Current Consumption in Ble5 LE Coded PHY

[Madhukeshwar]

Hi,

I am using nrf SDK -16.0 with board nrf52840. In Ble 5 we are using LE Coded PHY with S=8. 

for Ble 5, the average current consumption got doubled when compared to Ble 4. what is the expected power consumed when device is in Ble 5?

Thanks,

Madhukeshwar

[Hung Bui]

Hi Madhukeshwar,

When you use Coded PHY S=8 each bit of data is transferred as 8 symbols, meaning any packet you send in normal 1Mbps is transmitting at 8 times longer. This explain the higher power consumption you have. 

It's the trade off of having a longer range when using CODED PHY. 
Note that with BLE 5.x (or 6.x) you can still use normal 1Mbps instead of CODED PHY so you shouldn't have any current consumption change compare to BLE v4.x. If you want to reduce current consumption, you can consider using 2Mbps PHY. It would require half of the time to transmit the same data. The trade off, of course, is shorter range. 

[Madhukeshwar]

Hi Hung Bui,

Hung Bui said:

meaning any packet you send in normal 1Mbps is transmitting at 8 times longer. This explain the higher power consumption you have. 

yeah, it takes more time to transmit the same amount of data with a longer range right!. when take the average current, both Ble 5 CODED PHY and Ble 4 average current should be same. but we got almost double.

so we wanted expected current consumption for Ble 5 CODED PHY. 

[Hung Bui]

Hi again, 

Could you elaborate more on this ? 

Madhukeshwar said:

when take the average current, both Ble 5 CODED PHY and Ble 4 average current should be same.

Why would average current should be the same ? When you use more time to send the same data, the radio has to be active longer hence draw more current. As I said, it's the trade off when you have more range with CODED PHY. 
Please show us more data of your measurement. 

[Madhukeshwar]

Hi,

Hung Bui said:

Why would average current should be the same ?

The average current depends on both the total charge and the time duration. average current is inversely proportional to time. so, if the time interval is increased average should also decrease right?!

Hung Bui said:

When you use more time to send the same data, the radio has to be active longer hence draw more current.

Yeah, I agree to this point. but Total consumption may increase. how does it contribute on average current?

[Hung Bui]

Hi,

Madhukeshwar said:

The average current depends on both the total charge and the time duration. average current is inversely proportional to time. so, if the time interval is increased average should also decrease right?!

It's only correct if you continuously transmit all the time (radio always active) then the switch between 1Mbps and CODED PHY doesn't change the power consumption.
However, in common use cases with BLE the radio is inactive most of the time. So when you switch to CODED PHY the radio has to be active 4 times longer on the same connection interval. This will increase the average current consumption. Think of something like this: