TPS61080 / TPS61080 wled driver

AFM

hi all,

i want to know how to calculate the current output of the Iled. for example, in figure 24 of the datasheet, how the 10.5V and 200mA were calculated ?

thanks

over 12 years ago

0 Chris Glaser over 12 years ago

TI__Guru**** 150750 points

I believe this app note answers your question: http://www.ti.com/lit/an/slyt279/slyt279.pdf

0 AFM over 12 years ago in reply to Chris Glaser

Intellectual 560 points

thanks. in this application the Iwled= Iss x R1/R3

but with R1=80k ; R3=1R and Iss=5uA how i get 200mA and 10.5V ?

0 Chris Glaser over 12 years ago in reply to AFM

TI__Guru**** 150750 points

10.5V is just an estimate of the forward voltage of the LEDs, as determined by them. 200 mA is achieved when you switch in the other 80k resistor, giving 40k equivalent. So, the circuit steps from 400 mA to 200 mA LED current.

0 AFM over 12 years ago in reply to Chris Glaser

Intellectual 560 points

okay. but then Iled=Iss *(R1//R2)/R3

thanks

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TPS61080 / TPS61080 wled driver