BQ24188_15 Datasheet, PDF (37/52 Pages) Texas Instruments – bq24188 2A, 30V, Host-Controlled Single-Input, Single Cell Switchmode Li-Ion Battery Charger with Power Path Management and USB-OTG Support

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Typical Applications (continued)
10.2.1.1 Design Requirements
bq24188
SLUSC44A – DECEMBER 2014 – REVISED MAY 2015
Table 2. 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
50 mA
10.2.1.2 Detailed Design Procedure
The parameters are configurable using the EVM software.
The typical application circuit shows the minimum capacitance requirements for each pin. Options for sizing the
inductor outside the 1.5 μH recommended value and additional SYS pin 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.
10.2.2 bq24188 Typical Application – External Discharge FET
PMID
1 .5 µH
SW
1 µF
0 .033 µF
10 µF
47 µF
BOOT
VBUS
D+
D-
GND
4 .7 µF
SYS
IN
PGND
BGATE
2.2 µF
DRV
BAT
VDRV
1 µF
System
Load
STAT
D+
D–
TS
bq24188
INT
SDA
SCL
CD
TEMP
PACK +
PACK -
V SYS
(1.8V )
HOST
GPIO 1
SDA
SCL
Figure 27. bq24188 Typical Application Circuit
10.2.3 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 bq24188 is designed to work with 1.5 µH to 2.2 µH 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 2.2 µH inductor, however, due to the physical size of the inductor, this may
not be a viable option. The 1.5 µH inductor provides a good tradeoff between size and efficiency.
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