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LM65645-Q1: Inverting buck-boost

Dice-K
Mastermind 7470 points
Part Number: LM65645-Q1
Other Parts Discussed in Thread: LM70660, LM76005, LM68645-Q1

Tool/software:

Hi support team,

I am looking for an inverting buck-boost (IBB) converter that can achieve the following specifications.

VIN: 19～30.8V
VOUT: -6.6V-α
IOUT: 3A (Max)

Therefore, I am looking for a step-down converter with 40V input and 5A output that can support IBB.

Can the LM65645-Q1 achieve the above specifications?
Although the IOUT of the LM65645-Q1 when stepping down is 4.5A, I would like to consider it as a candidate when the IOUT is less than 3A when IBB.

Do you know when the official release date is?

I am also considering the LM76005 and LM70660.
Are there any other devices you could recommend?

Regards,
Dice-K

  • 0
    TI__Guru 72992 points

    Here are the calculations for IBB:

    Pout = 6.6V x 3A = 19.8W

    Pin = 19.8W / 0.9 = 22W

    Iin = 22W / 19V = 1.16A

    IL = Iin + Iout = 4.16A

    Allowing margin for startup and load transients, a 4.5A or 5A converter is really what's needed. As the SW voltage is Vin + Vout = 30.8V + 6.6V = 37.4V, take a look at the LM68645-Q1 65V, 4.5A converter as a possible option.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    Mastermind 7470 points

    Hi Tim,
    Thank you for your reply.

    Does this mean that both the LM65645-Q1 and the LM68645-Q1 are possible?

    I can't find detailed specifications for the LM68645-Q1 from SNVSCV8.
    Is the difference that the input withstand voltage is 5V higher than the LM65645-Q1 and that VSNS and nFAULT are added?

    These are preview products.
    Do you know when the official release dates for each are?

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    TI__Guru 72992 points

    Hi Dice-K,

    I recommend contacting your local FAE for more detail. Note we also have an IBB (inverting buck-boost) specific version of this family in 4A/6A/8A variants later this year.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    TI__Guru 72992 points

    PS: you could get away with a 4A part if you can derate the power at low Vin (as this is where Iin and thus IL are highest).