Maximum Voltage NRF51822 in Low Voltage Mode (External DCDC)

[Mathias]

Hi,

I am planning to use an external DCDC to supply the NRF51822 in Low Voltage Mode.

In the datasheet a voltage range of 1.75-1.95 on VDD and VDD1.8 is mentioned.

Since I am going to use an temperature sensor (ADS1118) with a minimum voltage of 2.0V, i wanted to ask if a supply of 2.0V (out of specs) would be possible too?

Thanks in advance!

Best regards, Mathias

[Håkon Alseth]

Hi Mathias,

It would then be better to run the nRF51-chip with internal LDO regulator power scheme. The current draw will be the same as in 1V8 mode. Exceeding the VDD_1V8 limit will most likely work (note: it's out of spec), but it will also decrease the lifetime of the device.

Best regards Håkon

[Mathias]

Hi, thanks for your quick response.

So would you say 2.0V is critical regarding the lifetime?

Best regards Mathias

[Håkon Alseth]

If your board uses 1.8 V low voltage mode, then powering the device with 2.0V is out-of-spec, and should not be used. You should configure it with power-scheme "schematic with internal LDO regulator" as shown in the product specification, chapter 11.2.1.

BR Håkon

[Mathias]

Hi Hakon,

do you know the additional current consumption of the internal LDO?

Another option might be to use 1,95V and to hope that the ADS1118 will work at this voltage.

Best regards, Mathias

[Håkon Alseth]

If you're using the 1.8V or the LDO (anywhere from VDD = 1.8 to 3.6V), the current consumption will be equal to the numbers in the datasheet. As it's an LDO, meaning that it drops to a given voltage internally and "burns" off the rest, the current consumption of the LDO will be equal to: Pldo = (VDD - VDDinternal) * I Where VDDinternal is around 1.7V.

I would recommend running on LDO power scheme at 2.0V, as the current that you "burn off" in the LDO is not very much.

Cheers, Håkon