SLUS821 Data sheet

SLUS821J October 2008 – May 2017

PRODUCTION DATA.

Package Options

Mechanical Data (Package|Pins)

RGT|16
- MPQF119H

Thermal pad, mechanical data (Package|Pins)

RGT|16
- QFND098S

Orderable Information

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

The bq2423x devices power the system while simultaneously and independently charging the battery. The input power source for charging the battery and running the system can be an AC adapter or a USB port. The devices feature dynamic power-path management (DPPM), which shares the source current between the system and battery charging and automatically reduces the charging current if the system load increases. When charging from a USB port, the input dynamic power management (V_IN-DPM) circuit reduces the input current limit if the input voltage falls below a threshold, preventing the USB port from crashing. The power-path architecture also permits the battery to supplement the system current requirements when the adapter cannot deliver the peak system currents.

The bq2423x can be configured as host controlled for selecting different input current limits based on the input source connected; or, as a fully stand-alone device for applications that do not support multiple types of input sources.

9.2 Typical Applications

9.2.1 Using The bq24232 In A Stand-Alone Charger Application

See Figure 22 for the Design Example Schematic.

V_IN= V_UVLO to V_OVP , I_FASTCHG = 200 mA, I_IN(MAX)= 500 mA, 25-mA Termination Current, ISET mode (EN1=0, EN2=1), Battery Temperature Charge Range 0°C to 50°C, 7.5-hour Fast Charge Safety Timer.

Figure 22. Using The bq24232 in a Stand-Alone Charger Application

9.2.1.1 Design Requirements

Supply voltage = 5 V
Fast-charge current of approximately 200 mA; ISET - pin 16
Input Current Limit =500 mA; ILIM - pin 12
Termination Current = 25 mA - pin 15 (bq24232)
Safety timer duration, Fast charge = 7.5 hours; TMR – pin 14
TS – Battery Temperature Sense = 10 kΩ NTC (103AT-2)

9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Calculations

9.2.1.2.1.1 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 = 4.35kΩ

Select the closest standard value, which for this case is 4.32 kΩ. Connect this resistor between ISET (pin 16) and V_SS.

9.2.1.2.1.2 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.

9.2.1.2.1.3 Program The Termination Current Threshold (ITERM, bq24232)

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

9.2.1.2.1.4 Program 7.5-hour Fast-Charge Safety Timer (TMR)

R_TMR = t_MAXCHG / (10 × K_TMR )

K_TMR = 48 s/kΩ from the electrical characteristics table.

R_TMR = (7.5 hr × 3600 s/hr) / (10 × 48 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.

9.2.1.2.2 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.

9.2.1.2.3 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 processor’s power rail and CHG and PGOOD.

9.2.1.2.4 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. Note, if the application is designed with high input voltage sources (bad adapters or wrong adapters), the capacitor needs to be rated appropriately. Ceramic capacitors are tested to 2x their rated values so a 16-V capacitor may be adequate for a 30-V transient (verify the tested rating with capacitor manufacturer).