Buck converter:
Start-up testing
Measure R between Vin and GND, Vin and SW, SW and GND, Vout and GND
Measure R of feedback resistors, frequency select resistor
Set up a start up test, 1 probe on SW and 1 probe on Vout. Set up oscilloscope to measure waveforms on SW and Vout and make sure to set trigger to single. Then quickly turn on and off the power supply. Hopefully the waveforms show that buck converter works or explain why it doesn’t work.
Load regulation
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Line regulation
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Load transient
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Vout ripple
Over current protection
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Load regulation
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Load transient
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Vout ripple
Set up: Oscilloscope AC coupled, 1GHz bandwidh
Over current protection
The video below is testing the over current protection feature of the buck chip only, the PCB only has the buck circuit assembled at this point. The e-fuse chips and pwm buffer are not populated at this point yet.
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Efuses
Setup:
With 47 Omhs connected, For U4, U3, U2 Measured Vout on board to be roughly 5.95V, U5 was roughly 0V
Over Current Test. Used 8, 10Omh Resistors in parallel, R_L = 1.25Omh, Current Loaded (ideal) = 4.8A
With 1.25Omhs connected For U4, U3, U2 Measured with DMM Vout on board to be 1.9V and steady decline till 1.3V, U5 was roughly 0V
EFuse U5: (At 4.8A Unresponsive)
EFuse U4 (4.8A):
EFuse U3 (4.8A):
EFuse U2 (4.8A):
Short-to-ground Test
EFuse U5: (Taken on Different Day)
Efuse U4:
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Efuse U3:
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Efuse U2 :
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Battery Inrush Test
Used 8, 10Omh Resistors in parallel, R_L = 1.25Omh, Current Loaded (ideal) = 4.8A
Channel 1 is Iout, Channel 2 is Vin after the filter, Channel 3 is Vout of the U2 efuse.
Compared to using 22K Resistor, Ideal current 0.27mA
Channel 1 is Iout, Channel 2 is Vin after the filter, Channel 3 is Vout of the U2 efuse.
Vout should increase to 6V to match the load. It’s a bit strange that there is no change once power ris connected.