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AD7795 External Clock

In single conversion mode the AD7795 powers up takes a conversion then returns to the power down mode. I presume the internal clock is stopped during power down mode.

I want to drive the ADC with an accurate microcontroller derived 128Khz clock for better immunity and synchronisation of multiple devices using the external clock divide by 2 option.

1) Do I need to stop the clock when I have read the conversion ?

2) Do I need to stop the clock when I read the conversion to get the same power down current as when using an internal clock.

3) Are there any side effects of stopping the external clock between conversions. Presumably the 1ms clock stabilisation time with the internal clock is not required with an external clock.

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  • Hi, Pat.

    Yes, external clock can be more accurate since it can be accurately controlled than the internal clock which is trimmed within a specified accuracy of +/-3% for AD7795. Using the internal clock lessen the need for external clock circuit and helps you minimize the board size and cost. It really depends on your application if the internal clock accuracy is sufficient in your application or you really need a more accurate external clock circuit.

    Thanks,

    Jellenie

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  • Hi, Pat.

    Yes, external clock can be more accurate since it can be accurately controlled than the internal clock which is trimmed within a specified accuracy of +/-3% for AD7795. Using the internal clock lessen the need for external clock circuit and helps you minimize the board size and cost. It really depends on your application if the internal clock accuracy is sufficient in your application or you really need a more accurate external clock circuit.

    Thanks,

    Jellenie

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