Other Parts Discussed in Thread: LM5116
Hello,
"At some boards with LM25116, Oscillation phenomenon occurs, causing overcurrent in the input power supply. I have technical questions.
We believe that there is a problem with the design of the error amplifier and that there is insufficient phase margin."
above question came from customer.
Because there are many questions,
even partial reply is okay.
Questions from customers are described below.
The inside of () is my guess.
Q1.
In the datasheet P24 there is a description of "CIN> 10 × LIN".
What does this LIN mean?
(Is it parasitic inductance of the input?)
Q2.
DataSheet P21 In the circuit shown in Figure 33,
Why is a 1 μF capacitor connected to Vccx?
(Is it a bypass capacitor?)
Q3.
Is there a way to decide the capacitor of Q2?
Q4.
Does the LM25116 operate with no load?
Q5.
The values of Rcomp and Ccomp are determined using "LM5116_Quickstart.xls".
Is the value calculated here supported from low load to high load?
Q6.
Is not it necessary to calculate the capacitor connected after the power supply circuit?
Q7.
With the value calculated using LM5116_Quickstart.xls,
I measured the loop.
Phase margin and gain margin will vary with load.
Where should the load be set?(Iout max？)
Q8.
Our system has a liquid crystal panel.
The input voltage swings on the pulse by the backlight of the liquid crystal.
Does this state affect phase compensation and operation?
Q9.
At low load,
Is it possible to enter diode emulation mode even if RDEMB is used?
Where is the point to enter diode emulation?
Best regards,
watanabe
