LMG1025-Q1: R1 (OUTH) & R2 (OUTL) control

Hi Hoonil,

R1 (resistor connected between OUTH and the FET gate) is used to slow down the turn on time. 

R2 (resistor connected between OUTL and the FET gate) is used to slow down the turn off time.

If what you care about is the rising time, then a smaller R1 value will give you a faster and stronger rise time, and a higher R1 resistance will give you a slower rise time with less ringing. Based on your application, you want to use a resistor value that gives you a rise time fast enough for your application but making sure that the ringing doesn't exceed the recommended operating conditions of the device. 

Regarding your questions:

"1) Would using sufficiently large R2 be helpful to reduce ringing if we want to use R1 smaller than 2 ohms?" -> The resistor between OUTL and gate would only help to reduce ringing during turn off, and the resistor between OUTH and gate would only help to reduce ringing during turn on.

2) Can R1 be shorted for a fast-rising time as in the case of the shorted R2 for a fast falling in the datasheet? (please see the attached figure) -> You can do this as long as the ringing during turn on doesn't exceed the recommended maximum ratings of the driver and the FET. We recommend at least 2 ohm to avoid this voltage overstress.

Best regards,

Leslie

Hi Leslie,

Thanks a lot for the comment. We will try it.

Best regards,

Hoonil