19-2323; Rev 2; 12/05
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
Features
The MAX6427–MAX6438 are single/dual-level battery monitors with internal hysteresis. These devices are offered with
single (MAX6427/MAX6428/MAX6429, MAX6433/
MAX6434/MAX6435) or dual (MAX6430/MAX6431/
MAX6432, MAX6436/MAX6437/MAX6438) low-battery output indicators, which can be used to indicate three battery
conditions: battery is good (operate system in normal
mode), battery is weak (operate system in low-power
mode), or battery is empty (disable the system).
These devices are ideal for monitoring single lithium-ion
(Li+) cells or multicell alkaline/NiCd/NiMH power supplies.
When the power-supply voltage drops below the specified
low threshold, the low-battery output asserts. When the
voltage rises above the specified high threshold, the lowbattery output is deasserted following a 140ms minimum
timeout period. The timeout period ensures that the supply
voltages have stabilized before power-converter or microprocessor activity is enabled.
♦ Factory-Trimmed or User-Adjustable Threshold
Options
Factory-Trimmed Low Thresholds from 1.6V to
2.1V or 2.6V to 3.1V in 100mV Increments
(MAX6427–MAX6432)
Factory-Trimmed High Thresholds from 2.3V to
2.6V or 3.3V to 3.6V in 100mV Increments
(MAX6427–MAX6432)
User-Adjustable Low/High Thresholds with
615mV Internal Reference (MAX6433–MAX6438)
♦ Low Current (1µA, typ)
♦ Single or Dual Low-Battery Outputs
♦ Push-Pull LBO, Open-Drain LBO, and Open-Drain
LBO Options
♦ 140ms Minimum LBO Timeout Period
♦ Immune to Short Battery Voltage Transients
♦ Guaranteed Valid LBO Logic State to BATT = 1.0V
♦ -40°C to +85°C Operating Temperature Range
♦ Small 3, 4, 5 and 6-Pin SOT Packages
♦ No External Components Required
(MAX6427–MAX6432)
The MAX6427–MAX6438 family is available with several
monitoring options. The MAX6427/MAX6428/MAX6429
offer factory-trimmed battery-monitor thresholds, with a single low-battery output. The MAX6430/MAX6431/MAX6432
also feature factory-trimmed thresholds, but have two lowbattery outputs.
The MAX6433–MAX6438 have user-adjustable threshold
voltages permitting the user to select the hysteresis range,
and consequently the sensitivity of the system to noise. A
wide hysteresis range also prevents chattering that can
result due to battery recovery after load removal. Single
low-battery outputs are supplied by the MAX6433/
MAX6434/MAX6435 and dual low-battery outputs by the
MAX6436/MAX6437/MAX6438.
The MAX6427–MAX6438 family is available with three output logic options for convenient interface with system
power circuitry or microprocessors. The family is offered in
small SOT23 and SOT143 packages and is fully specified
over temperature.
________________________Applications
Battery-Powered Systems (Single-Cell Li+ or
Two/Three-Cell NiMH, NiCd, Alkaline)
Cell Phones/Cordless Phones
Pagers
Portable Medical Devices
PDAs
Electronic Toys
MP3 Players
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6427_ _UR-T
-40°C to +85°C
3 SOT23-3
Ordering Information continued at end of data sheet.
†The
MAX6427–MAX6432 are available with factory-trimmed
battery-monitor thresholds. Select the desired thresholds
using Tables 1 or 2 and enter the corresponding letters in
the part number by replacing “_ _”.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Note: There are 26 standard versions with a required order
minimum of 2500 pieces. Sample stock is generally held on
the standard versions only (see Standard Versions Table).
Required order increment is 10,000 pieces for nonstandard
versions. Contact factory for availability. All devices available in tape-and-reel only.
Pin Configurations
TOP VIEW
LBO
1
(LBO)
MAX6427
MAX6428
MAX6429
3
GND
BATT 2
SOT23-3
Typical Operating Circuit appears at end of data sheet.
( ) ARE FOR THE MAX6429.
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX6427–MAX6438
General Description
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
ABSOLUTE MAXIMUM RATINGS
BATT, VDD to GND ................................................-0.3V to +6.0V
HTHIN, LTHIN Inputs to GND.....................-0.3V to (VDD + 0.3V)
Open-Drain LBO/LBO, LBOH/LBOH,
LBOL/LBOL to GND .........................................-0.3V to +6.0V
Push-Pull LBO/LBO, LBOH/LBOH,
LBOL/LBOL to GND ................-0.3V to (BATT or VDD + 0.3V)
Input Current (all pins) ........................................................20mA
Output Current (all pins) .....................................................20mA
Continuous Power Dissipation (TA = +70°C)
3-Pin SOT23-3 (derate 4.0mW/°C above +70°C) .......320mW
4-Pin SOT143-4 (derate 4.0mW/°C above +70°C) .....320mW
5-Pin SOT23-5 (derate 7.1mW/°C above +70°C) .......571mW
6-Pin SOT23-6 (derate 8.7mW/°C above +70°C) .......696mW
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
(BATT = 1.0V to 5.5V or VDD = 1.6V to 5.5V, TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.)
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
TA = -40°C to +85°C
1.2
5.5
TA = 0°C to +70°C
1.0
5.5
1.6
5.5
V
Operating Voltage Range
VBATT
V
Operating Voltage Range
VDD
TA = -40°C to +85°C
BATT Supply Current
IBATT
VBATT = 3.7V, no load (MAX6427–MAX6432)
1
1.5
µA
VDD Supply Current
IDD
VDD = 3.7V, no load
(MAX6433–MAX6438)
1
1.5
µA
FACTORY-FIXED THRESHOLDS (MAX6427–MAX6432)
HTH Threshold
(Note 2)
VHTH
Factory-fixed options, BATT rising,
LBO deasserted when BATT rises above
VHTH (MAX6427/MAX6428/MAX6429)
-2.5
+2.5
%
LTH Threshold
(Note 2)
VLTH
Factory-fixed options, BATT falling,
LBO asserted when BATT falls below VLTH
(MAX6427/MAX6428/MAX6429)
-2.5
+2.5
%
HTH- Threshold
(Note 2)
VHTH-
Factory-fixed options, BATT falling, LBOH
asserted when BATT falls below VHTH(MAX6430/MAX6431/MAX6432)
-2.5
+2.5
%
HTH+ Threshold
(Note 3)
VHTH+
Factory-fixed options, BATT rising,
LBOH deasserted when BATT rises above
VHTH+ (MAX6430/MAX6431/MAX6432)
-2.5
+2.5
%
LTH- Threshold
(Note 2)
VLTH-
Factory-fixed options, BATT falling,
LBOL asserted when BATT falls below VLTH(MAX6430/MAX6431/MAX6432)
-2.5
+2.5
%
LTH+ Threshold
(Note 3)
VLTH+
Factory-fixed options, BATT rising,
LBOL deasserted when BATT rises above
VLTH+ (MAX6430/MAX6431/MAX6432)
-2.5
+2.5
%
2
_______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
(BATT = 1.0V to 5.5V or VDD = 1.6V to 5.5V, TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.)
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
VHTHIN
User-adjustable options, HTHIN rising,
LBO is deasserted when HTHIN rises above
VHTHIN-, VREF = 615mV
(MAX6433/MAX6434/MAX6435)
VLTHIN
TYP
MAX
UNITS
-2.5
+2.5
%
User-adjustable options, LTHIN falling,
LBOH is asserted when LTHIN falls below
VLTHIN-, VREF = 615mV
(MAX6433/MAX6434/MAX6435)
-2.5
+2.5
%
VHTHIN+
User-adjustable options, HTHIN rising,
LBOH is deasserted when HTHIN rises
above VHTHIN+, VREF = 615mV
(MAX6436/MAX6437/MAX6438)
-2.5
+2.5
%
VHTHIN-
User-adjustable options, HTHIN falling,
LBOH is asserted when HTHIN falls below
VHTHIN-, VREF = 585mV
(MAX6436/MAX6437/MAX6438)
-2.5
+2.5
%
VLTHIN+
User-adjustable options, LTHIN rising,
LBOL is deasserted when LTHIN rises
above VLTHIN+, VREF = 615mV
(MAX6436/MAX6437/MAX6438)
-2.5
+2.5
%
VLTHIN-
User-adjustable options, LTHIN falling,
LBOL is asserted when LTHIN falls below
VLTHIN-, VREF = 585mV
(MAX6436/MAX6437/MAX6438)
-2.5
+2.5
%
20
nA
USER-ADJUSTABLE THRESHOLDS (MAX6433–MAX6438)
HTHIN Threshold
(Note 4)
LTHIN Threshold
(Note 4)
HTHIN+ Threshold
(Note 4)
HTHIN- Threshold
(Note 5)
LTHIN+ Threshold
(Note 4)
LTHIN- Threshold
(Note 5)
HTHIN/LTHIN Leakage Current
(Note 6)
ILKG
VHTHIN or VLTHIN > 400mV
_______________________________________________________________________________________
3
MAX6427–MAX6438
ELECTRICAL CHARACTERISTICS (continued)
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
ELECTRICAL CHARACTERISTICS (continued)
(BATT = 1.0V to 5.5V or VDD = 1.6V to 5.5V, TA = -40°C to +85°C, unless otherwise specified. Typical values are at TA = +25°C.)
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
140
210
280
ms
LOW-BATTERY OUTPUTS (LBO, LBO, LBOH, LBOH, LBOL, LBOL )
Timeout Period
tLBOP
BATT or VDD/HTHIN/LTHIN rising above
threshold
Delay
tLBOD
BATT or VDD/HTHIN/LTHIN falling below
threshold
LBO/LBOL/LBOH Output LOW
(Push-Pull or Open-Drain)
LBO Output HIGH (Push-Pull
Only) (Note 7)
LBO Output Leakage Current
(Open-Drain Only)
LBO/LBOL/LBOH Output
LOW (Open-Drain Only)
LBO Output Leakage Current
(Open-Drain Only)
VOL
VOH
ILKG
VOL
ILKG
100
BATT or VDD ≥ 1.6V, ISINK = 100µA,
asserted low
0.3
BATT or VDD ≥ 2.7V, ISINK = 1.2mA,
asserted low
0.3
BATT or VDD ≥ 4.5V, ISINK = 3.2mA,
asserted low
0.4
BATT or VDD ≥ 1.6V, ISOURCE = 200µA,
deasserted
0.8 × VSUPPLY
BATT or VDD ≥ 2.7V, ISOURCE = 500µA,
deasserted
0.8 × VSUPPLY
BATT or VDD ≥ 4.5V, ISOURCE = 800µA,
deasserted
0.8 × VSUPPLY
500
BATT or VDD ≥ 1.6V, ISINK = 100µA,
deasserted low
0.3
BATT or VDD ≥ 2.7V, ISINK = 1.2mA,
deasserted low
0.3
BATT or VDD ≥ 4.5V, ISINK = 3.2mA,
deasserted low
0.4
LBO asserted
500
_______________________________________________________________________________________
V
V
LBO deasserted
Note 1: Production testing done at TA = +25°C, limits over temperature guaranteed by design only.
Note 2: Percentage of selected factory-fixed HTH- or LTH- threshold voltage.
Note 3: Percentage of 1.05 ✕ (selected factory-fixed threshold voltage).
Note 4: Percentage of 615mV voltage reference.
Note 5: Percentage of 585mV voltage reference.
Note 6: Guaranteed by design.
Note 7: VSUPPLY is BATT or VDD.
4
µs
nA
V
nA
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
0.9
0.6
VBATT = 2V
0.3
1.005
1.000
0.995
OUTPUT ASSERTS
60
40
20
OUTPUT DOES
NOT ASSERT
LBO NOT ASSERTED
0
0
0.990
0
20
40
60
-40
80
-20
0
20
40
60
10
80
NORMALIZED UPPER AND LOWER
TRIP VOLTAGES vs. TEMPERATURE
1000
LBO OUTPUT vs. ISINK
300
MAX6427 toc05
1.050
100
LBO COMPARATOR OVERDRIVE (mV)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX6427 toc04
250
1.025
LBO OUTPUT (mV)
-20
NORMALIZED TRIP VOLTAGES (V)
-40
MAX6427 toc03
MAXIMUM TRANSIENT DURATION (µs)
VBATT = 3.3V
80
MAX6427 toc02
1.5
NORMALIZED LBO TIMEOUT PERIOD
VBATT = 5V
SUPPLY CURRENT (µA)
1.010
MAX6427 toc01
1.8
1.2
MAXIMUM TRANSIENT DURATION
vs. LBO COMPARATOR OVERDRIVE
NORMALIZED LBO TIMEOUT PERIOD
vs. TEMPERATURE
SUPPLY CURRENT
vs. TEMPERATURE
LOWER TRIP VOLTAGE
1.000
UPPER TRIP VOLTAGE
200
150
100
0.975
50
0.950
OPEN-DRAIN LBO
ASSERTED
0
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
0
2
4
6
8
10
ISINK (mA)
_______________________________________________________________________________________
5
MAX6427–MAX6438
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
MAX6427–MAX6438
Pin Description
PIN
MAX6427/
MAX6428/
MAX6429
MAX6433/
MAX6434/
MAX6435
MAX6436/
MAX6437/
MAX6438
NAME
FUNCTION
1
—
4
—
LBO/
LBO
Low-Battery Output. LBO/LBO is asserted when BATT drops
below VLTH (MAX6427/MAX6428/MAX6429) or when LTHIN
(MAX6433/MAX6434/MAX6435) drops below VLTHIN, and
remains asserted for at least 140ms after BATT exceeds VHTH
(MAX6427/MAX6428/MAX6429) or VHTHIN (MAX6433/
MAX6434/MAX6435).
2
3
—
—
BATT
Battery-Voltage Input. Input for battery-voltage threshold
monitors and device power supply for factory-trimmed
threshold versions.
3
1
2
2
GND
Ground
—
6
MAX6430/
MAX6431/
MAX6432
2
—
5
LBOH/
LBOH
Low-Battery Output High. LBOH/LBOH is asserted when BATT
drops below VHTH- (MAX6430/MAX6431/MAX6432) or when
HTHIN drops below VHTHIN- (MAX6436/MAX6437/ MAX6438). It
remains asserted for at least 140ms after BATT exceeds VHTH+
(MAX6430/MAX6431/MAX6432) or HTHIN rises above VHTHIN+
(MAX6436/MAX6437/MAX6438).
—
4
—
4
LBOL/
LBOL
Low-Battery Output Low. LBOL/LBOL is asserted when BATT
drops below VLTH- (MAX6430/MAX6431/MAX6432) or when
LTHIN drops below VLTHIN- (MAX6436/MAX6437/
MAX6438). It remains asserted for at least 140ms after BATT
exceeds VLTH+ (MAX6430/MAX6431/MAX6432) or LTHIN rises
above VLTHIN+ (MAX6436/MAX6437/MAX6438).
—
—
1
1
HTHIN
HTH Threshold Monitor Input. A resistor-divider network sets
the high threshold associated with LBOH/LBOH.
—
—
3
3
LTHIN
LTH Threshold Monitor Input. A resistor-divider network sets
the low threshold associated with LBOL/LBOL.
—
—
5
6
VDD
VDD Supply Voltage Input. Device power supply for adjustable
threshold versions.
_______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
The MAX6427–MAX6438 family is available with several
monitoring options. The MAX6427/MAX6428/MAX6429
offer factory-trimmed battery-monitor thresholds, with a
single low-battery output (see Figure 1). The
MAX6430/MAX6431/MAX6432 also feature factorytrimmed thresholds, but have two low-battery outputs
(see Figure 2). The factory-trimmed thresholds of the
MAX6427–MAX6432 eliminate the requirement for
external components.
The user sets the threshold voltages for the
MAX6433–MAX6438, which permit the user to select
the hysteresis range, and consequently the sensitivity
of the system to noise. A wide hysteresis range prevents chattering that can result during battery recovery
or load removal. The MAX6433/MAX6434/ MAX6435
have single low-battery outputs and the MAX6436/
MAX6437/MAX6438 have dual low-battery outputs (see
Figures 3 and 4).
The MAX6427–MAX6438 combine a 615mV reference
with two comparators, logic, and timing circuitry to provide the user with information about the charge state of
the power-supply batteries. The MAX6427–MAX6438
monitor separate high-voltage and low-voltage thresholds 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.
User-programmable versions are also available with
thresholds determined using an external resistordivider (see Resistor-Value Selection).The adjustable
versions can monitor down to 0.62V, making them suitable for monitoring single-cell alkaline, NiMH, and NiCd
applications (VDD ≥ 1.6V).
When the power-supply voltage drops below the specified low threshold, the low-battery output asserts (see
Low-Battery Output). When the voltage rises above the
specified high threshold following a 140ms (min) timeout period, the low-battery output is deasserted (see
Threshold Monitoring). This ensures the supply voltage
has stabilized before power-converter or microprocessor activity is enabled.
Low-Battery Output
The low-battery outputs are available in active-low
(LBO, LBOH, LBOL, push-pull and open-drain) and
active-high (LBO, LBOL, LBOH, open-drain) configurations. Push-pull outputs are referenced to BATT (for
factory-trimmed versions) or VDD (for adjustable threshold versions).
The open-drain devices can be pulled to a voltage independent of VDD or BATT, up to 5.5V. This allows the
VBATT
VBATT
615
+
mV -
R
Q
S
Q
LBO
(LBO)
LBO TIMEOUT
PERIOD
( ) ARE FOR THE MAX6429
Figure 1. MAX6427/MAX6428/MAX6429 Functional Diagram
_______________________________________________________________________________________
7
MAX6427–MAX6438
Detailed Description
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
VBATT
HYSTERESIS SWITCH
LBO
TIMEOUT
PERIOD
LBOL
(LBOL)
LBOH
(LBOH)
VBATT
615
+
mV HYSTERESIS SWITCH
( ) ARE FOR THE MAX6432
Figure 2. MAX6430/MAX6431/MAX6432 Functional Diagram
device to monitor and operate from direct battery voltage
while interfacing to higher voltage microprocessors.
The MAX6427/MAX6428/MAX6429/MAX6433/MAX6434/
MAX6435 single-output voltage monitors provide a single low-battery output, LBO/LBO. The MAX6427/
MAX6428/MAX6429 fixed-threshold parts assert
LBO/LBO when BATT drops below V LTH . The
MAX6433/MAX6434/MAX6435 adjustable-threshold
parts assert LBO/LBO when the LTHIN input drops
below the VLTHIN threshold (615mV) (see Figure 5).
The MAX6430/MAX6431/MAX6432/MAX6436/MAX6437/
MAX6438 dual-output voltage monitors provide two lowbattery outputs, LBOH/LBOH and LBOL/LBOL. The
MAX6430/MAX6431/MAX6432 fixed-threshold parts
assert LBOH/LBOH when BATT drops below V HTH-,
and assert LBOL/LBOL when BATT drops below VLTH-.
The MAX6436/MAX6437/MAX6438 adjustable-threshold parts assert LBOH/LBOH when HTHIN drops below
VHTHIN-, and assert LBOL/LBOL when LTHIN drops
below VLTHIN- (see Figure 6).
8
Threshold Monitoring
The MAX6433–MAX6438 HTHIN and LTHIN inputs are
high-impedance inputs to comparators. An external resistor-divider network is required between the monitored
voltage, HTHIN, LTHIN, and GND to select the desired
thresholds (see Resistor-Value Selection). The
MAX6433/MAX6434/MAX6435 single-output voltage
monitors assert LBO/LBO when LTHIN drops below the
internal LTHIN reference (615mV). LBO/LBO is deasserted when HTHIN rises above the internal HTHIN reference
level (615mV) for at least 140ms (see Figure 6).
The MAX6436/MAX6437/MAX6438 dual-output voltage
monitors assert LBOL/LBOL when LTHIN drops below
the LTHIN- threshold and deassert LBOL/LBOL when
LTHIN rises above the LTHIN+ threshold for at least
140ms. LBOH/LBOH is asserted when HTHIN drops
below the HTHIN- threshold and is deasserted when
HTHIN rises above the HTHIN+ threshold for at least
140ms (see Figure 7).
_______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
MAX6427–MAX6438
VBATT
VDD
LTHIN
R
Q
S
Q
HTHIN
VDD
LBO
(LBO)
LBO TIMEOUT
PERIOD
+
EXTERNAL
RESISTORDIVIDER
615 mV
( ) ARE FOR THE MAX6435
Figure 3. MAX6433/MAX6434/MAX6435 Functional Diagram
Hysteresis
Hysteresis increases the comparator’s noise margin by
increasing the upper threshold or decreasing the lower
threshold (see Figure 8). The hysteresis prevents the
output from oscillating (chattering) when BATT or VDD
is near the low-battery threshold. This is especially
important for applications where the load on the battery
creates significant fluctuations in battery voltages.
Fixed Hysteresis (MAX6427–MAX6432)
The MAX6427/MAX6428/MAX6429 total hysteresis is the
difference between the factory-trimmed VLTH and VHTH.
For the MAX6430/MAX6431/MAX6432, the total hysteresis
is the difference between the factory-trimmed VHTH- and
VHTH+ or VLTH- and VLTH+ values, approximately 5%.
Adjustable Hysteresis (MAX6433–MAX6438)
Figure 7 shows the correct connections for the external
resistor-dividers. To adjust the low-battery threshold
and hysteresis connect resistor R1 between VDD and
LTHIN, resistor R2 between LTHIN and HTHIN, and R3
between HTHIN and GND. The hysteresis for the
MAX6433–MAX6438 is determined by an external resistor-divider network (see Resistor-Value Selection section of Applications Information). The hysteresis for the
MAX6436/MAX6437/MAX6438 is the differences
between VHTHIN- and VHTHIN+ (~5%) or VLTHIN- and
VLTHIN+ (~5%).
_______________________________________________________________________________________
9
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
VBATT
VDD
LTHIN
HTHIN
LBO
TIMEOUT
PERIOD
HYSTERESIS SWITCH
LBOL
(LBOL)
LBOH
(LBOH)
VBATT
615 +
mV HYSTERESIS SWITCH
( ) ARE FOR THE MAX6438
Figure 4. MAX6436/MAX6437/MAX6438 Functional Diagram
VHTH
VBATT
VLTH
tLBOP
tLBOP
LBO
Figure 5. Single Low-Battery Output Timing
10
______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
MAX6427–MAX6438
VHTH+
VHTHVBATT
VLTH+
VLTH-
tLBOP
tLBOP
LBOL
LBOH
tLBOP
tLBOP
Figure 6. Dual Low-Battery Output Timing
VDD
LBO
VDD
LBO
MAX6433
R1
VHTH
VHYST
VBATT
LTHIN
VLTH
R2
tLBOP
HTHIN
R3
GND
LBO
HTH = BATTERY VOLTAGE GOOD, ENABLE OPERATION.
LTH = BATTERY VOLTAGE LOW, SUSPEND/DISABLE OPERATION.
Figure 7. Adjustable Threshold Selection
Figure 8. Hysteresis
______________________________________________________________________________________
11
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
Applications Information
Resistor-Value Selection (Programming
the Adjustable Thresholds)
MAX6433/MAX6434/MAX6435
(See Figure 5)
VREF = VLTHIN = VHTHIN = 615mV
R1 + R2 + R 3
VTRIPHIGH = VHTL- = VREF
R3
R1 + R2 + R3
VTRIPHIGH = VHTL = VREF
R3
RTOTAL = R1 + R2 + R3
R TOTAL = R1 + R2 + R 3
Use the following steps to determine values for R1, R2,
and R3 of Figure 8.
1) Choose a value for RTOTAL, the sum of R1, R2, and
R3. Because the MAX6433/MAX6434/MAX6435
have very high input impedances, RTOTAL can be
up to 5MΩ.
2) Calculate R3 based on R TOTAL and the desired
upper trip point:
VREF × RTOTAL
585mV × RTOTAL
=
VTRIPHIGH
VTRIPHIGH
3) Calculate R2 based on R TOTAL , R3, and the
desired lower trip point:
R2 =
615mV × RTOTAL
VTRIPLOW
−
R3
R2
−
−
Use the following steps to determine values for R1, R2,
and R3 of Figure 8.
1) Choose a value for RTOTAL, the sum of R1, R2, and
R3. Because the MAX6436/MAX6437/MAX6438
have very high input impedances, RTOTAL can be
up to 5MΩ.
2) Calculate R3 based on R TOTAL and the desired
upper trip point:
R3 =
VREF × RTOTAL
585mV × RTOTAL
=
VTRIPHIGH
VTRIPHIGH
3) Calculate R2 based on R TOTAL , R3, and the
desired lower trip point:
585mV × RTOTAL
− R3
VTRIPLOW
4) Calculate R1 based on RTOTAL, R3, and R2:
R1 = RTOTAL
4) Calculate R1 based on RTOTAL, R3, and R2:
R1 = RTOTAL
VREF = VLTHIN- = VHTHIN- = 585mV
LBOL / LBOL OUTPUT :
R1 + R2 + R 3
VTRIPLOW = VLTH- = VREF
R2 + R 3
LBOH / LBOH OUTPUT :
R1 + R2 + R3
VTRIPLOW = VLTH = VREF
R2 + R3
R3 =
MAX6436/MAX6437/MAX6438
(See Figure 6)
−
R2
−
R3
VHTH+ = VHTH- ✕ 1.05, VLTH+ = VLTH- ✕ 1.05
R3
DC-to-DC Converter Application
IN
VBATT
BATT
OUT
MAX6431 LBOL
SHDN
LBOH
GND
Figure 9. DC-to-DC Converter Application
12
VCC
DC/DC
µP
NMI
GND
The MAX6430/MAX6431/MAX6432 and MAX6436/
MAX6437/MAX6438 dual-output battery monitors can
be used in conjunction with a step-up DC-to-DC converter to power 5V microprocessor systems using a single Li+ cell or two to three alkaline/NiCd/NiMH cells
(Figure 9). 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 microprocessor is removed.
______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
Li+ Battery Charger Application
The MAX6430/MAX6431/MAX6432 and MAX6436/
MAX6437/MAX6438 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 (Figure 10). Many battery chargers,
such as the MAX1879, provide the user with a CHG
output, which tells the system that the battery is
charged. The MAX6430/MAX6431/MAX6432 and
MAX6436/MAX6437/MAX6438 dual-output battery mon-
itors provide two outputs, which can be used to relay
the battery condition to the system. This information is
useful in determining which system resources can be
powered by the battery at the current charge state.
CURRENTLIMITED
AC WALL
ADAPTER
LED
GATE
IN
BATT
CHG
MAX1879
PULSE-WIDTH
SELECT INPUT
TSEL
THERM
GND
ADJ
1-CELL
Li+
BATTERY
VBATT
LBOL
MAX6430
LBOH
GND
THERMISTOR
Figure 10. Lithium-Ion Cell Charger Application (using MAX1879)
Typical Operating Circuit
VBATT
VCC
BATT
µP
MAX6427
LBO
NMI
______________________________________________________________________________________
13
MAX6427–MAX6438
Microprocessor power will not return until the battery has
recharged to a voltage greater than HTH+ (Figure 6).
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
Ordering Information (continued)
PART
TEMP RANGE
PIN-PACKAGE
MAX6428_ _UR-T
-40°C to +85°C
3 SOT23-3
MAX6429_ _UR-T
-40°C to +85°C
3 SOT23-3
MAX6430_ _US-T
-40°C to +85°C
4 SOT143-4
MAX6431_ _US-T
-40°C to +85°C
4 SOT143-4
MAX6432_ _US-T
-40°C to +85°C
4 SOT143-4
MAX6433UK-T
-40°C to +85°C
5 SOT23-5
MAX6434UK-T
-40°C to +85°C
5 SOT23-5
MAX6435UK-T
-40°C to +85°C
5 SOT23-5
MAX6436UT-T
-40°C to +85°C
6 SOT23-6
MAX6437UT-T
-40°C to +85°C
6 SOT23-6
MAX6438UT-T
-40°C to +85°C
6 SOT23-6
Pin Configurations (continued)
GND
1
4
LBOL
(LBOL)
3
BATT
MAX6430
MAX6431
MAX6432
LBOH
(LBOH)
2
SOT143-4
†The
MAX6427–MAX6432 are available with factory-trimmed
battery-monitor thresholds. Select the desired thresholds
using Tables 1 or 2 and enter the corresponding letters in
the part number by replacing “_ _”.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Note: There are 26 standard versions with a required order
minimum of 2500 pieces. Sample stock is generally held on
the standard versions only (see Standard Versions Table).
Required order increment is 10,000 pieces for nonstandard
versions. Contact factory for availability. All devices available in tape-and-reel only.
( ) ARE FOR THE MAX6432
HTHIN
1
GND 2
TRANSISTOR COUNT: 905
PROCESS TECHNOLOGY: BiCMOS
VDD
4
LBO
(LBO)
MAX6433
MAX6434
MAX6435
LTHIN 3
Chip Information
5
SOT23-5
( ) ARE FOR THE MAX6435
HTHIN 1
GND 2
MAX6436
MAX6437
MAX6438
LTHIN 3
6
VDD
5
LBOH
(LBOH)
4
LBOL
(LBOL)
SOT23-6
( ) ARE FOR THE MAX6438
14
______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
(LTH/LTH-)
LOWER THRESHOLD
UPPER THRESHOLD (HTH/HTH-)
3.4V
3.5V
VOLTAGES
3.3V
2.6V
AG
AH
AI
3.6V
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
3.1V
FG
FH
FI
FJ
Table 2. Factory-Trimmed Lower and Upper Threshold Combinations for Two-Cell
Alkaline/NiCd/NiMH Applications (MAX6427–MAX6432)
(LTH/LTH-)
LOWER THRESHOLD
UPPER THRESHOLD (HTH/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
2.1V
PQ
PR
PS
PT
Standard Versions
PART
TOP MARK
PART
MAX6427DH
FZKZ
MAX6430MR
TOP MARK
KAEL
MAX6427EH
FZLA
MAX6430OR
KAEM
MAX6427EI
FZLB
MAX6431DH
KAES
MAX6427MR
FZLF
MAX6431EH
KAET
MAX6427OR
FZLG
MAX6431EI
KAEU
MAX6428DH
FZLC
MAX6431MR
KAEN
MAX6428EH
FZLD
MAX6431OR
KAEO
MAX6428EI
FZLE
MAX6433UK
ADVH
MAX6428MR
FZLH
MAX6434UK
ADVI
MAX6428OR
FZLI
MAX6435UK
ADVJ
MAX6430DH
KAEP
MAX6436UT
ABAB
MAX6430EH
KAEQ
MAX6437UT
ABAC
MAX6430EI
KAER
MAX6438UT
ABAD
______________________________________________________________________________________
15
MAX6427–MAX6438
Table 1. Factory-Trimmed Lower and Upper Threshold Combinations for Single-Cell Li+
or Three-Cell Alkaline/NiCd/NiMH Applications (MAX6427–MAX6432)
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
Selector Guide
ACTIVELOW PUSHPULL
OUTPUT
ACTIVELOW OPENDRAIN
OUTPUT
—
!
—
—
!
—
—
—
!
—
!
—
!
—
—
—
!
!
—
!
—
!
—
—
—
!
!
—
—
!
—
—
!
MAX6432
!
—
—
—
!
—
!
MAX6433
—
!
!
—
—
!
—
MAX6434
—
!
—
!
—
!
—
MAX6435
—
!
—
—
!
!
—
MAX6436
—
!
!
—
—
—
!
MAX6437
—
!
—
!
—
—
!
MAX6438
—
!
—
—
!
—
!
PART
FACTORYFIXED
THRESHOLDS
USERADJUSTABLE
THRESHOLDS
MAX6427
!
MAX6428
!
MAX6429
MAX6430
MAX6431
16
ACTIVEHIGH OPENDRAIN
OUTPUT
SINGLE
OUTPUT
______________________________________________________________________________________
DUAL
OUTPUT
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
SOT23 L.EPS
PACKAGE OUTLINE, 3L SOT-23
21-0051
F
1
1
______________________________________________________________________________________
17
MAX6427–MAX6438
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.)
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.)
SOT-143 4L.EPS
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
PACKAGE OUTLINE, SOT-143, 4L
21-0052
18
______________________________________________________________________________________
E
1
1
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
SOT-23 5L .EPS
PACKAGE OUTLINE, SOT-23, 5L
21-0057
E
1
1
______________________________________________________________________________________
19
MAX6427–MAX6438
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.)
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.)
6LSOT.EPS
MAX6427–MAX6438
Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis
PACKAGE OUTLINE, SOT 6L BODY
21-0058
G
1
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.
20 ____________________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.