Other Parts Discussed in Thread: LMG1205, LMG1210
Hello,
I believe I am up to date in terms of the recommendation to use an external boostrap diode to improve startup bootstrap times for the LM5113. It's my understanding that it is not needed, but can help. This topic is thoroughly covered here.
What I do not understand, is exactly how poor the startup behavior is with just the internal diode. What exactly happens in the chip that degrades functionality at startup vs during operation? Is it simply that there is significant resistance in series with the internal diode? We chose to use the internal diode because we wanted to have the protection of the internal clamp circuit, which we learned here, only functions when the internal diode is used.
We are now seeing that sometimes the high side drive takes ~5ms to start switching. When operating normally, the bootstrap cap charges way faster than this. There looks to be a dependence on what the switch node voltage is before switching occurs. Can this long 5ms time span be attributed to the startup loss in performance by having an internal diode?