nRF52840 QSPI Power Consumption

RE: nRF52840 QSPI Power Consumption

Simonr — Tue, 28 Jul 2020 10:16:36 GMT

Hi Nathan

I'm sorry, but we don't have any exact numbers of the QSPI current consumption, as this wasn't prioritized for the nRF52840 PS. Yes, the current consumption you're seeing seems to be correct, mostly due to the erratum I mentioned, where the QSPI draws current even if it's not in use. So in order to attain the lowest possible current consumption, you should uninitialize the QSPI like what I did below.

For reference, the current consumption should be similar to those of the SPI depending on which regulator is in use, which HF clock, and the frequency used, as it's the regulator, clock, and DMA that decides the current consumption, and not the peripheral itself.

Best regards,

Simon

RE: nRF52840 QSPI Power Consumption

ntennies — Tue, 28 Jul 2020 02:55:38 GMT

Simon, thank for you the note about the erratum. However, we'd still like to understand if the power consumption we're seeing when the QSPI controller is enabled is correct or if it is indicative of a problem. Can you provide numbers regarding expected QSPI controller power consumption at runtime (but when not actively transmitting)?

Specifically, we're seeing power consumption jump by at about 3 mW in run mode just after enabling QSPI but not actively transmitting anything. Is that what we should expect?

RE: nRF52840 QSPI Power Consumption

Simonr — Mon, 27 Jul 2020 12:33:28 GMT

Hi Nathan

Sorry about the inconvenience, but due to the summer vacation period here in Norway, we're low on staff this week, and delayed replies must be expected.

In order to achieve the lowest possible current consumption when using QSPI, you'll have to uninitialize the QSPI driver. You should also be aware of the erratum 122 present in the nRF52840, so the uninit should look something like this before you go to sleep.

    *(volatile uint32_t *)0x40029010ul = 1ul;
    *(volatile uint32_t *)0x40029054ul = 1ul;
    nrf_drv_qspi_uninit();

Best regards,

Simon

RE: nRF52840 QSPI Power Consumption

ntennies — Sat, 25 Jul 2020 00:28:22 GMT

> The flash chip itself consumes much more current when CS is pulled low

Right, but I don't see how that's relevant here. The QSPI controller is setting nCS high when QSPI is initialized, and we're not performing any operations on the QSPI bus that would cause the QSPI controller to set nCS low. Certainly not in sleep mode.

Also, as I indicated, we're seeing this relatively high power consumption by the QSPI controller even when we configure it to use pins that are not connect to a Flash part, so that can't be what's causing the increase in power consumption.

> The QSPI peripherial keeps CS low when using XIP mode - in order to minimize acess latency.. You can exit XIP mode by using the regular nrfx_qspi_read() on a dummy address

We're not using XIP mode.

RE: nRF52840 QSPI Power Consumption

Turbo J — Fri, 24 Jul 2020 22:14:37 GMT

The flash chip itself consumes much more current when CS is pulled low. The QSPI peripherial keeps CS low when using XIP mode - in order to minimize acess latency.

You can exit XIP mode by using the regular nrfx_qspi_read() on a dummy address.