Post Go back to editing

LTC3890 Demo Board DC2236A modification not working

Using the DC2236A board as reference, I narrowed the input voltage using the same LTC3890 part from 14V < VIN < 18V but run at a higher frequency of about 400Khz at max current 18A.

using the available LTpowerCAD, I obtained those adjusted values as show and built my own board.

Without Load, the output voltage is fine (Vout = 12V) at Vin=14V, 15V, 16v, and 18V.  As soon a load of 14A (target 18A) is attached, the output drops to 8V and current limited to 8A (almost half of what was intended).

The ILIM pin 28 is floating, PLLIN/MOD pin 5 is jumped to INTVCC, The inductors are 1.5uH, the two sense resistor are 4.0mohm. 

The EXVCC pin 20 is at ground to use internal INTVCC per datasheet.  Does anyone experience this issue before?