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LP-MSPM0L1306: ADC Parameters

Eric Christenson
Prodigy 160 points
Part Number: LP-MSPM0L1306
Other Parts Discussed in Thread: MSPM0L1306

I need to design "front end" circuitry to target the ADC pins on the MSPM0L1306, but I don't have any specifics from the datasheet on 

a) DC leakage current

b) sample and hold structure.

These are important because I'd like to avoid op-amps and use high impedance resistive dividers to sense, for example, my 9V battery voltage and I'll want those resistors to be as large as possible to maximize battery life. 

There's also typically some cross-talk and charge injection  between channels due to the charge stored on the sample and hold capacitor from the previous conversion, so how much is that?  I need to know how long to sample for a given accuracy given the circuitry I have!

E.

  • 0
    TI__Guru 71216 points

    HI Eric,

    I'm checking with our designers on this.  I do know that leakage current goes up at higher temps, but I don't know how much or at what temps.  Hopefully the design team can come back with some numbers.

  • 0 in reply to Dennis Lehman
    TI__Guru 71216 points

    Hi Eric,

    According to our designers where Scomp is the no. of clock cycles during sampling phase of ADC.

    In below case, for “scomp=5” means 5 clock cycles of 32M CLK. 

    And with elevated temps, expect higher leakage currents.  We don't have an characterization data on this.

  • 0
    Prodigy 160 points

    So this says we get good accuracy just waiting 8 clocks for sampling time.

    Is there a pre-amplifier in front of the sample/hold capacitor?  80dB on a 12-bit ADC seems like we are into fractional bit errors, at which point something has to be said about the noise.

    And of course the leakage current increases with temperature; the first person to find a material for which that is not true without a phase transition will be quite famous!