Don't press a screwdriver against the component.it gets stronger if I press a screwdriver against the component.
I don't see any meaningful debugging here. Do you have an
oscilloscope?
I don't see any meaningful debugging here. Do you have an
oscilloscope?
I might suspect that the load dependence of this "noise"
may have to do with the source you are powering the
converter with, and maybe you are dropping it into UVLO
due to inadequate input filter capacitance / quality, or a
current delivery limitation of the upstream supply. The
chip switching frequency is evidently fixed at 650kHz so
this is not subharmonic related. There appears to be no
user accessible frequency compensation, the part says it
is "constant on time" (hysteretic, PFM, I guess) with a
"quasi-constant-frequency mode" (whatever that is
supposed to mean). Heavy load should increase fSW
and I would not expect it to be down in the audible
range (but here a 'scope would be real handy).
How high is your output inductor's saturation current?
If you lose the L, from saturating, you will -slam- the
input filter and source with uncontrolled current, and
maybe start all this off.
thanks for the hints, I will go through it within the next days (christmas/family time...)
I'm using the DR73-1R5-R inductor 1.5uH 6.52A 0.013ohms.
Should I cut the power trace and add a shunt resistor for measuring the current?
Is the assumption that the spike of the voltage on the input is caused due to a spike of the current on the output? (the voltage seems to be okay on the output) 1.05V.
??? I presume you mean SW rather than SS pin.There's not much of a "design" left anymore.
I have loosely soldered the inductor directly on the SS pin and cut the traces from the PCB; there's still some noise there.
I don't think there's a problem on the layout since I have tried several variations.
And the fact, that you did not yet show us your PCB layout .... lets me assume: There is a good chance that the problem is caused by the layout.the ground was really bad, however I have completely fixed that
I'll update this discussion once the parts arrive, everything else is speculation at the moment.
Once the TI EVB arrives I can also swap in the current parts to check if they are okay.
If you are an experienced SMPS PCB designer (and you are aware of current paths and HF behaviour) you may create a suitable single side PCB layout.cut it into a single layer PCB and soldered it
Hi,
If there is audible noise, then most probably the regulator is not continously (clean) switching.
* either it is in hickup mode (high load current) or in burst mode (low lowd current).
Jumping load current or jumping input voltage may also cause discontinous operation.
*******
If you are an experienced SMPS PCB designer (and you are aware of current paths and HF behaviour) you may create a suitable single side PCB layout.
If you are not that experienced in this field, then a single side PCB layout may work "by accident". But
* The function will not be reliable (may fail at different input or output conditions, varied temperature, after weeks, months...)
* most probably will violate EMI / EMC regulations
Klaus
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