nRF52840 Power consumption difference with operating voltage of 1.8V and 3.3V

[Sridharr]

nRF52840 power consumption same when we operate with 1.8V and 3.3V? 
When i simulate in the online Power profiler, i see 1.8V power consumption is 22% lesser than 3.3V with DC-DC regulator.
I believe the Power consumption should be same with in the operating voltage range. Can you please share any test date with 1.8V vs 3.3V power consumption.

We are operating with battery, even 10% of current consumption difference will have big impact on our product. What is your recommended operating voltage for low power consumption.

 

[haakonsh]

"When i simulate in the online Power profiler, i see 1.8V power consumption is 22% lesser than 3.3V with DC-DC regulator."

That does not make any sense, I'd expect the current to be less in 3V than 1.8V, not the other way around. What settings did you use with the online power profiler?

The reason the current should be lower at 3V compared to 1.8V is that the amount of energy needed to perform any action is roughly the same at any supply voltage.

With Ohms law, P = U*I, where P is constant at 1mW, and U changes from 3V to 1.8V ==> 
1mW = 3V * 0.334µA
1mW = 1.8V * 0.556µA

The rate of energy delivered from the source to the load is the same in both cases, but due to different supply voltages the current needed to deliver the energy is higher at lower supply voltages. 

You also have to account for the fact that DCDC regulators are usually slightly more energy efficient at higher voltage deltas. 



 

[Sridharr]

I totally agree with you regarding power calculation. Below are the settings and calculation as per the tool.

https://devzone.nordicsemi.com/nordic/power

Chip: nRF52840

Voltage: 1.8V & 3.3V

DCDC Regulator: ON

LF Clock: External crystal

Radio TX Power: 0dBm

BLE Settings Role: Advertising (Connected)

Advertising interval (ms): 50 ms

TX payload (Byte): 20 Bytes

 

In DCDC mode:

With 1.8V, the current is 321uA.

Power (W)=1.8*321uA=577.8uW

 

With 3.3V, the current is 226uA.

Power(W)=3.3*226uA= 745.8uW

 The overall power difference is very high >22%. Please comment.

[haakonsh]

I misspoke. The DCDC regulator is less efficient at higher input voltages