Honeywell is experiencing a problem with their LM3478. As they drop Vin from 4.8V to 4.7V, the part stops SW and the gate drive signal stays high (100% duty cycle). I have attached a schematic and a .ppt illustrating this behavior. Another thing to note is that they are pulsing the input voltage from 0 to Vin.
Vout = 44V
Iout < 350mA
Their voltage at Vsense (shown in slides 1 and 2) is <100mV. In the datasheet, the lower limit is specd at 125mV. I can't find what happens when you're below the lower threshold in the datasheet.
what's the current limit on the input power supply (the supply that generates 4.7V)?
Sorry for not closing this out. You actually provided the answer to me on this via email (attached).
8182.RE SperianHoneywell LM3478 support.msg
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