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NFAULT LED Error always on

Chirag Ashok Jaidhara
Prodigy 50 points
Part Number: TIOL1115EVM

I think i have connected the L+ and L- wires wrongly with the CQ line and due to which the Nfault LED is always on and the VCC out is only giving me 2.4V instead of 5V. 

All the other LED's are now very dim as compared to earlier when they were lit brightly.

Is the device now spoilt ? how can i diagnose the Nfault error ?

  • 0
    TI__Mastermind 33030 points

    Hi Chirag,

    The device was designed to be resistant to incorrect wiring and has polarity various polarity protection diodes and a large abs min/max rating on the L+, L-, and CQ pins, but there is still the possibility of damage, particularly if the Current Fault Detection and Auto Recovery feature is disabled by leaving the ILIM_ADJ pin floating.

    Can you describe the current configuration of the board and what is connected to it?  Do you currently have just the 24V supply connected between the L+ and L- (GND) pins, or do you also have something connected to the CQ pin and/or the digital IO pins?

    The NFAULT is the Logical OR of the Over Current, Over Temperature, or Under Voltage fault conditions and will respond according to the state diagram.

    What is the state of your ILIM_ADJ pin, or where do you have the shunt installed on the JMP1 header?  Or is the pin floating?  How this pin is configured can alter how the current fault indication and recovery works.

    The LDO should remain on for all device states so when you say you only get 2.4V instead of 5V, this may indicate the device has been damaged.  Are you measuring this with a multimeter, or are you looking at this with a scope?  If you are using a meter, do you have the ability to use a scope to see if there is any fluctuation to the voltage such as in the form of it possibly turning on and off at some frequency which would result in an average voltage of 2.4V?  Because 2.4V is almost exactly half of 5V, I'm wondering if the device is turning on and off in a cycle.

    Also, do you see any other oscillations or any unusual waveforms on any of the other pins? I would not expect this but it may be something verify the state of all pins.

    Regards,

    Jonathan

  • 0 in reply to Jonathan Nerger
    Prodigy 50 points

    Hello Jonathan, 

    Currently, i have the L+, L- and CQ lines from the master connected to the board.

    The JMP1 was connected to the GND for ILIM_ADJ

    I have measured the LDO via the Multimeter and it shows me 2.4V instead of 5V and also with the osciloscope it is a simple 2.4V line without any fluctuations.

  • 0 in reply to Chirag Ashok Jaidhara
    TI__Mastermind 33030 points

    Hello Chirag,

    Thanks for the information.  It sounds like the device may be damaged if it is only producing 2.4V on the LDO output.  Can you also monitor how much current is being drawn by the device?  With no activity and just the L+ 24V supply connected, the EVM should draw less than 10mA with the LEDs being the largest consumer of current at about 2mA each. If you see higher current, this too could point to a damaged device.

    If the device is not damaged, I can't explain why the LDO is only producing 2.4V and I have not seen this before. There are no configuration settings that can alter the LDO.

    Regards,

    Jonathan