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DAC8760 separate voltage & current out

Genius 3300 points
Other Parts Discussed in Thread: DAC8760, DAC8750

I have a application in which i need separate voltage & current out. AVDD will be +10V to +36V, voltage output required is 0to5V & current out required is 4-20mA. No hart is required. Current loop compliance required is AVDD-2.5V. So have selected DAC8760 for this purpose.

1. IS DAC8760 right for this application.
2. Datasheet says it has only one DAC data register. So how do I right voltage & current value. Suppose I want 2V and 20mA out separability.
3. Attached is the ciruict which I had made using DAC8760 & ISO7641. Is it ok?

3716.circuit.pdf

  • Hi Vindhyachal,

    Vindhyachal Takniki said:
    1. IS DAC8760 right for this application.
    2. Datasheet says it has only one DAC data register. So how do I right voltage & current value. Suppose I want 2V and 20mA out separability.

    Unfortunately it seems that a single DAC8760 will not be able to accommodate your needs. The voltage and current outputs can be enabled at the same time but must track each others output using the same DAC register. The best approach would be to use a couple of DAC8760 in order to be able to generate two independent outputs. You could also use a DAC8760 , and a DAC8750 (current-only version).

    Vindhyachal Takniki said:
    3. Attached is the ciruict which I had made using DAC8760 & ISO7641. Is it ok?

    I do have a few questions/recommendations on your schematic.

    If you are still interested in using a pair of DAC8760, I can give you a full schematic review.

  • I understand that both current out & voltage data register are same so have to give same readings. This will also work ok for me. Can you further comments on schematic. i have made schematic with following pints in mind.
    1. Shorted all ground pins together.
    2. Decoupled DVDD with 0.1uF & 1uF caps
    3. Alarm pin is pulled up with 10K to internal 4.6V
    4. CLR-set is pulled down with 10K, no need in the circuit.
    5. CLR pin is also pulled low by 10K, no need in circuit.
    6. SPI pins are brought out to a digital isolator.
    7. ISET-R is decoupled by 0.022u cap.
    8. Internal reference is used, so REFIN & REFout are shorted together & decoupled by 0.1uF.
    9. HART-In is also decoupled by 0.022u cap.
    10. CMP,BOOST & IOUT pins are used to drive external BJT as in attached ciruict, please check if resistor/cap values are ok & BJT selected is fine.
    11. DVDD-EN is left floating to enable internal voltage. But it is an input pin, is it ok to leave it floating?
    12. Vsense+ & Vsense- are shorted to Vout connector, for best results.
    13. AVDD is decoupled by 0.1u,1u & 100p caps.
    14. Digital ISO used is ISO7641FMDW, which on one sied is powered by DAC8760 internal 4.6V
  • Hi ,

    Any update on this..
  • Hi Vindhyachal,

    Apologies for the delay, I must have missed the notification. I have just finished reviewing your schematic and your pin connection descriptions. Everything is connected correctly.

    Vindhyachal Takniki said:
    11. DVDD-EN is left floating to enable internal voltage. But it is an input pin, is it ok to leave it floating?

    Yes. You can leave it floating.

  • Thanks Mejia