Detailed Description
The MAX6439–MAX6442 family is available with several
monitoring options. The factory-trimmed thresholds
eliminate the requirement for external components. The
MAX6439/MAX6440 have single low-battery outputs
and the MAX6441/MAX6442 have dual low-battery out-
puts (see Figure 1a and Figure 1b).
The MAX6439–MAX6442 combine a 1.23V reference
with two comparators, logic, and timing circuitry to pro-
vide the user with information about the charge state of
the power-supply batteries. The MAX6441/MAX6442
monitor separate high-voltage and low-voltage thresh-
olds to determine battery status. The output(s) can be
used to signal when the battery is charged, when the
battery is low, and when the battery is empty. Factory-
trimmed thresholds are ideal for monitoring single-cell
Li+ or multicell alkaline/NiCd/NiMH power supplies.
When the power-supply voltage drops below the speci-
fied low threshold, the low-battery output asserts. When
the voltage rises above the specified high threshold fol-
lowing a 150ms (min) timeout period, the low-battery
output is deasserted. This ensures the supply voltage
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
_______________________________________________________________________________________ 7
Pin Description
PIN
MAX6439/
MAX6440
MAX6441/
MAX6442
NAME FUNCTION
11V
BATT
Battery Voltage Input. Input for battery voltage threshold monitors and device power supply
if V
BATT
is greater than V
CC
.
23MR
Manual Reset Input, Active-Low, Internal 1.5kΩ Pullup to V
CC
. Pull low to assert a one-shot
edge-triggered RESET output for the MR reset timeout period. Leave unconnected or
connect to V
CC
if unused. The MR input is debounced for MR rising edges to prevent false
reset events.
3—LBO
Low-Battery Output, Active Low, Open Drain. LBO is asserted when V
BATT
drops below the
LTH specification and remains asserted until V
BATT
rises above the HTH specification for at
least 150ms.
45RESET
Reset Output, Active Low, Push-Pull or Open Drain. RESET changes from high to low when
the V
CC
input drops below the selected reset threshold and remains low for the V
CC
reset
timeout period after V
CC
exceeds the reset threshold. RESET is one-shot edge-trigger
pulsed low for the MR reset timeout period when the MR input is pulled low. RESET is an
open-drain output for the MAX6439/MAX6441, and a push-pull output for the
MAX6440/MAX6442. The push-pull outputs are referenced to V
CC
. RESET is guaranteed to
be in the correct logic state for V
BATT
or V
CC
> 1.0V.
5 2 GND Ground
68V
CC
V
CC
Voltage Input. Input for V
CC
reset threshold monitor and device power supply if V
CC
is
greater than V
BATT
.
—6LBOH
Low-Battery Output High, Active Low, Open Drain. LBOH is asserted when V
BATT
drops
below the HTH- specification. LBOH is deasserted when V
BATT
rises above the HTH+
specification for at least 150ms.
—7LBOL
Low-Battery Output Low, Active Low, Open Drain. LBOL is asserted when V
BATT
drops
below the LTH- specification. LBOL is deasserted when V
BATT
rises above the LTH+
specification for at least 150ms.
—4LBOLH
Low-Battery Output Low/High, Active Low, Open Drain. LBOLH is asserted when V
BATT
drops below the LTH- specification. LBOLH is deasserted when V
BATT
rises above the
HTH+ specification for at least 150ms.
