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CC1352P: Battery powered reference design?

Arthur Thompson27
Expert 1840 points

Part Number: CC1352P
Other Parts Discussed in Thread: TPS62840, TPS62740, CC2640

Hello,

I was just wondering if TI has any reference designs for any of the SimpleLink MCUs which feature a rechargeable battery.  I am curious how to implement the CC1352P with a Li-ion battery given that the maximum input voltage rating is 3.8V and the battery may be charged as high as 4.2V.  

Thanks,

Arthur

  • 0
    TI__Guru** 106705 points

    Hi Arthur,

    To power the device from a battery you need to use an external regulator. The TPS62840 is a good choice for example. I would recommend setting the output power to 1.9 V to have some margin to the BOD threshold which is right below 1.8 V.

    Regards,
    Fredrik

  • 0 in reply to Fredrik K
    Expert 1840 points

    Hi Fredrik, what's the reason for setting the voltage so low?

    Will 1.9V allow us to use the integrated sub 1 GHz +20dBm power amplifier?

    From 9.2 of http://www.ti.com/lit/an/swra640c/swra640c.pdf:

    Maximum efficiency is obtained by using the internal DC/DC converter, and it requires an external inductor (LDCDC) and capacitor (CDCDC). The components should be placed as close as possible to the CC13xx/CC26xx device and it is important to have a short current return path for from the CDCDC ground to the pad on the chip (see Section 4.6). In addition, the bulk capacitor on VDDS should be placed close to the VDDS_DCDC-pin. The actual value of LDCDC, CDCDC and CBULK vary from device to device. For the actual values, see the device-specific reference design.

    When operating in DC/DC mode, the power system dynamically switches between the Global LDO and DC/DC converter depending on the required load to achieve maximum efficiency. If VDDS drops below 2.0 V, the DC/DC converter will be less efficient than the LDO and the device will run in global LDO mode. For systems operating with VDDS less than 2.0 V, consider either global LDO or external regulator mode to save component cost and board area.

  • 0 in reply to Arthur Thompson27
    TI__Guru** 106705 points

    Hi Arthur,

    Good questions! 

    Normally, when using an external high efficiency regulator, you would set the output voltage lower than the cut-off for the internal DCDC, thus saving the cost for the 6.8 uH inductor. 

    You raise a very good point though, which I completely overlooked. The 20 dBm PA output power is dependent on the supply voltage (see figure 5-39 in the CC1352P datasheet).

    In other words, for the CC1352P, you would set the regulator output voltage to what ever is a good balance between your lowest battery voltage and the target PA output power.

    Regards,
    Fredrik

  • 0 in reply to Fredrik K
    Expert 1840 points

    Fredrik,

    Thank you, that sounds good. I think I will target 3.3V.  Had you recommended TPS62840 because it's in the "DCS" family?  If so I might check out some other options such as TPS62740.

    Thanks,

    Arthur

  • 0 in reply to Arthur Thompson27
    TI__Guru** 106705 points

    Hi Arthur,

    Yes, due to DCS and their claim to be "RF friendly". We have evaluated TPS62740 with the CC2640 earlier: www.ti.com/.../swra498

    Regards,
    Fredrik