MAXIM MAX6427, MAX6438 User Manual

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.

________________________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

Features

♦ 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)

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

________________________________________________________________ Maxim Integrated Products 1

19-2323; Rev 1; 9/03

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.

Ordering Information

Typical Operating Circuit appears at end of data sheet.

Ordering Information continued at end of data sheet.

Pin Configurations 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 “_ _”.

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.

BATT

1

3 GND

( ) ARE FOR THE MAX6429.

MAX6427
MAX6428
MAX6429

SOT23-3

TOP VIEW

2

LBO

(LBO)

Pin Configurations

查询MAX6427供应商

PART TEMP RANGE PIN-PACKAGE

MAX6427_ _UR-T -40°C to +85°C 3 SOT23-3

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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)

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, VDDto GND ................................................-0.3V to +6.0V

HTHIN, LTHIN Inputs to GND.....................-0.3V to (V

DD

+ 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 V

DD

+ 0.3V)

Input Current (all pins) ........................................................20mA

Output Current (all pins) .....................................................20mA

Continuous Power Dissipation (T

A

= +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

Operating Voltage Range V

Operating Voltage Range V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

BATT

DD

TA = -40°C to +85°C

TA = 0°C to +70°C

TA = -40°C to +85°C 1.6 5.5 V

1.2 5.5

1.0 5.5

V

BATT Supply Current I

VDD Supply Current I

FACTORY-FIXED THRESHOLDS (MAX6427–MAX6432)

HTH Threshold
(Note 2)

LTH Threshold
(Note 2)

HTH- Threshold
(Note 2)

HTH+ Threshold
(Note 3)

LTH- Threshold
(Note 2)

LTH+ Threshold
(Note 3)

BATT

V

V

V

HTH-

V

HTH+

V

V

LTH+

DD

HTH

LTH

LTH-

V

= 3.7V, no load (MAX6427–MAX6432) 1 1.5 µA

BATT

= 3.7V, no load

V

DD

(MAX6433–MAX6438)

Factory-fixed options, BATT rising,
LBO deasserted when BATT rises above
V

(MAX6427/MAX6428/MAX6429)

HTH

Factory-fixed options, BATT falling,
LBO asserted when BATT falls below V
(MAX6427/MAX6428/MAX6429)

Factory-fixed options, BATT falling, LBOH
asserted when BATT falls below V
(MAX6430/MAX6431/MAX6432)

Factory-fixed options, BATT rising,
LBOH deasserted when BATT rises above
V

(MAX6430/MAX6431/MAX6432)

HTH+

Factory-fixed options, BATT falling,
LBOL asserted when BATT falls below V
(MAX6430/MAX6431/MAX6432)

Factory-fixed options, BATT rising,
LBOL deasserted when BATT rises above
V

(MAX6430/MAX6431/MAX6432)

LTH+

HTH-

LTH

LTH-

1 1.5 µA

-2.5 +2.5 %

-2.5 +2.5 %

-2.5 +2.5 %

-2.5 +2.5 %

-2.5 +2.5 %

-2.5 +2.5 %

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

_______________________________________________________________________________________ 3

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)

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)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

User-adjustable options, HTHIN rising,

V

HTHIN

V

LTHIN

V

HTHIN+

V

HTHIN-

V

LTHIN+

LBO is deasserted when HTHIN rises above
V

, V

HTHIN-

(MAX6433/MAX6434/MAX6435)

User-adjustable options, LTHIN falling,
LBOH is asserted when LTHIN falls below
V

LTHIN-

(MAX6433/MAX6434/MAX6435)

User-adjustable options, HTHIN rising,
LBOH is deasserted when HTHIN rises
above V
(MAX6436/MAX6437/MAX6438)

User-adjustable options, HTHIN falling,
LBOH is asserted when HTHIN falls below
V

HTHIN-

(MAX6436/MAX6437/MAX6438)

User-adjustable options, LTHIN rising,
LBOL is deasserted when LTHIN rises
above V
(MAX6436/MAX6437/MAX6438)

REF

, V

REF

HTHIN+

, V

REF

LTHIN+

= 615mV

= 615mV

, V

REF

= 585mV

, V

= 615mV

REF

= 615mV

-2.5 +2.5 %

-2.5 +2.5 %

-2.5 +2.5 %

-2.5 +2.5 %

-2.5 +2.5 %

LTHIN- Threshold
(Note 5)

HTHIN/LTHIN Leakage Current
(Note 6)

V

LTHIN-

I

LKG

User-adjustable options, LTHIN falling,
LBOL is asserted when LTHIN falls below

, V

or V

= 585mV

REF

> 400mV 20 nA

LTHIN

V

LTHIN-

(MAX6436/MAX6437/MAX6438)

V

HTHIN

-2.5 +2.5 %

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

4 _______________________________________________________________________________________

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: V

SUPPLY

is BATT or VDD.

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)

LOW-BATTERY OUTPUTS (LBO, LBO, LBOH, LBOH, LBOL, LBOL )

Timeout Period t

Delay t

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)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

LBOP

LBOD

V

OL

V

OH

I

LKG

V

OL

I

LKG

BATT or VDD/HTHIN/LTHIN rising above
threshold

BATT or VDD/HTHIN/LTHIN falling below
threshold

BATT or V

≥ 1.6V, I

DD

SINK

= 100µA,

asserted low

BATT or V

≥ 2.7V, I

DD

SINK

= 1.2mA,

asserted low

BATT or V

≥ 4.5V, I

DD

SINK

= 3.2mA,

asserted low

BATT or V

≥ 1.6V, I

DD

SOURCE

= 200µA,

deasserted

BATT or V

≥ 2.7V, I

DD

SOURCE

= 500µA,

deasserted

BATT or V

≥ 4.5V, I

DD

SOURCE

= 800µA,

deasserted

LBO deasserted 500 nA

BATT or V

≥ 1.6V, I

DD

SINK

= 100µA,

deasserted low

BATT or V

≥ 2.7V, I

DD

SINK

= 1.2mA,

deasserted low

BATT or V

≥ 4.5V, I

DD

SINK

= 3.2mA,

deasserted low

LBO asserted 500 nA

140 210 280 ms

100 µs

0.3

0.3

0.4

0.8 × V

SUPPLY

0.8 × V

SUPPLY

0.8 × V

SUPPLY

0.3

0.3

0.4

V

V

V

0

0.6

0.3

1.2

0.9

1.5

1.8

-40 20 40-20 0 60 80

SUPPLY CURRENT

vs. TEMPERATURE

MAX6427 toc01

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

V

BATT

= 5V

V

BATT

= 3.3V

V

BATT

= 2V

LBO NOT ASSERTED

1.010

1.005

1.000

0.995

0.990

-40 20-20 0 40 60 80

NORMALIZED LBO TIMEOUT PERIOD

vs. TEMPERATURE

MAX6427 toc02

TEMPERATURE (°C)

NORMALIZED LBO TIMEOUT PERIOD

80

60

40

20

0

10 100 1000

MAXIMUM TRANSIENT DURATION

vs. LBO COMPARATOR OVERDRIVE

MAX6427 toc03

LBO COMPARATOR OVERDRIVE (mV)

MAXIMUM TRANSIENT DURATION (µs)

OUTPUT DOES
NOT ASSERT

OUTPUT ASSERTS

0.950

0.975

1.025

1.000

1.050

-40 0-20 20 40 60 80

NORMALIZED UPPER AND LOWER

TRIP VOLTAGES vs. TEMPERATURE

MAX6427 toc04

TEMPERATURE (°C)

NORMALIZED TRIP VOLTAGES (V)

LOWER TRIP VOLTAGE

UPPER TRIP VOLTAGE

0

100

50

200

150

250

300

010

MAX6427 toc05

I

SINK

(mA)

4268

LBO OUTPUT vs. I

SINK

LBO OUTPUT (mV)

OPEN-DRAIN LBO
ASSERTED

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

6 _______________________________________________________________________________________

Pin Description

PIN

M AX6427/
M AX6428/
M AX6429

1 — 4 —

23——BATT

3 1 2 2 GND Ground

M AX6430/
M AX6431/
M AX6432

M AX6433/
M AX6434/
M AX6435

M AX6436/
M AX6437/
M AX6438

— 2 — 5

— 4 — 4

NAME FUNCTION

Low-Battery Output. LBO/LBO is asserted when BATT drops

(MAX6427/MAX6428/MAX6429) or when LTHIN

LTH

(MAX6430/MAX6431/MAX6432) or when

HTH-

(MAX6430/MAX6431/MAX6432) or when

LTH-

(MAX6430/MAX6431/MAX6432) or LTHIN rises

LTH+

(MAX6436/MAX6437/MAX6438).

LTHIN+

(MAX6436/MAX6437/ MAX6438). It

HTHIN-

(MAX6436/MAX6437/

LTHIN-

LBO/

LBO

LBOH/

LBOH

LBOL/

LBOL

below V
(MAX6433/MAX6434/MAX6435) drops below V
remains asserted for at least 140ms after BATT exceeds V
(MAX6427/MAX6428/MAX6429) or V
MAX6434/MAX6435).

Battery-Voltage Input. Input for battery-voltage threshold
monitors and device power supply for factory-trimmed
threshold versions.

Low-Battery Output High. LBOH/LBOH is asserted when BATT
drops below V
HTHIN drops below V
remains asserted for at least 140ms after BATT exceeds V
(MAX6430/MAX6431/MAX6432) or HTHIN rises above V
(MAX6436/MAX6437/MAX6438).

Low-Battery Output Low. LBOL/LBOL is asserted when BATT
drops below V
LTHIN drops below V
MAX6438). It remains asserted for at least 140ms after BATT
exceeds V
above V

HTHIN

LTHIN

(MAX6433/

, and

HTH

HTH+

HTHIN+

—— 1 1 HTHIN

—— 3 3 LTHIN

—— 56V

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

DD

threshold versions.

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

_______________________________________________________________________________________ 7

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. 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 (V

DD

≥ 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 VDDor BATT, up to 5.5V. This allows the

Figure 1. MAX6427/MAX6428/MAX6429 Functional Diagram

V

BATT

V

BATT

615

+

mV

-

( ) ARE FOR THE MAX6429

LBO TIMEOUT

PERIOD

R

S

Q

LBO

Q

(LBO)

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

8 _______________________________________________________________________________________

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 V

LTHIN

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 V

LTH-

.

The MAX6436/MAX6437/MAX6438 adjustable-thresh­old parts assert LBOH/LBOH when HTHIN drops below
V

HTHIN-

, and assert LBOL/LBOL when LTHIN drops

below V

LTHIN-

(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).

Figure 2. MAX6430/MAX6431/MAX6432 Functional Diagram

V

BATT

V

BATT

615

+

mV

-

( ) ARE FOR THE MAX6432

HYSTERESIS SWITCH

HYSTERESIS SWITCH

LBO

TIMEOUT

PERIOD

LBOL

(LBOL)

LBOH
(LBOH)

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

_______________________________________________________________________________________ 9

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 V

DD

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 V

LTH

and V

HTH.

For the MAX6430/MAX6431/MAX6432, the total hysteresis
is the difference between the factory-trimmed V

HTH-

and

V

HTH+

or V

LTH-

and V

LTH+

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 V

DD

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 sec-
tion of Applications Information). The hysteresis for the
MAX6436/MAX6437/MAX6438 is the differences
between V

HTHIN-

and V

HTHIN+

(~5%) or V

LTHIN-

and
V

LTHIN+

(~5%).

Figure 3. MAX6433/MAX6434/MAX6435 Functional Diagram

V

BATT

V

DD

LTHIN

HTHIN

V

DD

+

615

EXTERNAL
RESISTOR-

DIVIDER

( ) ARE FOR THE MAX6435

mV

-

R

LBO TIMEOUT

PERIOD

Q

LBO

QS

(LBO)

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

10 ______________________________________________________________________________________

Figure 4. MAX6436/MAX6437/MAX6438 Functional Diagram

Figure 5. Single Low-Battery Output Timing

V

BATT

V

DD

LTHIN

HTHIN

V

BATT

615

+

-

mV

( ) ARE FOR THE MAX6438

V

HTH

V

BATT

V

LTH

HYSTERESIS SWITCH

HYSTERESIS SWITCH

LBO

TIMEOUT

PERIOD

LBOL

(LBOL)

LBOH
(LBOH)

LBO

t

LBOP

t

LBOP

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

______________________________________________________________________________________ 11

Figure 6. Dual Low-Battery Output Timing

Figure 7. Adjustable Threshold Selection

Figure 8. Hysteresis

V

HTH+

V

HTH-

V

BATT

V

LTH+

V

LTH-

t

LBOL

LBOH

LBOP

V

DD

R1

R2

V

DD

MAX6433

LTHIN

HTHIN GND

LBO

t

LBOP

LBO

t

LBOP

t

LBOP

V

HTH

V

t

LBOP

HYST

V

BATT

V

LTH

LBO

R3

HTH = BATTERY VOLTAGE GOOD, ENABLE OPERATION.
LTH = BATTERY VOLTAGE LOW, SUSPEND/DISABLE OPERATION.

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

12 ______________________________________________________________________________________

Applications Information

Resistor-Value Selection (Programming

the Adjustable Thresholds)

MAX6433/MAX6434/MAX6435

(See Figure 5)

Use the following steps to determine values for R1, R2,
and R3 of Figure 8.

1) Choose a value for R

TOTAL

, the sum of R1, R2, and
R3. Because the MAX6433/MAX6434/MAX6435
have very high input impedances, R

TOTAL

can be

up to 5MΩ.

2) Calculate R3 based on R

TOTAL

and the desired

upper trip point:

3) Calculate R2 based on R

TOTAL

, R3, and the

desired lower trip point:

4) Calculate R1 based on R

TOTAL

, R3, and R2:

MAX6436/MAX6437/MAX6438

(See Figure 6)

Use the following steps to determine values for R1, R2,
and R3 of Figure 8.

1) Choose a value for R

TOTAL

, the sum of R1, R2, and
R3. Because the MAX6436/MAX6437/MAX6438
have very high input impedances, R

TOTAL

can be

up to 5MΩ.

2) Calculate R3 based on R

TOTAL

and the desired

upper trip point:

3) Calculate R2 based on R

TOTAL

, R3, and the

desired lower trip point:

4) Calculate R1 based on R

TOTAL

, R3, and R2:

V

HTH+

= V

HTH-

✕ 1.05, V

LTH+

= V

LTH-

✕ 1.05

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.

RR RR

TOTAL

123 = −−

5853mV R

V

R

TOTAL

TRIPLOW

×

−

R

VR

V

mV R

V

REF TOTAL

TRIPHIGH

TOTAL

TRIPHIGH

3

585

=

×

=

×

Figure 9. DC-to-DC Converter Application

VV V mV

===

REF LTHIN HTHIN

VVV

TRIPLOW LTH REF

VVV

TRIPHIGH HTL REF

RRRR

TOTAL

=+ +

==

==

12 3

VR

×

3

=

REF TOTAL

V

TRIPHIGH

R

2

mV R

6153=×

V

TRIPLOW

615

RR R

++

12 3






RR

+

23

RR R

++

12 3






R

3

mV R

×

V

TRIPHIGH

R

−

R

=

585

TOTAL






TOTAL






VV V mV

===

REF LTHI HTHIN

LBOL

VVV

LBOH

VVV

RRRR

LBOL OUTPUT

/:

TRIPLOW LTH REF

/:

TRIPHIGH REF

TOTAL

N- -

==

-

LBOH OUTPUT

==

=+ +

HTL-

12 3

585



RR R

++

12 3



RR

+

23





++

RR R

12 3




R

3











RR RR

123 = −−

TOTAL

V

BATT

BATT

MAX6431

LBOL

LBOH

GND GND

IN

DC/DC

SHDN

OUT

NMI

V

CC

µP

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

______________________________________________________________________________________ 13

Microprocessor power will not return until the battery has
recharged to a voltage greater than HTH+ (Figure 6).

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.

Figure 10. Lithium-Ion Cell Charger Application (using MAX1879)

Typical Operating Circuit

CURRENT-

LIMITED
AC WALL
ADAPTER

LED

PULSE-WIDTH
SELECT INPUT

IN

CHG

TSEL

THERM ADJ

GATE

BATT

MAX1879 MAX6430

GND

V

1-CELL
Li+
BATTERY

BATT

LBOL

LBOH

GND

THERMISTOR

BATT

V

BATT

MAX6427

LBO

NMI

V

CC

µP

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

14 ______________________________________________________________________________________

Chip Information

TRANSISTOR COUNT: 905

PROCESS TECHNOLOGY: BiCMOS

†

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 “_ _”.

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.

Ordering Information (continued)

Pin Configurations (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

LBOL

4

1

GND

LBOH

(LBOH)

( ) ARE FOR THE MAX6432

2

SOT143-4

15V

HTHIN

2

GND

MAX6430
MAX6431
MAX6432

MAX6433
MAX6434
MAX6435

(LBOL)

3 BATT

DD

LTHIN

34

SOT23-5

( ) ARE FOR THE MAX6435

16V

HTHIN

GND

LTHIN

( ) ARE FOR THE MAX6438

MAX6436

2

MAX6437
MAX6438

34

SOT23-6

5 LBOH

LBO
(LBO)

DD

(LBOH)

LBOL
(LBOL)

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

______________________________________________________________________________________ 15

Table 1. Factory-Trimmed Lower and Upper Threshold Combinations for Single-Cell Li+
or Three-Cell Alkaline/NiCd/NiMH Applications (MAX6427–MAX6432)

Table 2. Factory-Trimmed Lower and Upper Threshold Combinations for Two-Cell
Alkaline/NiCd/NiMH Applications (MAX6427–MAX6432)

LOWER THRESHOLD

(LTH/LTH-)

LOWER THRESHOLD

(LTH/LTH-)

Standard Versions

VOLTAGES 3.3V 3.4V 3.5V 3.6V

2.6V

2.7V

2.8V

2.9V

3.0V

3.1V FG FH FI FJ

AG AH AI AJ

BG BH BI BJ

CG CH CI CJ

DG DH DI DJ

EG EH EI EJ

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

UPPER THRESHOLD (HTH/HTH-)

PART TOP MARK

MAX6427DH FZKZ

MAX6427EH FZLA

MAX6427EI FZLB

MAX6427MR FZLF

MAX6427OR FZLG

MAX6428DH FZLC

MAX6428EH FZLD

MAX6428EI FZLE

MAX6428MR FZLH

MAX6428OR FZLI

MAX6430DH KAEP

MAX6430EH KAEQ

MAX6430EI KAER

PART TOP MARK

MAX6430MR KAEL

MAX6430OR KAEM

MAX6431DH KAES

MAX6431EH KAET

MAX6431EI KAEU

MAX6431MR KAEN

MAX6431OR KAEO

MAX6433UK ADVH

MAX6434UK ADVI

MAX6435UK ADVJ

MAX6436UT ABAB

MAX6437UT ABAC

MAX6438UT ABAD

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

16 ______________________________________________________________________________________

Selector Guide

FACTORY-

PART

MAX6427  —  ——  —

MAX6428  —— —  —

MAX6429  ——— —

MAX6430  —  —— — 

MAX6431  —— —— 

MAX6432  ——— — 

MAX6433 — ——  —

MAX6434 —  —  —  —

MAX6435 —  —— —

MAX6436 — —— — 

MAX6437 —  —  —— 

MAX6438 —  —— — 

FIXED

THRESHOLDS

USER-

ADJUSTABLE

THRESHOLDS

ACTIVE-

LOW PUSH-

PULL

OUTPUT

ACTIVE-

LOW OPEN-

DRAIN

OUTPUT

ACTIVE-

HIGH OPEN-

DRAIN

OUTPUT

SINGLE

OUTPUT

DUAL

OUTPUT

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

______________________________________________________________________________________ 17

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

.)

SOT23 L.EPS

PACKAGE OUTLINE, 3L SOT-23

1

21-0051

F

1

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

18 ______________________________________________________________________________________

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

PACKAGE OUTLINE, SOT-143, 4L

21-0052

1

E

1

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors

with Hysteresis

______________________________________________________________________________________ 19

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-23 5L .EPS

PACKAGE OUTLINE, SOT-23, 5L

1

21-0057

E

1

MAX6427–MAX6438

Low-Power, Single/Dual-Level Battery Monitors
with Hysteresis

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

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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

PACKAGE OUTLINE, SOT-23, 6L

1

21-0058

F

1