What is the minimum reference clock frequency input for the AD9913, both with and without the PLL multiplier enabled?
The minimum reference clock for the AD9913 is not indicated on its data sheet. But for optimum performance, I would recommend a 250MHz reference clock without the PLL multiplier enabled and a 25MHz reference clock with the PLL multiplier enabled and set to 10x. But the part is capable of multiplication factor of up to 64x so you can use lower values for your reference clock and just adjust the multiplication factor to have 250MHz.
I want to run it at 10MHz, most probably with the multiplier enabled. Thanks, Gerald
Just to clarify, you want the system clock of the part to be 10MHz or you will be supplying 10MHz to the part as its reference clock?
Hi Mark, the 10MHz would be external. Will probably need to use the PLL to multiply up to 100 MHz for the system clock. Gerald
Yes. You can use 10MHz as reference clock and use the PLL.
Thanks. Can you site where that is confirmed? I couldn't find it explicitly in the datasheet.
Gerald - The minimum was not characterized for either mode. If you are bypassing the PLL, I am not aware of anything limiting the device on the low end of the reference frequency, I would expect it will run fine even below 1kHz if you really wanted to do so. When using the PLL, the PFD frequency is a potential limiter. It would be very surprising if it did not work down to 100kHz or below on the ref in. In such instances, I would expect customers to bypass the PLL anyway since the cost of a cleaner reference source at those frequencies is relatively low.
EDIT - LouijieC has looked at this in the lab, and the practical limit for REFIN with the clock multiplier active appears to be around 700 kHz, so higher than my expectation called out above.
This was helpful. We figure that we could at least run the PLL down to 4MHz since the max freq was 250 and the max multiplier was 64x. Thank you. Gerald
Only the maximum reference clock frequency is indicated on the datasheet.
Retrieving data ...