LP5811: LED Forward Voltage

Hi Nagaraju,

Yes, it can work since LP5811 can work in pass through mode if the VIN is higher than the VOUT configuration.

But based on your application, I think maybe LP5810 linear version can suit for you. Please free to contact me via email(jared-zhou@ti.com) if you have any questions.

BR, Jared

Hi Jared,

Thanks for your response.

The LED forward voltage VS Forward current graph is shown below. As shown, at lower LED current, the VF is as low as 1.7V and maximum is 2.5V.

Is there any limitation or minimum VOUT expected in Pass through mode in this case? In other words, will it work if we set VOUT as 5.5V , VIN as 3.3V ?

I believe you got my concern since the driver is working on boost mode.

The LP5810 does not have the external enable pin. Otherwise, I would have used LP5810.

Thanks and Regards

G R K Nagaraju

Hi Nagaraju,

Thanks for your explanation for choosing LP5813.

For the pass through mode, the device will enter into pass through mode if the VOUT setting value is lower than your VIN voltage. For example, if the VIN voltage is 3.3V and your VOUT setting value is 3V, then the VOUT will be 3.3V.

And if you set the VOUT to 5V, once the VOUT setting value is higher than VIN, the boost converter will be started.

BR, Jared

Hi Jared,

I think I still did not understand fully.

With 3.3V as input voltage, to drive the LED that has VF in the range of 1.7V to 2.5V, what should be the VOUT set for?

Thanks and Regards

G R K Nagaraju