I imported the ADA4932.cir into LTSpice and I am using it to design a single-ended-to-differential level-shifted ADC driver for the AD9257. I use a single-ended 5V supply and just put in 0.9 V for the Vocm. However, the AC analysis shows the circuit is completely broken. Only a Vocm of 2.5 will work with the circuit. Am I modeling this wrong?
Here is the circuit:
ADA4932's Vocm is specified to be −VS + 1.2 to +VS − 1.2 when operating at Vsy=5V. This will translate to 1.2V to 3.8 V operating range. With that being said, Vcm=0.9V will definitely won't work.
Thanks! I overlooked that - I had previous worked with higher voltage ADCs and didn't have a problem, and so didn't think about it this time.
FWIW, the SPICE model still required VEE to be about 1.5 V lower than Vocm to work.