Powering External Circuits from EFR32 DC-DC

by <a href="http://community.silabs.com/t5/Welcome-and-Announcements/Community-Ranking-System-and-Recognition-Program/m-p/140490#U140490"><font color="#000000"><font size="2">Ninja Employee</font></font> </a> wmpaull on ‎11-07-2016 01:14 PM - edited on ‎02-21-2017 11:03 AM by Administrator Nari

The on board voltage regulator lends itself for use in powering more than just certain power pins on the EFR32 itself.  Typically the DC-DC is recommended for powering the EFR32 RFVDD, DVDD and sometimes the PAVDD power pins (for desired transmit power levels 13 dBm and lower).  There may also be custom applications where it is appropriate to use the DC-DC regulated output for powering additional EFR32 power supply pins or even other device power pins.  In cases where the DC-DC is to be used for powering peripherals and / or the IOVDD supply, the designer should:

 

  • Review the sleep management requirements to be sure that power pins powered by the DC-DC are not required to be powered during the energy management modes that may be possible for the design application.
  • Estimate the static current draw from the datasheet, using the uA/MHz numbers for the core and the typical current consumption numbers for the radio.
  • Implement a few worst case hardware test cases to:
    • Ensure the static max current (radio tx + max core freq + max external load) is below the DC-DC's max current.
    • Ensure the dynamic current draw for any external loads doesn't cause the EFR to brown out.  Using an oscilloscope, verify there aren't significant droops in the output supply when the external load is enabled.  For example, if an external load looked like a large capacitor, the transient current might cause the DC-DC output to droop. 

 

Note that all validation testing has been at 1.8V and therefore datasheet parameters may be different for DC-DC outputs other than 1.8 V.

 

If one of the peripheral devices is also an EFR32, do not power that EFR32’s DVDD pin, due to DVDD will short to AVDD internally upon exiting reset and cause a potential over-current situation for the source DC-DC.

 

For additional information about the EFR32 DC-DC, please review the application note AN948.

 

When done, Silicon Labs recommends you submit your finalized design for review in the customer portal.