BQ4050 Datasheet, PDF (42/53 Pages) Texas Instruments – CEDV Gas Gauge and Protection Solution

bq4050
SLUSC67A – MARCH 2016 – REVISED MARCH 2016
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9 Power Supply Recommendations
The device manages its supply voltage dynamically according to the operation conditions. Normally, the BAT
input is the primary power source to the device. The BAT pin should be connected to the positive termination of
the battery stack. The input voltage for the BAT pin ranges from 2.2 V to 26 V.
The VCC pin is the secondary power input, which activates when the BAT voltage falls below minimum Vcc. This
allows the device to source power from a charger (if present) connected to the PACK pin. The VCC pin should
be connected to the common drain of the CHG and DSG FETs. The charger input should be connected to the
PACK pin.
10 Layout
10.1 Layout Guidelines
A battery fuel gauge circuit board is a challenging environment due to the fundamental incompatibility of high-
current traces and ultra-low current semiconductor devices. The best way to protect against unwanted trace-to-
trace coupling is with a component placement, such as that shown in Figure 43, where the high-current section is
on the opposite side of the board from the electronic devices. Clearly this is not possible in many situations due
to mechanical constraints. Still, every attempt should be made to route high-current traces away from signal
traces, which enter the bq4050 directly. IC references and registers can be disturbed and in rare cases damaged
due to magnetic and capacitive coupling from the high-current path. Note that during surge current and ESD
events, the high-current traces appear inductive and can couple unwanted noise into sensitive nodes of the gas
gauge electronics, as illustrated in Figure 44.
Figure 43. Separating High- and Low-Current Sections Provides an Advantage in Noise Immunity
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