BQ24232H_15 Datasheet, PDF (27/42 Pages) Texas Instruments – bq2423xx USB-Friendly Lithium-Ion Battery Charger and Power-Path Management IC

www.ti.com
bq24230H, bq24232H
SLUSBI8A – JANUARY 2014 – REVISED DECEMBER 2014
Typical Application (continued)
10.2.2 Detailed Design Procedure
10.2.2.1 Calculations
10.2.2.1.1 Program the Fast-Charge Current (ISET):
R_ISET = K_ISET / I_CHG
K_ISET = 870 AΩ from the electrical characteristics table.
R_ISET = 870 AΩ/0.2 A = 4.35 kΩ
Select the closest standard value, which for this case is 4.32 kΩ. Connect this resistor between ISET (pin 16)
and V_SS.
10.2.2.1.2 Program the Input Current Limit (ILIM)
R_ILIM = K_ILIM / I_{I_MAX}
K_ILIM = 1530 AΩ from the electrical characteristics table.
R_ISET = 1530 AΩ / 0.5 A = 3.06 kΩ
Select the closest standard value, which for this case is 3.06 kΩ. Connect this resistor between ILIM (pin 12) and
V_SS.
10.2.2.1.3 Program the Termination Current Threshold (ITERM)
R_ITERM = R_ISET × I_TERM / K_ITERM
K_ITERM = 0.03 A from electrical characteristics table
R_ITERM = 4.32 kΩ × 0.025 A/0.03 A = 3.6 kΩ
Select the closest standard value, which for this case is 3.57 kΩ. Connect this resistor between ITERM (pin 15)
and V_SS
10.2.2.1.4 Program 6.25-Hour Fast-Charge Safety Timer (TMR)
R_TMR = t_MAXCHG / (10 × K_TMR )
K_TMR = 40 s/kΩ from the electrical characteristics table.
R_TMR = (6.25 hr × 3600 s/hr) / (10 × 40 s/kΩ) = 56.25 kΩ
Select the closest standard value, which for this case is 56.2 kΩ. Connect this resistor between TMR (pin 2) and
V_SS.
10.2.2.2 TS Function
Use a 10-kΩ NTC thermistor in the battery pack (103AT). To disable the temperature sense function, use a fixed
10-kΩ resistor between the TS (pin 1) and V_SS. Pay close attention to the linearity of the chosen NTC so that it
provides the desired hot and cold turnoff thresholds.
10.2.2.3 CHG and PGOOD
LED Status: connect a 1.5-kΩ resistor in series with a LED between OUT and CHG and OUT and PGOOD.
Processor Monitoring Status: connect a pullup resistor (approximately 100 kΩ) between the power rail of the
processor and CHG and PGOOD.
10.2.2.4 Selecting IN, OUT, AND BAT Pin Capacitors
In most applications, all that is needed is a high-frequency decoupling capacitor (ceramic) on the power pin,
input, output, and battery pins. Using the values shown on the application diagram is recommended. After
evaluation of these voltage signals with real system operational conditions, the user can determine if capacitance
values can be adjusted toward the minimum recommended values (DC load application) or higher values for fast,
high-amplitude, pulsed load applications.
Copyright © 2014, Texas Instruments Incorporated
Product Folder Links: bq24230H bq24232H
Submit Documentation Feedback
27