MAX6849KAYD3+T [MAXIM]
Power Supply Support Circuit, Adjustable, 1 Channel, +2.188VV, BICMOS, PDSO8, LEAD FREE, MO-178, SOT-23, 8 PIN;
| 型号： | MAX6849KAYD3+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Power Supply Support Circuit, Adjustable, 1 Channel, +2.188VV, BICMOS, PDSO8, LEAD FREE, MO-178, SOT-23, 8 PIN 信息通信管理 光电二极管 |
| 文件： | 总12页 (文件大小：251K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2947; Rev 1; 11/05
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
General Description
Features
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
♦ 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
an independent µP supervisor that monitors V
and
to 3.3V Systems
CC
provides an active-low reset output. A manual reset
function is available to reset the µP with a pushbutton.
♦ Available with 150ms (min) or 1.2s (min) V
CC
Reset Timeout Period Options
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.
♦ 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
Ordering Information
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.
PART
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
MAX6846KA_D_-T
MAX6847KA_D_-T
MAX6848KA_D_-T
MAX6849KA_D_-T
Note: The first “_” is the V
The MAX6846–MAX6849 monitor system voltages
(V ) from 1.8V to 3.3V with seven fixed reset threshold
CC
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.
reset threshold level, suffix found
CC
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.
The MAX6846–MAX6849 are offered in a SOT23 pack-
age and are fully specified over a -40°C to +85°C temp-
erature range.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Applications
Pin Configurations
Battery-Powered Systems (Single-Cell Li+ or
Multicell NiMH, NiCd, Alkaline)
TOP VIEW
Cell Phones/Cordless Phones
Portable Medical Devices
Digital Cameras
Pagers
V
1
2
3
4
8
7
6
5
V
V
1
2
3
4
8
7
6
5
V
CC
DD
CC
DD
GND
LTHIN
LBO
HTHIN
MR
GND
LTHIN
LBOL
HTHIN
LBOH
RESET
MAX6846
MAX6847
MAX6848
MAX6849
PDAs
RESET
MP3 Players
SOT23
SOT23
Electronic Toys
________________________________________________________________ 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
ABSOLUTE MAXIMUM RATINGS
DD CC
V
, V
to GND....................................................-0.3V to +6V*
Continuous Power Dissipation (T = +70°C)
A
Open-Drain LBO, LBOH, LBOL to GND .................-0.3V to +6V*
Open-Drain RESET to GND ....................................-0.3V to +6V*
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
Push-Pull RESET to GND............................-0.3V to (V
HTHIN, LTHIN to GND................................-0.3V to (V
MR to GND .................................................-0.3V to (V
+ 0.3V)
+ 0.3V)
+ 0.3V)
CC
DD
CC
Input/Output Current, All Pins .............................................20mA
*Applying 7V for a duration of 1ms does not damage the device.
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 = 1.6V to 5.5V, V = 1.2V to 5.5V, T = -40°C to +85°C, unless otherwise specified. Typical values are at T = +25°C.) (Note 1)
DD
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
1.6
1.0
1.2
TYP
MAX
5.5
5.5
5.5
7
UNITS
V
Operating Voltage Range
V
V
DD
CC
CC
DD
T
T
= 0°C to +85°C
A
V
Operating Voltage Range
V
V
CC
= -40°C to +85°C
= 3.6V, V = 3.3V, no load (Note 2)
A
V
+ V
Supply Current
I
+ I
V
2.5
µA
DD
CC
DD
DD
CC
MAX6846/MAX6847 V
THRESHOLDS
DD
HTHIN rising, LBO is deasserted when
HTHIN rises above V
HTHIN Threshold
V
600
600
615
615
630
630
mV
mV
HTH
HTH
LTHIN falling, LBO is asserted when LTHIN
falls below V
LTHIN Threshold
V
LTH
LTH
MAX6848/MAX6849 V
HTHIN+ Threshold
THRESHOLDS
DD
HTHIN rising, LBOH is deasserted when
HTHIN rises above V
V
600
567
600
567
615
582
615
582
630
597
630
597
mV
mV
mV
mV
HTH+
HTH+
HTHIN falling, LBOH is asserted when
HTHIN falls below V
HTHIN- Threshold
LTHIN+ Threshold
V
HTH-
LTH+
HTH-
LTHIN rising, LBOL is deasserted when
LTHIN rises above V
V
LTH+
LTHIN falling, LBOL is asserted when
LTHIN falls below V
LTHIN- Threshold
V
LTH-
LTH-
MAX6846–MAX6849
HTHIN/LTHIN Leakage Current
LBO , LBO L, LBO H Timeout Period
LBO, LBOL, LBOH Delay Time
I
V
or V
≥ 400mV
LTHIN
20
nA
ms
µs
LKG
HTHIN
t
HTHIN/LTHIN rising above threshold
HTHIN/LTHIN falling below threshold
150
225
100
300
LBOP
LBOD
t
(V
low
or V ) ≥ 1.2V, I
= 50µA, asserted
DD
CC
SINK
SINK
SINK
SINK
0.3
0.3
0.3
0.3
(V
DD
or V ) ≥ 1.6V, I
= 100µA,
CC
asserted low
LBO, LBOL, LBOH Output Low
V
V
OL
(V or V ) ≥ 2.7V, I
= 1.2mA,
DD
CC
asserted low
(V or V ) ≥ 4.5V, I
= 3.2mA,
DD
CC
asserted low
2
_______________________________________________________________________________________
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
ELECTRICAL CHARACTERISTICS (continued)
(V = 1.6V to 5.5V, V = 1.2V to 5.5V, T = -40°C to +85°C, unless otherwise specified. Typical values are at T = +25°C.) (Note 1)
DD
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
LBO, LBOL, LBOH Output
Open-Drain Leakage Current
Output deasserted
500
nA
MAX68_ _ _ _ T
MAX68_ _ _ _ S
MAX68_ _ _ _ R
MAX68_ _ _ _ Z
MAX68_ _ _ _ Y
MAX68_ _ _ _ W
MAX68_ _ _ _ V
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
3.150
3.000
2.700
2.375
2.250
1.710
1.620
V
Reset Threshold
V
V
CC
TH
V
V
Reset Hysteresis
%
CC
CC
V
falling at 10mV/µs from (V + 100mV)
TH
CC
to RESET Delay
t
50
µs
RD
to (V - 100mV)
TH
MAX68_ _ _ _ _ D3
MAX68_ _ _ _ _ D7
150
225
300
V
to RESET Timeout Period
t
ms
V
CC
RP
1200
1800
2400
V
0.3 x V
CC
IL
MR Input Voltage
V
0.7 x V
1
IH
CC
MR Minimum Pulse Width
MR Glitch Rejection
t
µs
ns
ns
ms
Ω
MPW
100
200
225
1500
225
MR to RESET Delay
MR Reset Timeout Period
MR Pullup Resistance
MR Rising Debounce Period
t
150
750
150
300
2250
300
MRP
MR to V
CC
t
(Note 3)
ms
DEB
V
≥ 1.53V, I
= 100µA, RESET
= 500µA, RESET
CC
SOURCE
SOURCE
0.8 x V
0.8 x V
CC
CC
deasserted
RESET Output High
(Push-Pull)
V
V
OH
V
≥ 2.55V, I
CC
deasserted
V
V
V
≥ 1.0V, I
≥ 1.2V, I
= 50µA, RESET asserted
= 100µA, RESET asserted
0.3
0.3
CC
CC
SINK
SINK
RESET Output Low
V
V
OL
≥ 2.12V, I
= 1.2mA, RESET
CC
SINK
0.3
asserted
RESET Output Leakage Current
(Open Drain)
RESET deasserted
500
nA
Note 1: Production testing done at T = +25°C; limits over temperature guaranteed by design only.
A
Note 2: The device is powered up by the highest voltage between V
and V
.
DD
CC
Note 3: MR input ignores falling input pulses, which occur within the MR debounce period (t
) after a valid MR reset assertion.
DEB
This prevents invalid reset assertion due to switch bounce.
_______________________________________________________________________________________
3
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
Typical Operating Characteristics
(V
= 3.6V, V
= 3.3V, unless otherwise specified. Typical values are at T = +25°C.)
CC A
DD
SUPPLY CURRENT
vs. TEMPERATURE
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED LBO TIMEOUT PERIOD
vs. TEMPERATURE
4
1.100
1.050
1.000
0.950
0.900
1.10
1.05
1.00
0.95
0.90
V
= 3.3V, V = 3.6V
DD
CC
3
2
1
0
TOTAL
DD
I
I
CC
-40 -20
0
20
40
60
80
-40 -20
0
20
40
60
80
-40 -20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAXIMUM V /V
TRANSIENT DURATION
MAXIMUM V TRANSIENT DURATION
CC
LTH HTH
vs. THRESHOLD OVERDRIVE
vs. THRESHOLD OVERDRIVE
120
110
100
90
100
90
80
70
60
50
40
30
20
LBO ASSERTS ABOVE THIS LINE
RESET OCCURS ABOVE THIS LINE
80
70
60
10
100
1000
10
100
1000
THRESHOLD OVERDRIVE (mV)
THRESHOLD OVERDRIVE (mV)
4
_______________________________________________________________________________________
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
Typical Operating Characteristics (continued)
(V
= 3.6V, V
= 3.3V, unless otherwise specified. Typical values are at T = +25°C.)
CC A
DD
NORMALIZED UPPER AND LOWER LBO TRIP
VOLTAGES vs. TEMPERATURE
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
LBO OUTPUT
vs. SINK CURRENT
1.050
1.025
1.000
0.975
0.950
1.050
1.025
1.000
0.975
0.950
120
100
80
60
40
20
0
V
= V = 3.3V
DD
CC
-40 -20
0
20
40
60
80
-40 -20
0
20
40
60
80
0
2
4
I
6
8
10
TEMPERATURE (°C)
TEMPERATURE (°C)
(mA)
SINK
RESET OUTPUT
vs. SINK CURRENT
RESET OUTPUT
vs. SOURCE CURRENT
140
120
100
80
3.50
V
= 2.1V, V = 3.6V
DD
CC
V
= 3.3V, V = 3.6V
DD
CC
3.25
3.00
2.75
2.50
60
40
20
0
0
2
4
6
8
10
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5
(mA)
I
(mA)
I
SOURCE
SINK
_______________________________________________________________________________________
5
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
Pin Description
PIN
NAME
FUNCTION
Supply. Device power supply if V is greater than V
MAX6846/MAX6847 MAX6848/MAX6849
1
2
1
2
V
V
.
CC
DD
DD
DD
GND
Ground
LTH Threshold Monitor Input. A resistor-divider network sets the low
threshold associated with LBOL and LBO.
3
3
LTHIN
Low-Battery Output, Active-Low, Open-Drain. LBO is asserted when LTHIN
4
—
LBO
drops below the V
specification and remains asserted until HTHIN rises
LTH
above the V
specification for at least 150ms.
HTH
Reset Output, Active-Low, Push-Pull, or Open-Drain. RESET goes from high
to low when the V input drops below the selected reset threshold and
CC
remains low for the V
reset timeout period after V
exceeds the reset
CC
CC
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 MAX6846/MAX6848, and a push-pull output for the
5
6
5
RESET
MAX6847/MAX6849. The push-pull outputs are referenced to V . RESET
CC
is guaranteed to be in the correct logic state for V
or V
≥ 10V.
CC
DD
Manual Reset Input, Active-Low, Internal 1.5kΩ Pullup to V . Pull MR low
CC
to assert a one-shot reset output pulse for the MR reset timeout period.
—
MR
Leave unconnected or connect to V
if unused. The MR input is
CC
debounced for MR rising edges to prevent false reset events.
HTH Threshold Monitor Input. A resistor-divider network sets the high
threshold associated with LBOH and LBO.
7
8
7
8
HTHIN
V
Voltage Input. Input for V
reset threshold monitor and device power
.
CC
CC
V
CC
supply if V
is greater than V
DD
CC
Low-Battery Output High, Active-Low, Open-Drain. LBOH is asserted when
—
—
6
4
LBOH HTHIN drops below the V
specification. LBOH is deasserted when
specification for at least 150ms.
HTH-
HTHIN rises above the V
HTH+
Low-Battery Output Low, Active-Low, Open-Drain. LBOL is asserted when
LTHIN drops below the V
specification. LBOL is deasserted when
LBOL
LTH-
LTHIN rises above the V
specification for at least 150ms.
LTH+
adjustable thresholds are ideal for monitoring single-
cell Li+ or multicell alkaline/NiCd/NiMH power supplies.
Detailed Description
The MAX6846–MAX6849 family is available with several
monitoring options. The MAX6846/MAX6847 have single
low-battery outputs and the MAX6848/MAX6849 have
dual low-battery outputs (see Figures 1a and 1b).
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
has stabilized before power-converter or microproces-
sor activity is enabled.
The MAX6846–MAX6849 combine a 615mV 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 MAX6848/MAX6849
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. User-
These devices also have an independent µP supervisor
that monitors V
and provides an active-low reset out-
CC
put. A manual reset function is available to allow the
user to reset the µP with a pushbutton.
6
_______________________________________________________________________________________
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
V
DD
V
DD
LTHIN
MAX6847
MAX6848
LTHIN
LTH
DETECT
LTH
DETECT
LBOL
LBOH
HTHIN
R
Q
Q
5%
HYST
HTHIN
S
LBO
TIMEOUT
PERIOD
LBO
HTH
DETECT
LBO TIMEOUT
PERIOD
HTH
DETECT
5%
HYST
615mV
615mV
V
CC
V
CC
V
CC
RESET
RESET
TIMEOUT
PERIOD
V
TH
DETECT
RESET
RESET
TIMEOUT
PERIOD
V
TH
DETECT
V
CC
1.23V
1.23V
MR
Figure 1a. MAX6847 Functional Diagram
Figure 1b. MAX6848 Functional Diagram
Low-Battery Output
The low-battery outputs are available in active-low
(LBO, LBOL, LBOH), open-drain configurations. The
low-battery outputs can be pulled to a voltage indepen-
rises above V
. LBOL asserts when LTHIN drops
HTH+
below V
and remains asserted for at least 150ms
LTH-
after LTHIN rises above V
(see Figure 3). For fast-
LTH+
rising V
input, the LBOL timeout period must com-
DD
dent of V
or V , up to 5.5V. This allows the device
DD
plete before the LBOH timeout period begins.
CC
to monitor and operate from direct battery voltage while
interfacing to higher voltage microprocessors.
Reset Output
The MAX6846–MAX6849 provide an active-low reset
The MAX6846/MAX6847 single-output voltage monitors
provide a single low-battery output, LBO. LBO asserts
output (RESET). RESET is asserted when the voltage at
V
falls below the reset threshold level. Reset remains
CC
when LTHIN drops below V
and remains asserted
LTH
asserted for the reset timeout period after V
exceeds
CC
for at least 150ms after HTHIN rises above V
(see
HTH
the threshold. If V
goes below the reset threshold
CC
Figure 2). The MAX6848/MAX6849 dual-output voltage
before the reset timeout period is completed, the inter-
nal timer restarts (see Figure 4). The MAX6846/
MAX6848 have open-drain reset outputs, while the
MAX6847/MAX6849 have push-pull reset outputs.
monitors provide two low-battery outputs: LBOH and
LBOL. LBOH asserts when HTHIN drops below V
HTH-
and remains asserted for at least 150ms after HTHIN
_______________________________________________________________________________________
7
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
V
MONITORED
HTHIN = 615mV
V
TRIPHIGH HTH
V
HYST
LTHIN = 615mV
V
TRIPLOW LTH
t
t
t
LBOP
LBOP
LBOD
LBO
= HYSTERESIS
V
HYST
Figure 2. Single Low-Battery Output Timing
V
MONITORED
HTHIN = 615mV
HTHIN = 582mV
(V
+5%) HTH+
HTH-
TRIPHIGH
V
V
= 5%
= 5%
HYST
V
TRIPHIGH
LTHIN = 615mV
LTHIN = 582mV
(V
+5%)
LTH+
LTH-
TRIPLOW
HYST
V
TRIPLOW
t
LBOD
LBOL
t
t
LBOP
LBOP
t
t
LBOP
LBOD
LBOH
= HYSTERESIS
t
LBOP
V
HYST
Figure 3. Dual Low-Battery Output Timing
V
CC
V
TH
GND
MR
SWITCH
BOUNCE
SWITCH
BOUNCE
SWITCH
BOUNCE
SWITCH
BOUNCE
GND
RESET
GND
t
t
t
RP
MRP
MRP
t
t
DEB
DEB
t
t
MPW
MPW
Figure 4. RESET Timing Diagram
8
_______________________________________________________________________________________
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
Manual Reset
Many microprocessor-based products require manual
LBO*
V
V
DD
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
DD
R1
MAX6846
MAX6847
MAX6848
MAX6849
LTHIN
HTHIN
(LBOH)
(LBOL)
an internal 1.5kΩ pullup resistor to V
and can be left
CC
R2
R3
unconnected if not used. MR can be driven with CMOS-
logic levels, open-drain/open-collector outputs, or a
momentary pushbutton switch to GND (the MR function
GND
is internally debounced for the t
timeout period) to
DEB
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).
* FOR THE MAX6846/MAX6847.
) FOR THE MAX6848/MAX6849.
(
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 monitor input is near the
low-battery threshold. This is especially important for
applications where the load on the battery creates sig-
nificant fluctuations in battery voltages (see Figures 2
and 3).
Figure 5. Adjustable Threshold Selection
2) Calculate R3 based on R
and the desired
TOTAL
upper trip point:
615mV × R
TOTAL
R3 =
V
TRIPHIGH
3) Calculate R2 based on R
lower trip point:
, R3, and the desired
For the MAX6846/MAX6847, hysteresis is set using three
external resistors (see Figure 5). The MAX6848/MAX6849
have dual, low-battery input levels. Each input level has a
5% (typ) hysteresis.
TOTAL
615mV × R
TOTAL
R2 =
- R3
V
TRIPLOW
Applications Information
4) Calculate R1 based on R
, R3, and R2:
TOTAL
Resistor-Value Selection (Programming
the Adjustable Thresholds)
R1 = R
- R2 - R3
TOTAL
MAX6846/MAX6847
MAX6848/MAX6849
V
= V
= 615mV
V
= V
= 582mV
LTH
HTH
LTH-
HTH-
LBOL low-trip level:
= V ×
LTH-
R1+ R2 + R3
R2 + R3
V
= V
×
×
TRIPLOW
LTH
R1+ R2 + R3
R2 + R3
V
R1 + R2 + R3
TRIPLOW
V
= V
HTH
TRIPHIGH
R3
LBOH low-trip level:
R
= R1+ R2 + R3
TOTAL
R1+ R2 + R3
Use the following steps to determine values for R1, R2,
and R3 of Figure 5.
V
R
= V
×
HTH-
TRIPHIGH
R3
1) Choose a value for R , the sum of R1, R2, and
TOTAL
= R1+ R2 + R3
TOTAL
R3. Because the MAX6846/MAX6847 have very high
input impedance, R can be up to 500kΩ.
TOTAL
Use the following steps to determine values for R1, R2,
and R3 of Figure 5.
_______________________________________________________________________________________
9
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
1) Choose a value for RTOTAL, the sum of R1, R2, and
R3. Because the MAX6848/MAX6849 have very high
input impedance, RTOTAL can be up to 500kΩ.
2) Calculate R3 based on RTOTAL and the desired
upper trip point:
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-DC converter, power to the microprocessor is
removed. Microprocessor power does not return until the
582mV × R
TOTAL
R3 =
V
TRIPHIGH
battery has recharged to a voltage greater than V
LTH+
3) Calculate R2 based on R
lower trip point:
, R3, and the desired
TOTAL
(see Figure 7).
Table 1. Factory-Trimmed V
Threshold Levels
Reset
CC
582mV × R
TOTAL
R2 =
- R3
V
TRIPLOW
PART NO.
SUFFIX
( _ )
V
NOMINAL
RESET
CC
4) Calculate R1 based on R
, R3, and R2:
TOTAL
THRESHOLD (V)
R1 = R
- R2 - R3
TOTAL
T
S
3.075
2.925
2.625
2.313
2.188
1.665
1.575
5) LBOL high-trip level:
R
Z
V
✕ 1.05
✕ 1.05
TRIPLOW
6) LBOH high-trip level:
Y
V
TRIPHIGH
W
V
Monitoring Multicell Battery Applications
For monitoring multicell Li+ (or a higher number of alka-
line/NiCd/NiMH cells), connect VDD to a supply voltage
between 1.6V to 5.5V. Figure 6 shows VDD connected
directly to VCC. To calculate the values of R1, R2, and
R3, see the Resistor-Value Selection section.
Table 2. V
Guide
Reset Timeout Period Suffix
CC
ACTIVE TIMEOUT PERIOD (ms)
TIMEOUT
PERIOD SUFFIX
DC-DC Converter Application
The MAX6848/MAX6849 dual battery monitors can be
used in conjunction with a DC-DC converter to power
microprocessor systems using a single Li+ cell or two
MIN
150
MAX
300
D3
D7
1200
2400
V
CC
IN
OUT
DC-DC
V
V
SHDN
DD
CC
V
Li+
3.6V
MONITORED
R1
LBO*
V
V
DD
LBOL
V
CC
CC
MAX6846
MAX6847
MAX6848
MAX6849
LBOH
NMI
LTHIN
HTHIN
(LBOL)
(LBOH)
GND
LTHIN
R2
R3
µP
MAX6848
MAX6849
RESET
RESET
HTHIN
GND
GND
* FOR THE MAX6846/MAX6847.
) FOR THE MAX6848/MAX6849.
(
Figure 6. Monitoring Multicell Li+ Applications
10 ______________________________________________________________________________________
Figure 7. DC-DC Converter Application
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
Selector Guide
OPEN-DRAIN
SINGLE LOW-
BATTERY OUTPUT
DUAL LOW-BATTERY
OUTPUT
PART
PUSH-PULL RESET
RESET
MAX6846
MAX6847
MAX6848
MAX6849
X
—
X
—
X
X
X
—
—
X
—
X
—
—
—
X
Typical Application Circuit
Standard Versions Table
PART
TOP MARK
AEJI
MAX6846KARD3
MAX6846KASD3
MAX6846KAWD3
MAX6846KAZD3
MAX6847KARD3
MAX6847KASD3
MAX6847KAWD3
MAX6847KAZD3
MAX6848KARD3
MAX6848KASD3
MAX6848KAWD3
MAX6848KAZD3
MAX6849KARD3
MAX6849KASD3
MAX6849KAWD3
MAX6849KAZD3
DC-DC
AEJD
AEJK
AEJJ
Li+
3.6V
V
V
CC
CC
LBO
MR
NMI
AEJE
AEJL
MAX6846
MAX6847
V
DD
µP
AEJN
AEJM
AEJP
AEJO
AEJR
AEJQ
AEJT
RESET
RESET
LTHIN
HTHIN
AEJS
AEJV
AEJU
GND
GND
Chip Information
TRANSISTOR COUNT: 1478
PROCESS: BiCMOS
______________________________________________________________________________________ 11
Low-Power, Adjustable Battery Monitors with
Hysteresis and Integrated µP Reset
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.)
SEE DETAIL "A"
SYMBOL
MIN
MAX
e
b
A
0.90
0.00
0.90
0.28
0.09
2.80
2.60
1.50
0.30
1.45
0.15
1.30
0.45
0.20
3.00
3.00
1.75
0.60
C
L
A1
A2
b
C
D
E
C
C
L
E1
L
E
E1
L
0.25 BSC.
L2
e
PIN 1
I.D. DOT
(SEE NOTE 6)
0.65 BSC.
1.95 REF.
0∞
e1
0
8∞
e1
D
C
C
L
L2
A2
A
GAUGE PLANE
A1
SEATING PLANE
C
0
L
NOTE:
1. ALL DIMENSIONS ARE IN MILLIMETERS.
2. FOOT LENGTH MEASURED FROM LEAD TIP TO UPPER RADIUS OF
HEEL OF THE LEAD PARALLEL TO SEATING PLANE C.
DETAIL "A"
3. PACKAGE OUTLINE EXCLUSIVE OF MOLD FLASH & METAL BURR.
4. PACKAGE OUTLINE INCLUSIVE OF SOLDER PLATING.
5. COPLANARITY 4 MILS. MAX.
6. PIN 1 I.D. DOT IS 0.3 MM ÿ MIN. LOCATED ABOVE PIN 1.
PROPRIETARY INFORMATION
TITLE:
7. SOLDER THICKNESS MEASURED AT FLAT SECTION OF LEAD
BETWEEN 0.08mm AND 0.15mm FROM LEAD TIP.
PACKAGE OUTLINE, SOT-23, 8L BODY
8. MEETS JEDEC MO178.
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0078
D
1
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.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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