Part Number:LM5175-Q1
Dear all,
I've got some issues using LM5175. I can't manage to drawn the current design for, when I increase the current, the output voltage fall down to 0V.
When looking at the gates signals, I observe strange glitches :
Capture made for : Vin = 28V, Vout = 24V Iout = 3A
Legend : Yellow : HDRV1 / Green : LDRV1 / Purple : HDRV2 / Blue : LDRV2
The glitches observed decreases when the load decreases and I think the glitches on the gates becomes high enough to trigger the mosfets when it shouldn't and my output voltage fall to 0V.
Here is my schematic :
For the capture above, I've made some change :
I've add a 100µF capacitor at the output -> no effects
I've replaced the inductor by a 10µH --> I can drawn more current but the output voltage is less stable.
R10 is replaced by a 10R resistor with a diode schottky in // to increase the rise time and not the fall time --> avoid cross conduction between Q2 and Q4 but no effect on the maximum current available.
I've put a diode schottky between Q3 drain and GND --> no effect on the current available
I've put a pull down resistor of 1K on Q3 gates to calm the spike --> no changes.
I notice the inductor is really hot and the maximum output current decreases when the voltage decreases.
Also to be in buck mode (Q3 always off and Q1 always on) I should increase the input voltage higher (around 34V), is it normal ? The buck boost mode remains even when Vin > Vout.
Thank you very much for your help.
Michael