MAX6439UTA MAXIM [Maxim Integrated Products], MAX6439UTA Datasheet - Page 10

• Manufacturer Part Number: MAX6439UTA
• Description: Low-Power, Single-/Dual-Level Battery Monitors with Hysteresis and Integrated uP Reset
• Manufacturer: MAXIM [Maxim Integrated Products]

Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
Figure 5. Hysteresis
Figure 7. DC-to-DC Converter Application
Many microprocessor-based products require manual
reset capability, allowing the operator, a test technician,
or external logic circuitry to initiate a reset while the
monitored supplies remain above their reset thresholds.
These devices have a dedicated active-low MR pin.
When MR is pulled low, RESET asserts a one-shot low
pulse for the MR reset timeout period. The MR input has
an internal 1.5kΩ pullup resistor to V
unconnected if not used. MR can be driven with CMOS-
10
V
LBO
BATT
3.6V
V
V
HTH = BATTERY VOLTAGE GOOD, ENABLE OPERATION.
LTH = BATTERY VOLTAGE LOW, SUSPEND/DISABLE OPERATION.
Li+
______________________________________________________________________________________
HTH
LTH
V
MR
IN
BATT
MAX6441
MAX6442
DC/DC
SHDN
LBOL
GND
t
LBOP
V
RESET
HYST
LBOH
V
OUT
CC
CC
Manual Reset
NMI
RESET
and can be left
V
GND
µP
CC
logic levels, open-drain/open-collector outputs, or a
momentary push-button switch to GND (the MR function
is internally debounced for the t
create a manual reset function. If MR is driven from long
cables, or if the device is used in a noisy environment,
connect a 0.1µF capacitor from MR to GND to provide
additional noise immunity (see Figure 4).
Hysteresis increases the comparator’s noise margin by
increasing the upper threshold or decreasing the lower
threshold. The hysteresis prevents the output from
oscillating (chattering) when V
tery threshold. This is especially important for applica-
tions where the load on the battery creates significant
fluctuations in battery voltages (see Figure 5).
The MAX6441/MAX6442 dual-output battery monitors
can be used in conjunction with a battery charger to
provide a system with additional information about the
battery charge state. Many battery chargers, such as
the MAX1879, provide the user with a CHG output,
which tells the system when the battery is charged. The
MAX6441/MAX6442 dual-output battery monitors pro-
vide three outputs, which can be used to relay the bat-
tery condition to the system. This information is useful in
determining which system resources can be powered by
the battery at the current charge state (see Figure 6).
Figure 6. Li+ Charger Application (Using MAX1879)
CURRENT-
ADAPTER
AC WALL
LIMITED
PULSE-WIDTH
SELECT INPUT
LED
THERMISTOR
CHG
TSEL
Li+ Battery Charger Application
THERM
Applications Information
IN
MAX1879
ADJ
GATE
BATT
GND
BATT
DEB
1-CELL
Li+
BATTERY
is near the low-bat-
timeout period) to
DC/DC CONVERTER
V
IN
BATT
Hysteresis
MAX6441
MAX6442
V
OUT
GND
CC
LBOLH
RESET
LBOH
SHDN
LBOL