Hi David, The thought crossed my mind but I really built it for my own use. The design presently was optimized for whatever parts I had laying around and is made using a veroboard. I would have to do a PCB layout. I'll think about it. Sean On Thu, Feb 15, 2018 at 3:25 PM, Van Horn, David < david.vanhorn@backcountryaccess.com> wrote: > Is this something you'll be selling? > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of Sean Breheny > Sent: Thursday, February 15, 2018 1:19 PM > To: Microcontroller discussion list - Public. > Subject: Re: [EE] 7-16V to 350-400V SMPS boost IC? > > Thanks! > > I have used MLCCs for bulk decoupling on some motor drives. They have > three big advantages over aluminum electrolytics: > 1) much longer life at high temperatures > 2) very low ESR/ESL which can be distributed around the board to provide > an overall very low impedance between any point on the power plane to any > point on the ground plane, which comes in very handy to prevent ground > bounce effects when switching FETs on and off hard at high currents > 3) much better specs on internal heating from ripple current (by better > specs, I don't necessarily mean that the MLCCs can handle more ripple > current but rather that the electrolytic caps' ability to handle high > frequency ripple depends on the details of internal heat transfer which a= re > not characterized or controlled well by most manufacturers) > > The big disadvantages are higher cost, infancy reliability problems due t= o > flex cracking, and capacitance change with voltage. > > I would often get requests to evaluate additional possible suppliers for > these caps and I often had to check the dC/dV myself because many > manufacturers do not provide that data, although the situation is getting > better and most do provide it now. > > I was bitten by this the first time I used them - I was shocked to find > that the voltage ripple on the motor drive bus was twice what I had > calculated it should be, which I then traced back to the caps having > roughly half their nominal capacitance at 50% bias (DC bias equal to half > the rated max working voltage). At that time, Taiyo Yuden (where I was > getting the caps) did not provide this info in their datasheets. I think > they now do provide it. I got lucky because I had overspec'd the quantity > of capacitance by about a factor of 2 because of uncertainties so it just > worked out (with no additional margin). > > The device I built to perform this test works by simply connecting a very > accurate low-value current source, with a compliance to at least 100V, to > the capacitor under test. A microcontroller (NXP ARM, not PIC) watches th= e > voltage rise, computes the slope at various points along the rise and > computes the capacitance from the slope and the known current. The micro > also has the task of stopping the current flow when the desired max volta= ge > is reached. It reports the data over a USB-based virtual COM port in a > text-based format. It can handle a range of 100pF to 100uF accurately > (typically I get about 0.3% and I am still tweaking the firmware to use > various techniques to try to be able to guarantee 0.5% at all times) > > Sean > > > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .