BQ25100: Battery Charger TS Pin Input Impedance

Jorge De La Rocha

Part Number: BQ25100

Hello, I would need to know whether pin TS is a high impedance node looking into it such that I can also route the thermistor terminals to a fuel gauge which also uses this thermistor. Both the BQ25100YFPR and the FG would be simultaneously connected to the thermistor. If both parts present a high impedance, then it should work.

Thank you.

over 2 years ago

0 Juan Ospina over 2 years ago

TI__Genius 14755 points

Hi,

The BQ25100 TS function works by biasing the Thermistor with an internal 50 uA current source and reading the resulting voltage at the TS pin. I believe that the impedance looking into a current source is typically high but I would have to confirm this. It would be important to analyze how this input source would affect your configuration with the parallel fuel gauge, is this something you have taken into account?

How are you aiming to implement the thermistor configuration?

Best Regards,

Juan Ospina

0 Jorge De La Rocha over 2 years ago in reply to Juan Ospina

Prodigy 150 points

Hi Juan,

OK, if the pull-up current is 50uA, then the output impedance of the sourcing PMOS is 1/(lambda*Ids), so in the several kohms; not huge...

To know lambda, you need to know the process characteristics.

Thank you.

+1 Juan Ospina over 2 years ago in reply to Jorge De La Rocha

TI__Genius 14755 points

Hi Jorge,

Thanks for the feedback. Would you need additional/specific information to implement your design?

Best Regards,

Juan Ospina

0 Jorge De La Rocha over 2 years ago in reply to Juan Ospina

Prodigy 150 points

Hi Juan,

I found out the other IC with which I wanted to share the thermistor, also does not have a high impedance so I won't be able to do this scheme.

Thank you.

Jorge

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BQ25100: Battery Charger TS Pin Input Impedance