I am back looking at RFID/NFC modules and I am grappling with a basic circuit design challenge.
As some of you might know the NXP PN5180, the PN7150 (NRND) and the PN7160 controller chips allow you to apply a 5V input to antenna, which boosts performance. But it will also accept a 3V3 supply.
So I am trying to come up with a circuit that will apply either voltage to Vin_antenna but 5V will always take preference. As in, if 5V is detected apply this voltage, otherwise apply 3V3. This means that 5V input can be optional.
I had always had in my head that this circuit would work, but I clearly hadn't studied the circuit closely enough until very recently, when I realised that this circuit applies a VBUS charge to VBAT, if VBUS is detected. Not quite what I wanted. But then maybe I could simply insert another diode to ensure one way traffic on the VBAT or 3V3 line.
Then, I discovered the tiny LM66100DCKR integrated diode IC. I think this potentially could work but I was not sure how well it would work with the 2 different voltages. I just don't fully understand the ins and outs of this IC. I just want to ensure that the 5V bus took priority over 3V3.
https://www.ti.com/lit/ds/symlink/lm66100.pdf
(see section 9 of PDF).
So, any thoughts and suggestions greatly appreciated. Thanks.
