LM20343: LM20343 Duty Cycle and Feedback Resistor Check

Randy Wang

Part Number: LM20343

Hi Team,

My customer is using LM20343 for 24Vin_15Vout/2.5A application and they would like to check some parameters in datasheet:

Max Duty Cycle: datasheet shows typical value is 80%, but didn’t shows the Min value, could you help to provide this data?
Feedback resistor suggested only up to 5V, and my customer is using it in 15Vout application, I’m wondering if you can comments what value should we choose.
I didn't see Absolute Maximum Ratings has temperature range like -40-150C, could you help to confirm maximum temperature range for LM20343?

thanks.

over 4 years ago

0 David Baba over 4 years ago

TI__Mastermind 30460 points

Hello Randy,

The operating temperature range for the device is up to 125C. This is what I recommend you keep the temperature below under worse case conditions.

Follow equation 6 in the datasheet using a 10k Bottom FB resistor to calculate Top FB resistor.

Unfortunately the minimum max duty cycle is not specified. Also the max duty cycle of the converter is based on a number of factors not detailed in the datasheet. I advise you check for your design based on the paper in the link below. Check against your minimum input voltage.

http://www.ti.com/lit/an/slyt293/slyt293.pdf

0 Ankit Gupta95 over 4 years ago

TI__Expert 4555 points

Hello Randy,

1. Max Duty Cycle: datasheet shows typical value is 80%, but didn’t shows the Min value, could you help to provide this data? -- I need to talk product engineering team for this. Will get back to you on this as soon as possible.

2. Feedback resistor suggested only up to 5V, and my customer is using it in 15Vout application, I’m wondering if you can comments what value should we choose.-- I would recommend Rfbt=169K and Rfbb = 9.53K

3. I didn't see Absolute Maximum Ratings has temperature range like -40-150C, could you help to confirm maximum temperature range for LM20343? -- Operating Temperature Range of this part is -40C to 125C. And Absmax values are valid across the temperature range.

Best Regards,

Ankit Gupta

Application Engineer

0 David Baba over 4 years ago in reply to Ankit Gupta95

TI__Mastermind 30460 points

Hello Randy,

We have not heard from you in a few days. We will assume we have answered your questions and close this thread? If you have any further questions or concerns, please feel free to reopen.

Thanks.

0 Randy Wang over 4 years ago in reply to David Baba

TI__Intellectual 1705 points

Hi David,

You still didn't answer my question for Duty Cycle question, what's the min and max duty cycle?

0 Marshall_Beck over 4 years ago in reply to Randy Wang

TI__Mastermind 30600 points

Randy, please email me.

0 Marshall_Beck over 4 years ago in reply to Marshall_Beck

TI__Mastermind 30600 points

Assume the minimum of the maximum duty cycle to be 70%.

Please keep in mind, we can not guarantee this by datasheet and should only be used as reference.

Power management

Power management forum

LM20343: LM20343 Duty Cycle and Feedback Resistor Check