LMX2594: Is there any issue with using the category 3 sync with full VCO assist?

Kevin Lai

Part Number: LMX2594

Hi team,

customer is having a small issue with the LMX2594. When we tune a couple devices to 13040 MHz using auto calibration, and then synchronize them using Category 3 sync, everything syncs up. But when we use full VCO assist to tune the same output frequency, and then synchronize the same way, the devices don’t sync. They maintain the same phase as if the sync pin is muted. The register sets in the parts are identical in the two modes except for the Register 8 and 20 differences that are used to force the cal values for full assist.

Is there any issue with using category 3 sync with full vco assist?

Thanks,

Kevin

over 3 years ago

0 Vibhu Vanjari over 3 years ago

TI__Genius 11900 points

Hello Kevin,

I wouldn't think so. Can you maybe ask customer to try the same thing but use the same configuration in both devices? That is configure register 8 and 20 the same as well?

Thanks,

Vibhu

0 Kevin Lai over 3 years ago in reply to Vibhu Vanjari

TI__Intellectual 2916 points

Hi Vibhu,

The configuration in the two devices that are being synchronized is the same. The phase of the devices can be synchronized when both parts have FCAL_EN=1 and the parts use internal calibration. The parts can’t be synchronized when FCAL_EN=0 and full VCO assist is used to load the calibration information directly to the registers. Section 7.3.10.3 in the datasheet says that If FCAL_EN=0 then the sync pin doesn’t function.

Is there any way to apply Category 3 sync when FCAL_EN=0 and full VCO assist is applied without triggering the internal calibration?