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LMV1091: LMV1091 Pre AMP no function

Jacky Lo
Prodigy 40 points

Part Number: LMV1091
Other Parts Discussed in Thread: TLV320ADC3120, TLV320AIC3204, TLV320AIC3262

LMV1091 we output 1KHz , 18mV difference single from single generator is ccuurnely applied to MIC1+ and MIC1-. The supply voltage VDD is set to 3.3V and SD=VDD. The MODE is ser to MIC1 =on and Mute is set to "MIC2 Mute

The single generator is connected across R1(M1+) ans R5 (M1-). The MIC_BIAS we measuremt 1.96V and MIC_P nd MIC_ are 0.98V, these waveform I show the word file please reference.

Could you plrase help check wate the potential issue might be, it seem LMV1091 Pre AMP no function, and Post AMP work OK. 

Look forward to your reply.

Unication_LMV1091.docx 

  • 0
    TI__Expert 5640 points

    Hi Jacky,

    The maximum AC output voltage is 1.2Vrms (around 3.4Vp-p), and with your current configuration of 18mVp-p input + pre-amp gain=36dB + post-amp gain=18dB, the output would exceed this at 3.19Vrms (9Vp-p). Can you try a lower gain setting combination, such as Pre Amp gain = 20dB, Post Amp gain = 6dB?

    Regards,

    Isaac

  • 0 in reply to Isaac Buliva
    Prodigy 40 points

    LMV1091 setting below and attach the test waveform to you reference, it see still no function

    Currently supplying a 1 kHz, 18 mV differential signal to MIC1+ and MIC1- using a signal generator. VDD is maintained at 3.3V, SD = VDD, MODE is set to MIC 1 ON, and Mute is set to Mic 2 mute (as there is no signal when both Mic 1 and Mic 2 are muted)

    Unication_LMV1091_Wavform.docx

  • 0 in reply to Jacky Lo
    TI__Expert 5640 points

    Your schematic and settings for configuration look correct, I would suggest probing directly at the device pins to ensure all of the expected voltages are seen by the device, and try using a standard load impedance values, RL = 100kΩ, and CL = 4.7pF are used in the datasheet EC table.

    Regards,

    Isaac

  • 0 in reply to Isaac Buliva
    Prodigy 40 points

    We have grounded the front-end capacitors (C7 & C8) of Mic2+ and Mic2-, and set MODE1 = 0 and MODE0 = 1, but the pre-amplifier still fails to amplify properly. GA0-GA3 and GB0-GB2 are 3.3V (=VDD), when set to HIGH= 3.3V and set to LOW=0V. Currently, we are using a signal generator to supply a 1kHz, 18mV differential signal to MIC1+ and MIC1-, with VDD supplied at 3.3V and SD = VDD."

    Please refer the attach for waveform information

    Unication_LMV1091_Wavform 20261008.docx

  • 0 in reply to Jacky Lo
    TI__Expert 5640 points

    Hi Jacky,

    Is this issue consistent across all units in your testing? I would suggest trying to swap out the unit to check this.

  • 0 in reply to Isaac Buliva
    Prodigy 40 points

    Our client tested 7 boards, and all of them exhibit the same issue where the LMV1091 fails to function. They also measured that pins GA0 to GA3 are at a High level, and the input signal is an 18 mV AC signal generated by an Agilent/HP 8903B. Are there any other recommended methods for verification?

  • 0 in reply to Jacky Lo
    TI__Expert 5640 points

    Hi Jacky,

    I will check to see if we have any EVM for this device to help debug this.

    Regards,

    Isaac

  • 0 in reply to Isaac Buliva
    Prodigy 40 points

    Hi Isaac,

    Thank you for your assistance. I look forward to your update

    BR

    Jacky Lo

  • 0 in reply to Jacky Lo
    TI__Expert 5640 points

    Hi Jacky,

    After checking, we do not have any hardware platform reference or EVM for LMV1091, and continued debugging efforts will be difficult to support for an older device like this. I would recommend looking into newer devices with better capabilities and features.

    I have compiled some info from older threads here on E2E on suggestions:
    "    You can use other ADCs like TLV320ADC3120 to capture the data from a couple microphones, although you'll need to perform the noise cancelling algo on the host processor. The ADC includes some features that could help to improve performance, but not the algorithm itself. ADCx120 family includes a VAD block that can be used to detect voice activity at the input and notify the host processor. It also includes biquad filters that you may use to filter voice bandwidth (~300Hz to ~3kHz) before sending to host processor."

    "Similar functionality could be implemented using op amps and ADC or CODEC with noise cancelling capabilities. Alternatively similar analog noise cancelling could be implemented with discrete electronics."

    "A lot of our more modern ADCs have mic preamps and mic biases built in such as the TLV320ADCx140 family. There's many codecs that have a front end as well, such as the TLV320AIC3204. We don't officially support Active Noise Cancellation but it can be done with an integrated DSP codec such as the TLV320AIC3262, some customers opt to do noise cancellation and other similar algorithms on the SoC."

    Regards,

    Isaac