Part Number: TRF7970A
Hello,
I am having a problem with approximately 15% of our boards failing to start the TRF7970A crystal oscillator after re-starting from power down as indicated by B6 of the RSSI Levels and Oscillator Status Register (0x0F). I see this on two different board designs each using the same circuit which is duplicate of the . We replaced 10 of the parts with the start up problem and the issue was resolved. I see the issue with two different lots of parts. The Supply Regulator Setting is set for 3V and Automatic regulator setting. We have tried delays up to 100mS after we drive EN to a logic 1 to wake the part from power down mode. EN2 is connected to ground. We are using a 13.56MHz crystal from Kyocera P/N: CX2520DB13560H0FLJC1. It has a load capacitance of 12pF and an ESR of 150. We are using load capacitor values of 15pF. We tried swapping out one of the crystals for a 27.12MHz device, but and leaving the oscillator setting at 27.12MHz, but the oscillator still would not start. The circuit we are using is a copy of the TRF7970AEVM with out own 50 ohm matching circuit to our antenna.
Device Lot numbers: AE7L, AXK5
Regards,
Dan
