Linear Technology PMIC (LTC3566) – powering circuit entirely from VOUT1

battery-chargingdc/dc converterliposwitching-regulator

I'm looking into Linear Technology's LTC3566 PMIC for an upcoming portable design. Its a really nice PMIC with a buck-boost regulator on-board. Here is the typical application:

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The reason I want to use this part is cause it allows me to save board space by not having to include a DC/DC regulator. In my application, I would power my entire circuit of Vout1 and skip the use of Vout altogether.

The one part I'm not clear about is this section here in the pin descriptions:

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I have two concerns:

  1. It says the majority of the load should be powered by Vout – In
    my application i would power my entire application from Vout1. Is
    this a concern?
  2. The chip is smart enough to partition input power between Vout and the battery. Do I still get that functionality by using Vout1?

Best Answer

Please look at the block diagram on page 11 of the datasheet. You'll see that there are two separate sections.

  1. System that takes power in from Vbus and outputs to Vout and to/from the battery.
  2. Buck/boost taking power from Vin1 and outputting to Vout1.

In the sample schematic you copied, notice that Vout is connected to Vin1. Therefore, Vou1 is downstream from Vout and what was said about giving priority to Vout also applies to Vou1.

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