����������������������������������������������������������������� Maxim Integrated Products 9

MAX17048/MAX17049

Micropower 1-Cell/2-Cell Li+ ModelGauge ICs

Battery Swap Detection

of the previous battery does not affect that of the new

one. See the Quick-Start and VRESET/ID Register (0x18)

sections.

Quick-Start

If the IC generates an erroneous initial SOC, the battery

insertion and system powerup voltage waveforms must

be examined to determine if a quick-start is necessary,

as well as the best time to execute the command. The IC

fully relaxed, even the best sampled voltage can appear

greater or less than OCV. Therefore, quick-start must be

used cautiously.

Most systems should not use quick-start because the

ICs handle most startup problems transparently, such as

intermittent battery-terminal connection during insertion.

If battery voltage stabilizes faster than 17ms, as illus-

trated in Figure 6, then do not use quick-start.

The quick-start command restarts fuel-gauge calcula-

tions in the same manner as initial power-up of the IC.

If the system power-up sequence is so noisy that the

initial estimate of SOC has unacceptable error, the sys-

tem microcontroller might be able to reduce the error

by using quick-start. A quick-start is initiated by a rising

edge on the QSTRT pin, or by writing 1 to the quick-start

bit in the MODE register.

Power-On Reset (POR)

POR includes a quick-start, so only use it when the

battery is fully relaxed. See the Quick-Start section.

This command restores all registers to their default

values. After this command, reload the custom model.

See the CMD Register (0xFF) section.

Hibernate Mode

The ICs have a low-power hibernate mode that can

accurately fuel gauge the battery when the charge/

discharge rate is low. By default, the device automati-

cally enters and exits the hibernate mode according to the

charge/discharge rate, which minimizes quiescent current

(below 5FA) without compromising fuel-gauge accuracy.

The ICs can be forced into hibernate or active modes. Force

the IC into hibernate mode to reduce power consumption in

applications with less than C/4-rate maximum loading. For

applications with higher loading, Maxim recommends the

default configuration of automatic control of hibernate mode.

In hibernate mode, the device reduces its ADC conver-

sion period and SOC update to once per 45s. See the

HIBRT Register (0x0A) section for details on how the IC

automatically enters and exits hibernate mode.

Figure 6. Insertion Waveform Not Requiring Quick-Start Command

Figure 7. Insertion Waveform Requiring Quick-Start Command

STEADY SYSTEM

LOAD BEGINS

VCELL HAS

FULLY RELAXED

TIME

INITIAL SAMPLE

DEBOUNCE WINDOW

TIME

INITIAL SAMPLE

DEBOUNCE WINDOW

QUICK-START DURING

THIS TIME SPAN

STEADY

SYSTEM

LOAD BEGINS

BEST TIME TO

QUICK-START

FULLY RELAXED