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XTR305: Over Temperature flag unstable

Part Number: XTR305
Other Parts Discussed in Thread: XTR105

XTR305 has been configured as per figure 40 of the datasheet with V+ at +24V, V- at -5V and logic supply at +3.3V. M1 tied to DGND with M2 and OD\ being controlled by a PIC microcontroller. Ciruit works as expected in current and voltage mode except the overtemperature flag output EFOT being unstable and becomes stable only with a very low value pull-up resistor in the range of 13Ω - 15Ω. i.e. 22mA to 25mA current drain. Why?

Overtemperture flag output EFOT without any pull-up resistor

Overtemperture flag output EFOT with 1kΩ pull-up


  • Hi Vithy,

    hhm, as shown in figure 40 of datasheet a pull-up of 4k7...10k should be fully enough at the EFot output. In no case you should use a 13R...15R pull-up. This is way too small and might damage the chip.

    I think the XTR305 has been damaged during experimenting. I would take a fresh one and check again. Or is the XTR105 abnormeously getting hot?

    Kai

  • Hi Kai,

    The IC is not getting hot as I do not leave it with 13R - 15R pull-up continuously.

    The device seems to be working otherwise.

    However I have check with a different device (seperate PCB) as you have suggested.

    These devices have been hand placed (Thanks to Corona Virus) and may not have good soldering to the center pad – datasheet says it must be connected to V- on page 3.

    Could this have an effect on the overtemperature flag.

    Regards

    Vithy

  • HI Vithy,

    As you have mentioned, the underside center pad must be biased/connected to the most negative potential supply (V-), this pad needs to be soldered.

    If the issue continues after replacing the device and soldering the underside center pad, please post the schematic and board layout showing all the XTR305 connections, board layout and the state of M2 when the issue occurs.

    Thank you and Regards,

    Luis

  • Hi Vithy,

    yes, indeed. Leaving the pad unconnected can have a bad effect, as already mentioned by Luis.

    Kai

  • Hi Kai / Luis,

    Thanks for your help and proper soldering of the centre pad resolved the issue.

    Regards

    Vithy

  • Hi Vithy,

    that's good to hear :-)

    Good luck,

    Kai