DCDC Startup Time

[Ken N]

We are looking to use the DCDC to reduce the maximum current during radio operations, but minimize the overall current by enabling it as late as possible before radio use (due to its 300uA operating current when enabled).

The startup time of the DCDC is often mentioned in posts, but no figures are ever quoted, nor does there appear to be anything published in the Nordic documentation. Does anyone have any figures for startup times, be they typical or a range?

Thanks

[Einar Thorsrud]

I do not have the number up front, but the startup time depend (significantly) on the current consumption. However, it may not be necessary to know, as the management of the DC/DC was changed in revision 3. In that revision you only have to enable the DC/DC once, and it is automatically used when the radio is active and disabled at all other times. Thus, assuming you use the SoftDevice, you only have to make a call to sd_power_dcdc_mode_set() at startup, and you can forget about it.

The behavior of the DC/DC in revision 3 chips is documented in Section 12.1.3 of the reference manual.

You can compare the current consumption when using the radio for DC/DC disabled (Section 8.5.2) and enabled (Section 8.5.3) in the product specification.

[Ken N]

Thanks for the response Einar.

In fact that is how we are currently using the DCDC. However in this article, one of your colleagues mentions the DCDC consuming 300uA when enabled, admittedly for Rev 2 hardware. So if this is no longer the case with rev 3, and once enabled the DCDC is only active when the radio is operating, then is it correct that the DCDC uses no current other than when the radio is active?

If that is the case then presumably any DCDC startup time is absorbed into the startup time of the radio.

Thanks