Hi TI team,
I need your support regarding the design and testing of the buck-boost regulator using LM5118-Q1. The corresponding schematic is attached and the specifications are:
- Output voltage = 12V
- Minimum input voltage = 5V
- Maximum output voltage = 42V
- Maximum load = 1.5A
The first test I ran on this design is as described:
- No Load
- I start to increase progressively the Input voltage CL30_RBP from 5V to 42V
- The desired output voltage does not appear until I reach an input voltage of ~7V. How could you explain it because the circuit should boost starting from 5V at the input voltage?
- The output voltage remains stable until the maximum input voltage
2nd test:
- No Load
- I resupply the circuit starting from 42V and progressively decreasing to 5V
- The desired output voltage does not appear until I reach an input voltage of ~10V!!
- The output voltage remains stable until ~7 and then drops to 0.
During the 2nd test, it appears that the buck switch is not switching. This is confirmed when I probed on HO pin and found no PWM as if the driver is disabled! In addition the VCC output voltage is just 3.65V which means that there is an under voltage lockout. It seems to me that the regulator operates in the HICCUP mode.
For our application, this circuit should work fine from min to max (or max to min) input voltage.
What is your feedback about this behavior and what is your proposal to resolve this issue?
Please feel free to ask for any other information.
Thanks in advance for your feedback.
Regards,
Abderrahman
