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ADC12D1000: VCMO distribution

Alen Barisic
Intellectual 1300 points
Part Number: ADC12D1000

Hi,

we are using the ADC12D1000 in a mature product and have a question regarding the reference voltage output VCMO:

In the datasheet, it is specified to vary from 1.15V to 1.35V with a typical value of 1.25V.

Are there any data on the statistical distribution of this voltage or the probability to reach the min max voltages?

it is slightly temperature dependent 6mV over Tmin=-40 to Tmax=85 and considering 1.25V.

The rest of the VCMO variation is probably due to the process corners since it appears to be a bandgap voltage.

Thanks,

Alen

  • 0
    TI__Mastermind 25260 points

    Hi Alen,

    I can check into this for you. However, we are not allowed to give out statistical distribution data on our products.

    I will see what kind of guidance I can find for you.

    Regards,

    Rob

  • +1 in reply to Rob Reeder
    TI__Mastermind 25260 points

    Hi Alen,

    Vcmo output voltage is only utilized in DC-coupled mode to set the CM voltage of driver amplifiers. As long as the amplifier chain can hold the applied Vcm to the Vcmi limits in Table 6.3 everything will work fine, regardless of the variation on Vcmo.

    Keep in mind, Vcmo voltage isn’t relevant when the pin is pulled to ground to select AC-coupled mode.

    Also from the datasheet...

    8.1.1.7 DC-Coupled Input Signals In DC-coupled Mode, the ADC12D1x00 differential inputs must have the correct common-mode voltage. This voltage is provided by the device itself at the VCMO output pin. TI recommends using this voltage because the VCMO output potential will change with temperature and the common-mode voltage of the driving device should track this change. Full-scale distortion performance falls off as the input common mode voltage deviates from VCMO. Therefore, TI recommends keeping the input common-mode voltage within 100 mV of VCMO (typical), although this range may be extended to ±150 mV (maximum). See VCMI in Electrical Characteristics: Analog Input/Output and Reference and ENOB vs. VCMI in Typical Characteristics. Performance in AC- and DC-coupled Mode are similar, provided that the input common mode voltage at both analog inputs remains within 100 mV of VCMO.

    So, as long as you use the vcm from the device then there should not have a problem over temp.

    Regards,

    Rob