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CC2642R: Efficiency in Internal DC/DC Converter Mode

David Tandri
Expert 1355 points

Part Number: CC2642R
Other Parts Discussed in Thread: CC2640R2F, TPS62840

Hi,

I know that when CC2642R is running in internal DC/DC converter mode and the Vdds is supplied with 1.8V, the internal DC/DC converter will be less efficient.

This is based on CC26XX application report:

How much difference is the efficiency when Vdds is supplied with 1.8v and supplied with above 2.0v?

Based on the statement above, I would like to know how much less is "less" the efficiency is to be exact.

Thanks

  • 0
    Expert 2170 points

    Hi David,

    You should take a look at the plots in the "Typical Characteristics" section of the datasheet. They will show you current consumption vs. supply voltage. As you can see, as supply voltage decreases (DCDC input voltage goes towards DCDC output voltage), the current consumption will increase and eventually converge with LDO mode. This behavior is common for all DCDC regulators, and the performance is identical between CC2640R2F and CC2642R (referring to you original post). Note that there is a SW cut-off of the DCDC around 2.1 V. 

    Would you be able to increase the system voltage in your application to 1.9 V? If so, I would simply run everything off a TPS62840. 

    Regards,
    Fredrik

  • 0 in reply to fredrikgk
    Expert 1355 points

    Hi,

    I don't really get your point. 

    I just want to know how much less the internal DC/DC converter efficiency is when Vdds is supplied with 1.8V.

    Thanks.

  • 0 in reply to David Tandri
    Expert 2170 points

    The DCDC does not run below 2.1 V, so the question does not make sense.

    Did you look at the plots in the Datasheet? Looking at figure 5-4 for example, you can see that the current consumption at 2.1 V is about 4.7 mA with DCDC and 5.5 mA with LDO for active MCU current. 

    It is current consumption you care about, right? Not really the DCDC efficiency. The point is that, as with all DCDCs, the input current will increase for lower input voltages. 

  • 0 in reply to fredrikgk
    Expert 2170 points

    By the way, which application note are you referring to? The wording is pretty bad.