Jason Creighton (asdf.delete@this.example.com) on May 12, 2020 9:15 am wrote:
> Travis Downs (travis.downs.delete@this.gmail.com) on May 12, 2020 7:53 am wrote:
> > What is the purpose of the LDO? Does it even reduce power draw? The voltage drop is a dead loss
> > in an LDO, in the sense that the reduced power I * (Vin - Vout) is just dissipated in the regulator,
> > but is there a secondary effect that saves power? Or is it just to better control the voltage
> > for another purpose (one could be to move power dissipation away from the core)?
>
> Linear voltage regulators (eg, an LDO) are used to produce a cleaner power rail with less ripple
> compared to switching regulators. When a really clean voltage rail is required, it's not uncommon
> to have a switching power supply (in this case, the motherboard VRM) that gets "close" to the
> desired voltage followed by a linear regulator (the on-die LDO) to smooth it out.
>
> The downside is that, indeed, this burns some extra power, but there's always
> power loss in power supply design, so it's not necessarily a bad trade-off.
>
> Jason

Thanks Jason, makes sense.