Over load protection on the TPS61166...

The OLP voltage is the OVP voltage of 19V typical (18V minimum), as noted on page 4 of the datasheet.  Your 9.9V string will operate fine.

Hi Chris,

Thanks for your reply.  The overload protection is stated as a current not a voltage.  For my application I will need to generate a 9.9V output and supply 240mA current into a string of LEDs. Certainly it won't trigger the over voltage protection, but the 240mA is within the range of the over current trigger, I_OL min : 200mA, typ : 300mA.

When I go back and read the data sheet again it does state that the over load current is measure across the isolation switch, and will shut down the regulator when this is reached.  I imagine that the 300mA figure is a room temperature and the minimum would occur at -40 degrees celcius.  So for product with an operational temperature range of 0 to 40 degC, the minimum OLP trip point is likely to be 267mA approximately.

Regards,

Colin

Thank you for pointing out my mistake.  I apologize for not reading your first post correctly.

Yes, the OLP current will be 200 mA minimum.  This includes all sources of variation: Vin, Vout, temperature, part to part, etc.  Since you have a much narrower temperature range, I would expect that a lot of the variation in the 300 mA typical number would be eliminated.

What is your Vin range?

Let me dig into this a little deeper for you.  Due to the holidays, it may be next week before I find out more.

Thanks Chris, the Vin may range between 11V to 12.6V.

Regards (and Merry Christmas),

Colin

Oh, that will be a problem for 2 reasons.  1) the maximum Vin of the TPS61166 is 10V and 2) the TPS61166 is a boost converter.  So, when Vin is > Vout, it will be unable to step down the input and regulate the current.

For your input voltage range, I would recommend the TL4242.  It is a simple, step down LED driver.

Woops, my mistake, that should be 4.5 to 5.5V.  My appologies, I have been looking into other solutions and got this regulator solution confused with others.

Colin

Thanks Jeff for clarifying that.

Colin,

If you need 240 mA through your LEDs, we cannot recommend using the TPS61166.  Will the TPS61081 meet your needs?

Another option, if you don't need PWM dimming, is to bypass the OLP FET by connecting Vo to OUT on the TPS61166.  Another downside of this is that the LEDs will always be connected to Vin through the inductor and diode.

Thanks Jeff... Chris,

The dimming feature is required so neither of these alternatives will do.  But at least this question has been answered.  I do have a few other designs I'm working on, using other manufacturer's parts.  Thanks again for responses/help.

Regards,

Colin

The TPS61165 will meet your power requirements.  It performs analog dimming not PWM dimming, however.

The TPS61195, with all of its current sinks tied together, could also meet your needs.