in. VCC5.5 is switched off if there is no input signal for N seconds and switched on again if an inout signal is detected.

In the case of failure, the circuit still works in the sense that analog passes through the device but the change in effective input impedance drastically lowers the signal level so that the audio detect no longer works unless you hit the guitar really hard.

Is there anything additional that I should do in terms of device protection? The TVS diode will allow an ESD spike to hit the TS5A63517 of approx. +/-5V. I've checked some of your reference designs that use this device but none of them have a device near an input terminal.

Appreciate any advice.

Kind regards,

AC

  • 0
    TI__Mastermind 24885 points
    Hello Andrew,

    I have contacted the appropriate person to address your request.

    Best,
    Michael
  • 0 in reply to Michael J Schultis
    TI__Genius 12190 points

    Hi Andrew,

    Shreyas and I spoke about this issue on the phone. The recommendation is to change the bi-directional TVS to a uni-directional one. TPD1E04U04 fits this bill and has very low clamping voltages during an ESD event. A uni-directional TVS will drastically lower the clamping voltages during negative ESD events. This should solve the issue.

    Regards,

  • 0 in reply to Guy Yater
    Expert 1625 points
    Hi Guy,

    Many thanks for your reply. The guitar input is a bipolar signal with approx 2V p-p maximum signal level so the TPD1E04U04 will clip the negative going signal to around 800-900mV (according to the data sheet).

    I could put the TPD1E04U04 between ground and the junction of C11 and R9 which has a voltage swing of 2.75V +/- 1V. What are your thoughts on this approach?

    Kind regards,
    AC