I want to use the LTC7810 to make a step-down converter with up to 75 V input and 15 V 30 A output.
I made a PCB and tested it, but it doesn't work properly.
Can you give me some advice?
The PCB is designed based on the circuit diagram in the attached image.
Many component layouts on PCBs follow the datasheet.
However, due to peripheral equipment, the current sense resistor and filter circuit are far from the IC, and the SENSE +/- signal path runs near the inductor.
The following shows a series of operations that occurred in the test.
All tests are conducted with no load.
1: Confirm that 75 V is supplied to VDD and 15 V is output. However, about 0.2 A flows in VDD and LTC7810 generates heat.
2: When checking the waveforms of SW1 and SW2 on the oscilloscope, SW1 is operating normally, but SW2 is at the GND level.
3: Consider the possibility that the filter of the current sense circuit is far from the IC, and connect 1 nF directly between the SENSE +/- pins of the IC.
4: Confirm that 75 V is supplied to VDD again and 15 V is output. However, about 0.2 A flows in VDD and LTC7810 generates heat.
5: When the waveform of SW2 is confirmed, a switching waveform with a peak of about 15 V is observed.
6: TG2 also observed a switching waveform with a peak of about 15 V, but BG2 remained at the GND level.
So far, we have tested a 15 V 30 A step-down converter, but we have also tested a 12 V 30 A circuit using the same circuit except for the value of the voltage feedback resistor.
This circuit also did not work properly, outputting about 8 V to 10 V compared to the command value of 12 V.
How can I get it to work properly?
Or has the IC already failed in step 1 above?