Hi All,
Im testing nRF52840 with reference circuit 4: battery powered, DCDC0 = ON and DCDC1 (for 1.3V core) as well.
Vdd is set to 1.8 Volt. Vbat = 3.6Volt. Both DCDC are running and switching.
When I measure the Vdd voltage it has a mean value of 1.8 Volt. Thats fine.
But the ripple on this Vdd is about 50 - 100 mV peak-peak. Against a mean value off 1.8 Volt this is quite much.
Depending on the current load the DCDC0 changes from burst to continuous mode. This changes the ripple.
Standard DCDC circuits have lower voltage ripple. Often better than 20 mV pp. I know that the ripple is a result of the burst mode.
To function more low power a lager burst mode interval is used, to reduce quisence current, but increases ripple.
I can not find any specification about the ripple value. So Is this ripple of 50 - 100 mV normal ??
I use a small (2 mA) current outside my board (external sensor) for this case the ripple is producing EMI noise..
of course i can use the LDO 0 instead of DCDC.
