Other Parts Discussed in Thread: CSD19502Q5B, LM5118, LM5170
Hi
I’m working with an LM5176 Evaluation Boardwith it acting as a boost converter. At the moment, I’ve been able to set the board up to regulate a 48V output with a 16V input with no load. However, whenever a load is set up, the LM5176 IC on the evaluation board breaks down. I’m unsure of why.
So far the set up has been replacing the secondary side fets Q5, Q7 with CSD19502Q5B N-Channel Fets, replacing the inductor with a 1mH inductor with a 500mA current rating as well as editing the control loop and soft start. The control loop capacitors, C28 to a 100pF cap and C22 to a .22uF. Soft start capacitor has been changed to a 1uF capacitor. The feedback loop off of the output voltage has also been changed such that R14 is 2 resistors at 243Kohms and R22 is an 8.25KOhm resistor.
The issues that came up even when the module was unloaded, the 2 mosfets on the secondary side have cross conduction issues. Current would spike during transitions as both fets would be on. One can see the gate’s on both the fets spiking, enough such that the bottom secondary fet turns on, and the sense resistor voltage would see spikes as well, up to 3V
Another issue that is seen is when probing across the gate and source of the secondary side fets, using a differential probe, specifically the Tektronix P5200, the IC keeps breaking.
Is there any more information that you would like in order to assist us?
What tips do you guys have?
