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LM3488: LM3488: Split-Rail Operation (like TPS4306x) possibe?

Part Number: LM3488
Other Parts Discussed in Thread: TPS43060

Hey Guys,

I'm just looking at the LM3488 and the TPS4306x boost controller.

In TPS4306x datasheet, page 19, it says:

"The TPS4306x can also operate in a split-rail topology where a separate voltage is provided to bias the VIN pin of the IC to 4.5 V or greater. The power for the boost power stage can then be powered from a separate input lower than the 4.5-V minimum VIN voltage. When operating in this mode, the boost power stage voltage must be greater than 2.5 V to bias the ISNS pins or the current limit accuracy may degrade. If used in split rail, the TPS4306x is enabled and disabled in the same VIN and EN conditions as described in Typical Operation (VIN < VOUT)."

There is no mention of anything like that in the LM3488 datasheet.

I'm just wondering if this "Split-rail" operation can be achieved with the LM3488.

The application is for device powered by a single cell li-ion battery. So input voltage: 2.5 ~ 4.2V.     Output voltage = 12V @ 1.5A

Cheers,

Blake

  • Hi Blake,

    Thank you for posting.  Yes the LM3488 can also be biased by a separate voltage rail at the VIN pin.  It was not mentioned because it is a common understanding for most PWM controllers.  The IC bias and the actual power rail can be different.  The reason that is specially mentioned in the TPS43060 datasheet is because of the additional caution:  the current sense pin common mode voltage should be maintained above 2.5V. 

    For your single cell application, where do you get the 4.5V in the first place?  You may consider the TPS610xx series boost converters which can provide the needed voltage to bias the TPS4306x. 

    Thanks,

    Youhao Xi,  Applications Engineering.

  • Cool. I will have a look at the TPS610xx series.

    Thank you Youhao