current peak on the nrf51822

RE: current peak on the nrf51822

ovrebekk — Fri, 15 Dec 2017 15:43:10 GMT

At that low voltage the difference will be minimal I am sure.
We didn't have time to test it today, but we can do it next week if you like.

Best regards

RE: current peak on the nrf51822

Jorge — Thu, 14 Dec 2017 13:43:06 GMT

Hi @Torbjorn,

I found out that I can set the supply voltage to 2.15V for the nRF. Can you make the test for the current? or this would be close to the 15mA?

RE: current peak on the nrf51822

ovrebekk — Tue, 12 Dec 2017 16:13:57 GMT

No problem, I only wish I had better news...
The best of luck with your project!

RE: current peak on the nrf51822

Jorge — Tue, 12 Dec 2017 15:51:38 GMT

Yes, you are correct I think, since the other chip has a possibility to give 1.8V to the nrf51. Thank you for the help nonetheless.

RE: current peak on the nrf51822

ovrebekk — Tue, 12 Dec 2017 15:36:47 GMT

By chip do you mean module?

The nRF51822 has a minimum supply voltage of 1.8V without DC/DC, and 2.1V with DC/DC, so I would have to assume there is a buck/boost converter in the module that scales up the voltage from the battery.

If so there is very little to gain from using a DC/DC with the nRF51822, as the supply voltage is probably at the lower end of the scale.

Best regards

RE: current peak on the nrf51822

Jorge — Tue, 12 Dec 2017 13:11:17 GMT

The supply voltage is 2V maximum and minimum 1.05V for the chip I am using (that has an nrf51822 inside). The size 10 battery has a voltage of 1.45V.

RE: current peak on the nrf51822

ovrebekk — Tue, 12 Dec 2017 13:01:14 GMT

Do you know the voltage of the battery?
As I said, the efficiency of the DC/DC is highly voltage dependent.

I would expect a peak current of around 13mA @3V. If you want a more accurate number just give me the supply voltage, and we can run a quick test.

RE: current peak on the nrf51822

Jorge — Tue, 12 Dec 2017 12:18:54 GMT

Ok, that makes sense because I tested and it had still the high peaks. Ok, I am going to talk with the hardware guys. Then should I expect a peak current of what? 13-14 mA?

I am afraid that this is still too much, but I will try to test it.

RE: current peak on the nrf51822

ovrebekk — Tue, 12 Dec 2017 12:03:16 GMT

If the PCB is already made you might not be able to add the DC/DC, as this requires two additional inductors in your design (for details refer to the reference schematic).

Reducing the output power will shave a couple of mA's off the TX peak current, but unfortunately the RX current is the larger one in the nRF51822 (unless you use +4dBm output power today), so the largest peak will still remain.

Best regards

RE: current peak on the nrf51822

Jorge — Tue, 12 Dec 2017 08:13:38 GMT

This is meant to be a hearing aid, that is why I need to use these kind of batteries.

RE: current peak on the nrf51822

Jorge — Tue, 12 Dec 2017 08:12:34 GMT

Hi,

the problem is that the PCBs are already made, so I am trying to reduce it as much as possible. I cannot change or add parts to the PCB...

I will check the DC/DC regulator. I also saw that if I reduce the TX power it will reduce the average current, but does it reduce the peak current? Or does this stays the same?

I know there are some devices using this chip (nrf51822) that use the battery size 10 but I don't know how they deal with the peak currents.

RE: current peak on the nrf51822

Dave_couling — Mon, 11 Dec 2017 21:53:52 GMT

Adding more power-line capacitance will reduce the peak currents. Won't affect overall current consumption, but will reduce the "hit/impact" to your battery if you're using a coin cell which have low peak current capabilities.

RE: current peak on the nrf51822

Turbo J — Mon, 11 Dec 2017 19:20:17 GMT

I recommend using larger size batteries - two size 10 in series might not be able to deliver enough current to pull the NRF chip out of POR, regardless of how many µF there are in parallel.

RE: current peak on the nrf51822

ovrebekk — Mon, 11 Dec 2017 17:16:24 GMT

Hi Jorge

What is the voltage of your battery?

If you enable the DC/DC regulator you can reduce the radio peak currents by about 2-3mA, but it is more effective at the higher end of the supply range (3V or higher).

If low peak currents are critical I would strongly recommend going for an nRF52 series part. They have a much more efficient DC/DC architecture, and as you can see from the nRF52 online power profiler the peaks are significantly lower.

Best regards
Torbjørn