DAC8574: DAC8574 power on/off issue

Hi Shahzad,

Welcome to E2E and thank you for your query.

Regarding your first question, the marking might be the Lot Trace Code (LTC). Could you please let us know your procurement source so that I might be able to provide additional details on this?

Regarding your second question, I am not very clear on the actual question and the circuit details. The DAC itself doesn't have a memory and with power-on/off it is not supposed to retain any value unless the on/off is so fast that the capacitors don't let the device turn off and on properly. Could you please provide more details on the problem? It would be great if you can share schematics, software algorithm etc so that we can debug the issue properly.

Regards,
Uttam Sahu
Applications Engineer, Precision DACs

Thank you very muck for your kind reply.

Following are the answers to your questions.

1 ) Our procurement source is Digi-Key Electronics.

2) We are using STM32F407vg with DAC8574 using I2C protocol. Problem we are facing is whenever we program the controller & set 4.5V value on dac & turn off the circuit for 4-5 seconds and turn it on for ten times , it shows correct value sometimes. But randomly, channel shows 0.987V instead of 4.5V.

Following are the DAC schmatic and software algo:

void dac()
{									//VREFL = 0V, VREFH = 5V, VOUT = 4.5V
        aa=65536/5;                 //VOUT  =  VREFL + (VREFH - VREFL)  * (D / 65536) from DAC8574 datasheet
        aa=aa*4.5;
        cc1=aa;
        bb=cc1>>8;
        
        delay_ms(10);
        
        delay_ms(10);                   
        //0x98          //Address Byte 
		
        delay_ms(10);
        //0x10          //Control Byte
		
        delay_ms(10);
        //bb            //MSB data 
		
        delay_ms(10);
        //aa            //LSB data 
		
        delay_ms(10);
       
}

Hi Shahzad,

I don't think your actual question has any link to the procurement source or the manufacturing lot. Hence, I am discontinuing that discussion here on.

Regarding the main question, the DAC is not intended to be used as a memory device. If you use capacitors as charge storage components, invariably there will be leakage and also the result will not be repeatable because of the real-time dynamics of switching. If you are planning to use the output capacitors as analog memory components, the design is even trickier.

If you can provide more details on your actual application I will be able to suggest an appropriate architecture for implementation.

As such I see some fundamental issues with the schematics, but I would like to reserve my comment till I understand the application properly.

Regards,
Uttam

I am not using dac8574 as memory device, you can see the code

aa=aa*4.5;

that I am just  setting direct 4.5V on each power off/on.

Hi Shahzad,

Could you please do a scope capture of the I2C waveform both in the working and non-working conditions? Please mark the traces properly so that I am able to interpret them properly.

Regards,
Uttam