give external supply to nrf51

[nordicbeginner]

hello there,

i am giving external supply to nrf51. my external supply is usb 3.3 v. but when i connect it with nordic and then if i check it on multimeter , it shows me 2.12 v. can you tell me why??

[nordicbeginner]

supply voltage of LM1117 is 5 v. output is 3 v

[Sigurd]

Are you using the same schematics as shown in the datasheet here (page 1)?

[Roger Clark]

LM117T is a 3.3V regulator.

If you are getting 3.0v offload, you already have a problem before you attach the nRF51.

[nordicbeginner]

i am getting 3.3 v. but i am using variable resistor to voltage

[Sigurd]

Hi,

According to the datasheet(page 6) the adjustable version of the LM1117 needs a minimum load current of 1.7mA to maintain regulation. The nRF51 will typically not use this much current, and the adjustable version of LM1117 is therefore not suited for low-power applications.