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CC2640R2F: Question about VDDR behavior

Joshua Uyeda
Prodigy 20 points
Part Number: CC2640R2F

We're using the DC DC converter with the recommended capacitors and inductor and sets SET_CCFG_MODE_CONF_DCDC_RECHARGE and SET_CCFG_MODE_CONF_DCDC_ACTIVE to 0x0 in a custom ccfg.c file. Our project's code is based off of the simple peripheral example project, and we define POWER_SAVING.

We have a couple of questions about VDDR:

  • Should the microcontroller turn off the DC DC converter when in one of the low power states? The DC DC converter seems to be pumping VDDR on some duty cycle (up to ~1.7V) where the VDDR voltage level is allowed to discharge for some time (down to ~1.5V) before being pumped up again. VDDS is 2.8V.
  • If we switch to using the LDO by setting SET_CCFG_MODE_CONF_DCDC_RECHARGE and SET_CCFG_MODE_CONF_DCDC_ACTIVE to 0x1 and making the recommended schematic changes, would we expect the same duty cycling on VDDR with respect to power states?
  • Can the RF Core that uses VDDR be shut down by the application code running on the M3 when the system does not need to advertise or connect and then be reinitialized again before BLE communication is needed?

Thanks in advance.

  • 0
    TI__Expert 6520 points

    Hi Joshua,
    I think that your questions can be answered by referring to Section 6 of the CC2640R2f TRM https://www.ti.com/lit/ug/swcu117i/swcu117i.pdf 

    Question 1:
    The voltage regulators are not disabled except in the "shutdown" mode. See 6.6 of the TRM for the power modes. This app note https://www.ti.com/lit/an/swra478d/swra478d.pdf  has additional detail in Chapter 2.

    Question 2:
    Yes, VDDR domain would see recharge events whether the GLDO or DCDC is used.

    Question 3:
    Yes the RF Core can be shutdown. See Chapter 6 of the TRM. In particular Table 6-5. Here you can see that the RFCORE_PD is powered down in "Standby" mode. If you wanted to disable it in other modes then you could either by powering down the power domain PRCM:PDCTL0.RFC_ON = 0 and PRCM:PDCTL1.RFC_ON = 0. (See Figure 6-2) or by clock gating by PRCM.RFCCLKG.CLK_EN = 0. What you choose depends on your system requirements such as startup time vs power consumed. See table 6-1 "Power Saving Features" for an overview.

  • 0 in reply to Jake Pulliam
    Prodigy 20 points

    Thanks for the response and confirmation of points 1 and 2.

    For question 3, if we manually shut down the RF Core from application code running on the M3, will that also shut off the VDDR recharge events (VDDR would fall to ~0V), or is there something else in the system that requires VDDR that will keep it pumping while the RF Core is in shutdown?

    Additionally, if we shut down the RF Core, do we need to do anything else in application code on the M3 to get it re-initialized and powered back up before we use it, or is simply setting PRCM:PDCTL0.RFC_ON = 1 and PRCM:PDCTL1.RFC_ON = 1 enough?

  • 0 in reply to Joshua Uyeda
    TI__Expert 6520 points

    Hi Joshua,

    No VDDR will not be disabled except in shutdown mode. As you can see from the information provided above the RFCORE is powered down in standby mode, in standby mode the regulator is still charging the capacitor to support the VDDR voltage. VDDR is used throughout the device.

    In general I would direct you to use the power management resources already provided by TI - see https://www.ti.com/lit/ug/sprui18j/sprui18j.pdf 

    If this doesn't resolve your questions regarding power management then it would be helpful to understand your use case a little bit better and understand what you're trying to achive.

    Jake

  • 0 in reply to Jake Pulliam
    Prodigy 20 points

    I will reach out via email with some more details.

    Thanks!