TPS2663: dVdT Capacitor Remains Low and then randomly switches on

Hello Martin,

What's total COUT and start-up load? Use this design calculator to check if device goes into thermal shut-down.

https://dr-download.ti.com/design-tools-simulation/calculation-tool/MD-QV4CzjZsl1/01.00.00.0B/slvc765b.zip

Device can go into TSD if inrush current is high and leads to thermal shut down.

Thanks 

The normal load that is connected is a servo with a capacitance of 50 uF.  The odd thing is that even without anything connected the dVdT cap remains low. We also noticed that given enough time while powered the dVdT cap does at some point charge up. 

Please add higher cap on dVdT and check for example 1uF

The fault pin is not triggered during startup. I do not suspect that the device is entering TSD given that with a thermal camera the device remains at 40 °C

Hello martin,

Device can go into thermal shutdown during start-up because of inrush current or start-up load. This is because VDS voltage is less, and more power dissipates.

Also check the input current.

You can remove the servo motor and check if device starts in no-load. Also prove IIN, VIN, VOUT and FLT with and without load to debug this.

Thanks

Amrit 

As mentioned earlier even with the servo disconnected we see this behaviour. So no load causes the E-Fuse to not switch on at power up.

Hello Martin,

Is the board bring up done? Do you have TI EVM to check? You can place the IC on EVM and check if it starts.

Can you check soldering on board if it's done right!