Actually I‘ve posted a lot questions about a VGA(variable gain amplifier) chip named HMC960LP4E. However, I cannot totally understand how to use it.
In fact, I just want to use the parallel ports to control the gain without SPI BUS. I want to amplify the differential signals with handreds of KHzfrequency.
So, the biggest problem is that I don't know what to do with some ports.
1、I provide the chip with 5V supply. Then, what should CMI and CMO be set? 2.5V, 3V,or 3.3V? Otherwise, they are all OK?
2、In datdsheet, I notice the Differential Input impedance(100Ω mode & 400Ω mode) and Full Scale Differential Input. But the reference circuit don't show any 100Ω or 400Ω resistance. Should I connect a 100Ω or 400Ω between the differential input or just leave it alone?
3、If I utilize it to control gain without SPI. Does it mean that I don't need to change values in registers, for that default values choose parallel ports as gain-controlling source.
4、If I have any question, which ports should I test to find out the problems. Namely, which characters should I check to remove the faults.
All in all, may be the problems look easy. I do appreciate your help.
Please check out the attachments for more details.