Can I connect the AD9690 SYNCINB input to a single-ended 3.3V CMOS?
Should I add a serial resistor to limit the input current (e.g. 1K? 5K? 10K?)
OK, I understand better now and will ask the team to clarify the CMOS compatibility statement on the next d/s revision. Given the ability of the SYNCINB to accommodate a fairly wide range of input common modes (0.6V to 2.0V) and the internal divider configuration shown in fig 57 a 10k series resistor should accommodate and provide adequate protection for your 3.3V SE CMOS input level.
Instructions for operating the AD9690 SYNCINB in single-ended CMOS mode are provided on datasheet pages 49-50.
"The SYNCINB± pins can also be configured to run in CMOS (single-ended) mode, by setting Bit in Register 0x572. When running SYNCINB± in CMOS mode, connect the CMOS SYNCINB signal to Pin 21 (SYNCINB+) and leave Pin 20 (SYNCINB−) floating."
I've asked about using 3.3V CMOS. Sorry but just specifying CMOS or TTL is insufficient...
In the EVB ADI used 1.8V CMOS/LVTTL.
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