Part Number: THS4551
Other Parts Discussed in Thread: ADS127L01
Hello Team,
we are building a 500 kHz low pass active filter for driving an ADS127L01 according to THS4551 & ADS127L01 datasheets.
After the pcb has been routed and assembled, the DC linearity measurement of circuit has been performed. The results of measurement was quite surprising for us, because the measured nonlinearity is in range of 20ppm for -1V to +1V of output voltage of THS4551 powered by 3.3V High PSRR and low noise LDO.
As Rg and Rf resistors the LT5400-4 was used, other resistors are 0.1%, 10ppm/C. All capacitors excluding bypassing ones (X7R) are NPO. We use 4 layer stack up for pcb and we strictly meet all criteria recommended in THS4551 & ADS127L01 datasheets for pcb layout, IC bypassing, fully symmetrical routing etc.
Our measurement setup includes: Fluke 5720A Calibrator (calibrated approx. two months ago) used as a signal source, Wavetek 1281 (calibrated approx. month ago) used as voltage meter. The whole circuit was powered from 6V lead acid battery. All measurement cables, power cables and pcb itself was properly shielded to reject environment influence.
If schematic is needed, we could send it offline.
Do you have any ideas what could be the issue? Is it some characteristics feature of the FDA due to its internal structure or might it be some natural behavior of FDA itself?
Thanks for your help,
TI Customer
