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TPS65090 Charger Feedback Divider Selection, Single Thermistor Configuration, and Sense Resistor Value Selection

Eric Ho
Prodigy 50 points
Other Parts Discussed in Thread: TPS65090

Dear All,

 

I have some Tps65090 question,

a. If customer wanna use 3S battery, how do i design the FBC pin resistor??

b. For TS pin design, could I combine two to one to sense?

c. For the input R-sense & output R-sense, the EVM design is 10mohm, if customer wanna change to 15mohm or 20mohm, do we need to change software code or not?

 

Thank you

  • 0
    TI__Genius 17240 points

    Per question A:

    The feedback divider is described in section 3.1.2 of the TPS65090 datasheet.

    Feedback divider resistor values for a common 3-series cell of 12.V is shown the Table 3-2 of the datasheet and in the schematic of the TPS65090EVM User's Guide, where R3 = 1100k and R4 = 220k.

    This divider should be designed similar as it would be for a DCDC converter as described in this app note: http://www.ti.com/lit/an/slyt469/slyt469.pdf.
    In addition, one must become familiar with the JEITA charging profile (as shown in figure 3-9 of the datasheet) and the different states of the charger which are dictated by the voltage at the charger feedback pin as specified in the charger section of the electrical characteristics table on page 8 of the datasheet.

    B: Yes, one thermistor can be used  just as descibed in the datasheet section, 3.1.7 CHARGER BATTERY TEMPERATURE SENSING. 
    "If only one temperature sense resistor is used, the sense resistor network must be connected to TS1 and TS2."

    C: These sense resistors set the current limit for the AC adapter input and charger current limts. This must be set in hardware by the value of the resistors. The 10mOhm sense resistors between ACP and ACN, and SRP and SRN, in the EVM design are set to give a 40 mV drop at 4A, thereby limiting the AC adapter current and the battery charge current to 4A. If you use 15mOhm you will have a current limit of 2.67 and for 20mOhm a 2A current limit, where current limit = 40mV/Rsense. Selection of these values is described in the datasheet section 3.1.3 PROGRAMMING INPUT DPM CURRENT AND CHARGE CURRENT.