BQ40Z50-R1 datasheet(35/55 Pages) TI1

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bq40z50-R1

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SLUSCB3 – JULY 2015

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.

Figure 30. ESD Protection for SMB Communication

9.2.2.2.5

FUSE Circuitry

The FUSE pin of the bq40z50-R1 is designed to ignite the chemical fuse if one of the various safety criteria is

violated. The FUSE pin also monitors the state of the secondary-voltage protection IC. Q5 ignites the chemical

fuse when its gate is high. The 7-V output of the bq294700 is divided by R16 and R6, which provides adequate

gate drive for Q5 while guarding against excessive back current into the bq294700 if the FUSE signal is high.

Using C3 is generally a good practice, especially for RFI immunity. C3 may be removed, if desired, because the

chemical fuse is a comparatively slow device and is not affected by any sub-microsecond glitches that come from

the FUSE output during the cell connection process.

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