One of my customers needs the following information on LM3100 part:
simulating LM3100 using Webbench , there are no bode plot simulation is available.
Please address the following queries:
1. Since no external compensation is required, Is there need to check
the phase and magnitude through plot for determining the stability of
2. If so, what are
the stability parameters for this converter (Phase Margin, Cross over frequency
3. It seems output
filter section contribute two poles(Cout and L) and one zero(ESR). How does one
ensure that phase margin is greater than 45 degrees at fc(cross
4. What will be the
gain of Contant - On time Modulator? Is it possible to model it as a linear
system for plotting the blod plot?
Can anyone help me to get this information? Thanks for your help in advance.
The short answer is that the LM3100 is a constant-on-time regulator, and as such is inherently stable. However, we will provide a more detailed answer shortly.
- Wanda Garrett (WEBENCH Team)
Wanda GarrettWEBENCH Design CenterTexas Instruments
Thanks for your help, Wanda
The LM3100 is one type of hysteric topology and it utilizes a constant on-time (COT) control scheme with input voltage feed forward. This provides a topology that has excellent transient response without the need for compensation. The input voltage feed forward ensures that a constant switching frequency is maintained across the entire VIN range it’s pretty similar to what TI calls them D-CAP mode devices.
Thanks a lot for your help, Howard.
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