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DAC8760: No data on DAC register

Heikki Korhonen
Prodigy 10 points
Part Number: DAC8760


Hi,

I am having issues when I am trying to control and communicate with the DAC8760 IC. I am trying to get the either one of the outputs to work but with no success.

Here is the initializing for the DAC:

DACx760WriteReg(spi, ADDR_RESET, 0x01); //software reset
DACx760WriteReg(spi, ADDR_CTRL, (0x01<<CTRL_RANGE)|(0<<CTRL_OVR)|(1<<CTRL_OUTEN)); //0-10V
DACx760WriteReg(spi, ADDR_CONFIG, 0x0300); //I Out 4...20mA, Dual enabled
DACx760WriteReg(spi, ADDR_DATA, 0x7FFF); //set data to 0.5

And here are the readings from different registers and final message it to set the output for 50% 

As seen on the first readout for data register I get nothing, Control register is OK, Configuration is OK but Status is NOK since I should have open circuit bit when the... circuit is open?

What am I missing here? Why can't I set or read the DAC register? 

Here is the schematics, SPI1_CLR is always low.

  • 0
    TI__Guru 54313 points

    Hi Heikki,

    I am concerned that the the ISET-R resistor is causing the OPEN condition.  ISET-R should have a 15kΩ resistor connected to GND, not IOUT.  It might not be able to resolve the gain correctly.  Please remove the RSET resistor and check if your system recovers.

    thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 10 points

    Hi Paul,

    Thanks for the feedback. I made the suggested changes for the PCB and I was able to get the status register working (got 0x04) that says that there is Open circuit. Need to inform the designer to make changes for the PCB now.

    This didn't fully solve the issue but it gave me a really good hint where to look. I didn't make the necessarty initialization for the clear pin and it was more or less floating even tough I was driving it as stated before. When I connected the analyzer to CLR pin it started working since it was pulling it down. After this I fixed the pin initialization and what do you know:

    Now I have CLR pulse before DAC write.

    And now I am able to read the register also and the Current out will change accordingly.

    Thanks for the assistance!