Part Number:TPS54140A
Dear Forum,
My assigned customer has found some early field failures at minimum input voltage (10.8V), due to the device not starting up properly with their 60mA minimum load. As Vout is 9.5V (dropout of only 1.3V min) - I suspect the issue is related to this thread:
https://e2e.ti.com/support/power_management/non-isolated_dcdc/f/196/p/466590/1674306#1674306
Once Vin is increased, the issue goes away, which ties up with the above.
I passed along this http://www.ti.com/lit/an/slva547a/slva547a.pdf which may help, but they believe the easiest way might be to switch in an additional 100+mA load to increase frequency and hence ensure enough charge is available for the HS FET bootstrap.
Q: is it possible to get advice (or data / curve) on minimum load current vs. dropout voltage to ensure proper start up?
So far the parts are starting with load currents from 1-150mA, so is there a min current above which all parts can start? (if not which low Iq buck do we recommend without this issue).
Schematic and waveform attached.
Many thanks, Mike.(Please visit the site to view this file)