A microcontroller is connected to a port IO Expander, ADC and DAC chips through SPI. All of them use +5V supply except the uC at 3.3V and is 5V tolerant. The port IO expander VIH Min is 4V and the ADC & DACs VIH Min is 3.5V, figures taken from datasheets at 0.8VDD and 0.7VDD. But the uC can output a max. of 3.3V only. A few test boards have been working without any issues for about an year. They are about to ship some boards, I found this one out on a casual review and said they are not meeting the specs. My comment was not well received!
Please suggest me whether this is ok.
Please suggest me whether this is ok.