Problem ADAs3023 signal BUsY and sDO

Hi, I have a problem with ADA3023 since I cannot read the conversion with a dPIC, first of all the first thing I have done is the following check:
there is a voltage of 5V and + -15V. In the ACAP PIN, RCAP and REFIN there are 2.5V and in REF1.2 = 4.096V, I have left the default CFFF register FFFF and use the datasheet initialization sequence for the power supply.

After these checks I have done the ADC readings by the sPI and they fluctuated. After analyzing with the oscilloscope I have noticed that the BUsY PIN does not change, it is always at zero it does not warn that the conversion is finished. I have changed the ADA3023 for two times for a new one, assuming this was a problem but the PIN BUsY remains the same.

I don't know what else I can do!

thanks!



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[edited by: @skowalik at 6:39 PM (GMT 0) on 29 Dec 2019]
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  • 0
    •  Analog Employees 
    on Dec 29, 2019 6:36 PM over 1 year ago

    Niuton,

    Can you tell me a bit more about how you have the device serial interface connected?   For example is CS always driven low?

    Regards

    Sean

  • Hi, thank you very much for answering.

    the communications are controlled by the dsPIC




    This is the sequence I use to activate the ADAs and read the sDO output

    //Power secuence

    L_ADAS_RESET = 1;
    L_ADAS_PD = 1;
    L_ADAS_CNV = 0;
    L_ALIM_CS_DVDD = 0;
    L_ALIM_CS_AVDD = 0;
    L_ALIM_CS_VDD = 0;
    __delay_ms(100);
    L_ALIM_CS_VDD = 1;
    __delay_ms(1);
    L_ALIM_CS_DVDD = 1;
    __delay_ms(1);
    L_ALIM_CS_AVDD = 1;
    __delay_ms(200);

    L_ADAS_PD = 0;
    __delay_ms(100);
    L_ADAS_RESET = 0;
    __delay_ms(200);

    //Enable CNV

    L_ENABLE_CS = 1;
    L_ADAS_CNV = 0;
    __delay_us(10);
    L_ADAS_CNV = 1;
    __delay_us(5);
    L_ADAS_CNV = 0;
    __delay_us(20);
    L_ENABLE_C= 0;
    result1 = SPI1_WR(0xFFFF);
    L_ENABLE_CS = 1;

    The red channel in the Cs PIN and the yellow one the CNV PIN.

    thanks

  • 0
    •  Analog Employees 
    on Dec 31, 2019 6:15 PM over 1 year ago in reply to Niuton

    Nuiton,

    I would try pulling PD and RESET to your +5V supply with weak pull-up resistors (10K),  this will account for any start-up related delay in the dsPIC driving PD and RESET.   My suspicion is that although it appears you followed the start-up sequence that the device may still be coming up in a bad state.

    Have you tried making any of the other edits recommended?

    Sean

  • Hello, first happy new year 2020.

    I have connected to AGND, REFN and REFN_2. I added the 10k resistor and it stays the same, it doesn't change the BUSY PIN.

    I have read that ACAP and DCAP are output from two different 2.5V regulators, could this be causing problems?
    I will try to modify the PCB I have to separate these 2 PINs and comment again.

    thanks

  • Hello again, thank you very much for everything, the signal in the PIN BUsY has already appeared. To solve this, I have made the modifications you mentioned to me.
    In addition I had to add a reset in the boot sequence.

    thank a lot!!.

    Now another problem has appeared, the PIN Cs remains at a value of 1.5V 'high' or 0V 'low' does not reach 5V. The Cs is connected to a dspic PIN and a 10K resistor at 5V voltage.

    If I measure the PIN of the dspic on the air I get the square signal 0V, 5V and when measuring the PIN Cs with the 10K resistor connected to 5V, fluctuations of 0V and 5V appear (should this not happen since I have the 10K repeatability, right? ?)

  • 0
    •  Analog Employees 
    on Jan 8, 2020 3:45 PM over 1 year ago in reply to Niuton

    Niuton,

    I would review what has been changed as the original plot you sent did not have this problem from what I recall.   My suspicion is that there is an unintended leakage path to a signal like SCLK or CNV that is creating contention.

    The CS pin itself is a digital input so it should not be loading the signal from the dsPIC.

    Hope that helps 

    Sean

  • thank you very much again.

    the system is already working, the PIN CS was linked to SDO.

    thanks

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