this design is our own, not a direct recommendation for the ADHV4702-1. We ordered two EvalKits now for the LT8365 (one for -HV Application and one for +HV-Application) to check if the sporadic design is provoced by the dimensions of external components or by layout. Also damage during the soldering process or thermal issues in operation could be possible. Or maybe the components were flawed by the distributor already, but I think thit is unlikely. We will see and have contacted now an employee of Analog Devices. Thank you anyway.
Hi Chrisbo, I'm not familiar with the LT8365. To clarify, is this possibly the design that is used on the Eval Board, or is the power supply a design of your own? I believe the Power group would be the right group to address this, unless it's the Power Supply that is recommended as a reference design for the ADHV4702-1. Please let me know. Best Rgds, Brian Beucler
now that we have tested the ADHV4702-1 with the new PCB Design, we got another problem with the HV Supply. We are using two LT8365 Converters for the negative and positive HV Supply Rails. Under certain circumstances some of the boards are working fine while others do not. There is a sporadic failure for which we have no explanation yet. By chance, can you also support this topic? I asked some questions in the associated Engineer Zone Category once, but the response activity was quite less. If so, I would like to give you a detailed description of the problem.
Thank you for your response! We were aware that there is parasitic capacitance to charge and discharge. We tried to minimize this with cutting out the ground plane where the large signals take path, letting the signals paths as short as possible and using tracks with a width just as necessary. But okay, maybe there is still significant parasitic capacitance and like you described, we mistargeted the purpose of the Radj feature anyway.
So, in a second design of the PCB, we improved the driving capability of the HV Supply by using a different step-up converter than before with a higher switching current. Also we are using bigger coils now with lower resistive losses so that the overall performance was significantly improved. In that way, is it possible to drive the HV stages with a shorted Radj. The PCB will be manufactured and tested soon. Thank you for your help and explanations!