Article: Power Delivery in a Modern Processor
By: Travis Downs (travis.downs.delete@this.gmail.com), May 13, 2020 6:44 am
Room: Moderated Discussions
Yoav (no_drink.delete@this.gmail.com) on May 13, 2020 3:56 am wrote:
> If not all domains under the save Voltage regulator need the same voltage, LDOs can save a lot of power.
>
> Example:
> Domain1 need 0.8V, and Domain2 need 1.2V.
> So VR gives 1.2V.
> Without LDO, domain1 would get 1.2V, and burn a lot of power.
> With LDO, it can use 0.8V, and burn less power.
Right, but to drop from 1.2V to 0.8V the LDO has to dissipate internally that 0.4V * I, so my question was "where's the savings, or do you just move the consumption from the core to the LDO"?
As David points out, the savings comes at least in part because the core power use is quadratic in voltage, so the linear dissipation in the LDO is more than compensated for.
> If not all domains under the save Voltage regulator need the same voltage, LDOs can save a lot of power.
>
> Example:
> Domain1 need 0.8V, and Domain2 need 1.2V.
> So VR gives 1.2V.
> Without LDO, domain1 would get 1.2V, and burn a lot of power.
> With LDO, it can use 0.8V, and burn less power.
Right, but to drop from 1.2V to 0.8V the LDO has to dissipate internally that 0.4V * I, so my question was "where's the savings, or do you just move the consumption from the core to the LDO"?
As David points out, the savings comes at least in part because the core power use is quadratic in voltage, so the linear dissipation in the LDO is more than compensated for.