Hi Allan,

Can you please share the schematic for this design.

Also, is there a way that you can measure current in each path ?

Hi Praveen,

Schematic was attached already. We will try to do current measurement and let you know.

Regards,

Allan

Hi Allan,

Thanks for sharing the schematics. For me to review the schematics, I would require the design specifications for this design.

To check the design SOA margin and design feasibility, can you please get filled up design calculator from the customer and share it with me for review. The design calculator is available at : http://www.ti.com/product/TPS24742/toolssoftware . 

Please go through the videos in below link before using Design Calculator.

https://training.ti.com/node/1133677

https://training.ti.com/node/1133673

https://training.ti.com/node/1133664

https://training.ti.com/node/1133681

Also, please share waveforms with current measurement in each path. This will help us a lot in finding the root cause of the issue.

We measure system current, system 12V, U63 GATE voltage as follow picture this morning.

When we plug out and plug in power module, system will reboot high probability .

The left white circle in picture, we don’t know why U63 GATE close after open shortly.

Our current is not enough to trigger OCP, are there have any other conditions to close U63 GATE?

Thanks

Yellow line: system current

Green line: U63 GATE voltage

Purple line: system 12V

Hi Al Chang,

Can you please help with the following,

• Explain how you are forcing AUX turn OFF and MAIN channel takeover ? Also, the voltages on each rail during switch over ?
• System Current is the sum of current flowing in Main and Aux channels, right ? We would like to see the current flowing through each channel because this is important to know if there is negative current flowing in any of the channels.
• Please share the filled design calculators for each rail. Links to the design calculator and training videos shared in previous post.
• Looks like you are sharing the gate signal of ORing FET. Please probe gate signal of the Hotswap FET. 
• Please share waveforms as below during switch over from AUX to MAIN,
  • Main Channel: Vin, Vout, Iin (Main), Hgate 
  • Main Channel: Vout, Iin(Main), Bgate , Hgate
  • Aux Channel: Vin, Vout, Iin (Aux), Hgate 
  • Aux Channel: Vout, Iin (Aux), Bgate , Hgate

Sorry for asking so much information but we require them to find the root cause for drop in output voltage during switch over from Aux to Main Channels. 

Explain how you are forcing AUX turn OFF and MAIN channel takeover ? Also, the voltages on each rail during switch over ?

Al:we plug in the Main power (the power is up during this time) the voltage should be 12V

System Current is the sum of current flowing in Main and Aux channels, right ? We would like to see the current flowing through each channel because this is important to know if there is negative current flowing in any of the channels.

Al:yes ,we will try to measure the current 

Please share the filled design calculators for each rail. Links to the design calculator and training videos shared in previous post.

Al :as attach file

Looks like you are sharing the gate signal of ORing FET. Please probe gate signal of the Hotswap FET. Al : we probe the How Swap gate ,when our system reboot the ORing and HOT SWAP gate is turn off at the same time 

Please share waveforms as below during switch over from AUX to MAIN,

Al:ok

note that when our system reboot, the TINR and TFLT is always low

and we can saw that is gate is off, the restart time is about 1.9ms 

7585.TPS2474x Design Calculator_RevA .xlsx

Hello Sir:

  we measure the waveform  

Main Channel: Vin, Vout, Iin (Main), Hgate 

Yellow line: system current

Green line: Main 12V

red line: system 12V

Purple line: Hgate

we got 2 different situation here

1.system will reboot 

2. system will not reboot

we can see that the system reboot because the 12V in system got power drop cause the gate for main is turn off

,some time the gate for 12V  main  is not close, in that moment our system is keep working,but we didn't why will cause 

this happened?? do you know how to keep the   TPS2474 always workinig on  situation 2 (system not reboot)

thanks