Other Parts Discussed in Thread: ADS8353, ADS8860, ADS8332
I had some initial problems with the ADS8363 which were related to the timing between the Rd pulse and the clock pulse. I changed that timing which kind of solved the problem. The reading tracks very well from 0 to 32,768, but the most significant bit is always zero. In that application 15 bits was adequate, but now I am using the ADS8363 in an application that requires 16 bit accuracy. I am interfacing the ADS8363 with an STM32F407 processor and uses the standard SPI hardware and a separate port to pulse Rd. Using a separate port I have not been able to generate an Rd pulse that meets the requirement of less than 1 clock pulse. My Rd starts about 200nS before the first clock and ends about 10nS before the rise of the second clock pulse, see attached logic analyzer capture. This seems to work very well, but may be what is causing the MSB to always be zero. However, if the input is a few millivolts below zero the MSB then goes high. Could the Rd timing be what is causing my MSB to always be zero?
The ADS8363 is in Mode 1V, the negative inputs of the ADCs are all grounded and the positive inputs are used as single ended inputs. The reference voltage is 2.5V. With an input of +2.5V the reading is 32,676, which seem strange because if the Rd timing was the cause of the problem I would have expected the output to saturate at 32,768 with an input of 1.25V, not 2.5V.LogicPort Input = 2.5V.pdf
