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Tool/software: WEBENCH® Design Tools
Please see attached the schematic recommended by the WEBENCH and the schematic we implemented.
On our schematic, please see the STEP-UP REGULATOR and the CURRENT SENSE pages for all pertaining information.
If we short pins 5 and 6 on U7 (ISNS- and ISNS+) the design delivers minimum 4A at 22V on a resistive load.
If we leave the design as is, with 3 mOhm current sense resistor, the voltage output is cut to 12V when the output current is about 0.7A
The design behaves as the current peak in the inductor is 4 times greater than expected.
Dear Sir,
So you have finished the sch and pcb layout at your side, right?
And I noticed you didn't add gate-drive resistor, this is not good for TPS43060.
The datasheet is not too clear on this. Could you please elaborate?
Would you recommend one resistor or two? 1ohm or 2ohms?
You need to series at least 5.1 ohm resistor both at the high side and low side driver. And if possible, please share your sch and pcb layout with us. Thanks!
We tried with resistors from 2 ohms to 10 ohms, with no change. Same result. Current limit kick in way too early.
Please note that the WEBENCH generated schematic does not have any gate resistors.
Schematic is attached. The Step-up regulator is on page 3. Current sensing resistor is on page 8.0508.Schematic.pdf
Dear Sir,
Thanks for the schematic. I need to check how is the current sense circuit connects on your PCB board.
We can discuss through email. Please accept my friendship request. Thanks!
Hello Mihai,
I am very sorry to hear this. If you are still willing to further dig into the issue, it would be interesting to see a scope plot of the current sense signals.
Hi Mihai,
To solve the problem, we need to dig out the root cause. A possible reason is wrong signal detected out on the current sense resistor. usually it is caused by the poor layout. That's why we need to check your pcb layout.
Could you please accept my friendship request if you can't share the pcb on E2E?
I understand. Unfortunately we do not have a good enough scope to trace the signals.
We tried but we loose the current peaks.
So, please share the pcb layout with us, we can help to check the routing. We can discuss by email.