About Tx current consumption in nRF54L

RE: About Tx current consumption in nRF54L

Kazi Afroza Sultana — Fri, 11 Jul 2025 12:07:15 GMT

Hello Hiroki,

The current consumption change is a physical effect of the mismatch, not an active adjustment by the SoC itself. When impedance mismatches between the power amplifier (PA) and the antenna, most of the transmitted power is reflected back into the power amplifier rather than being radiated. This causes PA to draw more current, sometimes significantly more. This is not unique for nRF54L15 but is a general characteristic of RF systems when antenna matching network is designed for 50ohm impedance.

Regarding your initial query, Following is the reply from relevant team.

'' In chapter Current consumption:

In chapter RADIO Electrical specification:

The discrepancy of the current consumption values in those two places is expected.

Because in RADIO Electrical spec table, the I_{TX,MaxdBm,QFN}I_{TX,MaxdBm,CSP}values are the calculated radio standalone current consumption.

While in Current consumption chapter, the current was measured from system level, see test conditions description, the I_{RADIO_TX2} is 9.8 mA as it takes clock, CPU, cache, RAM current consumption into account.''

RE: About Tx current consumption in nRF54L

H-ogawa — Thu, 03 Jul 2025 01:16:15 GMT

Hi,Kazi

[quote userid="108933" url="~/f/nordic-q-a/122221/about-tx-current-consumption-in-nrf54l/541173"]The antenna impedance will change when you touch it. A lower impedance will increase the current. The datasheet numbers are measured with a 50 ohm load on the antenna port. A "real" antenna will not always be 50 ohm so the current may differ.[/quote]

Thank you for your comment.

Why does the current consumption change when the impedance changes? Is it because the nRF54l15 has a function to automatically adjust the wireless output value?

best regards,

Hiroki

RE: About Tx current consumption in nRF54L

Kazi Afroza Sultana — Wed, 02 Jul 2025 12:50:25 GMT

Hello,

"Also, the current consumption changes when I touch the pattern antenna.

What causes this change in current consumption?"

The antenna impedance will change when you touch it. A lower impedance will increase the current. The datasheet numbers are measured with a 50 ohm load on the antenna port. A "real" antenna will not always be 50 ohm so the current may differ.

RE: About Tx current consumption in nRF54L

H-ogawa — Fri, 27 Jun 2025 06:05:59 GMT

Hi,Kazi

In order to quickly identify the cause of the problem, we modified the DK so that 3.0V was applied only to the nRF54l15.

As a result, the current consumption during transmission changed depending on the nRF54l15dk's pattern antenna state.

With pattern A, the current consumption was 12 mA.

With pattern B, the current consumption was 9.8 mA, approaching the typical value on the data sheet.

Also, the current consumption changes when I touch the pattern antenna.

What causes this change in current consumption?

best regards,

Hiroki

RE: About Tx current consumption in nRF54L

H-ogawa — Thu, 26 Jun 2025 23:38:27 GMT

Hi, Kazi

The data sheet at the following URL is used as reference. This is v0.9.

Is this version up to date?

https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/keyfeatures_html5.html

It is understood that the following values are measured on Nordic's internal board.

The following values are typical values measured under the conditions described in 11.1.1 Conditions.

I don't understand why there is a difference in the above in the first place, so I would like an explanation.

Also, the module we developed is far from the typ in 11.1.2.5, so could you tell me what you think the cause could be?

PS
The Rx and Sleep values for the module we developed are close to the typ in the data sheet.

best regards,

Hiroki

RE: About Tx current consumption in nRF54L

Kazi Afroza Sultana — Thu, 26 Jun 2025 08:32:02 GMT

Hello Hiroki,

[quote user="H-ogawa"]When measured with Nordic's dedicated board, it is 9.1mA, but the Tx 8dBm listed in the data sheet below is 9.8mA. Why is there a difference?[/quote]

Can you please tell which version of datasheet you are mentioning here? This is not documented in the current datasheet.

RE: About Tx current consumption in nRF54L

H-ogawa — Wed, 18 Jun 2025 01:46:33 GMT

Hi, Kazi

[quote userid="108933" url="~/f/nordic-q-a/122221/about-tx-current-consumption-in-nrf54l/539517"]Here Set up the DK is the description of setup.[/quote]

I have checked, but do I need to remove the following parts?
Do I need to remove U4 and U5 physically, not via a pattern?

[quote userid="108933" url="~/f/nordic-q-a/122221/about-tx-current-consumption-in-nrf54l/539545"]The nRF54L15 DK is using QFN, the spec 9.1 mA is from characterization on internal RF boards instead of DKs.[/quote]

The above was verified using Nordic's own board so we cannot verify it, right?

[quote userid="108933" url="~/f/nordic-q-a/122221/about-tx-current-consumption-in-nrf54l/539545"]

Test env: 25°C,3V, DCDC mode on (that you need to set in the config file), HFXO, BLE1M, TX OP +8dBm.

We can also test on DKs but in terms of price that is not efficient.

[/quote]

The module we are developing is different from the results in the datasheet, so we would like to first check if there are any differences with Nordic's board.

When measured with Nordic's dedicated board, it is 9.1mA, but the Tx 8dBm listed in the data sheet below is 9.8mA. Why is there a difference?

best regards,

Hiroki

RE: About Tx current consumption in nRF54L

Kazi Afroza Sultana — Tue, 17 Jun 2025 12:34:32 GMT

Hello,

Regarding this ''Could you tell us the environment in which you measured IRADIO_TX2'' query, did you get the screenshot from previous version of product documentation? Our latest specification looks like this

Radio current consumption (transmitter)

The nRF54L15 DK is using QFN, the spec 9.1 mA is from characterization on internal RF boards instead of DKs.

Test env: 25°C,3V, DCDC mode on (that you need to set in the config file), HFXO, BLE1M, TX OP +8dBm.

We can also test on DKs but in terms of price that is not efficient.

RE: About Tx current consumption in nRF54L

Kazi Afroza Sultana — Tue, 17 Jun 2025 10:47:46 GMT

Hello Hiroki,

'' how can I measure the 3.0V current with nRF54ldk?'' For measuring current with 3V, you need to connect ampere meter or oscilosscope or power analyzer on P6 port.

Here Set up the DK is the description of setup.

''Could you tell us the environment in which you measured IRADIO_TX2''. I need to talk to team about this. I will get back to you when there is an update.

RE: About Tx current consumption in nRF54L

H-ogawa — Thu, 12 Jun 2025 07:25:58 GMT

Hi,Kazi

Thank you for your reply.

We don't have the ppk2 tool, so we can't measure it.

Could you tell us the environment in which you measured IRADIO_TX2?

Also, how can I measure the 3.0V current with nRF54ldk?

I can't measure it properly because I have an nPM1300.

best regards,

Hiroki

RE: About Tx current consumption in nRF54L

Kazi Afroza Sultana — Thu, 12 Jun 2025 07:04:57 GMT

Hello Hiroki,

Can you try to measure the power with ppk2?

Kazi