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LTC4211 not conducting

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napster4electronics

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Hey

I use a LTC 4211 to limit the inrush-current of a capacitorbank. The first problem was that we pulled the FAULT and RESET pin to 5V after the FET (so at start the pins aren't pulled up). We solved this issue by connecting those pull-up resistors to VCC.

Hereafter the LTC starts conducting for a few seconds after shutting down and pulling the FAULT pin low. I thought my powersupply was too slowly adapting the current and therefore the LTC went in FAULT mode. ( We are using a 3 mOhm shunt as sensresistor.) We disconnected the powersupply and discharged the capacitorbank. Whereafter we reconnected the powersupply through a multimeter in currentmode (because we thought the powersupply was to slow). And then the LTC went on and stayed on.

This is strange because the series resistor added by connecting the multimeter is very low. So it barely restrict the current and it also isn't added to the shunt (viewed from the LTC point of view). Afterwards I tried the same with a 10 ohm power-resistor and the LTC didn't start conducting.
 

Hi,

Sorry, I can't follow all your description.

Please show your schematic,
your PCB layout and
a detailed description of the applied and measured signals.

Klaus
 

Are you sure you discharged the cap bank completely?

Have you calculated the energy in the cap bank to verify that the chosen mosfet and timing configuration can handle it.

I'd change the timing cap or reduce your cap bank.

And are you aware of LTSpice simulation tool (its totally free)? Completely simulate your exact circuit and see if it goes into fault or not. If so you can debug it much quicker in the simulator. There is a full model and 'test fixture' circuit in LTSpice
 

Hereby the schematic of our circuit. The +5V are already changed to +Vin, because this was giving a problem.
Schermafdruk van 2019-03-19 21-23-00.png

The capacitorbank was fully discharged to 45 mV.
Reducing the Cap bank isn't a possible.

We are simulating the circuit atm. We'll post once we're done with simulating.
 

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