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Bq25504 in a WSN

markos losada
Prodigy 205 points
Other Parts Discussed in Thread: BQ25504, BQ25570, BQ25505, TPS62736, TPS62737

Hi,

We are working in a sensor nodes that aim to be similar to that it is shown in  http://www.ti.com/lit/ml/slyt472/slyt472.pdf. It is intended to make use of the depicted devices, but we are having some questions about BQ25504?

1. Which are the differences between BQ25504 and a typical battery charger such as Bq24XX? The functioning principle is the same, in fact, both are battery chargers. The single difference is that BQ25504 can be powered from a lower voltage source, is this true?

2. In order to be powered a microcontroller from this kind of Energy harvesting device, is it  needed a regulator(DC-DC conveter)? It will be well suited TPS6220x in combination with BQ25504?  which one is well suited?

3. If there is no input source, the microcontroller will make use of the battery without worrying about the input source?

Regards.

  • 0
    Prodigy 95 points

    Hello i was wondering if you got answers to all the three questions? I am a bit lost on the same problem

    any help would be apreciated

  • 0
    TI__Guru**** 166996 points

    Regarding 1, the the bq25504, bq25505 and bq25570 only prevent battery over discharge and over charge through a switch that separates the boost charger output (VSTOR) from the storage element (VBAT).  The charge current is not regulated as with other bq24xxx devices.  With such low power charging currents going to the battery, there is very little risk that battery will be harmed.

    Regarding 2, most microcontroller's have a VCC min and max that could be outside the range of the VSTOR voltage so a dc/dc converter is recommended.  A TPS62736 or TPS62737 with bq25504 or bq25505 is a good option of the bq25570 which has integrated buck converter is a good option.

    Regarding 3, if buck converter and/or microcontroller is powered from the battery through the VSTOR pin, no input source is needed.  The bq255xx's main circuitry is actually powered from the VSTOR=VBAT pins.