General Description
The MAX6775–MAX6781 low-power, 1%-accurate bat-
tery monitors are available in the ultra-small µDFN
package (1.0mm x 1.5mm) and SC70 packages. These
low-power devices are ideal for monitoring single lithi-
um-ion (Li+) cells, or multicell alkaline/NiCd/NiMH
power sources. These devices offer single (MAX6775/
MAX6776/MAX6777/MAX6778) or dual (MAX6779/
MAX6780/MAX6781) low-battery outputs and feature
fixed or resistor-adjustable hysteresis. Hysteresis elimi-
nates the output chatter sometimes associated with bat-
tery voltage monitors, usually due to input-voltage noise
or battery terminal voltage recovery after load removal.
These devices are available in several versions: with
single- or dual-voltage monitors, and with fixed or
adjustable hysteresis. The MAX6775/MAX6776 offer a
single battery monitor and factory-set hysteresis of
0.5%, 5%, or 10%. The MAX6779/MAX6780/MAX6781
have two battery monitors in a single package and fac-
tory-set hysteresis of 0.5%, 5%, or 10%. The MAX6777/
MAX6778 offer a single battery monitor with external
inputs for the rising and falling thresholds, allowing
external hysteresis control.
For convenient interface with system power circuitry or
microprocessors, both open-drain and push-pull out-
puts are available. The single-channel devices are
available with open-drain or push-pull outputs. The
dual-channel devices are available with both outputs
open-drain, both outputs push-pull, or one of each
(see the
Selector Guide
). This family of devices is
offered in small 5-pin SC70 and ultra-small 6-pin µDFN
packages, and is fully specified over the -40°C to
+85°C extended temperature range.
Applications
Battery-Powered Systems (Single-Cell Li+ or
Multicell NiMH, NiCd, Alkaline)
Cell Phones/Cordless Phones
Pagers
Portable Medical Devices
PDAs
Electronic Toys
MP3 Players
Features
o1.0%-Accurate Threshold Specified Over
Temperature
oSingle/Dual, Low-Battery Output Options
oLow 3µA Battery Current
oOpen-Drain or Push-Pull Low-Battery Outputs
oFixed or Adjustable Hysteresis
oLow-Input Leakage Current Allows Use of Large
Resistors
oGuaranteed Valid Low-Battery-Output Logic State
Down to VBATT = 1V
oImmune to Short Battery Transients
oFully Specified from -40°C to +85°C
oSmall 5-Pin SC70 or Ultra-Small 6-Pin µDFN
(1mm x 1.5mm) Package
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
LBI
3.6V LBO
BATT
MAX6775
SHDN OUT
DC-DC
CONVERTER
IN
Typical Operating Circuit
19-3774; Rev 4; 5/09
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Ordering Information continued at end of data sheet.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
MAX6775/MAX6776/MAX6779/MAX6780/MAX6781 are available
with factory-trimmed hysteresis. Specify trim by replacing “_”
with “A” for 0.5%, “B” for 5%, or “C” for 10% hysteresis.
Pin Configurations appear at end of data sheet.
PART TEMP RANGE PIN-PACKAGE
MAX6775XK_+T -40°C to +85°C 5 SC70
MAX6775LT_+T -40°C to +85°C 6 µDFN
MAX6776XK_+T -40°C to +85°C 5 SC70
MAX6776LT_+T -40°C to +85°C 6 µDFN
MAX6777XK+T -40°C to +85°C 5 SC70
MAX6777LT+T -40°C to +85°C 6 µDFN
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VBATT = 1.6V to 5.5V, TA= -40°C to +85°C, unless otherwise specified. Typical values are at TA= +25°C.) (Note 1)
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.
BATT to GND............................................................-0.3V to +6V
LBI, LBL, LBH, LBI1, LBI2 to GND ...............-0.3V to minimum of
((VBATT + 0.3V) and +6V)
LBO, LBO1, LBO2 to GND (open-drain) .................-0.3V to +6V
LBO, LBO1, LBO2 to GND (push-pull).........-0.3V to minimum of
((VBATT + 0.3V) and +6V)
Input Current (all pins) ........................................................20mA
Output Current (all pins) .....................................................20mA
Continuous Power Dissipation (TA= +70°C)
5-Pin SC70 (derate 3.1mW/°C above +70°C)..............247mW
6-Pin µDFN (derate 2.1mW°C above +70°C) ..............168mW
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
TA = 0°C to +70°C 1.0 5.5
Operating Voltage Range
(Note 2) VBATT TA = -40°C to +85°C 1.2 5.5 V
VBATT = 3.7V, no load 4 7
Supply Current IQVBATT = 1.8V, no load 3.2 6 µA
FIXED HYSTERESIS (MAX6775/MAX6776/MAX6779/MAX6780/MAX6781)
0.5% hysteresis version 1.2037 1.2159 1.2280
5% hysteresis version 1.1493 1.1609 1.1725
LBI, LBI_ Falling Threshold
(Note 3) VLBIF
10% hysteresis version 1.0888 1.0998 1.1108
V
LBI Rising Threshold VLBIR 1.2098 1.222 1.2342 V
LBI Input Leakage Current 0.2V ≤ VLBI ≤ VBATT - 0.2V -5 +5 nA
ADJUSTABLE HYSTERESIS (MAX6777/MAX6778)
LBL, LBH Threshold VBATT = 1.8V to 5.5V 1.2098 1.222 1.2342 V
LBL, LBH Input Leakage Current VBATT - 0.2V ≥ VLBL/LBH ≥ 0.2V -5 +5 nA
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 1.6V to 5.5V, TA= -40°C to +85°C, unless otherwise specified. Typical values are at TA= +25°C.) (Note 1)
Note 1: Devices are tested at TA= +25°C and guaranteed by design for TA=T
MIN to TMAX, as specified.
Note 2: Operating range ensures low-battery output is in the correct state. Minimum battery voltage for electrical specification is 1.6V.
Note 3: The rising threshold is guaranteed to be higher than the falling threshold.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LOW-BATTERY OUTPUTS (LBO, LBO1, LBO2)
Propagation Delay tPD VLBI_ + 100mV to VLBI_ - 100mV 9 µs
Startup Time VBATT rising above 1.6V 3 ms
VBATT ≥ 1.2V, ISINK = 100µA 0.3
VBATT ≥ 2.7V, ISINK = 1.2mA 0.3
Output Low (Push-Pull or
Open-Drain) VOL
VBATT ≥ 4.5V, ISINK = 3.2mA 0.3
V
VBATT ≥ 1.6V, ISOURCE = 100µA 0.8 x
VBATT
VBATT ≥ 2.7V, ISOURCE = 500µA 0.8 x
VBATT
Output High (Push-Pull ) VOH
VBATT ≥ 4.5V, ISOURCE = 800µA 0.8 x
VBATT
V
Output Leakage Current
(Open-Drain) Output not asserted, VLBO_ = 5.5V -100 +100 nA
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
MAX6775 toc01
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
603510-15
3.0
3.5
4.0
4.5
5.0
5.5
6.0
2.5
-40 85
VBATT = 5V
VBATT = 3.6V
VBATT = 3V
VBATT = 2.4V
VBATT = 1.6V
PROPAGATION DELAY
vs. TEMPERATURE
MAX6775 toc02
TEMPERATURE (°C)
PROPAGATION DELAY (µs)
603510-15
8
9
10
11
12
7
-40 85
VBATT = 5V
100mV OVERDRIVE
VBATT = 1.6V
MAXIMUM TRANSIENT DURATION
vs. THRESHOLD OVERDRIVE
MAX6775 toc03
THRESHOLD OVERDRIVE VTH - VCC (mV)
MAXIMUM TRANSIENT DURATION (µs)
10010
10
20
30
40
50
60
70
0
1 1000
OUTPUT ASSERTED ABOVE THIS LINE
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
4 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
NORMALIZED THRESHOLD VOLTAGES
vs. TEMPERATURE, MAX67__A
MAX6775 toc04
TEMPERATURE (°C)
THRESHOLD VOLTAGE (mV)
603510-15
-4
-3
-2
-1
0
1
-5
-40 85
NORMALIZED AT TA = +25°C
RISING
FALLING
NORMALIZED THRESHOLD VOLTAGES
vs. TEMPERATURE, MAX67__B
MAX6775 toc05
TEMPERATURE (°C)
THRESHOLD VOLTAGE (mV)
603510-15
-3
-2
-1
0
1
-4
-40 85
NORMALIZED AT TA = +25°C
RISING
FALLING
NORMALIZED THRESHOLD VOLTAGES
vs. TEMPERATURE, MAX67__C
MAX6775 toc06
TEMPERATURE (°C)
THRESHOLD VOLTAGE (mV)
603510-15
-2
-1
0
1
-3
-40 85
NORMALIZED AT TA = +25°C
RISING
FALLING
LBO OUTPUT VOLTAGE
vs. SINK CURRENT
MAX6775 toc07
SINK CURRENT (mA)
OUTPUT VOLTAGE (V)
12963
0.1
0.2
0.3
0.4
0.5
0
015
VBATT = 5.0V
VBATT = 1.8V VBATT = 3.3V
LBO OUTPUT VOLTAGE
vs. SOURCE CURRENT
MAX6775 toc08
SOURCE CURRENT (mA)
OUTPUT VOLTAGE (V)
4321
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
1.0
05
VBATT = 5.0V
VBATT = 3.3V
VBATT = 1.8V
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
_______________________________________________________________________________________ 5
Pin Description
MAX6775/
MAX6776
MAX6777/
MAX6778
MAX6779/
MAX6780/
MAX6781
µDFN
SC70 µDFN SC70
µDFN
NAME FUNCTION
1 1 — — — GND2 Reserved. Must be connected to GND. Do not use as the only
GND connection.
2 2 2 2 2 GND Ground
3 3 — — — LBI Low-Battery Input. Connect to the resistive divider to set the
trip level.
4444 — LBO
Low-Battery Output, Active-Low. When VLBI/VLBL falls below
the falling threshold, LBO asserts. LBO deasserts when
VLBI/VLBH exceeds the rising threshold voltage.
5 — 5 — — N.C. No Connection. Not internally connected.
6 5 6 5 6 BATT Battery Input. Power supply to the device.
— — 1 1 — LBH Rising-Trip-Level Input. Connect to a resistive divider to set the
rising trip level.
— — 3 3 — LBL Falling-Trip-Level Input. Connect to a resistive divider to set the
falling trip level.
— — — — 1 LBI2 Low-Battery Input 2. Connect to a resistive divider to set the
trip level.
— — — — 3 LBI1 Low-Battery Input 1. Connect to a resistive divider to set the
trip level.
———— 4 LBO1
Low-Battery Output 1, Active-Low. When VLBI1 falls below the
falling threshold voltage, LBO1 asserts. LBO1 deasserts when
VLBI1 exceeds the rising threshold voltage. LBO1 is push-pull
on the MAX6779/MAX6781 and open-drain for the MAX6780.
———— 5 LBO2
Low-Battery Output 2, Active-Low. When VLBI2 falls below the
falling threshold voltage, LBO2 asserts. LBO2 deasserts when
VLBI2 exceeds the rising threshold voltage. LBO2 is open-drain
for the MAX6780/MAX6781 and push-pull for the MAX6779.
MAX6775–MAX6781
Detailed Description
These battery monitors have an active-low output that
asserts when the input falls below a set voltage. They
also offer hysteresis for noise immunity, and to remove
the possibility of output chatter due to battery terminal
voltage recovery after load removal. They are available
with one or two monitors per package, with push-pull or
open-drain outputs, and with internally set or externally
adjustable hysteresis (dual-channel devices offer only
internally fixed hysteresis). Figures 1, 2, and 3 show
block diagrams and typical connections. See the
Selector Guide
for details.
Low-Battery Output
All devices are offered with either push-pull or open-
drain outputs (see the
Selector Guide
). The MAX6781
has one push-pull output and one open-drain output,
configured as in Table 1.
On all devices with open-drain outputs an external
pullup resistor is required. The open-drain pullup resis-
tor can connect to an external voltage up to +6V,
regardless of the voltage at BATT.
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
6 _______________________________________________________________________________________
Table 1. MAX6781 Outputs
DEVICE LBO1 LBO2
MAX6781 Push-Pull Open-Drain
LBI1
LBO1
0
1
BATT
GND
VREF
VBATT
LBI2
LBO2
0
1
MAX6779
MAX6780
MAX6781
HYSTERESIS
CONTROL
Figure 2. Dual-Channel Fixed-Hysteresis Block Diagram
LBI
LBO
0
1
BATT
GND
RL
VREF
VBATT
RH
MAX6775
MAX6776
HYSTERESIS
CONTROL
Figure 1. Single-Channel Fixed-Hysteresis Block Diagram
LBL
LBO
0
1
LBH
BATT
GND
RHYST
VREF
VBATT
RH
RL
MAX6777
MAX6778
Figure 3. Single-Channel Adjustable-Hysteresis Block Diagram
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
_______________________________________________________________________________________ 7
The MAX6779, MAX6780, and MAX6781 monitor two
battery levels or two independent voltages. A common
application for this type of dual-battery monitor is to use
one output as an early warning signal and the other as
a dead-battery indicator.
Hysteresis
Input hysteresis defines two thresholds, separated by a
small voltage (the hysteresis voltage), configured so
the output asserts when the input falls below the falling
threshold, and deasserts only when the input rises above
the rising threshold. Figure 4 shows this graphically.
Hysteresis removes, or greatly reduces, the possibility of
the output changing state in response to noise or battery
terminal voltage recovery after load removal.
Fixed Hysteresis
The MAX6775/MAX6776/MAX6779/MAX6780/MAX6781
have factory-set hysteresis for ease of use, and reduce
component count. For these devices, the absolute hys-
teresis voltage is a percentage of the internally generat-
ed reference. The amount depends on the device
option. “A” devices have 0.5% hysteresis, “B” devices
have 5% hysteresis, and “C” devices have 10% hystere-
sis. Table 2 presents the threshold voltages for devices
with internally fixed hysteresis.
Adjustable Hysteresis
The MAX6777/MAX6778 offer external hysteresis con-
trol through the resistive divider that monitors battery
voltage. Figure 3 shows the connections for external
hysteresis. See the
Calculating an External Hysteresis
Resistive Divider
section for more information.
Applications Information
Resistor-Value Selection
Choosing the proper external resistors is a balance
between accuracy and power use. The input to the volt-
age monitor, while high impedance, draws a small cur-
rent, and that current travels through the resistive
divider, introducing error. If extremely high resistor val-
ues are used, this current introduces significant error.
With extremely low resistor values, the error becomes
negligible, but the resistive divider draws more power
from the battery than necessary and shortens battery
life. Figure 1 calculates the optimum value for RHusing:
where eAis the maximum acceptable absolute resistive
divider error (use 0.01 for 1%), VBATT is the battery volt-
age at which LBO should activate, and ILis the worst-
case LBI leakage current. For example, with 0.5%
accuracy, a 2.8V battery minimum, and 5nA leakage,
RH= 2.80MΩ.
Calculate RLusing:
where VLBIF is the falling threshold voltage from Table 2.
Continuing the above example, select VLBIF = 1.0998V
(10% hysteresis device) and RL= 1.81MΩ.
RVxR
VV
LLBIF H
LBIF BATT
=−
−
RexV
I
HA BATT
L
=
VBATT
LBO
VLBIR
VLBIF
VHYST
tPD
tPD
MAX6775
MAX6776
Figure 4. Hysteresis
Table 2. Typical Falling and Rising Thresholds for
MAX6775/MAX6776/MAX6779/MAX6780/MAX6781
DEVICE OPTION PERCENT
HYSTERESIS (%)
FALLING THRESHOLD
(VLBIF) (V)
RISING THRESHOLD
(VLBIR) (V)
HYSTERESIS VOLTAGE
(VHYST) (mV)
A 0.5 1.2159 1.222 6.11
B 5 1.1609 1.222 61.1
C 10 1.0998 1.222 122
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
8 _______________________________________________________________________________________
Selector Guide
PART LBO OUTPUT OUTPUT TYPE HYSTERESIS PIN-PACKAGE
MAX6775XK_+T Single Push-Pull Fixed 5 SC70
MAX6775LT_+T Single Push-Pull Fixed 6 µDFN
MAX6776XK_+T Single Open-Drain Fixed 5 SC70
MAX6776LT_+T Single Open-Drain Fixed 6 µDFN
MAX6777XK+T Single Push-Pull Adjustable 5 SC70
MAX6777LT+T Single Push-Pull Adjustable 6 µDFN
MAX6778XK+T Single Open-Drain Adjustable 5 SC70
MAX6778LT+T Single Open-Drain Adjustable 6 µDFN
MAX6779LT_+T Dual Push-Pull Fixed 6 µDFN
MAX6780LT_+T Dual Open-Drain Fixed 6 µDFN
MAX6781LT_+T Dual Mixed Fixed 6 µDFN
Calculating an External
Hysteresis Resistive Divider
Setting the hysteresis externally requires three external
resistors, as shown in Figure 3. Select RHusing the fol-
lowing formula:
where eAis the allowable error due to input leakage
current (typically 0.005 or less), VBATT_RISING is the
desired rising threshold, and ILis the worst-case leak-
age current (5nA). Then calculate RLO (which is the
sum of RLand RHYST):
where VLBI is 1.222V and VBATT_FALLING is the desired
falling threshold. Calculate RLusing:
and finally, calculate RHYST:
Monitoring a Battery Voltage Higher
Than the Allowable VBATT
For monitoring higher voltages, supply power to BATT
that is within the specified supply range, and power the
input resistive divider from the high voltage to be moni-
tored. Do not exceed the
Absolute Maximum Ratings
.
Adding External Capacitance to
Reduce Noise and Transients
If monitoring voltages in a noisy environment, add a
bypass capacitor of 0.1µF from BATT to GND as close
as possible to the device. For systems with large tran-
sients, additional capacitance may be required. A small
capacitor (<1nF) from LBI_ to GND may provide addi-
tional noise immunity.
RRR
HYST LO L
=−
RVRR
V
LLBI H LO
BATT RISING
=×+
()
_
RVR
VV
LO LBI H
BATT FALLING LBI
=×
−
_
ReV
I
HA BATT RISING
L
≤×_
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
_______________________________________________________________________________________ 9
Top Marks
PART TOP MARK
MAX6775XKA+T ASA
MAX6775XKB+T ASB
MAX6775XKC+T ASC
MAX6775LTA+T BU
MAX6775LTB+T BW
MAX6775LTC+T BX
MAX6776XKA+T ASJ
MAX6776XKB+T ASK
MAX6776XKC+T ASL
MAX6776LTA+T BY
MAX6776LTB+T BZ
MAX6776LTC+T CA
PART TOP MARK
MAX6777XK+T ASD
MAX6777LT+T CB
MAX6778XK+T ASI
MAX6778LT+T CC
MAX6779LTA+T BL
MAX6779LTB+T BM
MAX6779LTC+T BN
MAX6780LTA+T BO
MAX6780LTB+T BP
MAX6780LTC+T BQ
MAX6781LTA+T BR
MAX6781LTB+T BS
MAX6781LTC+T BT
Ordering Information (continued)
PART TEMP RANGE PIN-PACKAGE
MAX6778XK+T -40°C to +85°C 5 SC70
MAX6778LT+T -40°C to +85°C 6 µDFN
MAX6779LT_+T -40°C to +85°C 6 µDFN
MAX6780LT_+T -40°C to +85°C 6 µDFN
MAX6781LT_+T -40°C to +85°C 6 µDFN
+
Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
MAX6775/MAX6776/MAX6779/MAX6780/MAX6781 are available
with factory-trimmed hysteresis. Specify trim by replacing “_”
with “A” for 0.5%, “B” for 5%, or “C” for 10% hysteresis.
Chip Information
PROCESS: BICMOS
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
10 ______________________________________________________________________________________
GND
LBOLBI
1 5 BATTGND2
MAX6775
MAX6776
SC70
+
+
TOP VIEW
2
34
123
456
BATT LBON.C.
GND2 LBIGND
MAX6775
MAX6776
μDFN
123
456
BATT LBON.C.
LBH LBLGND
MAX6777
MAX6778
μDFN
123
456
BATT LBO1LBO2
LBI2 LBI1GND
MAX6779
MAX6780
MAX6781
μDFN
GND
LBOLBL
1 5 BATTLBH
MAX6777
MAX6778
SC70
2
34
Pin Configurations
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
5 SC70 X5-1 21-0076
6 µDFN L611-1 21-0147
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX6775–MAX6781
Low-Power, 1%-Accurate Battery
Monitors in µDFN and SC70 Packages
Heaney
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________
11
© 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
4 5/09 Updated Calculating an External Hysteresis Resistive Divider section 8
