LMX2594: Does TI offer a synthesizer that will change frequency on the rising edge of the SPI chip select not line?

Noel,

The LMX2582 was the synthesizer I used in my previous design and it had the same issue I am having with the LMX2594. The post where I notified IT about the datasheet issue is:

https://e2e.ti.com/support/clock-and-timing/f/48/p/660407/2426532

Unfortunately the datasheet still needs to be updated 18 months later.

Noel,

I found that the LMX2594 loads its registers on the rising edge of the last CLK signal not when the CSB line goes high as stated in the last sentence of section 7.5 of the manual. Can you please confirm this discrepancy?

Thank you,

Matt

Hi Matt,

That is correct, the registers are loaded on the rising edge of the last CLK signal.

Noel,

Do you know of a synthesizer whose registers are loaded on the rising edge of the CSB signal?

Noel,

Can you please confirm this for me. I have found the datasheets to be in error for both the LMX2582 and the LMX2594 regarding this specific function. The test should simple: hold the LE pin low, send data to a register that will change the output, measure the output for the change while keeping the LE pin low.

Thank you,

Matt

Hi Matt,

OK, I can hook up a test to verify. 

In the mean time, what output frequency and performance are you looking for? Can LMX2581 support your need?

Noel,

I will be using the synthesizer to make 110 to 111 MHz.

Noel,

I do not mean to be a pain but can you please describe the steps you used to verify this?

Noel,

Did you manually control LE line so that the time between the last edge of the clock and the rising edge of the LE could be controlled to prove it was the LE pin not the clock line?