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19-2947; Rev 1; 11/05
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
General Description
The MAX6846–MAX6849 are a family of ultra-low-power
battery monitors with integrated microprocessor (µP)
supervisors. The user-adjustable battery monitors are
offered with single 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 system operation), and when the battery is dead
(to disable system operation). These devices also have
an independent µP supervisor that monitors V
CC
and
provides an active-low reset output. A manual reset
function is available to reset the µP with a pushbutton.
The MAX6846–MAX6849 are ideal for single-cell lithium-
ion (Li+) or multicell alkaline/NiCd/NiMH applications.
When the battery voltage drops below each adjusted low
threshold, the low-battery outputs are asserted to alert
the system. When the voltage rises above the adjusted
high thresholds, the outputs are deasserted after a
150ms minimum timeout period, ensuring the voltages
have stabilized before power circuitry is activated or pro-
viding microprocessor reset timing.
These devices have user-adjustable battery threshold
voltages, providing a wide hysteresis range to prevent
chattering that can result due to battery recovery after
load removal. Single low-battery outputs are supplied
by the MAX6846/MAX6847 and dual low-battery out-
puts are supplied by the MAX6848/MAX6849. All bat-
tery monitors have open-drain low-battery outputs.
The MAX6846–MAX6849 monitor system voltages
(V
CC
) 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 MAX6846/
MAX6848 are offered with an open-drain
RESET
output
and the MAX6847/MAX6849 are offered with a push-
pull
RESET
output.
The MAX6846–MAX6849 are offered in a SOT23 pack-
age and are fully specified over a -40°C to +85°C temp-
erature range.
Features
♦
User-Adjustable Thresholds for Monitoring
Single-Cell Li+ or Multicell Alkaline/NiCd/NiMH
Applications
♦
Single and Dual Low-Battery Output Options
♦
Independent µP Reset with Manual Reset
♦
Factory-Set Reset Thresholds for Monitoring 1.8V
to 3.3V Systems
♦
Available with 150ms (min) or 1.2s (min) V
CC
Reset Timeout Period Options
♦
150ms (min)
LBO
Timeout Period
♦
Immune to Short-Battery Voltage Transients
♦
Low Current (2.5µA, typ at 3.6V)
♦
-40°C to +85°C Operating Temperature Range
♦
Small 8-Pin SOT23 Packages
MAX6846–MAX6849
Ordering Information
PART
MAX6846KA_D_-T
MAX6847KA_D_-T
MAX6848KA_D_-T
MAX6849KA_D_-T
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 SOT23-8
8 SOT23-8
8 SOT23-8
8 SOT23-8
Note:
The first “_” is the V
CC
reset threshold level, suffix found
in Table 1. The “_” after the D is a placeholder for the reset
timeout period suffix found in Table 2. All devices are available
in tape-and-reel only. There is a 2500 piece minimum order
increment for standard versions (see Standard Versions table).
Sample stock is typically held on standard versions only. Non-
standard versions require a minimum order increment of
10,000 pieces. Contact factory for availability.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Applications
Battery-Powered Systems (Single-Cell Li+ or
Multicell NiMH, NiCd, Alkaline)
Cell Phones/Cordless Phones
Portable Medical Devices
Digital Cameras
Pagers
PDAs
MP3 Players
Electronic Toys
TOP VIEW
Pin Configurations
V
DD
GND
LTHIN
1
2
3
8
7
V
CC
HTHIN
MR
RESET
V
DD
GND
LTHIN
1
2
3
8
7
V
CC
HTHIN
LBOH
RESET
MAX6846
MAX6847
6
5
MAX6848
MAX6849
6
5
LBO
4
LBOL
4
SOT23
SOT23
________________________________________________________________
Maxim Integrated Products
1
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.
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
MAX6846–MAX6849
ABSOLUTE MAXIMUM RATINGS
V
DD
, V
CC
to GND ....................................................-0.3V to +6V*
Open-Drain
LBO, LBOH, LBOL
to GND .................-0.3V to +6V*
Open-Drain
RESET
to GND ....................................-0.3V to +6V*
Push-Pull
RESET
to GND............................-0.3V to (V
CC
+ 0.3V)
HTHIN, LTHIN to GND................................-0.3V to (V
DD
+ 0.3V)
MR
to GND .................................................-0.3V to (V
CC
+ 0.3V)
Input/Output Current, All Pins .............................................20mA
*Applying
7V for a duration of 1ms does not damage the device.
Continuous Power Dissipation (T
A
= +70°C)
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
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.
ELECTRICAL CHARACTERISTICS
(V
DD
= 1.6V to 5.5V, V
CC
= 1.2V to 5.5V, T
A
= -40°C to +85°C, unless otherwise specified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
V
DD
Operating Voltage Range
V
CC
Operating Voltage Range
V
CC
+ V
DD
Supply Current
SYMBOL
V
DD
V
CC
I
CC
+ I
DD
T
A
= 0°C to +85°C
T
A
= -40°C to +85°C
V
DD
= 3.6V, V
CC
= 3.3V, no load (Note 2)
HTHIN rising,
LBO
is deasserted when
HTHIN rises above V
HTH
LTHIN falling,
LBO
is asserted when LTHIN
falls below V
LTH
HTHIN rising,
LBOH
is deasserted when
HTHIN rises above V
HTH+
HTHIN falling,
LBOH
is asserted when
HTHIN falls below V
HTH-
LTHIN rising,
LBOL
is deasserted when
LTHIN rises above V
LTH+
LTHIN falling,
LBOL
is asserted when
LTHIN falls below V
LTH-
V
HTHIN
or V
LTHIN
≥
400mV
HTHIN/LTHIN rising above threshold
HTHIN/LTHIN falling below threshold
(V
DD
or V
CC
)
≥
1.2V, I
SINK
= 50µA, asserted
low
(V
DD
or V
CC
)
≥
1.6V, I
SINK
= 100µA,
asserted low
V
OL
(V
DD
or V
CC
)
≥
2.7V, I
SINK
= 1.2mA,
asserted low
(V
DD
or V
CC
)
≥
4.5V, I
SINK
= 3.2mA,
asserted low
150
225
100
0.3
0.3
V
0.3
0.3
CONDITIONS
MIN
1.6
1.0
1.2
2.5
TYP
MAX
5.5
5.5
5.5
7
UNITS
V
V
µA
MAX6846/MAX6847 V
DD
THRESHOLDS
HTHIN Threshold
LTHIN Threshold
V
HTH
V
LTH
600
600
615
615
630
630
mV
mV
MAX6848/MAX6849 V
DD
THRESHOLDS
HTHIN+ Threshold
HTHIN- Threshold
LTHIN+ Threshold
LTHIN- Threshold
MAX6846–MAX6849
HTHIN/LTHIN Leakage Current
LBO
,
LBOL, LBOH
Timeout Period
LBO, LBOL, LBOH
Delay Time
I
LKG
t
LBOP
t
LBOD
20
300
nA
ms
µs
V
HTH+
V
HTH-
V
LTH+
V
LTH-
600
567
600
567
615
582
615
582
630
597
630
597
mV
mV
mV
mV
LBO, LBOL, LBOH
Output Low
2
_______________________________________________________________________________________
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 1.6V to 5.5V, V
CC
= 1.2V to 5.5V, T
A
= -40°C to +85°C, unless otherwise specified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
LBO, LBOL, LBOH
Output
Open-Drain Leakage Current
SYMBOL
CONDITIONS
Output deasserted
MAX68_ _ _ _ T
MAX68_ _ _ _ S
MAX68_ _ _ _ R
V
CC
Reset Threshold
V
TH
MAX68_ _ _ _ Z
MAX68_ _ _ _ Y
MAX68_ _ _ _ W
MAX68_ _ _ _ V
V
CC
Reset Hysteresis
V
CC
to
RESET
Delay
V
CC
to
RESET
Timeout Period
MR
Input Voltage
MR
Minimum Pulse Width
MR
Glitch Rejection
MR
to
RESET
Delay
MR
Reset Timeout Period
MR
Pullup Resistance
MR
Rising Debounce Period
RESET
Output High
(Push-Pull)
t
DEB
t
MRP
MR
to V
CC
(Note 3)
V
CC
≥
1.53V, I
SOURCE
= 100µA,
RESET
deasserted
V
OH
V
CC
≥
2.55V, I
SOURCE
= 500µA,
RESET
deasserted
V
CC
≥
1.0V, I
SINK
= 50µA,
RESET
asserted
RESET
Output Low
V
OL
V
CC
≥
1.2V, I
SINK
= 100µA,
RESET
asserted
V
CC
≥
2.12V, I
SINK
= 1.2mA,
RESET
asserted
RESET
deasserted
150
750
150
0.8 x V
CC
V
0.8 x V
CC
0.3
0.3
0.3
500
nA
V
t
RD
t
RP
V
IL
V
IH
t
MPW
0.7 x V
CC
1
100
200
225
1500
225
300
2250
300
V
CC
falling at 10mV/µs from (V
TH
+ 100mV)
to (V
TH
- 100mV)
MAX68_ _ _ _ _ D3
MAX68_ _ _ _ _ D7
150
1200
3.000
2.850
2.550
2.250
2.125
1.620
1.530
3.075
2.925
2.625
2.313
2.188
1.665
1.575
0.3
50
225
1800
300
2400
0.3 x V
CC
MIN
TYP
MAX
500
3.150
3.000
2.700
2.375
2.250
1.710
1.620
%
µs
ms
V
µs
ns
ns
ms
Ω
ms
V
UNITS
nA
MAX6846–MAX6849
RESET
Output Leakage Current
(Open Drain)
Note 1:
Production testing done at T
A
= +25°C; limits over temperature guaranteed by design only.
Note 2:
The device is powered up by the highest voltage between V
DD
and V
CC
.
Note 3:
MR
input ignores falling input pulses, which occur within the
MR
debounce period (t
DEB
) after a valid
MR
reset assertion.
This prevents invalid reset assertion due to switch bounce.
_______________________________________________________________________________________
3
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
MAX6846–MAX6849
Typical Operating Characteristics
(V
DD
= 3.6V, V
CC
= 3.3V, unless otherwise specified. Typical values are at T
A
= +25°C.)
SUPPLY CURRENT
vs. TEMPERATURE
MAX6846-49 toc01
NORMALIZED LBO TIMEOUT PERIOD
vs. TEMPERATURE
MAX6846-49 toc02
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED RESET TIMEOUT PERIOD
MAX6846-49 toc03
4
V
CC
= 3.3V, V
DD
= 3.6V
3
TOTAL
2
1.10
NORMALIZED LBO TIMEOUT PERIOD
1.100
SUPPLY CURRENT (µA)
1.05
1.050
I
DD
I
CC
1.00
1.000
1
0.95
0.950
0
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
0.90
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
0.900
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
MAXIMUM V
LTH
/V
HTH
TRANSIENT DURATION
vs. THRESHOLD OVERDRIVE
MAXIMUM V
LTH
/V
HTH
TRANSIENT DURATION (µs)
MAX6846-49 toc04
MAXIMUM V
CC
TRANSIENT DURATION
vs. THRESHOLD OVERDRIVE
MAXIMUM V
CC
TRANSIENT DURATION (µs)
90
80
70
60
50
40
30
20
10
100
THRESHOLD OVERDRIVE (mV)
1000
RESET OCCURS ABOVE THIS LINE
MAX6846-49 toc05
120
110
LBO ASSERTS ABOVE THIS LINE
100
90
80
70
60
10
100
THRESHOLD OVERDRIVE (mV)
100
1000
4
_______________________________________________________________________________________
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