The AD9901 is a digital phase/frequency discriminator capable of directly comparing phase/frequency inputs up to 200 MHz. Processing in a high speed trench-oxide isolated process, combined with an innovative design, gives the AD9901 a linear detection range, free of indeterminate phase detection zones common to other digital designs. With a single +5 V supply, the AD9901 can be configured to operate with TTL or CMOS logic levels; it can also operate with ECL inputs when operated with a 5.2 V supply. The open-collector outputs allow the output swing to be matched to post-filtering input requirements. A simple current setting resistor controls the output stage current range, permitting a reduction in power when operated at lower frequencies.