I'm currently trying to use the TPS2590 (3-V to 20-V High-Current Load Switch) within a design to report a current fault as well as current limit the output.
EN_FALSE = driven low by a micro-controller (not seen on the attached schematic), pull up to disable device unless being driven by the microcontroller
VIN = 12V
RETRY_FALSE = floating
ILIM = connected resistors in series which totals 663k (expecting <but having issues with> a currently limit of 303mA)
IFLT = connected resistors in series which totals 728k (expecting <but having issues with> a current fault at 275mA)
CT = connected to a 1uF cap (successfully see cap voltage rise for the expected 38mS)
GND = tied to the circuit-board's ground (the thermal pad is also tied to the same GND)
OUT = output to the load
FLT_FALSE = sent to a micro-controller to monitor, and report over current fault conditions, contains a pull up to ensure only faults driven by the TPS2590 are seen
We are applying loads to output of the TPS2590 and we see faults occurring at current levels much lower than what is set with the IFLT level. We have done some experiments where we have been varying the IFLT resistance and we seem to find that the equation as described in the data sheet to calculate the RFLT may not be valid. The equation seen in the data-sheet is RRFLT = 200kOhm / IFAULT. During various loads and various modifications to the IFLT threshold, it appears that the constant 200kOhm seen in the equation may be varying down in the 150kOhm or even in the 100kOhm range. We suspect that the device is possibly not designed to successfully current limit at levels in the 200-300mA range, since within the data-sheet there is test that indicates "High-Current" and the electrical characteristics table indicates threshold data for when the settings are in the 1-4Amp range. Do you know if the data-sheet is missing information which should indicate the lowest allowable current levels at which it can perform. With our extensive tests, this is the only thing we can imagine may be the issue. However attached is a PDF schematic which should confirm that the above configuration is described correctly. Any insight as to why we are seeing un-expected current faults at levels below the set threshold would be greatly appreciated!
-Andre'
--> attached schematic: 8468.TPS2590 Circuit.pdf
