Hardware design and antena

[FormerMember]

Designing a custom pcb, we have a few questions, and maybe you could help a little bit.

On this Nordic design ,before proceeding to layouts :

1. Can I skip pins 45/46/47 and not puting L2/L3 ? I did not see them on other designs.(what are they?)
2. If I won't use NFC, can I skip all the parts on pins 11/12 and simply use them as outputs ?
3. Can we locate the chip on one pcb side and the antena right on the other side beneath the chip? ( extreme size constrains on pcb..)
4. Can I flash this design using nrf52 dev kit on the debug connector ?

Are there any specific pins that can't do specific things ? (I could see serial/I2C/SPI/PWM works on all of them)

Thank you !

[WestCoastDaz]

Rani,

1. Pin 45 is VSS, ground, so you definitely need that. Pin is the output of the internal 1.3V LDO which needs to be decoupled. Notice that cap is connected between it and ground. Pin 47 is the output of the internal DC/DC and L2 and L3 are required for this. If you are not using the DC/DC in your design then you may be able to remove L2 and L3 but check with Nordic first.

2. Yes, you can use pins 11/12 as GPIOs but you need to use a special define in your code since they default to NFC control. Its CONFIG_NFCT_PINS_AS_GPIOS.

3. That you will have to check with Nordic on. If you do this you will likely have to due RF-PHY testing to get SIG certification since you have changed from the reference design.

4. Yes, you can flash this chip using the Debug Out connector on the DK. Note the supply voltage of your board has to be 3.0V to be compatible with the DK.

The only special pins other than the power and antenna pins are the analog pins and the debugging pins.

Hope this helps, Darren

[FormerMember]

Help indeed ! thanks. regarding pins 46-47 , if you look at Sparkfun design of the chip (a well known company) here you will see they took out L2/3 . Anyway I am not sure I understand this point. Do I need the internal LDO ? should I use external one for 5V inputs or can I use the internal ?

[WestCoastDaz]

Rani,

Looking at the Sparkfun schematic at the top of the nRF5832 block you will see it says supply range 1.7V to 3.6VDC. The chip can ran from range. Internally the chip uses an LDO to reduced the voltage to the radio and CPU core. So yes you need the LDO. But from their schematic you can't use the internal DC/DC which can help improve efficiency when the radio is on when running from a high supply voltage.

Also the nRF52832 doesn't have 5V tolerant inputs. The maximum I/O input voltage is VDD + 0.3V when VDD is <= 3.6V. Again this is listed in the data sheet.

See section 17 of the datasheet infocenter.nordicsemi.com/.../nRF52832_PS_v1.3.pdf

Cheers, Darren