nRF52840 Current Consumption

Question

Hi, 
 the following are the TX's current consumption for 0 dBm from the datasheet:
 
 I assume the second line refers to the measurements when the internal LDO is used and where VDD is supplied at 3V. Can someone confirm please? 
 Background:
I am searching for the best power configuration when the device is to be powered from a Li-Ion battery and battery lifetime is a very critical aspect. If an external DCDC "switcher" is used to get from the battery to the 3V for VDD, and the nRF52840 is configured to use an LDO, will I still get measurement figures like given in the second line? 
 Also, can somebody explain more about the difference between ITX,0dBm,DCDC and I0dBm(DCDC, 3V) ? 
 
 Thanks.

ovrebekk · Accepted Answer

Hi 
 The second line refers to the case when running the internal LDO, that is correct.
When using the LDO the current doesn't change with supply voltage, which is why the voltage is not specified. The number is the same regardless. 
 Best regards

ovrebekk · Answer

Hi 
 The current drawn by the nRF52840 in LDO mode will be the same regardless of the external regulators. 
The current measured out of the battery will probably be lower, but this depends on the efficiency of your external DCDC, and the battery voltage. 
 An ideal DCDC should reduce the current by a factor proportional to the voltage difference. As an example, if the input voltage is double the output voltage, the current should be reduced by a factor of 2. 
Obviously an ideal DCDC doesn't exist, but 80-90% efficiency is pretty common. 
 The I 0dBm(DCDC, 3V) value is the total system current when you run the radio alone, including the clocks and regulators necessary for radio operation. 
When calculating current for multiple peripherals you should use the ITX.. value, but when measuring the radio alone it is the I0dBm number that is relevant. 
 Best regards 
Torbjørn

nRF52840 Current Consumption

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