Hi all.
In bq24610 datasheet application schematis and bq24610 EVM battery current sense resistor SRP-SRN (R18 on EVM schematic, RSR in datasheet) is placed between output inductor (L1 - both schemes) and output capacitor (C20, C23, C25, C27 - EVM; C12, C13 - datasheet). May be it will be better (for battery current control accuracy) to place battery current sense resistor after output capacitors? Or is this R used for switch current control also?
Thanks a lot in advance.
Maxim.
Hello Martin.
There are a number of reasons for the placement of the current sense resistor in its position before the filtering capacitors.
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One of them has to do with providing a low impedance and therefore low loss for the external BATFET. Placing the sense resistor on the inductor side of filter capacitors allow the filter capacitors to supply transient power from the battery and not arbitrarily increase the path impedance which would increase the losses along this path.
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The placement of the output sense resistor also is used for comparisons between the input and output current sense pins. This is used to effectively control the BATFET to quickly switch it on and off in according to where the current is coming for the output of the system.
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Also having the SRN node closer to the output capacitors and the battery assists in the battery detection algorithm when the SRN sinks 8 mA of current as discussed on Pg. 22 &23 of the datasheet.
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These are just a few of the reasons for the placement of the sense resistor. Let me know if you have any other questions.
