We are using the LTC3789 alonside the LTC4000 in an arrangment which is identical to the DC1721A-A Demo board (schematic and layout) for a LiFe battery charger and portable radio PSU application. Unfortunately we have had half a dozen failures of the LTC3789, causing product failure in the field. The 3789 device fails without warning and ends up running very hot, The VCCINT regulator output has been seen at 9V+ on some failed boards, so it looks like the internal 5V5 regulators are cooked. We don't know if the failure coincides with a user operation, e.g. connecting/disconnecting Vin or the load. The input voltage is 12V nominal, and we have plentry of extra protection (surge and polarity) on the board ahead of the LTC3789. The 12V is supplied from a good quality AC-DC adapter block spec'd for an 11.5A output. Our maximum load is approx 6A at 12V, and we sometimes run the load with the 12V input supply connected to the board, regardless of battery charge state.
if anyone can give me some pointers as to what could be causing the failures than it would be much appreciated.
Looks like this is a loop filter issue. Using just a series C and R between the CC and ITH pins on the 4000 charger and removing the 3-component filter between the ITH pin and GND on the 3789 switcher…
I am trying to design a four mode buck boost converter based on the LTC3789 controller such that I want to completely substitute all the PLL functions, clock and everything else internal to it so that I can exercise complete control using a PIC16F877 micro for my charge controller project. Please How do I do this tellthebell?