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Original question:

TPS552882: Average inductor current limit not working

TPS552882: Laser drive DCDC with adjustable current limit

Paul Carson1
Prodigy 220 points

Part Number: TPS552882
Other Parts Discussed in Thread: TPS55288

Hi,

Product A:

I thought I could use the TPS552882 to drive a laser with constant current, however the current limit range are too unstable and not suitable as I require an adjustable limit 0.55 - 3.6A.

Input range 6-19V

Output voltage max 2.2V

Product B:

If possible, I would also like to use the product A selected device on a similiar product but without the current limit, the voltage range & output current are at different 5-24V & 13A pulsed.

Could you please suggest a suitable part for design A at least?

  • 0
    TI__Mastermind 20770 points

    Hi Paul,

    Thank you for reaching out. For design A, you can consider TPS55288 with I2C to adjust output current limit.

    For design B, is output voltage fixed or not? What is the Vout value?

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 220 points

    Hi Mulin,

    Thanks, the TPS55288 looks good for product A & B when we move from prototype to production design.

    I note the datasheet page 7 indicates a range on the average constant current limit, is this caused by Supply Voltage variation or Temperature dependent or both?

    We don't have a control device in our prototype and therefore no I2C control possible, can the ILIM resistor be used to reduce to 0.55A?

    BR,

    Paul

  • +1 in reply to Paul Carson1
    TI__Mastermind 20770 points

    Hi Paul,

    This is due to chip-to-chip variations. Accuracy may decrease at lower current limits; specifically, maintaining precision at a 0.55A limit is difficult to guarantee. We recommend using I2C control instead.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 220 points

    Hi Mulin,

    I've ordered the TPS55288 EVAL PCB but for this prototype we will proceed with a LTM8056 eval PCB (AD) we already have characterised across supply range and can use ILIM reliably it appears.

    If we go to production design we can then change to the TPS55288 and use the I2C with an MSP430FR part we already use in other products.

    Thanks again for your quick response.

    On a related matter we have a problem with TI (and  also AD BTW) eval PCBs whereby the layout engineers appear to never have heard of Thermal Relief, making modifications very very difficult - you could raise this issue up the design chain please.

    It'd make life a lot easier in future.