Vtune of VCO HMC586 is shorted after multiple uses

Question

Dear, 
 
 I am using HMC586 sample part to excite a patch antenna. The VCO is given 5V supply via 7805 regulator. The VCO schematic is designed as per the EVAL-HMC586LC4B Kit design files. The Vtune of VCO is controlled using Digital to analog converter AD7533 and Arduino Mega 2560. I am also using a diode in series to vtune port to discard the negative voltage if any generated. The Vtune gets shorted to ground after few days of use. Not able to find the issue. Kindly Help!!

kieranb · Accepted Answer

Hi, 
 From what you have described, the issue may not with the HMC586 but the external circuitry. 
 1. Is it possible that the diode could be causing the issue? 
 2. Could the AD7533 be the cause of the short to ground? 
 Could you try removing the AD7533 from the part and applying a fixed voltage to the Vtune to narrow down which component is the problem.

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Vtune of VCO HMC586 is shorted after multiple uses

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