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DAC8760: How to programming the device by SPI

Brian Wang0928
Genius 14080 points
Part Number: DAC8760

Is there any flowchart to discribe how to program the DAC8760? My customer is trying to program/command it however it fail as attached example!!

Please help. thanks. DAC8760A量測資料.pdf

 

  • 0
    TI__Genius 14080 points

    Also, please check the calculated output value with DAC device if it's correct or not? pls find the attached file. thanks.

    (include schematic)

    Copy of DAC8760輸出計算公式.xlsx

  • 0 in reply to Brian Wang0928
    TI__Expert 5820 points

    Hi Brian,

    Thanks for providing the scope captures and schematic. The most basic way to program DAC8760 is to set the RANGE and OUTEN bits in the configuration register followed by writing the DAC Data register. This looks like the correct sequence based on the SPI waveforms provided. What are the two separate latch signals in the waveforms? Are they using two devices?

    When you say the programming failed what is the voltage at Vout? Is it an unexpected value or does it not change at all after writing the DAC Data register?

    One issue I noticed with the schematic is the CLR pin is pulled high to DVDD by R372. CLR is active high and must return low before a new value is programmed. Also, the external Rset (R400) should be a precision 15kohm to ground. The schematic shows ISET-R tied to DVDD.

    Thanks,

    Garrett

  • 0 in reply to Garrett Satterfield
    TI__Genius 14080 points

    - How to fill the value into register since data is 24bits and register is 15bits?

    -using 2x DAC

    - when value is progamming to IC, output shows unexpected value as 0V.

    - CLR is pulled low

    -Is 15K Rst necessary connected to Grounding?

  • 0 in reply to Brian Wang0928
    TI__Expert 5820 points

    Hi Brian,

    The most significant 8 bits represent the address of the register being written to. The lower 16 bits are the register data.

    Have they tried reading back the registers they have written to ensure they are correct? This is accomplished by writing to address 0x02 with the lower 6 bits in the data word representing the register to read described in Table 17 of the datasheet. Refer to section 8.5.1.3 of the datasheet for all the details on the read operation.

    Understood regarding the CLR pin. The schematic in the excel sheet indicates it is tied to '+5V_DAC'. Another concern I have about the schematic is how DVDD-EN is connected to both 'DAGND' and '+5V_DAC' through R451 and R207. If external DVDD is provided this should be connected to ground but if the internal supply is used it should be left floating. Are they using internal DVDD? If so ensure that DVDD is floating.

    The 15kohm connected to ISET-R will only affect the current output and only if used in external RSET mode.

    Thanks,

    Garrett

  • 0 in reply to Garrett Satterfield
    TI__Expert 5820 points
    Hi Brian,

    Since we are addressing this off the forum I will go ahead and close this thread.

    Thanks,
    Garrett