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BQ51050B: Resistor values for BQ51050BRHL

Arghya Sadhukhan
Prodigy 20 points
Part Number: BQ51050B
Other Parts Discussed in Thread: TIDA-00318,

We have currently designed a PCB with BQ51050BRHL and WR222230-26M8-G coil to charge a 250mah battery. Can you suggest proper values of R1, R3, and R4, as referred in the attached schematic,  for a charging current of less than 100mA?

5808.schematic.pdf

  • 0
    TI__Guru* 75656 points

    Hello

    Review the connections for ILIM, FOD and RECT, see typical application schematic figure 32 in data sheet.

    The BQ51050B is optimized for charge currents above 500mA, recommended min is 500mA.  Accuracy decreases at lower charge currents, recommend 150mA charge and 45mA (30% termination).  See TIDA-00318 for a better low current solution.

    1.) R1--TERM -- This is the termination current and recommend 30% of fast charge current, 30%=7.2k ohms. see data sheet equation 2

    2.) R3 -- ILIM to FOD -- R3 + R-fod to ground will set fast charge current, R1 + R-fod in data sheet. Starting value for R-fod=200 ohm and adjust after FOD Calibration.  Charge current = K-ILIM / ( R1+R-fod) -- 150mA = 3140 total, R1 = 2940 ohms, R-fod = 200 ohms, see data sheet equation 1.

    3.) R4 -- RECT to GND -- this does not look correct please review, possibly should connect from FOD to GND