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ADRF6510 and high 3'rd harmonic level at output

Question asked by fjot on Jan 10, 2012
Latest reply on Jan 11, 2012 by jdobler


we have an issue with 3'rd harmonic level at ADRF6510 outputs. The ADRF6510 is driven from ADL5387 directly in DC-coupled mode as it was described in Rev.0 datasheet of ADRF6510. (Rev.A datasheet does not include that reference design any more). The input signal to ADRF6510 has the third harmonic ~52dBc while at the output of ADRF6510 we observe the 3'rd harmonic @ ~32dBc. The gain of ADRF6510 is fixed to 0dB. The FE gain switch is at 6dB.

The input of ADRF6510 runs at 0.5Vp-p as well as te output (as the gain is 0dB).

What could be the reason for increased 3'rd harmonic at the output of ADRF6510?

The output (both N and P separatelly) of ADRF6510 drive resistor based (150Ohm, 100Ohm) divider for ADC common mode voltage matching.