nRF51822 internal LDO output pin

[Anton]

Hello,

I'm drawing schematic with nRF51822 internal LDO. I'm wondering what is the regulated LDO output from nRF51822. I need to connect that with peripherals in stable volatage. My power connection is as below.

3.7V Li-polly Battery < - > nRF51822 internal LDO < - > peripherals.

Thanks, Anton.

[MartinBL]

Hi. I'm not sure if I understand you correctly, but the voltage you will get on your GPIO pins is always equal to VDD, independent on what DC/DC or LDO configuration you use. The DC/DC and LDOs is only providing power to internal circuitry like the radio, flash, system, etc. Some of our customers ask if they can provide power to external components by using the DEC1 and DEC2 pins. As you can see in Chapter 12, "Power Management", in the Reference Manual V3.0 these pins are connected to internal LDOs, but they are only intended to be used for decoupling capacitors. We don't recommend using these pins as power supplies for external components and doing so will be at your own risk.

Also, 3.7 volts connected to VDD is beyond maximum specification, as specified in Chapter 7, "Operating conditions", in the Product Specification document V3.1. The maximum supply voltage is 3.6V and higher voltages than this might destroy your chip. If you want to use this kind of battery you will need an external voltage regulator.

[Anton]

I'm not clear in your last sentence. "If you are thinking about using the nRF51's LDOs by hooking up to the DEC1 or DEC2 pins this is something we don't recommend. "

[MartinBL]

As you can see in the figures in Chapter 12 "Power management" in the reference manual the DEC1 & 2 pins are connected to two internal voltage regulators, one 1.2V LDO and one 1.7V LDO. Some customers want to use these output pins to supply external components with 1.7 or 1.2 volts. This is not recommended.