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DAC80501: Can DAC80501 be used for Arbitrary waveform generation ?

Part Number: DAC80501
Other Parts Discussed in Thread: DAC80508

Hi

I am trying to made a current signal source for medical laser application which is required to generate an accurate arbitrary waveform. I found DAC80501 and DAC 80508 current source applications are well suitable for my project. But I am new for this and want to ask if those two DACs are capable  generate at least 20Hz sawtooth-type wave and kHz frequency sine wave?

Many thanks 

  • Hi,

    20Hz saw tooth shouldn't be an issue with DAC80501 or DAC80508.

    For sine wave what's the frequency you are looking at? any specifications for distortion?

    Do you have some idea about how many points you need in a sine wave?

    Regards,

    AK

  • Thanks for your reply

    sine wave should be programmed at 20kHz - 100 kHz. If I use 50MHz clock, How many points shall be sampled for 1 sine wave at 100KHz, 20points ? 

    Regards

    :) 

  • Hi,

    Even though SPI is running at 50MHz, you will be limited by settling time of the DAC for a faithful reproduction of the sine wave signal.

    For ¼ to ¾ scale and ¾ to ¼ scale settling to ±2 LSB, settling time is 5uS. Add this to your SPI transaction time, you can get fair idea of whats the max frequency of signal you can generate. Of course this assumes a square wave signal going from  ¼ to ¾ scale. For sine waves, sine points will be somewhat closely spaced, settling time will be lower.

    So for calculation, you need to add the following values from datasheet to arrive at update rate of the DAC80501.

    Please note that in the timing diagram, even though we need 24 clocks for single SPI frame, first half of the 1st bit and second half of the last bit has special timing requirements denoted by tSYNCS & tSYNCH. 

    Total interface time for one SPI frame will be  23* Tclk + tSYNCS + tSYNCH + tSYNCHIGH = 23*20 + 13 + 10 +160 = 643nS

    DAC50501 settling time is 5uS, so total time will be 5.643uS

    Update rate will be 1/5.643 = 177KSPS

    so for 20KHz sine wave this should be fine, but for 100kHz I wont recommend the same.

    Can I suggest alternate parts for 100KHz sine wave generation from our MDAC family of devices, which will have very low settling time requirements?

    Regards,

    AK

  • thanks, a great answer helps a lot. 

    regards