BQ4050 Datasheet, PDF (35/53 Pages) Texas Instruments – CEDV Gas Gauge and Protection Solution

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bq4050
SLUSC67A – MARCH 2016 – REVISED MARCH 2016
Because the System Present signal is part of the pack connector interface to the outside world, it must be
protected from external electrostatic discharge events. An integrated ESD protection on the PRES device pin
reduces the external protection requirement to just R29 for an 8-kV ESD contact rating. However, if it is possible
that the System Present signal may short to PACK+, then R28 and D4 must be included for high-voltage
protection.
Figure 29. System Present ESD and Short Protection
8.2.2.2.4 SMBus Communication
The SMBus clock and data pins have integrated high-voltage ESD protection circuits, however, adding a Zener
diode (D2 and D3) and series resistor (R24 and R26) provides more robust ESD performance.
The SMBus clock and data lines have internal pulldown. When the gas gauge senses that both lines are low
(such as during removal of the pack), the device performs auto-offset calibration and then goes into SLEEP
mode to conserve power.
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