General Description
The MAX6439–MAX6442 are a family of ultra-low-power
battery monitors with integrated microprocessor (µP)
supervisors. The battery monitors are offered with sin-
gle or dual low-battery output options that can be used
to signal when the battery is OK (enabling full system
operation), when the battery is low (for low-power sys-
tem operation), and when the battery is dead (to dis-
able system operation). These devices also have an
independent µP supervisor that monitors VCC and pro-
vides an active-low reset output. A manual reset func-
tion is available to reset the µP with a push-button. No
external components are required.
The MAX6439–MAX6442 are offered with several facto-
ry-trimmed low-battery threshold combinations ideal for
single-cell lithium-ion (Li+) or multicell alkaline/NiCd/
NiMH applications. When the battery voltage drops
below each specified low threshold, the low-battery out-
puts are asserted to alert the system. When the voltage
rises above the specified high thresholds, the outputs
are deasserted after a 150ms minimum timeout period,
ensuring the voltages have stabilized before power cir-
cuitry is activated or providing microprocessor reset tim-
ing. The low and high thresholds provide hysteresis in
battery-operated systems to eliminate output chattering.
The MAX6439/MAX6440 offer factory-trimmed battery
monitors with a single output. The MAX6441/MAX6442
offer factory-trimmed battery monitors with dual outputs.
All battery monitors have open-drain low-battery outputs.
The MAX6439–MAX6442 monitor system voltages
(VCC) from 1.8V to 3.3V with seven fixed reset threshold
options. Each device is offered with two minimum reset
timeout periods of 150ms or 1200ms. The MAX6439/
MAX6441 are offered with an open-drain RESET output
and the MAX6440/MAX6442 are offered with a push-
pull RESET output.
The MAX6439–MAX6442 are offered in a SOT23 pack-
age and are fully specified over a -40°C to +85°C temp-
erature range.
Applications
Battery-Powered Systems (Single-Cell Li+ or
Two-/Three-Cell NiMH, NiCd, Alkaline)
Cell Phones/Cordless Phones
Portable Medical Devices
Electronic Toys
Pagers
PDAs
MP3 Players
Features
♦Factory-Trimmed VBATT Threshold Options for
Monitoring Single-Cell Li+ or Multicell
Alkaline/NiCd/NiMH Applications
♦Immune to Short Battery Voltage Transients
♦Low Current (2.5µA typ at 3.6V)
♦Single and Dual Low-Battery Output Options
♦150ms Minimum LBO Timeout Period
♦Independent µP Reset with Manual Reset
♦Factory-Set Reset Thresholds for Monitoring VCC
from 1.8V to 3.3V
♦Available with 150ms (min) and 1.2s (min) VCC
Reset Timeout Period Options
♦-40°C to +85°C Operating Temperature Range
♦Small 6- and 8-Pin SOT23 Packages
♦No External Components
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
________________________________________________________________ Maxim Integrated Products 1
MR
RESETLBO
16VCC
5GND
VBATT
MAX6439
MAX6440
SOT23-6
TOP VIEW
2
34
Pin Configurations
Ordering Information
19-2535; Rev 0; 7/02
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PART TEMP RANGE PIN-PACKAGE
MAX6439UT_ _ _D_-T -40°C to +85°C 6 SOT23-6
MAX6440UT_ _ _D_-T -40°C to +85°C 6 SOT23-6
MAX6441KA_ _ _D_-T -40°C to +85°C 8 SOT23-8
MAX6442KA_ _ _D_-T -40°C to +85°C 8 SOT23-8
Note: The first two “_ _” are placeholders for the battery moni-
tor voltage levels. Desired threshold levels are set by the part
number suffix found in Tables 1 and 2. The third “_” is the VCC
reset threshold level suffix found in Table 3. The “_” after the D
is a placeholder for the reset timeout period suffix found in
Table 4. All devices are available in tape-and-reel only. There
is a 2500-piece minimum order increment for standard ver-
sions. Sample stock is typically held on standard versions only.
Nonstandard versions require a minimum order increment of
10,000 pieces. Contact factory for availability.
Pin Configurations continued at end of data sheet.
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
*Applying 7V for a duration of 1ms does not damage the device.
VBATT, VCC to GND.................................................-0.3V to +6V*
Open-Drain LBO, LBOH, LBOL, LBOLH to GND ...-0.3V to +6V*
Open-Drain RESET to GND ....................................-0.3V to +6V*
Push-Pull RESET to GND............................-0.3V to (VCC + 0.3V)
MR to GND .................................................-0.3V to (VCC + 0.3V)
Input/Output Current, All Pins .............................................20mA
Continuous Power Dissipation (TA= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C)............695mW
8-Pin SOT23 (derate 8.9mW/°C above +70°C)............714mW
Operating Temperature Range .......................... -40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(VBATT = 1.2V to 5.5V, VCC = 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise specified. Typical values are at TA= +25°C.) (Note1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
TA = 0°C to +85°C 1.0 5.5
VBATT Operating Voltage Range VBATT TA = -40°C to +85°C 1.2 5.5 V
TA = 0°C to +85°C 1.0 5.5
VCC Operating Voltage Range VCC TA = -40°C to +85°C 1.2 5.5 V
VCC + VBATT Supply Current ICC + IBATT VBATT = 3.6V, VCC = 3.3V, no load (Note 2) 2.5 7 µA
VBATT THRESHOLDS
MAX6439UT_ J, MAX6440UT_ J 3.510 3.60 3.690
MAX6439UT_ I, MAX6440UT_ I 3.413 3.50 3.588
MAX6439UT_ H, MAX6440UT_ H 3.315 3.40 3.485
MAX6439UT_ G, MAX6440UT_ G 3.218 3.30 3.383
MAX6439UT_ T, MAX6440UT_ T 2.535 2.60 2.665
MAX6439UT_ S, MAX6440UT_ S 2.438 2.50 2.563
MAX6439UT_ R, MAX6440UT_ R 2.340 2.40 2.460
HTH Threshold HTH
MAX6439UT_ Q, MAX6440UT_ Q 2.243 2.30 2.358
V
MAX6439UTF, MAX6440UTF 3.023 3.10 3.178
MAX6439UTE, MAX6440UTE 2.925 3.00 3.075
MAX6439UTD, MAX6440UTD 2.828 2.90 2.973
MAX6439UTC, MAX6440UTC 2.730 2.80 2.870
MAX6439UTB, MAX6440UTB 2.633 2.70 2.768
MAX6439UTA, MAX6440UTA 2.535 2.60 2.665
MAX6439UTP, MAX6440UTP 2.048 2.10 2.153
MAX6439UTO, MAX6440UTO 1.950 2.00 2.050
MAX6439UTN, MAX6440UTN 1.853 1.90 1.948
MAX6439UTM, MAX6440UTM 1.755 1.80 1.845
MAX6439UTL, MAX6440UTL 1.658 1.70 1.743
LTH Threshold LTH
MAX6439UTK, MAX6440UTK 1.560 1.60 1.640
V
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 1.2V to 5.5V, VCC = 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise specified. Typical values are at TA= +25°C.) (Note1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX6441UT_ J, MAX6442UT_ J 3.510 3.600 3.690
MAX6441UT_ I, MAX6442UT_ I 3.413 3.500 3.588
MAX6441UT_ H, MAX6442UT_ H 3.315 3.400 3.485
MAX6441UT_ G, MAX6442UT_ G 3.218 3.300 3.383
MAX6441UT_ T, MAX6442UT_ T 2.535 2.600 2.665
MAX6441UT_ S, MAX6442UT_ S 2.438 2.500 2.563
MAX6441UT_ R, MAX6442UT_ R 2.340 2.400 2.460
HTH- Threshold HTH-
MAX6441UT_ Q, MAX6442UT_ Q 2.243 2.300 2.358
V
MAX6441UT_ J, MAX6442UT_ J 3.686 3.780 3.875
MAX6441UT_ I, MAX6442UT_ I 3.583 3.675 3.767
MAX6441UT_ H, MAX6442UT_ H 3.481 3.570 3.659
MAX6441UT_ G, MAX6442UT_ G 3.378 3.465 3.552
MAX6441UT_ T, MAX6442UT_ T 2.662 2.730 2.798
MAX6441UT_ S, MAX6442UT_ S 2.559 2.625 2.691
MAX6441UT_ R, MAX6442UT_ R 2.457 2.520 2.583
HTH+ Threshold HTH+
MAX6441UT_ Q, MAX6442UT_ Q 2.355 2.415 2.476
V
MAX6441UTF, MAX6442UTF 3.023 3.100 3.178
MAX6441UTE, MAX6442UTE 2.925 3.000 3.075
MAX6441UTD, MAX6442UTD 2.828 2.900 2.973
MAX6441UTC, MAX6442UTC 2.730 2.800 2.870
MAX6441UTB, MAX6442UTB 2.633 2.700 2.768
MAX6441UTA, MAX6442UTA 2.535 2.600 2.665
MAX6441UTP, MAX6442UTP 2.048 2.100 2.153
MAX6441UTO, MAX6442UTO 1.950 2.000 2.050
MAX6441UTN, MAX6442UTN 1.853 1.900 1.948
MAX6441UTM, MAX6442UTM 1.755 1.800 1.845
MAX6441UTL, MAX6442UTL 1.658 1.700 1.743
LTH- Threshold LTH-
MAX6441UTK, MAX6442UTK 1.560 1.600 1.640
V
MAX6441UTF, MAX6442UTF 3.174 3.255 3.337
MAX6441UTE, MAX6442UTE 3.071 3.150 3.229
MAX6441UTD, MAX6442UTD 2.969 3.045 3.121
MAX6441UTC, MAX6442UTC 2.867 2.940 3.014
MAX6441UTB, MAX6442UTB 2.764 2.835 2.906
MAX6441UTA, MAX6442UTA 2.662 2.730 2.798
MAX6441UTP, MAX6442UTP 2.150 2.205 2.260
MAX6441UTO, MAX6442UTO 2.048 2.100 2.153
MAX6441UTN, MAX6442UTN 1.945 1.995 2.045
MAX6441UTM, MAX6442UTM 1.843 1.890 1.937
MAX6441UTL, MAX6442UTL 1.740 1.785 1.830
LTH+ Threshold LTH+
MAX6441UTK, MAX6442UTK 1.638 1.680 1.722
V
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 1.2V to 5.5V, VCC = 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise specified. Typical values are at TA= +25°C.) (Note1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LBO, LBOL, LBOH, LBOLH
Timeout Period tLBOP VBATT rising above threshold 150 225 300 ms
LBO, LBOL, LBOH, LBOLH
Delay Time tLBOD VBATT falling below threshold 100 µs
(VBATT or VCC) ≥ 1.2V, ISINK = 50µA,
asserted low 0.3
(VBATT or VCC) ≥ 1.6V, ISINK = 100µA,
asserted low 0.3
(VBATT or VCC) ≥ 2.7V, ISINK = 1.2mA,
asserted low 0.3
LBO, LBOL, LBOH, LBOLH
Output Low
(Open Drain)
VOL
(VBATT or VCC) ≥ 4.5V, ISINK = 3.2mA,
asserted low 0.3
V
LBO, LBOL, LBOH, LBOLH
Output Open-Drain Leakage
Current
ILKG Output deasserted 500 nA
MAX64_ _ _ _ _ _ T 3.000 3.075 3.150
MAX64_ _ _ _ _ _ S 2.850 2.925 3.000
MAX64_ _ _ _ _ _ R 2.550 2.625 2.700
MAX64_ _ _ _ _ _ Z 2.250 2.313 2.375
MAX64_ _ _ _ _ _ Y 2.125 2.188 2.250
MAX64_ _ _ _ _ _ W 1.620 1.665 1.710
VCC Reset Threshold VTH
MAX64_ _ _ _ _ _ V 1.530 1.575 1.620
V
VCC Reset Hysteresis 0.3 %
VCC to RESET Delay VCC falling at 10mV/µs from (VTH + 100mV)
to (VTH - 100mV) 50 µs
MAX64_ _ _ _ _ _ _ D3 150 225 300
VCC to RESET Timeout Period tRP MAX64_ _ _ _ _ _ _ D7 1200 1800 2400 ms
VIL 0.3 x VCC
MR Input Voltage VIH 0.7 x VCC
V
MR Minimum Pulse Width tMPW 1µs
MR Glitch Rejection 100 ns
MR to RESET Delay 200 ns
MR Reset Timeout Period tMRP 150 225 300 ms
MR Pullup Resistance MR to VCC 750 1500 2250 Ω
MR Rising Debounce Period tDEB (Note 3) 150 225 300 ms
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 1.2V to 5.5V, VCC = 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise specified. Typical values are at TA= +25°C.) (Note1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VCC ≥ 1.53V, ISOURCE = 100µA, RESET
deasserted 0.8 x VCC
RESET Output High
(Push-Pull) VOH VCC ≥ 2.55V, ISOURCE = 500µA, RESET
deasserted 0.8 x VCC
V
VCC ≥ 1.0V, ISINK = 50µA, RESET asserted 0.3
VCC ≥ 1.2V, ISINK = 100µA, RESET asserted 0.3
RESET Output Low VOL VCC ≥ 2.12V, ISINK = 1.2mA, RESET
asserted 0.3
V
RESET Output Leakage Current
(Open Drain) RESET deasserted 500 nA
Typical Operating Characteristics
(VBATT = 1.2V to 5.5V, VCC = 1.2V to 5.5V, unless otherwise specified. Typical values are at TA= +25°C.)
SUPPLY CURRENT vs. TEMPERATURE
VCC = 3.3V, VBATT = 3.6V
MAX6439 toc01
TEMPERATURE (°C)
TOTAL
IBATT
SUPPLY CURRENT (µA)
6040200-20
1
2
3
4
0
-40 80
ICC
NORMALIZED LBO TIMEOUT PERIOD
vs. TEMPERATURE
MAX6439 toc02
TEMPERATURE (°C)
NORMALIZED LBO TIMEOUT PERIOD
6040200-20
0.95
1.00
1.05
1.10
0.90
-40 80
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX6439 toc03
TEMPERATURE (°C)
NORMALIZED RESET TIMEOUT PERIOD
6040200-20
0.990
0.985
1.000
0.995
1.005
1.010
1.015
0.980
-40 80
Note 1: Production testing done at TA= +25°C; limits over temperature guaranteed by design only.
Note 2: The device is powered up by the highest voltage between VBATT and VCC.
Note 3: MR input ignores falling input pulses, which occur within the MR debounce period (tDEB) after a valid MR reset assertion.
This prevents invalid reset assertion due to switch bounce.
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VBATT = 1.2V to 5.5V, VCC = 1.2V to 5.5V, unless otherwise specified. Typical values are at TA= +25°C.)
120
110
100
90
80
70
60
10 100 1000
MAXIMUM VBATT TRANSIENT DURATION
vs. LTH THRESHOLD OVERDRIVE
MAX6439 toc04
LTH THRESHOLD OVERDRIVE (mV)
MAXIMUM VBATT TRANSIENT DURATION (µs)
LBO ASSERTS ABOVE
THIS LINE
60
55
50
45
40
35
30
25
20
10 100 1000
MAXIMUM VCC TRANSIENT DURATION
vs. VTH THRESHOLD OVERDRIVE
MAX6439 toc05
VTH THRESHOLD OVERDRIVE (mV)
MAXIMUM VCC TRANSIENT DURATION (µs)
RESET ASSERTS ABOVE
THIS LINE
NORMALIZED UPPER (HTH) AND LOWER
(LTH) TRIP VOLTAGES vs. TEMPERATURE
MAX6439 toc06
TEMPERATURE (°C)
NORMALIZED TRIP VOLTAGES
6040200-20
0.975
1.000
1.025
1.050
0.950
-40 80
LOWER TRIP VOLTAGE
UPPER TRIP VOLTAGE
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAX6439 toc07
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
6040200-20
0.975
1.000
1.025
1.050
0.950
-40 80
LBO OUTPUT vs. SINK CURRENT
VCC = 3.3V, VBATT = 2.1V
MAX6439 toc08
ISINK (mA)
LBO OUTPUT (mV)
8642
20
40
60
80
100
120
0
010
LBO ASSERTED
RESET OUTPUT vs. SINK CURRENT
VCC = 2.1V, VBATT = 3.6V
MAX6439 toc09
ISINK (mA)
RESET OUTPUT (mV)
8642
20
40
60
80
100
120
140
0
010
RESET ASSERTED
RESET OUTPUT vs. SOURCE CURRENT
VCC = 3.3V, VBATT = 3.6V
MAX6439 toc10
ISOURCE (mA)
RESET OUTPUT (V)
3.02.52.01.51.00.5
2.75
3.00
3.25
3.50
2.50
0 3.5
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 VBATT is greater than VCC.
23MR
Manual Reset Input, Active-Low, Internal 1.5kΩ Pullup to VCC. Pull low to assert a one-shot
edge-triggered RESET output for the MR reset timeout period. Leave unconnected or
connect to VCC 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 VBATT drops below the
LTH specification and remains asserted until VBATT 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 VCC input drops below the selected reset threshold and remains low for the VCC reset
timeout period after VCC 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 VCC. RESET is guaranteed to
be in the correct logic state for VBATT or VCC > 1.0V.
5 2 GND Ground
68V
CC VCC Voltage Input. Input for VCC reset threshold monitor and device power supply if VCC is
greater than VBATT.
—6LBOH
Low-Battery Output High, Active Low, Open Drain. LBOH is asserted when VBATT drops
below the HTH- specification. LBOH is deasserted when VBATT rises above the HTH+
specification for at least 150ms.
—7LBOL
Low-Battery Output Low, Active Low, Open Drain. LBOL is asserted when VBATT drops
below the LTH- specification. LBOL is deasserted when VBATT rises above the LTH+
specification for at least 150ms.
—4LBOLH
Low-Battery Output Low/High, Active Low, Open Drain. LBOLH is asserted when VBATT
drops below the LTH- specification. LBOLH is deasserted when VBATT rises above the
HTH+ specification for at least 150ms.
MAX6439–MAX6442
has stabilized before power-converter or microproces-
sor activity is enabled.
These devices also have an independent µP supervisor
that monitors VCC and provides an active-low reset out-
put. A manual reset function is available to allow the
user to reset the µP with a push-button.
Low-Battery Output
The low-battery outputs are available in active-low
(LBO, LBOL, LBOH, LBOLH), open-drain configura-
tions. The low-battery outputs can be pulled to a volt-
age independent of VCC or VBATT, up to 5.5V. This
allows the device to monitor and operate from direct
battery voltage while interfacing to higher voltage
microprocessors.
The MAX6439/MAX6440 single-output voltage monitors
provide a single low-battery output, LBO. These fixed-
threshold devices assert LBO when VBATT drops below
VLTH and remain asserted for at least 150ms after
VBATT rises above VHTH (see Figure 2). The MAX6441/
MAX6442 triple-output voltage monitors provide three
low-battery outputs: LBOH, LBOL, and LBOLH. LBOH
asserts when VBATT drops below VHTH- and remains
asserted for at least 150ms after VBATT rises above
VHTH+. LBOL asserts when VBATT drops below VLTH-
and remains asserted for at least 150ms after VBATT
rises above VLTH+. LBOLH asserts when VBATT drops
below VLTH- and remains asserted for at least 150ms
after VBATT rises above VHTH+ (see Figure 3). For fast-
rising VBATT input, the LBOL timeout period must com-
plete before the LBOH/LBOLH timeout period begins.
Reset Output
The MAX6439–MAX6442 provide an active-low reset
output (RESET). RESET is asserted when the voltage at
VCC falls below the reset threshold level. Reset remains
asserted for the reset timeout period after VCC exceeds
the threshold. If VCC goes below the reset threshold
before the reset timeout period is completed, the inter-
nal timer restarts. The MAX6439/MAX6441 have open-
drain reset outputs, while the MAX6440/MAX6442 have
push-pull reset outputs (see Figure 4).
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
8 _______________________________________________________________________________________
5%
HYST
LTH
DETECT
VTH
DETECT
5%
HYST
HTH
DETECT
VBATT
VCC 1.23V
LBO
TIMEOUT
PERIOD
RESET
TIMEOUT
PERIOD
VCC
LBOL
LBOH
LBOLH
RESET
MR
MAX6441
Figure 1b. Functional Diagram
MAX6440
LTH
DETECT
HTH
DETECT
R
S
Q
LBO TIMEOUT
PERIOD
RESET
TIMEOUT
PERIOD
VTH
DETECT
VCC
VCC
VBATT
LBO
RESET
VCC
1.23V
Q
MR
Figure 1a. Functional Diagram
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
_______________________________________________________________________________________ 9
LBO
LTH
HTH
VBATT
tLBOP tLBOD tLBOP
Figure 2. Single Low-Battery Output Timing
MR
GND
RESET tRP tMRP
GND
tMRP
tDEB
tMPW tMPW
tDEB
SWITCH
BOUNCE
SWITCH
BOUNCE
SWITCH
BOUNCE
SWITCH
BOUNCE
VTH
VCC
GND
Figure 4.
RESET
Timing Diagram
LBOL
LBOH
LTH-
LTH+
HTH-
HTH+ VBATT
tLBOP
tLBOP
tD
tLBOP
tLBOP
LBOLH
tD
Figure 3. Dual Low-Battery Output Timing
MAX6439–MAX6442
Manual Reset
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 1.5kΩpullup resistor to VCC and can be left
unconnected if not used. MR can be driven with CMOS-
logic levels, open-drain/open-collector outputs, or a
momentary push-button switch to GND (the MR function
is internally debounced for the tDEB timeout period) to
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
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 VBATT is near the low-bat-
tery threshold. This is especially important for applica-
tions where the load on the battery creates significant
fluctuations in battery voltages (see Figure 5).
Applications Information
Li+ Battery Charger Application
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).
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
10 ______________________________________________________________________________________
VBATT
LBO
tLBOP
VHTH
VLTH
VHYST
HTH = BATTERY VOLTAGE GOOD, ENABLE OPERATION.
LTH = BATTERY VOLTAGE LOW, SUSPEND/DISABLE OPERATION.
Figure 5. Hysteresis
BATT
GND
1-CELL
Li+
BATTERY
THERM ADJ
GATE
PULSE-WIDTH
SELECT INPUT
CHG
LED
THERMISTOR
IN
MAX1879 MAX6441
MAX6442
TSEL
GND
LBOL
LBOLH
RESET
LBOH
VBATT VCC
CURRENT-
LIMITED
AC WALL
ADAPTER IN
OUT
SHDN
DC/DC CONVERTER
Figure 6. Li+ Charger Application (Using MAX1879)
DC/DC
SHDN
MR
VBATT
RESET
MAX6441
MAX6442
NMI
RESET
µP
VCC
GND GND
VCC
Li+
3.6V
LBOL
LBOH
OUT
IN
Figure 7. DC-to-DC Converter Application
DC-to-DC Converter Application
The MAX6441/MAX6442 triple-output battery monitors
can be used in conjunction with a DC-to-DC converter
to power microprocessor systems using a single Li+
cell or two to three alkaline/NiCd/NiMH cells. The LBOH
output indicates that the battery voltage is weak, and is
used to warn the microprocessor of potential problems.
Armed with this information, the microprocessor can
reduce system power consumption. The LBOL output
indicates the battery is empty, and system power
should be disabled. By connecting LBOL to the SHDN
pin of the DC-to-DC converter, power to the microproces-
sor is removed. Microprocessor power does not return
until the battery has recharged to a voltage greater than
VLTH+ (see Figure 7).
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
______________________________________________________________________________________ 11
UPPER THRESHOLD (HTH)
VOLTAGES 3.3V 3.4V 3.5V 3.6V
2.6V AG AH AI AJ
2.7V BG BH BI BJ
2.8V CG CH CI CJ
2.9V DG DH DI DJ
3.0V EG EH EI EJ
LOWER
THRESHOLD
(LTH)
3.1V FG FH FI FJ
Table 1. Factory-Trimmed Lower and Upper Threshold Combinations for Single-Cell Li+
or Three-Cell Alkaline/NiCd/NiMH Applications
UPPER THRESHOLD (HTH)
VOLTAGES 2.3V 2.4V 2.5V 2.6V
1.6V KQ KR KS KT
1.7V LQ LR LS LT
1.8V MQ MR MS MT
1.9V NQ NR NS NT
2.0V OQ OR OS OT
LOWER
THRESHOLD
(LTH)
2.1V PQ PR PS PT
Table 2. Factory-Trimmed Lower and Upper Threshold Combinations for Two-Cell
Alkaline/NiCd/NiMH Applications
PART NO.
SUFFIX
( _ )
VCC NOMINAL
RESET
THRESHOLD (V)
T 3.075
S 2.925
R 2.625
Z 2.313
Y 2.188
W 1.665
V 1.575
Table 3. Factory-Trimmed VCC Reset
Threshold Levels
ACTIVE TIMEOUT PERIOD (ms)
TIMEOUT
PERIOD SUFFIX MIN MAX
D3 150 300
D7 1200 2400
Table 4. VCC Reset Timeout Period Suffix
Guide
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
12 ______________________________________________________________________________________
PART OPEN-DRAIN
RESET PUSH-PULL RESET SINGLE LOW-
BATTERY OUTPUT
DUAL LOW-BATTERY
OUTPUT
MAX6439 X —X—
MAX6440 —XX—
MAX6441 X —— X
MAX6442 —X—X
Selector Guide
PART TOP MARK
MAX6439UTDHRD3 ABMN
MAX6439UTDHSD3 ABMO
MAX6439UTEHRD3 ABMP
MAX6439UTEHSD3 ABMQ
MAX6439UTEIRD3 ABMR
MAX6439UTEISD3 ABMS
MAX6440UTDHRD3 ABMT
MAX6440UTDHSD3 ABMU
MAX6440UTEHRD3 ABMV
MAX6440UTEHSD3 ABMW
MAX6440UTEIRD3 ABMX
MAX6440UTEISD3 ABMY
MAX6441KADHRD3 AEEI
MAX6441KADHSD3 AEEJ
MAX6441KAEHRD3 AEEK
MAX6441KAEHSD3 AEEL
MAX6441KAEIRD3 AEEM
MAX6441KAEISD3 AEEN
MAX6442KADHRD3 AEEO
MAX6442KADHSD3 AEEP
MAX6442KAEHRD3 AEEQ
MAX6442KAEHSD3 AEER
MAX6442KAEIRD3 AEES
MAX6442KAEISD3 AEET
Standard Versions Table
Chip Information
TRANSISTOR COUNT: 1478
PROCESS: BiCMOS
DC/DC
MR
VBATT
MAX6439
MAX6440
NMI
RESET
µP
VCC
Li+
3.6V
RESET
LBO
VCC
GND GND
Typical Application Circuit
LBOH
RESETLBOLH
1
2
8
7LBOLGND
MR
VBATT
SOT23-8
TOP VIEW
3
4
6
5
MAX6441
MAX6442
VCC
Pin Configurations (continued)
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
______________________________________________________________________________________ 13
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
6LSOT.EPS
MAX6439–MAX6442
Low-Power, Single-/Dual-Level Battery Monitors
with Hysteresis and Integrated µP Reset
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
SOT23, 8L.EPS
