BQ24187 Datasheet, PDF (31/44 Pages) Texas Instruments – 1A USB-OTG Support

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Not Recommended for New Designs
bq24187
SLUSBM0 – APRIL 2014
9 Applications and Implementation
9.1 Application Information
The bq24187-625 evaluation module (EVM) is a complete charger module for evaluating the bq24187. The
application curves were taken using the bq24187EVM-625. See Related Documentation.
9.2 Typical Application
1uF
VBUS
D+
D-
GND
4.7uF
PMID
IN
SW
BOOT
CS+
1.5uH
0.033uF
20uF
DRV
1uF
STAT
BAT
PGND
TS
VDRV
1uF
TEMP
PACK+
USB PHY
PSEL
PACK-
bq24187
INT
SDA
SCL
CD
SYSTEM
VI/O
(1.8V)
HOST
GPIO1
SDA
SCL
Figure 16. bq24187 Typical Application Circuit
9.2.1 Design Requirements
Table 9. Design Requirements
DESIGN PARAMATER
Input Voltage Range
Input Current Limit
Input DPM Threshold
Fast Charge Current
Battery Charge Voltage
Termination Current
EXAMPLE VALUE
4.75 V to 5.25 V nominal, withstand 28 V
1500 mA
4.25 V
2000 mA
4.2 V
150 mA
9.2.2 Detailed Design Procedure
The parameters are configurable using the EVM software.
The typical application circuit shows the minimum capacitance requirements for each terminal. Options for sizing
the inductor outside the 1.5 μH recommended value and additional SYS terminal capacitance are explained in
the next section. The resistors on STAT and INT are sized per each LED's current requirements. The TS resistor
divider for configuring the TS function to work with the battery's specific thermistor can be computed from
Equation 1 and Equation 2. The external battery FET is optional.
9.2.2.1 Output Inductor And Capacitor Selection Guidelines
When selecting an inductor, several attributes must be examined to find the right part for the application. First,
the inductance value should be selected. The bq24187 is designed to work with 1.5µH to 2.2µH inductors. The
chosen value will have an effect on efficiency and package size. Due to the smaller current ripple, some
efficiency gain is reached using the 2.2µH inductor, however, due to the physical size of the inductor, this may
not be a viable option. The 1.5µH inductor provides a good tradeoff between size and efficiency.
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