Compact, Low-Cost 1S/2S Fuel Gauges

with Low-Battery Alert

10

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Figure 6 shows an example application for a 1S cell

pack. The MAX17043 is mounted on the system side

and powered directly from the cell pack. The external

the IC power supply and A/D measurement. In this

example, the ALRT pin is connected to the micro-

processor's interrupt input to allow the MAX17043 to

signal when the battery is low. The QSTRT pin is

unused in this application, so it is tied to GND.

Figure 7 shows a MAX17044 example application using

a 2S cell pack. The MAX17044 is mounted on the sys-

tem side and powered from a 3.3V supply generated

by the system. The CELL pin is still connected directly

to PACK+ through an external noise filter. The ALRT pin

is left unconnected because the interrupt feature is not

used in this application. After power is supplied, the

system watchdog generates a low-to-high transition on

the QSTRT pin to signal the MAX17044 to perform a

quick-start.

PACK-

PACK+

PROTECTION IC

(Li+/POLYMER)

SYSTEM GND

BATTERY

SYSTEM

MAX17043

CELL

EP

1

μF

1k

Ω

10nF

150

Ω

GND

CTG

SCL

SDA

QSTRT

ALRT

SYSTEM

μP

MASTER

INTERRUPT

INPUT

4.7k

Ω

Figure 6. MAX17043 Application Example with Alert Interrupt

PACK-

PACK+

PROTECTION IC

(Li+/POLYMER)

SYSTEM GND

BATTERY

SYSTEM

MAX17044

CELL

1

μF

1k

Ω

GND

CTG

SCL

SDA

QSTRT

SYSTEM PMIC

SYSTEM

μP

MASTER

3.3V OUTPUT

WATCHDOG

ALRT

EP

Figure 7. MAX17044 Application Example with Hardware Reset