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CC2640R2F-Q1: CC26xx External Regulator mode

paddu2017
Expert 2885 points

Part Number: CC2640R2F-Q1

Hi,

What would happen if we leave DCDC_SW open in External Regulator mode?

As per the manual VDDS_DCDC and DCDC_SW pins must be connected to ground when using in
external regulator mode.
But as there was no reference circuit in the datasheet,our custom board has DCDC_SW open
and VDDS_DCDC connected to external regulator.
Is this kind of usage allowed and will it damage the device. Currently the device is working normal though.

Best Regards
paddu

  • 0
    TI__Genius 11810 points
    Hi Paddu,

    When you don't use the internal DCDC converter, the TRM says VDDS_DCDC should be tied to VDDS and DCDC_SW should be left floating. Your setup is ok. I'll recommend to have a look at Figure 1-2 in chapter 1.3.13.1 in the TRM. That will give you a better understanding of the power supply system.

    We have one reference design with external DCDC called "CC2650EM-4XS-Ext-Reg". The design files can be found here: www.ti.com/.../swrc301

    Best regards,
    Simon
  • 0 in reply to Simon J
    Expert 2885 points

    Hi Simon,

    Thank you so much for the quick reply.
    Actually we desinged this application in urgency, so we may have done some mistake.
    This design was supposed to be used in External Regulator mode,
    but the external regultor is 3.3V as shown below.But the manual mentions that
    in external regulator mode voltage range should be 1.65 V to 1.95 V.
    Will this kind of usage damage the IC?

    Is it possible to use this circuit in Internal LDO mode?
    Will it be OK if we connect VDDR pins to 3.3V in Internal LDO mode?


    We have already made so many custom boards with this schematics,
    and the application is also working normal.Please let me know if we could
    continue use this board as it is or re-design it once again.

    Best Regards
    paddu

  • 0 in reply to paddu2017
    TI__Guru** 106705 points
    Hi Paddu,

    The name "External Regulator Mode" is perhaps a bit misleading, it actually means 1.8 V operation.

    In your case, where the power supply is 3.3 V, the configuration you have is correct. The device will not use the internal DCDC though, so the current consumption will not be as good as it can be.

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    Expert 2885 points
    Hi Fredrik,

    Thank you for the quick reply.

    Does it mean this application is running with Internal LDO?
    Can we assume it is safe to continue using this schematics?

    Best Regards
    paddu
  • 0 in reply to paddu2017
    TI__Genius 11810 points
    Hi Paddu,

    Yes, you are using the internal LDO, which is safe and one of the options described in the datasheet. You can continue to use this schematics, but as Fredrik mentioned, your current consumption will not be as good as when using the internal DCDC regulator.

    Best regards,
    Simon