TPS92692: Placing the LED current sense resistor at a lower position in the string

Philip Hodgson23

Part Number: TPS92692

I want to use the TPS92692 to drive 12 white LEDs from a supply between 9V and 36V. The calculator complains that I could exceed the 65V limit on the CSP / CSN inputs. Can I put the current sense resistor lower in the string at a location that doesn't reach 65V? How does this affect the OVP threshold? I would also like to be able to switch off 6 of the LEDs by shorting them out with a MOSFET. Will this impact the OVP threshold?

over 7 years ago

0 Clinton Jensen over 7 years ago

TI__Mastermind 25500 points

Hello Philip,

The current sense amplifier is rail-to-rail, so you can place it anywhere from 0V to 65V. So if you are doing a buck-boost design (which I suspect if the "output" is over 65V in this case) then you can place the current sense resistor at the bottom of the LED string. That way CSP/CSN will only see VIN. The OVP function is independent of where CSP/CSN is so that will not affect it. Shorting half of the string will also not affect the OVP level. But you may want to be careful shorting half of the string. If you have enough capacitance across the string and it is charge up then shorting half of it will dump all of that extra energy through the remaining 6 very quickly.

Regards,

Clint

0 Philip Hodgson23 over 7 years ago in reply to Clinton Jensen

Prodigy 250 points

Thanks Clinton. I only asked about the OVP setting because the spreadsheet higlights the voltage being over 65V in the OVP section.

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TPS92692: Placing the LED current sense resistor at a lower position in the string