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I'm at best a hobbyist EE and could use some help reading a schematic. I'm trying to test a chip (TI BQ76920) I found that will read the voltages from a multiple cell (1-5 cells in series) Lipo battery that can be accessed via I2C. I have plenty of practice with reading device registries from breakout PCBs but bread-boarding from a bare IC is new to me.

Anyway I have a schematic from the datasheet and it has values for some of the resistors and capacitors but not all. I highlighted the values in the image. There are 6 resistors called Rc on the left, next to them are 6 caps named Cc, on the bottom left toward the middle is a resistor called Rsns, then at the top to the right is a resistor called Rf and below that is a cap called Cf. Not sure what these are or how to calculate what they should be. Are these standard values that show up a lot and I should know what they mean? Any and all help is much appreciated.

Here is the schematic in question:

Ti bq769x0 schematic pg. 41

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    \$\begingroup\$ They are explained in the datasheet somewhere. \$\endgroup\$
    – Matt Young
    Aug 5, 2014 at 19:04
  • \$\begingroup\$ Seconded. Components without a value are explained in the text. \$\endgroup\$ Aug 5, 2014 at 19:11
  • \$\begingroup\$ Looking at the datasheet, this IC should handle from 3-5 cells, not 1-5? \$\endgroup\$
    – bitsmack
    Aug 5, 2014 at 19:34
  • \$\begingroup\$ I'd read the datasheet but I don't want to bother with TI's login process. Anyhow, Rc and Cc at least appear to be low pass filters, so the values you select will be based on the kind of response you want that filter to have. \$\endgroup\$
    – Phil Frost
    Aug 5, 2014 at 19:39
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    \$\begingroup\$ Strange, TI has never required a login except for prelim stuff before... \$\endgroup\$ Aug 5, 2014 at 19:51

1 Answer 1

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If you want to evaluate the IC I would start by ordering their eval board first. This will save you the trouble of designing your own board to work with that particular IC. You can then tweak it to get the performance you are after.

In the user guide it shows this circuit. Pg 36 here.

Here you can see they used 100Ω and 1u for Rc and Cc respectively. You can also see what they chose for the other values you were curious about. To figure out how to tweak these values to fit your needs will require reading all of the documentation. EE life isn't all glamor.

enter image description here

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