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TLV320AIC3106 Codec: maximum input voltage

d sandquist
Prodigy 160 points

Just to verify, the TLV320AIC3106 has individual attenuation on each audio / analog input channel as shown in Figure 31.  This says each channel has "a gain programmable from 0 dB to –12 dB in 1.5 dB steps".  It also says, "In general, the mixed signal should not exceed 2Vpp (single-ended) or 4Vpp (differential)". 

I'm just using one differential channel per PGA/ADC (Line2L_in, for instance.  I don't plan on using channels 1L or 3L.

Is it fair to assume that before attenuation the signal cannot exceed 4Vpp (differential)?  I'm assuming this is the case, but it would be great if the signal coming in could be 12 dB higher and it is attenuated -12 dB to the range 4Vpp (differential).  This would increase the input voltage to:  4Vpp(diff) * 10^(12/20) = 4Vpp(diff) * 3.98 = 15.9V(diff) in.

Depending on the design of the attenuator, this could be the case or not & I can't find it specifically called out.

thanks,

David

  • 0
    Prodigy 160 points

    If the input channels can handle rail to rail (0 to 3.3V) on each differential input, this would also help: ±6.6(diff) instead of ±4V(diff). Like I said, I doubt it, but it would be nice.

  • 0
    TI__Mastermind 28585 points

    the inputs have esd protection diodes to the rails so you can't exceed the rails by a diode drop or you risk damaging the part. If you stay within the safe range you won't damage the part but you could get some clipping due to internal offset in the part. You would have to check it.

  • 0 in reply to Converter Apps
    Prodigy 160 points

    A colleague performed a test where a signal larger than the ADC input range but still within 0 to 3.3V was applied to the input and were able to use the channel attenuators to bring the signal within the range of the ADC.  Because the results reported to me weren't in volts, I can't say how close to the rails the signal was, but clearly the inputs aren't limited by the full scale range of the ADC as long as you use the attenuation to bring it within range.  We used this to increase the ENOB/ dynamic range.

    This isn't spec'd so anyone who uses these results is subject to changes made to the design by TI, but it has been beneficial for our short term needs.