BQ4050 Datasheet, PDF (34/53 Pages) Texas Instruments – CEDV Gas Gauge and Protection Solution

bq4050
SLUSC67A – MARCH 2016 – REVISED MARCH 2016
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8.2.2.2.2 Power Supply Decoupling and PBI
The bq4050 has an internal LDO that is internally compensated and does not require an external decoupling
capacitor.
The PBI pin is used as a power supply backup input pin providing power during brief transient power outages. A
standard 2.2-µF ceramic capacitor is connected from the PBI pin to ground as shown in Figure 27.
Figure 27. Power Supply Decoupling
8.2.2.2.3 System Present
The System Present signal is used to inform the gas gauge whether the pack is installed into or removed from
the system. In the host system, this pin is grounded. The PRES pin of the bq4050 is occasionally sampled to test
for system present. To save power, an internal pullup is provided by the gas gauge during a brief 4-μs sampling
pulse once per second. A resistor can be used to pull the signal low and the resistance must be 20 kΩ or lower
to insure that the test pulse is lower than the VIL limit. The pull-up current source is typically 10 µA to 20 µA.
Figure 28. System Present Pull-Down Resistor
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