This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DAC8775: POWER Dissipation

Part Number: DAC8775
Other Parts Discussed in Thread: LM5166

Hi team

Hope you have a nice day.

I'm reaching out because the DAC8875IRWFT 's power dissipation at PVDD is 12V can' find in the datasheet , as you can see in the below picture.

Could you please give me some clue about this?

The background is my customer XINJE found in the same product, two PLC AO model shows different power dissipation.

There is only DAC8775 and some resistor/cap on the AO model.

PVDD is 12V, RL ==625Ω, so I just want to if it is over power dissipation limit


  • Irene,

    First the DAC8775 does reliably operate to 12V. This voltage is the minimum voltage for operation.

    The reason that this graph shows that the power supply goes to 12.5V is because of the way that the application circuit was put together. The plot from Figure 134 was created from the circuit of Figure 130:

    Here the AVDD is kept at 12V. However, because external power comes from the LM5166, it means that the field connection supply must be at least 12.5V for the synchronous buck converter.

    If you just subtract 0.5V from the x-axis of Figure 134, then you'll get that the device operates down to 12V.

    Joseph Wu

  • Hi Joseph

    Thanks for your quickly reply.

    As for the 12.5V, I still couldn't get it. The the x-axis of Figure 134 is PVDD, so do you mean the field power supply must be at least 12.5V?

     Beat regards!

  • Irene,

    The measurements were made with the field supply input at 12.5V and greater. In the diagram, you can see that the output of the LM5166 is set to +12V while the field supply is 13V - 64V. However for the power dissipation plot, they only used measurements from about 12.5V to 36V. 

    I'm not sure why they made measurements from a limited range, even with this DC DC converter, the field supply could be set to lower than 12V. However, DAC8775 definitely operates down to 12V, and the change in the power dissipation graph would be minimal.

    Joseph Wu

  • Thank you Joseph. That helps me a lot~