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AIC3106 on L138 eXperimenter board

Donald Reay
Expert 1545 points


Two (possibly related) questions here

1) The line-in input on the logicpd L138 eXperimenter board is connected via a single 10k resistor to ground and a 0.47uF capacitor to the LINE1LP pin on the AIC3106. The LINE1LM pin is not connected. According to the datasheet, the LINE1 input is differential - you can't configure it single-ended - is LINE1LM not connected accepted practice?

2) I'm a university lecturer and I've had my students using C31, C6711 and C6713 DSKs for many years. Currently I'm porting teaching demonstrations/lab experiments from the C6713 DSK to the L138 eXperimenter and I've now destroyed the analogue inputs to two AIC3106s. Over several years of equivalent student lab use, i.e. plugging/unplugging and using signal generators, microphones and mp3 players, of the other DSKs I've never seen the analogue input to an AD535 or AIC23 damaged. I've ported the experiments to an L137 EVM too and haven't damaged the AIC3106 on that board. I notice however that the circuit connecting line-in on the L137 EVM to the AIC3106 is more complex than that on the eXperimenter. (5k6/5k6 potential divider with 220pF across output, followed by series 0.1uF capacitor to LINE1LP.)

Why am I destroying the AIC3106 inputs on the eXperimenter board when the L137 EVM and C6713 DSKs seem impervious to similar (mis-?) treatment?

Incidentally, on the schematics I'm looking at, the input circuit on the L138 eXperimenter is referenced to 'DGND' while the equivalent on the L137 EVM is labelled 'GND-AIC'.

 

Donald

  • 0
    TI__Mastermind 28585 points

    The inputs on the AIC3106 can be configured for differential or single ended in the registers. The default is single ended.

     

    Either way, the inputs should be AC coupled due to the internal mid-rail bias on the inputs. The input full scale voltage to the AIC3106 is .707 Vrms single ended and 1.4 Vrms differential. Assuming that the inputs are AC coupled and you don’t exceed the full scale input range, you should be in good shape.

  • 0 in reply to Converter Apps
    Expert 1545 points

    My mistake about the input configuration.

    I'm not intentionally exceeding the full scale input voltage range (which is not to say that I'm not doing something with the input that the AIc3106 doesn't like) but although the AIC23 had a larger full scale input voltage range of 1.0 Vrms neither my students nor I ever damaged one. Are the inputs to the AIC3106 inherently more fragile than those of the AIC23?