BQ40Z50-R2 datasheet(39/51 Pages) TI1

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Low Level Circuits

BAT +

BAT –

bq40z50-R2

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SLUSCS4 – JUNE 2017

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10 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

enables 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.

11 Layout

11.1 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 bq40z50-R2 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

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

BQ40Z50-R2 数据表(PDF) 39 Page - Texas Instruments