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MSPM0G3507: MSPM0G3507/1107 ADC12 S/H capacitor charger/discharge

EK ZHOU
Prodigy 110 points
Part Number: MSPM0G3507
Other Parts Discussed in Thread: SYSCONFIG

Hello,

I m investigating if MSPM0G3507/1107 ADC S/H capacitor charger/discharge could help an issue finding. as known there is DL function __STATIC_INLINE void DL_ADC12_enableSAMPCAP(ADC12_Regs *adc12), it may be called by unchangable ti_msp_dl_config.c. how to enable it by SYSCONFIG or user code? TRM mentions that Sample and hold capacitor is discharged at the end of conversion if set RSTSAMPCAPEN, assume sequence ADC, wondering the end of conversion means that one channel ends or entire sequence ends. one more thing not really clear understood can you disclosure the internal why its input resistance only 0.5Kohm however usually ADC should be more than couple of 10Ks. thanks.

  • +1
    TI__Expert 3220 points

    Hi EK,

    The MSPM0G3507 cannot configure this bit field of the CTL2 register. The sample and hold capacitor automatically discharge after every conversion. In the case of the ADC operating in sequence mode, this means the capacitor will discharge after each channel has completed its conversion.

    For your second question, the Rin seen in the data sheet should be considered the sample and hold resistance of the ADC. If this value is too large, it will slow down the sampling rate. If you are concerned with signal drive and integrity, a buffer will help, or an OPA can be used to make a second order filter.

    Best Regards,
    Brian