Hi,I'm disty in Japan.
My customer is considering using LM25117Q to next model.
I have a question about the external synchronization pulse for LM25117Q.
It is described to 7.3.3 in data sheets P15 that "Care should be taken to make sure
that the RT pin voltage does not go below -0.3V at the falling edge of the
external pulse".
From the above, I think that the usable conditions of the external synchronization pulse
is limited strictly,if the RT pin is a high impedance input.
For example,in case of the circuit described in data sheets P23(Figure 29),
if the external synchronization pulse such as following conditions is inputted to
TP3(SYNC),the RT pin voltage will become approximately -2V.
*frequency:230kHz,Duty:20%,Vhigh:5V,Vlow:0V
*Cf. attached file test.xlsx
If the RT pin voltage has to become more than -0.3V,the high pulse width should be
approximately 100ns and the Duty should be a few percent.
Is my understanding mistaken,or is the RT pin not a simple high impedance input?
Best regards.