Other Parts Discussed in Thread: LM5164
Dear TI Expert,
We are using the LM5164-Q1 for converting 48V to 12.0V. Our operating range is 30-60V. Output current is 750mA (approximately) in NORMAL mode.
DCDC parameters:
L = 68uH
RON= 178Kohm
Cout = 4 X 4.7uF
Output Load = 750mA (Approx)
Type 3 Filter Parameters:
RA = 990 kohm
CA = 2.2 nF
CB = 47 pF
Feedback Resistor value:
RFB1 = 440 kOhm
RFB2 = 49.9 kOhm
We have observed that we are getting some unwanted switching during Low side switching when we are using 4 output capacitors. However, during testing there is no unwanted switching capacitor observed with 2 x 4.7uF Output capacitors. Additionally, we have captured the No Load/Light Load switching waveform as well.
Following is our list of queries that we need help on:-
1. We want to confirm the that why that unwanted switching is there with 4 output capacitors even at higher load?
2. We want to confirm the No Load/ Light Load switching pattern i.e. in Pulse skipping Mode waveform from your end?
3. We have observed one failure in the field (out of more than 250) in which we have found that Low side MOSFET has been damaged in LM5164 and High side MOSFET is OK? What could be the reason for this? Is it because of unwanted switching happening during low side switching over a period of time or any other factors are causing this failure?
4. What can be conclude by looking at the 2nd pin (i.e. input 48V supply pin) of the failed LM5164 IC image ? Is it damaged due to voltage spike or because of higher current ?
Please find the waveforms/images for your reference:
1. Waveform_4_CAP_with_snail_Prob (750mA)
2. Waveform_2_CAP_with_snail_Prob (750mA)
3. Waveform_Hside&LSide_SW_with_4_CAP_&_snail_Prob(Low Load)
4. Waveform_Hside&LSide_SW_with_4_CAP_&_snail_Prob(Low Load_Zoom_View)
5. Failed LM5164 Image from the field Pack
Kindly let me know if you need any further details are required from our end.
Looking forward to hearing from you.
Regards,
Chirayu Rajpurohit
