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 poi= nt 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 spe= cs, I don't necessarily mean that the MLCCs can handle more ripple current = but rather that the electrolytic caps' ability to handle high frequency rip= ple depends on the details of internal heat transfer which are not characte= rized or controlled well by most manufacturers) The big disadvantages are higher cost, infancy reliability problems due to = flex cracking, and capacitance change with voltage. I would often get requests to evaluate additional possible suppliers for th= ese caps and I often had to check the dC/dV myself because many manufacture= rs do not provide that data, although the situation is getting better and m= ost do provide it now. I was bitten by this the first time I used them - I was shocked to find tha= t 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 the= ir nominal capacitance at 50% bias (DC bias equal to half the rated max wor= king 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 addit= ional margin). The device I built to perform this test works by simply connecting a very a= ccurate low-value current source, with a compliance to at least 100V, to th= e capacitor under test. A microcontroller (NXP ARM, not PIC) watches the vo= ltage rise, computes the slope at various points along the rise and compute= s the capacitance from the slope and the known current. The micro also has = the task of stopping the current flow when the desired max voltage is reach= ed. It reports the data over a USB-based virtual COM port in a text-based f= ormat. 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 t= o try to be able to guarantee 0.5% at all times) Sean On Wed, Feb 14, 2018 at 3:01 PM, Van Horn, David < david.vanhorn@backcountr= yaccess.com> wrote: > Very good! Something more people should be paying attention to, I think. > > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On=20 > Behalf Of Mario > Sent: Wednesday, February 14, 2018 11:14 AM > To: Microcontroller discussion list - Public. ;=20 > Microcontroller discussion list - Public. > Subject: Re: [EE] 7-16V to 350-400V SMPS boost IC? > > At 02:44 2018-02-14, Sean Breheny wrote: > >I recently was able to make a simple boost converter (no transformer)=20 > >to provide 120V DC at 2mA from a USB 5V supply. About 70% efficiency. > >This is part of a capacitance meter which can measure the variation=20 > >in capacitance vs voltage for characterizing X7R and similar ceramic=20 > >chip > caps, up to 100V. > > Coolness. > > Few know of this characteristic/limit of MLCC's, but much fewer=20 > actually do even design tools to measure it. > > I would never use a MLCC where this info is not specified in the datashee= t. > I found that TDK does a very good job on it, but then again having a=20 > tool to actually measure this is very cool. Congratulations. > > > > > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=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 .