Hello,
I am running an ADC3424 at 100 MSPS and am having some difficulty understanding the test patterns. After powering up the ADC, I pulse the RESET pin, enable the test patterns by writing a 1 to bit 1 in register 06h, and then configure various test patterns such as zeros, ones, toggle, deskew, custom, and sine. I am not writing to any other registers except for when I set a custom pattern in registers 0Eh and 0Fh.
The zeros, ones, toggle, deskew, and custom patterns all read as I would expect. However, I don't quite understand what I'm seeing from the ramp and sine patterns. The ramp pattern repeats each value four times before incrementing. For example, I might read 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, .... I expected to see 0, 1, 2, 3, 4, 5, 6 based on what I read in the data sheet.
The sine wave pattern gives me a repeating sequence of eight samples, as stated in the data sheet, but the eight values I see do not match those stated in the data sheet. The data sheet reads: "8-point sine-wave: data are a repetitive sequence of the following eight numbers that form a sine-wave: 0, 599, 2048, 3496, 4095, 3496, 2048, and 599." When using the two's complement data format, I see the repeating sequence 0, 978, 1384, 978, 0, -979, -1385, -979. So, I see a sine-wave-like pattern, but with an amplitude different from what is specified in the data sheet.
Do these patterns make any sense? Am I misinterpreting the data sheet, or am I doing something wrong here?
Thanks a lot for reading!
