Data Sheet

bq24072

bq24073

bq24074

bq24075

bq24079

www.ti.com

SLUS810K –SEPTEMBER 2008–REVISED MARCH 2015

11 Power Supply Recommendations

Some adapters implement a half rectifier topology, which causes the adapter output voltage to fall below the

battery voltage during part of the cycle. To enable operation with adapters under those conditions, the bq2407x

family keeps the charger on for at least 20 msec (typical) after the input power puts the part in sleep mode. This

feature enables use of external adapters using 50 Hz networks. The input must not drop below the UVLO voltage

for the charger to work properly. Thus, the battery voltage should be above the UVLO to help prevent the input

from dropping out. Additional input capacitance may be needed.

12 Layout

12.1 Layout 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 bq2407x, 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 bq2407x family is 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 QFN/SON PCB Attachment Application Note

(SLUA271).

Product Folder Links: bq24072 bq24073 bq24074 bq24075 bq24079