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TPS61040EVM-002: Output current setup queries

Part Number: TPS61040EVM-002
Other Parts Discussed in Thread: TPS61040


I am planning to use TPS61040 in my design. There are a few doubts.

Need to drive 4 IR LEDs in series(VSMY1850X01) with forward current of 100mA.

The system is powered by a Li-ion Cell. 

These LEDs have a forward voltage of 1.65V.

How to calculate resistors R1, R2, R3 and R4?

I need PWM to control the intensity also. The minimum average current of 50mA and Max Average current of 100mA. Do these minimum and maximum values affect Resistor Values?

What is the purpose of D6? is it some kind of protection? Can this be omitted from BOM?

This is the Link to LED datasheet:

  • Hi Jitendra,

    Please refer to figure 21 of TPS61040 datasheet. This is very similar to your application. Change the resistor RS to 12.3ohm. Connect your PWM signal to EN pin to control the intensity. The D6 is a zener diode for protection.