Hi,
Can you provide some application note regarding the controller mode of the HMC602 (or equivalent log detector/controller) ? We recently acquired evaluation boards for the HMC602LP4E and HMC346AMS8GE in order to implement an analog ALC loop in an experiment (1-8GHz), unfortunately I can't seem to get the controller mode working properly.
The HMC602 works flawlessly in detector mode, so does the HMC346 (wired in single-line control as shown in page 8-5 of its datasheet), however, when decoupling Vset and LOGOUT, the error amplifier output either swings between 0V and 4V (with significant hysteresis), or shows large oscillations, almost regarless of the voltage applied to Vset.
The RF signal exiting the HMC346 is fed to the HMC602 through a 16dB directional coupler. The loop itself is implemented in a similar way to Fig. 43 of the AD8318 datasheet, with the difference that, in our case, LOGOUT is multiplied by 2.5 and -5V is added to it before being fed to V1 of the HMC346: an increase in LOGOUT translates to a V1 closer to 0V and therefore less attenuation (and vice versa).
Since either device work independently, I don't think I have defective parts, so I'm obviously either missing something important or doing something terribly stupid and we'd appreciate some input on how to get it working.
Best regards
