TPS61165: Feedback Circuit Calculation

Jack Shen2

Expert 4475 points

Part Number: TPS61165

We would like to know how to calculate the resistance for feedback circuit.

here is the application:

Vin = 5V
Vout = 6V for 2 LEDs in serial
Iout = 350mA

Thanks.

Jack

over 3 years ago

0 Mason Wang over 3 years ago

TI__Genius 9630 points

hi Jack

The FB resistor can be set according to the current requirement. Here is the formula: R=250mV/ILED.

So for this case, R=250mV/350mA=0.714ohm.

0 Jack Shen2 over 3 years ago in reply to Mason Wang

TI__Expert 4475 points

Hi Mason,

May you also guide me how to set the Vout to 6V?

Thanks.

Jack

0 Mason Wang over 3 years ago in reply to Jack Shen2

TI__Genius 9630 points

hi Jack

Basically, LED driver works as a current source. In this case, LED current will be regulated at 350mA and once the current is fixed, the voltage drop on LED will be 6V with 2 LED in series.

0 Jack Shen2 over 3 years ago in reply to Mason Wang

TI__Expert 4475 points

Hi Mason,

I have a question to check with you.

From the formula "R=250mV/ILED. ", it seems like the feedback voltage is regulated to 250 mV instead of 200mV. Should we use 250mV or 200mV?

Moreover, please correct me if I am wrong, TPS61165 can be use as a buck LED driver, right. for example, 12Vin to 5Vout to drive one LED.

Thanks.

0 Mason Wang over 3 years ago in reply to Jack Shen2

TI__Genius 9630 points

hi Jack

Sorry the value should be 200mV rather than 250mV. Besides, TPS61165 cannot work as a buck LED driver. It only supports boost topology.

Power management

Power management forum

TPS61165: Feedback Circuit Calculation