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About the time until the conversion result output of AD7172-2

Let me ask you about the time it takes for the AD7172-2 to get results in single conversion mode (the time it takes for the / RDY pin to go down).

All used with default settings (250Ksps, CH0 only ON, SIN5 + 1,SING_CYC = 1).

Reg: 0x01
DATA: 0xA11C

As a result of writing and starting conversion, the time until the / RDY pin goes down is 354 μS.
I thought that the result would be obtained with 32μS + 161μ (1/250Ksps × 5), but I needed another 161μS.

Q1: Is this correct?

(Virtual Eval Tool --In the BETA tool, the conversion mode is "continuous" and the condition is a little different, but the first conversion seems to be 32 μS + 1 / ODR × 5 and the result is obtained.)
Q2: Is it possible to eliminate the additional 161 μS?

I look forward to your advice.

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  • Hi, 

    Q1. Since in single conversion mode, the part is placed in standby mode after the conversion is complete. So it needs to come out of standby to power up and settle. Thus, the timing for the very first conversion will take longer than that in continuous conversion mode, approximately 128 modulator clocks so it should somehow be less than 161us. May I know how are you measuring the time of the first conversion, are you using the SYNC pin to control the start of conversion or are you just measuring it from the last bit of data written to the ADC mode register? 

    Q2. You can only remove the delay when you operate in continuous conversion mode or when not using the SYNC pin. Please take note that the extra delay time at the very first conversion is the setup time for the signal chain before the first conversion is available when the ADC is power up, coming up from standby mode or when using a /SYNC pin. 

    Thanks,

    Jellenie

  • thank you for your reply.
    The SYNC pin is not used, and the time since the register was written is measured.

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