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19-2323; Rev 0; 1/02
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis
General Description
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. 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.
Features
o 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) o Low Current (1A typ) o Single or Dual Low-Battery Outputs o Push-Pull LBO, Open-Drain LBO, and Open-Drain LBO Options o 140ms Minimum LBO Timeout Period o Immune to Short Battery Voltage Transients o Guaranteed Valid LBO Logic State to BATT = 1.0V o -40C to +85C Operating Temperature Range o Small 3, 4, 5 and 6-Pin SOT Packages o No External Components Required (MAX6427-MAX6432)
MAX6427-MAX6438
Ordering Information
PART MAX6427_ _UR-T TEMP RANGE -40C to +85C PIN-PACKAGE 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 "_ _".
________________________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
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
BATT 2
3
GND
SOT23-3
( ) ARE FOR THE MAX6429
Typical Operating Circuit appears at end of data sheet.
Pin Configurations continued at end of data sheet. 1
________________________________________________________________ Maxim Integrated Products
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Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
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 = +70C) 3-Pin SOT23-3 (derate 4.0mW/C above +70C) .......320mW 4-Pin SOT143-4 (derate 4.0mW/C above +70C) .....320mW 5-Pin SOT23-5 (derate 7.1mW/C above +70C) .......571mW 6-Pin SOT23-6 (derate 8.7mW/C above +70C) .......696mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = -40C to +85C, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER Operating Voltage Range Operating Voltage Range BATT Supply Current VDD Supply Current SYMBOL VBATT VDD IBATT IDD CONDITIONS TA = -40C to +85C TA = 0C to +70C TA = -40C to +85C BATT = 3.7V, no load (MAX6427-MAX6432) VDD = 3.7V, no load (MAX6433-MAX6438) MIN 1.2 1.0 1.6 1 1 TYP MAX 5.5 5.5 5.5 1.5 1.5 UNITS V V A A
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) Factory-fixed options, BATT falling, LBO asserted when BATT falls below VLTH (MAX6427/MAX6428/MAX6429) Factory-fixed options, BATT falling, LBOH asserted when BATT falls below VHTH(MAX6430/MAX6431/MAX6432) Factory-fixed options, BATT rising, LBOH deasserted when BATT rises above VHTH+ (MAX6430/MAX6431/MAX6432) Factory-fixed options, BATT falling, LBOL asserted when BATT falls below VLTH(MAX6430/MAX6431/MAX6432) Factory-fixed options, BATT rising, LBOL deasserted when BATT rises above VLTH+ (MAX6430/MAX6431/MAX6432) -2.5 +2.5 %
LTH Threshold (Note 2)
VLTH
-2.5
+2.5
%
HTH- Threshold (Note 2)
VHTH-
-2.5
+2.5
%
HTH+ Threshold (Note 3) LTH- Threshold (Note 2)
VHTH+
-2.5
+2.5
%
VLTH-
-2.5
+2.5
%
LTH+ Threshold (Note 3)
VLTH+
-2.5
+2.5
%
2
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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 = -40C to +85C, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX6427-MAX6438
USER-ADJUSTABLE THRESHOLDS (MAX6433-MAX638) HTHIN Threshold (Note 4) User-adjustable options, HTHIN rising, LBO is deasserted when HTHIN rises above VHTHIN-, VREF = 615mV (MAX6433/MAX6434/MAX6435) User-adjustable options, LTHIN falling, LBOH is asserted when LTHIN falls below VLTHIN-, VREF = 615mV (MAX6433/MAX6434/MAX6435) User-adjustable options, HTHIN rising, LBOH is deasserted when HTHIN rises above VHTHIN+, VREF = 615mV (MAX6436/MAX6437/MAX6438) User-adjustable options, HTHIN falling, LBOH is asserted when HTHIN falls below VHTHIN-, VREF = 585mV (MAX6436/MAX6437/MAX6438) User-adjustable options, LTHIN rising, LBOL is deasserted when LTHIN rises above VLTHIN+, VREF = 615mV (MAX6436/MAX6437/MAX6438) User-adjustable options, LTHIN falling, LBOL is asserted when LTHIN falls below VLTHIN-, VREF = 585mV (MAX6436/MAX6437/MAX6438) VHTHIN or VLTHIN > 400mV
VHTHIN
-2.5
+2.5
%
LTHIN Threshold (Note 4)
VLTHIN
-2.5
+2.5
%
HTHIN+ Threshold (Note 4)
VHTHIN+
-2.5
+2.5
%
HTHIN- Threshold (Note 5)
VHTHIN-
-2.5
+2.5
%
LTHIN+ Threshold (Note 4)
VLTHIN+
-2.5
+2.5
%
LTHIN- Threshold (Note 5)
VLTHIN-
-2.5
+2.5
%
HTHIN/LTHIN Leakage Current (Note 6)
ILKG
20
nA
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3
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
ELECTRICAL CHARACTERISTICS (continued)
(BATT = 1.0V to 5.5V or VDD = 1.6V to 5.5V, TA = -40C to +85C, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS BATT or VDD/HTHIN/LTHIN rising above threshold BATT or VDD/HTHIN/LTHIN falling below threshold BATT or VDD 1.6V, ISINK = 100A, asserted low LBO/LBOL/LBOH Output LOW (Push-Pull or Open-Drain) VOL BATT or VDD 2.7V, ISINK = 1.2mA, asserted low BATT or VDD 4.5V, ISINK = 3.2mA, asserted low BATT or VDD 1.6V, ISOURCE = 200A, deasserted LBO Output HIGH (Push-Pull Only) (Note 7) VOH BATT or VDD 2.7V, ISOURCE = 500A, deasserted BATT or VDD 4.5V, ISOURCE = 800A, deasserted LBO Output Leakage Current (Open-Drain Only) ILKG LBO deasserted BATT or VDD 1.6V, ISINK = 100A, deasserted low LBO/LBOL/LBOH Output LOW (Open-Drain Only) VOL BATT or VDD 2.7V, ISINK = 1.2mA, deasserted low BATT or VDD 4.5V, ISINK = 3.2mA, deasserted low LBO Output Leakage Current (Open-Drain Only) ILKG LBO asserted 0.8 x VSUPPLY 0.8 x VSUPPLY 0.8 x VSUPPLY 500 0.3 0.3 0.4 500 nA V nA V MIN TYP MAX UNITS
LOW-BATTERY OUTPUTS (LBO, LBO, LBOH, LBOH, LBOL, LBOL ) Timeout Period Delay tLBOP tLBOD 140 210 100 0.3 0.3 0.4 V 280 ms s
Note 1: Production testing done at TA = +25C, 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
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Low-Power, Single/Dual-Level Battery Monitors with Hysteresis
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
NORMALIZED LBO TIMEOUT PERIOD vs. TEMPERATURE
MAX6427 toc01 MAX6427 toc02
MAX6427-MAX6438
SUPPLY CURRENT vs. TEMPERATURE
1.8 VBATT = 5V 1.5 SUPPLY CURRENT (A) 1.2 0.9 0.6 0.3 LBO NOT ASSERTED 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) 0.990 -40 VBATT = 3.3V 1.010 NORMALIZED LBO TIMEOUT PERIOD
MAXIMUM TRANSIENT DURATION vs. LBO COMPARATOR OVERDRIVE
OUTPUT ASSERTS MAXIMUM TRANSIENT DURATION (s)
MAX6427 toc03
80
1.005
60
1.000
40
VBATT = 2V
0.995
20 OUTPUT DOES NOT ASSERT 0 10 100 LBO COMPARATOR OVERDRIVE (mV) 1000
-20
0
20
40
60
80
TEMPERATURE (C)
NORMALIZED UPPER AND LOWER TRIP VOLTAGES vs. TEMPERATURE
MAX6427 toc04
LBO OUTPUT vs. ISINK
MAX6427 toc05
1.050 NORMALIZED TRIP VOLTAGES (V)
300 250 LBO OUTPUT (mV) 200 150 100 50 OPEN-DRAIN LBO ASSERTED 0 2 4 6 8
1.025 LOWER TRIP VOLTAGE 1.000 UPPER TRIP VOLTAGE 0.975
0.950 -40 -20 0 20 40 60 80 TEMPERATURE (C)
0 10 ISINK (mA)
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5
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
Pin Description
PIN MAX6427/ MAX6428/ MAX6429 MAX6430/ MAX6431/ MAX6432 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). Battery-Voltage Input. Input for battery-voltage threshold monitors and device power supply for factory-trimmed threshold versions. Ground 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). 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). HTH Threshold Monitor Input. A resistor-divider network sets the high threshold associated with LBOH/LBOH. LTH Threshold Monitor Input. A resistor-divider network sets the low threshold associated with LBOL/LBOL. VDD Supply Voltage Input. Device power supply for adjustable threshold versions.
2 3
3 1
-- 2
-- 2
BATT GND
--
2
--
5
LBOH/ LBOH
--
4
--
4
LBOL/ LBOL
-- -- --
-- -- --
1 3 5
1 3 6
HTHIN LTHIN VDD
6
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Low-Power, Single/Dual-Level Battery Monitors with Hysteresis
Detailed Description
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. Factorytrimmed 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.
MAX6427-MAX6438
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
R
Q
S VBATT 615 + mV -
Q
LBO (LBO)
LBO TIMEOUT PERIOD
( ) ARE FOR THE MAX6429
Figure 1. MAX6427/MAX6428/MAX6429 Functional Diagram
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7
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
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 VHTH-, 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).
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).
8
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Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
VBATT
VDD LTHIN R Q
HTHIN S VDD 615 mV
+
Q
LBO (LBO)
LBO TIMEOUT PERIOD
EXTERNAL RESISTORDIVIDER
( ) 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%).
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9
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
VBATT
VDD LTHIN
HTHIN HYSTERESIS SWITCH
LBO TIMEOUT PERIOD
LBOL (LBOL) LBOH (LBOH)
VBATT 615 + mV HYSTERESIS SWITCH
( ) ARE FOR THE MAX6438
Figure 4. MAX6436/MAX6437/MAX6438 Functional Diagram
VHTH VBATT VLTH
tLBOP LBO
tLBOP
Figure 5. Single Low-Battery Output Timing
10
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Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
VHTH+ VHTHVBATT VLTH+ VLTH-
tLBOP LBOL
tLBOP
LBOH
tLBOP
tLBOP
Figure 6. Dual Low-Battery Output Timing
VDD
VDD
LBO
LBO
R1
MAX6433
VHTH VBATT VLTH VHYST
LTHIN
R2 tLBOP HTHIN GND LBO
R3
HTH = BATTERY VOLTAGE GOOD, ENABLE OPERATION. LTH = BATTERY VOLTAGE LOW, SUSPEND/DISABLE OPERATION.
Figure 7. Adjustable Threshold Selection
Figure 8. Hysteresis
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11
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
Applications Information
Resistor-Value Selection (Programming the Adjustable Thresholds) MAX6433/MAX6434/MAX6435
VREF = VLTHIN = VHTHIN = 615mV R1 + R2 + R3 VTRIPLOW = VLTH = VREF R2 + R3 R1 + R2 + R3 VTRIPHIGH = VHTL = VREF R3 RTOTAL = R1 + R2 + R3 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 5M. 2) Calculate R3 based on RTOTAL and the desired upper trip point: R3 = VREF x RTOTAL 615mV x RTOTAL = VTRIPHIGH VTRIPHIGH
MAX6436/MAX6437/MAX6438
VREF = VLTHIN- = VHTHIN- = 585mV R1 + R2 + R3 VTRIPLOW = VLTH- = VREF R2 + R3 R1 + R2 + R3 VTRIPHIGH = VHTL- = VREF R3 RTOTAL = R1 + R2 + R3 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 5M. 2) Calculate R3 based on RTOTAL and the desired upper trip point: R3 = VREF x RTOTAL 615mV x RTOTAL = VTRIPHIGH VTRIPHIGH
3) Calculate R2 based on R TOTAL , R3, and the desired lower trip point: 615mV x RTOTAL - R3 VTRIPLOW 4) Calculate R1 based on RTOTAL, R3, and R2:
3) Calculate R2 based on R TOTAL , R3, and the desired lower trip point:
R2 = 615mV x RTOTAL VTRIPLOW
-
R3
R1 = RTOTAL
-
R2
-
R3
4) Calculate R1 based on RTOTAL, R3, and R2: R1 = RTOTAL
-
VHTH+ = VHTH- 1.05, VLTH+ = VLTH- 1.05
R2
-
R3
DC-to-DC Converter Application
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. Microprocessor power will not return until the battery has recharged to a voltage greater than HTH+ (Figure 6).
IN VBATT BATT DC/DC
OUT VCC
MAX6431 LBOL
SHDN
P
LBOH GND
NMI GND
Figure 9. DC-to-DC Converter Application 12 ______________________________________________________________________________________
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 monitors 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.
MAX6427-MAX6438
CURRENTLIMITED AC WALL ADAPTER LED IN CHG GATE BATT 1-CELL Li+ BATTERY VBATT LBOL
MAX1879
PULSE-WIDTH SELECT INPUT TSEL THERM GND ADJ
MAX6430
LBOH GND
THERMISTOR
Figure 10. Lithium-Ion Cell Charger Application (using MAX1879)
Typical Operating Circuit
VBATT
VCC
BATT
MAX6427
LBO NMI
P
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13
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
Ordering Information (continued)
PART MAX6428_ _UR-T MAX6429_ _UR-T MAX6430_ _US-T MAX6431_ _US-T MAX6432_ _US-T MAX6433UK-T MAX6434UK-T MAX6435UK-T MAX6436UT-T MAX6437UT-T MAX6438UT-T
The
Pin Configurations (continued)
TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
PIN-PACKAGE 3 SOT23-3 3 SOT23-3 4 SOT143-4 4 SOT143-4 4 SOT143-4 5 SOT23-5 5 SOT23-5 5 SOT23-5 6 SOT23-6 6 SOT23-6 6 SOT23-6
LBOH (LBOH) 2 3 BATT GND 1 4 LBOL (LBOL)
MAX6430 MAX6431 MAX6432
SOT143-4
( ) ARE FOR THE MAX6432
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 "_ _". 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.
HTHIN
1
5
VDD
GND 2
MAX6433 MAX6434 MAX6435
4 LBO (LBO)
LTHIN 3
Chip Information
TRANSISTOR COUNT: 905 PROCESS TECHNOLOGY: BiCMOS
SOT23-5
( ) ARE FOR THE MAX6435
HTHIN 1
6
VDD
GND 2
MAX6436 MAX6437 MAX6438
5
LBOH (LBOH) LBOL (LBOL)
LTHIN 3
4
SOT23-6
( ) ARE FOR THE MAX6438
14
______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
Table 1. Factory-Trimmed Lower and Upper Threshold Combinations for Single-Cell Li+ or Three-Cell Alkaline/NiCd/NiMH Applications (MAX6427-MAX6432)
LOWER THRESHOLD
VOLTAGES 2.6V
(LTH/LTH-)
3.3V AG BG CG DG EG FG
UPPER THRESHOLD (HTH/HTH-) 3.4V 3.5V AH BH CH DH EH FH AI BI CI DI EI FI
3.6V AJ BJ CJ DJ EJ FJ
2.7V 2.8V 2.9V 3.0V 3.1V
Table 2. Factory-Trimmed Lower and Upper Threshold Combinations for Two-Cell Alkaline/NiCd/NiMH Applications (MAX6427-MAX6432)
UPPER THRESHOLD (HTH/HTH-)
LOWER THRESHOLD
VOLTAGES 1.6V
(LTH/LTH-)
2.3V KQ LQ MQ NQ OQ PQ
2.4V KR LR MR NR OR PR
2.5V KS LS MS NS OS PS
2.6V KT LT MT NT OT PT
1.7V 1.8V 1.9V 2.0V 2.1V
Standard Versions
PART MAX6427DH MAX6427EH MAX6427EI MAX6427MR MAX6427OR MAX6428DH MAX6428EH MAX6428EI MAX6428MR MAX6428OR MAX6430DH MAX6430EH MAX6430EI TOP MARK FZKZ FZLA FZLB FZLF FZLG FZLC FZLD FZLE FZLH FZLI KAEP KAEQ KAER PART MAX6430MR MAX6430OR MAX6431DH MAX6431EH MAX6431EI MAX6431MR MAX6431OR MAX6433UK MAX6434UK MAX6435UK MAX6436UT MAX6437UT MAX6438UT TOP MARK KAEL KAEM KAES KAET KAEU KAEN KAEO ADVH ADVI ADVJ ABAB ABAC ABAD
______________________________________________________________________________________
15
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
Selector Guide
PART FACTORYFIXED THRESHOLDS " " " " " " -- -- -- -- -- -- USERADJUSTABLE THRESHOLDS -- -- -- -- -- -- " " " " " " ACTIVELOW PUSHPULL OUTPUT " -- -- " -- -- " -- -- " -- -- ACTIVELOW OPENDRAIN OUTPUT -- " -- -- " -- -- " -- -- " -- ACTIVEHIGH OPENDRAIN OUTPUT -- -- " -- -- " -- -- " -- -- " SINGLE OUTPUT " " " -- -- -- " " " -- -- -- DUAL OUTPUT -- -- -- " " " -- -- -- " " "
MAX6427 MAX6428 MAX6429 MAX6430 MAX6431 MAX6432 MAX6433 MAX6434 MAX6435 MAX6436 MAX6437 MAX6438
16
______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis
Package Information
SOTPO3L.EPS
MAX6427-MAX6438
______________________________________________________________________________________
17
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
Package Information (continued)
18
______________________________________________________________________________________
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis
Package Information (continued)
SOT5L.EPS
MAX6427-MAX6438
______________________________________________________________________________________
19
Low-Power, Single/Dual-Level Battery Monitors with Hysteresis MAX6427-MAX6438
Package Information (continued)
6LSOT.EPS
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 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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