TIC12400-Q1: TIC12400 hangs

You probably need at least a series diode on the VS input to the board (before capacitors), and potentially also a transient suppressor from VS input to the VS return. Also ensure that the 12V and 0V inputs to the board are in the same area, and that the transient suppressor is right nearby.

Alihussain,

Is the Inductive load connected to a TIC12400 input pin in anyway?  Or is this simply an inductive load on the board that is unrelated to the TIC12400 device?

Inductive loads can be problematic in many ways and can often create large transient voltages that can cause Under Voltage, Over Voltage, and Reset conditions in the devices on the board.

Have you monitored the VS and VDD voltage rails when you turn on the inductive load with a scope to check for transients and supply over and under voltage conditions?

When you elaborate on what you mean by "unresponsive" a little more?  I am assuming you are referring to failed SPI communication.  If so, does it provide any response on the SO line?  Have you checked it with a scope or logic analyzer?

Have you tried to toggle the Reset pin after the inductive load is turned on?  Is there any change in the response of the device?

Is the microcontroller fully responsive and is it sending data to the TIC12400 on the SPI bus and capable of toggling the Reset pin?

Regards,

Jonathan

You probably need at least a series diode on the VS input to the board (before capacitors), and potentially also a transient suppressor from VS input to the VS return. Also ensure that the 12V and 0V inputs to the board are in the same area, and that the transient suppressor is right nearby.

There was no diode in series but after your suggestion I have tried that but it not working. We had TVS diode in our design. 

- Inductive load is not connected with TIC input, this simply an inductive load on the board that is unrelated to the TIC12400 device. They both share common supply.

-Yes, you are right. TIC is being reset. What can do you suggest to solve this problem?

-Yes, after your suggestion I have monitored the VSS and VDD. It seems to be going Under Voltage.

-It was my mistake to use word "unresponsive". It becomes reset and after reset occurs I was not configuring it back so I thought it was not working.

-Yes, microcontroller is able to toggle the reset pin. 

So I understand the problem now, when inductive load ON, device becomes reset because of OV and UV. Can you suggest me the solution? 

Hi Alihussain,

Thanks for the clarification and confirming my initial thoughts on the cause of the problem.  When the inductive load is turned on, there is an instantaneous change in the supply current which causes a voltage drop.  This is because the supply is unable to respond quickly enough the change in current draw.  You basically need to either slow down the rate of current change, increase the supply capability, or both.

I would suggest increasing the amount of decoupling capacitance on the supply pins of the TIC12400, and especially on the main board supply itself.  This will help source additional current to the load while the power supply has a chance to respond to the change in demand.

I don't know what type of inductive load you have, and what the application requirements are.  But limiting the current flow with a series resistor between either the supply voltage and load, or the load and GND, will help lower the change in current.  If this is not possible, turning on the inductor more slowly through a slow ramp of FET control voltage could help lower the change in current as well.

Once adjustments are made such that the supply voltage stays above the Under Voltage threshold when the inductive load is turned on, the TIC12400 registers should not be reset.

If you cannot make adjustments to the board that prevent an Under Voltage condition, then you will need to re-configure the TIC12400 registers after the inductive load is turned on.

Regards,

Jonathan