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MSP430F5438A ADC12_A delay

Other Parts Discussed in Thread: MSP430F5438A

Hi,


I am working on MSP430F5438a micro controller.

I was going through the sample codes for MSP430F5438A. There is a file msp430x54xA_adc12_02.c  (ADC12, Using the Internal Reference).

A delay of 75us is taken for 1MHz clock. I checked the MSP430F5438a datasheet. but I could find the calculation for choosing that value.

I am currently working on 12MHz clock. So how much delay should I choose (is it same 75us or does it depends on other parameters). Please if anyone could give me mathematical calculation for delay value.


Thanks

Yuvraj

  • Hi Yuvraj,

    The 75us is actually a settling time for the voltage reference after you turn it on, not the ADC itself. You can find this spec in the datasheet www.ti.com/lit/gpn/msp430f5438a p. 66 under the REF specs, it is marked as tSETTLE.

    Since the spec is for 75us, you will need to adjust the # of cycles that you delay when you use a different MCLK frequency, to ensure that it's still 75us delay at the higher speed. So for 12MHz, you will need 12 * 75 cycles delay = 900 cycles.

    Regards,

    Katie

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