I have an AD8318 Log Detector followed by an AD8138 Differential Driver. The log detector is behaving correctly, as VOUT goes between 0.8-4.0VDC over the dynamic range of the input RF signal. However, the AD8138 used to translate from single-ended to a differential voltage output remains stuck at a +5.3V differential. The +OUT pin is at +3.4V to ground, the -OUT is at -1.9V to ground, or +5.3V from +OUT to -OUT.
The AD8138 power supplies look good at +5V and -5V respectively. The only strange thing is that it takes ~15 seconds for the -5V rail to come up after the +5V.
Schematic is attached. Any ideas on what might be the reason for the AD8138 to be stuck?