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LM5176: LM5176: 4mA into Vin, but 65mA out of linear-regulator-fed VCC? I'm not getting it.

jeffg28CLY
Prodigy 50 points
Part Number: LM5176


Tool/software:

LM5176's datasheet says that Vin's operating current is 2mA typ, 4mA max. (And based on the block diagram, I would think that whether it's Vin-only or Vin+Vbias, the total current into the chip would be nearly the same, right?)

Vin then feeds what looks to be a simple linear LDO regulator, which is VCC's 6.95-7.88V.

The datasheet also says VCC's current limit is 65mA. 

If the linear regulator on Vin only takes in a max of 4mA, how is 65mA from VCC possible?
Or is the datasheet just saying that VCC has a built-in current-limiter, and it's set to 65mA? 

  • 0
    TI__Guru 61281 points

    Hi Jeff,

    this current is the current required for the LM5176 internal circuit.

    The LDO is mainly to supply the gate drivers for the external MOSFET gate signals. This current is not included in to the VIN current even if it needs to supplied there as well (if not supplied via BIAS). This value will give you the information what the device itself well require as current. What the MOSFET will need we can not control. But here the LDO as a max limit of 65mA.

    I hope this helps to solve your confusion.

    Best regards,

     Stefan