Tool/software:
Hello,
I want to use the TPS61094 in a design with a super cap.
My downstream load requires a voltage between 3.0 and 3.6 V to function properly. The load is constant current, therefore reducing the voltage is preferable for power saving.
My upstream supply is fixed at 3.3 V
My supercap can withstand up to 5.5 V
Initially, I thought to set OSEL to 3.0 V, and VCHG to 5.5 V to store maximum energy in the cap, but then I noticed that from SUP to VOUT the topology allows only for boost operation.
Right now I have set up VCHG to 3.6 V, which is the maximum my downstream circuit can withstand, and OSEL to 3.0 V.
In this way, this is what I think will happen:
1. When I connect my upstream 3V3, the output is 3.3 V as well because 3.3 > 3.0 + 100 m, meanwhile the cap is charged to 3.6 V
2. When the upstream 3V3 is removed or anyway falls below 3.1 = 3.3 - 100 mV, at first I will see full 3.6 V on the output and the cap discharges
3. When the cap goes below 3.0 V, the boost will start to operate to keep VOUT at 3.0 V
My big doubt is for point 2: I am unsure of the internal architecture of the boost, what happens if the target voltage is below the input voltage? I expect either a bypass operation so SW is shorted to VOUT, or perhaps the boost will operate in snooze mode, so provide a packet of energy to the output? Above all, I need to be sure of what maximum voltage the output will see because 3.6 V is the max operating for my downstream load, but it is not the absmax.
Thanks for your help!
Vladimir
