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TPS61199: "VOUT=80V, 30mA per channel" or "VOUT=60V, 60mA per channel"

Eric201902
Prodigy 120 points
Part Number: TPS61199
Other Parts Discussed in Thread: TPS61196

The setup of our current project required one of the two configurations to achieve:

"VOUT=80V, 30mA per channel" or "VOUT=60V, 60mA per channel"

In the TI TPS61199 EVM, we have achieved 80V by altering the R2 resistor. 

However, according to the website the Vout (Max) of the driver IC is 60V:

https://www.ti.com/product/TPS61199

Do you have any advice which configuration has better reliablity.

  • 0
    TI__Genius 12915 points

    Hi Eric,

    If the channel number could be reduced to 6, TPS61196 could be used.

    For TPS61199, I think the limitation is the IFB pin 30V max voltage. The IFB pins have a leakage current of 10uA minimum. The sum of the LEDs forward voltage per string, at that leakage current, needs to drop the output voltage below 30V.  You need to check the forward voltage at this leakage current per I-V curve in the LED datasheet.

  • 0 in reply to Hardy Wu
    Prodigy 120 points

    Can you provide more information regard how does the  30V max voltage related to the number of channels and current per channel?

  • 0 in reply to Eric201902
    TI__Genius 12915 points

    Hi Eric,

    The number of channels is related to a different device TPS61196, which can support up to 120V VOUT but only have 6 channels. I mentioned it to check with you that if your system need totally 8 channels like TPS61199, or if 6 channels can also be accepted, I think TPS61196 is a better choice.

    TPS61199's IFBx only have 30V max rating. When output off, the IFBx pin would be biased by (VOUT - LED string total forward voltage), due to the leakage current. It is up to your LED spec so you need to check it in LED datasheet for the Vf @ 10uA. If the dropped voltage exceeds 30V, there is potential risk that damage the device.

  • 0 in reply to Hardy Wu
    Prodigy 120 points

    Do you mean  (VOUT - LED string total forward voltage) cannot be > 30V? "If the dropped voltage exceeds 30V, there is potential risk that damage the device."<- Can you explain the situation more in detail?

  • 0 in reply to Eric201902
    Prodigy 120 points

    Our propose design will be VOUT=60V, " LED string total forward voltage"~=56V, with current of 60 mA on each channel

  • 0 in reply to Eric201902
    TI__Genius 12915 points

    Hi Eric,

    Yes I understand the normal work situation that your design set at 60mA output current. What I mean is that, during PWM dimming, here are some off time for all IFBx. But the current sinks still have max to 10uA leakage current, which would also flow through LEDs and cause forward voltage. The forward voltage @10uA (VF1) is much lower then the forward voltage @60mA (VF2). When outputs on, VOUT would be boost to around VF2. At the moment IFBx just off, VOUT is keeping at VF2, so that voltage at all IFBx pins would be pull up VF2-VF1, which possibly be above 30V and may damage the device.