BQ4050 Datasheet, PDF (31/53 Pages) Texas Instruments – CEDV Gas Gauge and Protection Solution

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bq4050
SLUSC67A – MARCH 2016 – REVISED MARCH 2016
Capacitors C1 and C2 help protect the FETs during an ESD event. Using two devices ensures normal operation
if one becomes shorted. To have good ESD protection, the copper trace inductance of the capacitor leads must
be designed to be as short and wide as possible. Ensure that the voltage rating of C1 and C2 are adequate to
hold off the applied voltage if one of the capacitors becomes shorted.
Figure 22. bq4050 Protection FETs
8.2.2.1.2 Chemical Fuse
The chemical fuse (Dexerials, Uchihashi, and so forth) is ignited under command from either the bq294700
secondary voltage protection IC or from the FUSE pin of the gas gauge. Either of these events applies a positive
voltage to the gate of Q5, shown in Figure 23, which then sinks current from the third terminal of the fuse,
causing it to ignite and open permanently.
It is important to carefully review the fuse specifications and match the required ignition current to that available
from the N-CH FET. Ensure that the proper voltage, current, and Rds(on) ratings are used for this device. The
fuse control circuit is discussed in detail in FUSE Circuitry.
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