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Original question:

TPS92511: Calculation for power dissipation

TPS92511: Do you have external MOSFET version of TPS92511?

Kazuya Nakai59
Guru 21595 points
Part Number: TPS92511
Other Parts Discussed in Thread: TPS92692, TPS92691, INA149

 Hello guys,

 One of my customers is looking for a device which external MOSFET version of TPS92511. If the switching MOSFET is external, it can be used for higher voltage input condition or a lot of LED in series condition using high VDS MOSFET and clampping VCC of the device with some external parts. The customer is looking for a TI LED driver like Microchip, HV9910B

http://ww1.microchip.com/downloads/en/DeviceDoc/20005344A.pdf

Do you have such device?

Your reply would be much appreciated.

 Best regards,

 Kazuya Nakai.

   

  • 0
    TI__Expert 3920 points
    Hi Nakai-san,

    Please refer to TPS92691 or TPS92692 for low-side NFET LED controllers.
    Thank you!
  • 0 in reply to Issac Hsu
    Guru 21595 points
    Hi Issac,

    Thank you for the prompt reply. Buck converter topology of TPS92691 like Figure 27 in the device datasheet(SLVSD68) could be used instera of HV9910B.

    I have a few questions.

    CSP/CSN terminal maximum input voltage is 65V. If input voltage for LED anode voltage is 220V, CSP/CSN terminal voltage may be more than 65V when switching is stopped by PWM=L.
    Is CSP/CSN needed to use for LED current sensing?
    Can LED current be control by IS terminal current sensing only?

    Thank you and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Expert 3920 points
    Hi Nakai-san,

    CSP and CSN are limited to 65 V absolute maximum. Same as the VIN pin.
    And the average LED current can only be regulated through CSP/CSN, not the IS pin.

    What is the LED string voltage?

    Can the customer accept analog dimming (reducing current through adjusting IADJ pin) instead of PWM dimming?
  • 0 in reply to Issac Hsu
    Guru 21595 points
    Hi Issac,

    The number of LED in series is 25~50pcs. Also LED is white LED. So the LED string voltage is about 87.5V ~ 175V.
    I think the customer could accept analog dimming. If you have any solution, could you please let me know?

    Thank you and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Expert 3920 points

    Hi Nakai-san,

    It would be difficult to use TPS92691/2 then because the CSP / CSN pins might still seeing voltage that is over 65 V, e.g. 220 V input with 87.5 V LED, the floating buck voltage will still be 132.5 V.

    The only thing I can think of is to add a current-sense amplifier, e.g. INA149, and convert the common-mode voltage referencing to ground with CSN connecting to ground and CSP connecting to the amplifier output.

    Analog dimming can be achieved by adjusting the IADJ input value. The output current is VIADJ / (14 * RSNS). Of course, there is some limitation that the VIADJ cannot be very small (we suggest VIADJ >= 0.14) and it's clamped at 2.4 V internally.

    See if it's a possible work-around.

  • 0 in reply to Issac Hsu
    Guru 21595 points
    Hi Issac,

    Thank you very much for your reply!

    Best regards,
    Kazuya Nakai.