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Power Management

NiHo_1308246
New Contributor II

I am deciding between the S6AE101A and a simple direct charging method. Maybe i am missing something but the S6AE101A appears to be worse off than the simple method for no battery operation.

Simple system would be solar panels directly charging a supercap with a few diodes as overvoltage protection. The supercap would be connected to a low dropout buck boost converter (0.2V-10V input range). From my understanding the S6AE101A would only power the load when the capacitor is in a narrow voltage range. The simple system using a boost converter would operate much longer given it will power the load down to 0.2V.

Our product is a wearable with solar panel band as the watch strap. We would like to save as much power in the daytime to a 0.1F supercap to allow it to run at night. Any ideas as to if the S6AE101A would fit this need? Or is the S6AE101A more for beacon type operation?

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1 Solution
EijiF_46
Employee

Refer to following block diagram and waveform.

I will show the benefit and consideration each circuits.

---------------------

Benefits:

- Use full capacity when the light is dark 

Consideration

- Take long charging time when the supercap was empty

- VOUT voltage will be toggled due to current of MCU Power-On-Reset 

- Total BOM cost will be high due to extra circuit

1.JPG

---------------------

Benefits:

- Very low quiescent current (250 nA),

- Low BOM cost, Simple Circuit

- Including control circuit (power gating, cutoff voltage ...)

Consideration

- It can't use full capacity when the light is dark  

- Take long charging time for 1st start-up

2.JPG

Regards

Eiji

View solution in original post

4 Replies
EijiF_46
Employee

Hi

I recommend to use the S6AE102A for your application. The S6AE102A supports a hybrid capacitor charging function. Refer to following block diagram and wave form.

If you use S6AE101A or simple diode protection, it will taking longer start-up time.

If you use S6AE102A with hybrid capacitor charging, it will be Quick start-up time using both VSTORE1 (Small Capacitance) and VSTORE2 (Large Capacitance).

キャプチャ.JPG

Regards

Eiji

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NiHo_1308246
New Contributor II

Thanks for the response Eiji.

It is a space constrained wearable system so the larger 102A die size wont fit. It seems however that the 101A and simple diode protection method are basically equivalent for battery less system so we will go with the simple method. To be honest i am still not certain what are the advantages of the S6AE101A. As i have said it seems like it only operates in a small margin of voltages while a simple OVP diode with buck-boost converter would utilize the full capacity of the supercap.

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EijiF_46
Employee

Refer to following block diagram and waveform.

I will show the benefit and consideration each circuits.

---------------------

Benefits:

- Use full capacity when the light is dark 

Consideration

- Take long charging time when the supercap was empty

- VOUT voltage will be toggled due to current of MCU Power-On-Reset 

- Total BOM cost will be high due to extra circuit

1.JPG

---------------------

Benefits:

- Very low quiescent current (250 nA),

- Low BOM cost, Simple Circuit

- Including control circuit (power gating, cutoff voltage ...)

Consideration

- It can't use full capacity when the light is dark  

- Take long charging time for 1st start-up

2.JPG

Regards

Eiji

View solution in original post

NiHo_1308246
New Contributor II

Thanks Eiji, thats much more clear on the differences. So what you are saying is the S6AE101A avoids the power toggling problem by allowing the supercap to charge to VOUTH after which it has (VOUTH-VOUTL) voltage margin to safely perform the boot operation. With the simple setup, if the supercap is close to the low voltage dropout of the boost converter then it may be at risk of switching on and off if the PSoC draws too much current at boot.

Our implementation avoids the toggling problem in firmware by reading the supercap voltage via ADC and putting the PSoC into deep sleep well before reaching the boost dropout voltage (say like 0.4V). I think this will allow us meet our requirement for night operation while also avoiding complicated power up circuitry as you pointed out.

Much thanks for the clear explanation,

-Nick

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