BQ24085_17 Datasheet, PDF (29/42 Pages) Texas Instruments – 750-mA Single-Chip Li-Ion and Li-Pol Charge Management IC With Thermal Regulation

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bq24085, bq24086, bq24087, bq24088
SLUS784E – DECEMBER 2007 – REVISED DECEMBER 2015
10 Power Supply Recommendations
The devices are designed to operate from an input voltage supply range between 3.5 V and 6.5 V and current
capability of at least the maximum designed charge current. This input supply should be well regulated. If located
more than a few inches from the bq24085/6/7/8 IN and GND terminals, a larger capacitor is recommended.
11 Layout
11.1 Layout Guidelines
It is important to pay special attention to the PCB layout. The following provides some guidelines:
• To obtain optimal performance, the decoupling capacitor from IN to GND (thermal pad) and the output filter
capacitors from OUT to GND (thermal pad) should be placed as close as possible to the bq2408x, with short
trace runs to both IN, OUT and GND (thermal pad).
• All low-current GND connections should be kept separate from the high-current charge or discharge paths
from the battery. Use a single-point ground technique incorporating both the small signal ground path and the
power ground path.
• The high current charge paths into IN pin and from the OUT pin must be sized appropriately for the maximum
charge current in order to avoid voltage drops in these traces.
• The bq2408x family are packaged in a thermally enhanced MLP package. The package includes a thermal
pad to provide an effective thermal contact between the IC and the printed circuit board (PCB); this thermal
pad is also the main ground connection for the device. Connect the thermal pad to the PCB ground
connection. Full PCB design guidelines for this package are provided in the application note entitled:
QFN/SON PCB Attachment Application Note, SLUA271.
11.2 Layout Example
Needs to be sized
properly
COUT/BAT
CIN
GND
Figure 23. bq2408x PCB Layout
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