AT86RF215 I/Q mode - no LVDS RXCLK
I'm using an AT86RF215 on the ATREB215-XPRO evaluation board in IQ mode. Everything seems to work except that I can't get a whisper out of the RXCLK LVDS lines. The RXDATA lines have an obvious signal, all the registers claim to have the right values and it responds in the way one would expect, but there is no RXCLK. And as the RXCLK is what drives the whole IQ interface, I'm stuck.
It's in IQ-only mode (IQIFC1.CHPM = 1); IQIFC0.CMV and IQIFC0.CMV1V2 set the common mode voltage on clock and data correctly; IQIFC0.DRV sets the RXDATA drive current OK (though not on the clock). VDD is 3.3V.
With no load on the clock and data lines, a scope shows about 2.5V pk-pk on RXDATA (either band, as enabled) but only 300mV pk-pk on RXCLK. With any load at all (eg just an unterminated open-circuit SATA cable), the RXCLK falls to 100mV. Into the recommended 100R resistor, it vanishes into the noise (<50mV).
It looks as though a driver isn't switched on, but there's nothing in the manual or errata about it.
Anyone have any ideas?