Tim,
Going to the downloads tab on the AM page you linked, then looking at the datasheet, I found that it supports several options:
- 10-bit Analog output - 2.6 kHz sampling rate
- 10-bit PWM output - 1024 positions per revolution, 1 kHz
- 12-bit PWM output - 4096 positions per revolution, 250 Hz
It looks like it's somehow program selectable among these modes.