Other Parts Discussed in Thread: LM5069
I'd like to ask some questions about the operation of LM5069EVAL(LM5069MMX-2/NOPB).
We are currently using the evaluation board "LM5069EVAL" to verify the basic operation for product adoption.
As a premise of this question, various settings in "LM5069EVAL" are used in the default state.
According to page 1 of the user guide (www.ti.com/.../snva184), the LM5069EVAL has a current limit threshold of 5.5 A ± 11.8%.
A DC power supply was connected to the input side of the LM5069EVAL, and an electronic load was connected to the output side of the LM5069EVAL.
Outputs 50 V from DC power source.
We tested the following two points.
No.1 test:
We increase the current value little by little in the electronic load, and confirm that the MOSFET is turned off after a fault timer when the threshold 5.5 A is reached.
No.2 test:
After No.1, we reduce the electronic load setting value and confirm that the MOSFET turns ON after the retry timer when the value falls below 5.5 A.
No 1 result:
We confirmed that the MOSFET turns off when the current setting of the electronic load is increased to 5.45 A from the threshold value of 5.5 A.
We understand that this works according to the specifications.
No.2 result:
However, after the No.1 test, we reduced the current setting of the electronic load to 5.5 A or less, and the MOSFET did not turn on again after waiting more than 7.7 seconds of the retry timer.
After that, we further reduced the current setting of the electronic load and confirmed that the MOSFET turned on again when the current setting of the electronic load was lowered to 1.0 A.
We did the same test over and over again, and it was all the same.
On page 12 of the LM 5069 datasheet (www.ti.com/.../lm5069), 8.3.1 Current Limit says:.
If the load current falls below the current limit threshold before the end of the fault timeout period, the LM5069 resumes normal operation.
From this sentence, we understood that if the current setting value of the electronic load is, for example, about 5.4A, the MOSFET turns on.
However, if the current setting of the electronic load is not lowered to 1.0 A, the MOSFET will not turn on, so we have doubts.
The following waveform when the MOSFET is turned on at the set value of the electronic load of 1.0 A is as follows.
ch1 (yellow): current (range 2.0A/div)
ch2 (light blue):gate voltage (range 10.0V/div)
ch3 (Purple) LM5069EVAL output voltage (range 10.0V/div)
ch4(Yellow Green):Timer voltage (range :1.0V/div)
M(red):FET Vgs i.e.ch2-ch3 (range :10,0V/div)
Horizontal Resolution: 10 ms/div
In addition, the waveform for when the MOSFET does not turn on even if the current setting of the electronic load is lowered to 3.0 A is attached for reference.
ch1 (yellow): current (range 2.0A/div)
ch2 (light blue):gate voltage (range 10.0V/div)
ch3 (Purple) LM5069EVAL output voltage (range 10.0V/div)
ch4(Yellow Green):Timer voltage (range :1.0V/div)
M(red):FET Vgs i.e.ch2-ch3 (range :10,0V/div)
Horizontal Resolution: 10 ms/div
After the No.1 test, when the MOSFET does not turn on unless the current setting value of the electronic load is lowered to 1.0 A,
please tell me whether the operation is based on the specifications of LM5069MMX-2/NOPB.
