BQ40Z50RSMR-R2 datasheet(34/55 Pages) TI2

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Figure 9-6. Differential Filter

9.2.2.2.2 Power Supply Decoupling and PBI

The BQ40Z50-R2 device 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 9-7.

C13

2.2 μF

PBI

VC4

VC3

VC2

VC1

SRN

SRP

PTCEN

PTC

LEDCNTLC

LEDCNTLB

LEDCNTLA

SMBC

SMBD

DISP

Figure 9-7. Power Supply Decoupling

9.2.2.2.3 System Present

The system present signal informs 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 BQ40Z50-R2 device is occasionally sampled to

test for system present. In ACTIVE mode, the PRES pin is pulsed every 250 ms for a duration of 5 ms (RHOEN

is on), and just before it is turned off, the state of the PRES pin is checked to see if it is low or high. The average

of the four measurements is used to determine if the PRES is asserted or not. In SLEEP mode, the PRES pin is

pulsed every "Sleep Voltage Time," and the state of the PRES pin is determined. A resistor can be used to pull

the signal low and the resistance must be 20 kΩ or lower to ensure that the test pulse is lower than the VIL limit.

The pullup current source is typically 10 µA to 20 µA. When the PRES pin is not pulsed, the PRES pin is tied

internally to VSS (RHOUT is on), and any pullup on the PRES pin will cause a battery drain when not charging.

Refer to the PRES pin diagram in

BQ40Z50-R2

SLUSCS4C – JUNE 2017 – REVISED APRIL 2021

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BQ40Z50RSMR-R2 Datenblatt(PDF) 34 Page - Texas Instruments