LMR14050-Q1: Settling time when changing between 5.4V to 8.7V

Kevin Wen

Part Number: LMR14050-Q1
Other Parts Discussed in Thread: LMR14050

Hi team,

My customer want to use LMR14050-Q1 in a automotive panel with local dimming function, in this project, the LMR14050 is used as power supply for LED and LED driver have a control pin connect to LMR14050 FB pin with a resistor in series. LED driver internal DAC would control the voltage on the control, thus changing LMR14050 output voltage.

in this project, customer need to change LED driving current from 120mA to 190mA, thus the LMR14050 output voltage is rised from 5.4V to 8.7V, customer want to know how long time does LMR14050 take to settle the output voltage. a general order of magnitudes should be enough, like less than 10ms/1ms/100us/10us/1us/100ns, etc..

thanks.

Kevin

over 7 years ago

0 Gavin Wang (Zejing) over 7 years ago

TI__Expert 3480 points

1.Can you upload the schematic?
2.What do you mean by "how long time does LMR14050 take to settle the output voltage"? After soft start time, Vo can be settled naturally.

0 Andy Chen over 7 years ago

TI__Mastermind 34875 points

Kevin,

It depends on actual loop bandwidth and FB voltage changing slew rate, however for your application condition, the load just step from 120mA to 190mA for only 70mA delta value, it's very small load transient for most buck regulators, the output will follow FB changing within 100us if Fsw set to 500KHz.

0 Kevin Wen over 7 years ago in reply to Andy Chen

TI__Intellectual 2235 points

Hi Andy,

Thanks for your help. Just double checked with customer, the condition should be load current from 2.1A to 3.1A, voltage from 9V to 9.5V, LMR14050 would switching between these two working condition, would you please suggest the settling time for both rising and falling condition? thanks.

Kevin

0 Andy Chen over 7 years ago in reply to Kevin Wen

TI__Mastermind 34875 points

Kevin,

The output settling time for 2.1A to 3.1A load transient is still within 100us.

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LMR14050-Q1: Settling time when changing between 5.4V to 8.7V