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UCC27611: increasing drive voltage

Wendy Carriger
Prodigy 10 points
Part Number: UCC27611
Other Parts Discussed in Thread: LMG1020

I am trying to use the UCC27611 GaN driver to drive the Laser Components QuickSwitch pulsed laser diode (which consist of a high current switch, charge storage capacitor and pulse laser diode in one package).  The Quickswitch application note suggests using the TI UCC27611 but recommends the +Vdrv be 5.4 volts.

Can an external LDO or other source be used to create a slightly higher and possibly faster drive voltage by connecting the output of a LDO regulator or other source to the VREF pin (through a zero ohm resistor)? 

If so, is there a small LDO voltage regulator or other part that TI would recommend to accomplish this?  Looking for the smallest footprint part to accomplish this.

 



  • 0
    TI__Genius 11770 points

    Hello Wendy,

    Can you share the Quickswitch application note? I don't believe this device supports inputs on VREF; the higher voltage will cause a DC current to flow through the device which would massively hurt efficiency and possibly damage it. I haven't tried on actual hardware, but a simulation showed this same effect. 

    If you want the 5.4V drive, I recommend using a different driver. LMG1020 supports that voltage (although it is at the top of recommended max) and is fairly similar to UCC27611.

    As for the LDOs, I can send your question to the LDO team. Just reply to let me know if you are still looking for an LDO given the info here.

    Thanks,

    Alex M

  • 0 in reply to Wendy Carriger
    TI__Genius 11770 points

    Hello Wendy,

    Thanks for sharing. Based on some conversations I have had with other team members- I believe this would work to raise the drive voltage. However, it will cause excess current (on the scale of 100's of mA depending on resistance and exact voltages) to flow into the VREF pin which could damage the device in the worst case.

    If you want to drive at 5.4V, I still believe the LMG1020 is the better option, as it explicitly supports that level of voltage. If you do decide to use this UCC27611 layout, I would suggest keeping +VDRV to 5.15V max, which is within the expected range of outputs on the VREF pin. 

    Thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    TI__Genius 11770 points

    Hello Wendy,

    I looked more into this and my estimate for the current was too high. Putting the higher voltage on the output LDO effectively disables it because it cannot sink current. For this reason, putting the external LDO at 5.4V is likely safer than I suggested. It still isn't really suggested by the datasheet, but as long as it is within 6V (absmax of that pin) it is most likely okay.

    Sorry about that. Let me know and I can send this thread to the LDO team. 

    Thanks,

    Alex M