DAC38J84: Documentation question: Config52 (SYNCb electrical configuration) semantics?

Todd Rockoff

Intellectual 480 points

Part Number: DAC38J84

Hi,

It looks like there are 4 drive current levels for the SYNCb output, specified in Config52[15:14].

My question is, what are the semantics of Config52[15:14]?

Hopeful thanks --todd

over 5 years ago

0 Kang Hsia over 5 years ago

TI__Guru 69754 points

Hello Todd,

These registers are meant to adjust the output current of the LVDS driver from 2mA to 4mA differential output. You can actually use our IBIS model to simulate the driver + PCB + your FPGA SYNC LVDS receiver altogether to see if any adjustment is needed for optimal loss profile + signal integrity.

www.ti.com/.../slam197

0 Todd Rockoff over 5 years ago in reply to Kang Hsia

Intellectual 480 points

G'day Kang,
Thank you for your prompt reply.
Unfortunately, I think you have restated the information given in the manual, which can be summed up as "the SYNCb LVDS differential output current is adjusted between 2mA to 4mA by config52[15:14]."
My specific question is, what LVDS output current corresponds to each of the 4 possible settings?
Hopeful thanks --todd

0 Kang Hsia over 5 years ago in reply to Todd Rockoff

TI__Guru 69754 points

Hello Todd,

We were able to measure the corresponding output voltage and current based on the settings. please see attached measurement results for reference. We also included the bias level in case you are interfacing with 0.9V based LVDS receiver.

SYNCB Characterization DAC38j84.xlsx

-Kang

0 Todd Rockoff over 5 years ago in reply to Kang Hsia

Intellectual 480 points

Dear Kang,
I am deeply grateful for your having carried out an empirical study that definitively resolves this issue. You in fact addressed a broader question that I would have asked were I a more astute electrical engineer. Thank you!
Sincerely --todd

Data converters

Data converters forum

DAC38J84: Documentation question: Config52 (SYNCb electrical configuration) semantics?