TPSI3100: TPSI3100-Q1 Solid State Relay Operation

Hello Mustafa,

Thank you for reaching out to our team on E2E. We will work to solve this issue. I have a number of concerns that may lead to issues. 

I am concerned that the isolation barrier my be compromised by your lab setup. Can you measure the resistance from TP19 (VSSS) to TP3 with your load connected and the power source turned off? Can you also verify the IC is working correctly? Can you please measure nFLT and nALM with reference to VSSP and measure VDRV with reference to VSSS when the device is enabled? I would expect to see 17V on VDRV and 5V on nFLT and nALM if the device is working properly. 

Please feel free to reach out to me for a call discuss this issue further.

Regards,

Jack Hemmersmeier 

Ji Jack,

The resistance from VSSS (TP19) to TP3 is 99Meg then multimeter goes into high load mode when load is connected and power source is turned off.

When I supply the device with 5V from the VDDP with reference to VSSP, I measeure VDRV with reference to VSSS as 16.939V. I also measure nFLT and nALM as 4.948V from the measurement points you point out.

What do you suggest further?

Thanks.

Hi Again,

I want to reexplain the problem, I think it can be mistakable. Cases are as follow.

When first IC supply or input voltage is high then current can be drawn from the load. In this process there is no problem.

However, if first load is active, it doesn't matter how much current you are drawing. I test the system even at 100mA. Then IC power and input voltage is activating, gate voltage is zero, I couldn't draw the mosfet gates. Whenever, I deactivate the load current and take it to the OFF position, then gate can be drawn and then load can be drawn. 

It doesn't matter from the supply type. I also supply 20V from the LDO input ports. Nothing would be change with this action. 

As a summary in SMPS literature, the IC couldn't manage to run while under load conditions.

Hi Again,

I believe this is my last update :) 

I lastly disassembled the R15, which cut the connection between current sensor and TPSI3100. With this the problem is solved but now I lost the overcurrent protection feature. I will plan to use overcurrent protection with shunt resistor. Now, I have two questions:

1. How can we fix in this scenario, when R15 inserted, device couldn't operate under load?

2. In the shunt resistor technique shown in Figure 9-1 in the datasheet also inserted back-to-back structure to this, will we face with a similar problem? Do you have any suggestions? 

Thanks for the understanding to my all questions.

Best regards.

Mustafa

Hello Mustafa,

I suspect there may be a current spike when you turn on the load, causing the device to hit OCP and turn off the gates. Using a back to back structure you may face similar problems with inrush current. The TPSI3100-Q1 will automatically attempt to turn back on after about 200us. To help the system react slower, install a 1nF or 1000pF capacitor for C18 and install a 1k resistor for R15. This may help. Are you able to share more about the load you're driving and the power source? 

Please feel free to reach out to me for a call discuss this issue further.

Regards,

Jack Hemmersmeier

Hi Jack,

My actual load profile is 220V. However, I test the EVALBOARD with 20V. In default 5A alarm level and 10A fault level. 

I apply your suggestions. Now, the system can operate up to 0.2A load profile at 20V. After 0.2A, the same problem will occur system couldn't manage to operate under load.

I actually wonder my real system scenario. In our system, operating voltage is 180-330V band. we will drive motor load from the phase shifted full bridge topology. Before the phase shifted full bridge, we will use this IC for solid state relay operation. I wonder that whether my system can fail or not at start up. Could you any opinions on this?

Thanks.

Hi Jack,

Thanks for your precious opinions. Let me try to demonstrate my design on the board in a couple of weeks. Then, If I have a further question, I will disturb you again. :) 

Thanks for all.

My regards.

Mustafa