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

[Mathias]

Hi Hakon,

thanks again for your reply!

So it isn't possible to deactivate the LDO when using an external DCDC, since I assume the LDO has an standby current in the range of some 100nA to sume uA?

[Håkon Alseth]

It doesn't make sense to deactivate the LDO, as the voltage you're getting from your external DCDC is around 2.0V.

Let's say that you lower this to 1.95V (just on the limit of what the low-voltage mode can support, assuming no voltage ripple), then you will save: 1 - (1.95/2) = 2.5 % power.

However, if the other ICs on your board does not support this voltage (temp sensors min voltage is 2.0V), you are forced to run the nRF-device on >=2.0V with LDO power scheme to ensure that your temperature sensor works within spec.

Cheers, Håkon