Datasheet MAX1666SEEE, MAX1666VEEP Datasheet (Maxim)

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General Description

The MAX1666 provides complete protection against over­voltage, undervoltage, overcharge current, overdischarge
current, and cell mismatch for 2-cell to 4-cell Lithium-Ion
battery packs. The voltage of each cell in the battery pack
is checked and compared to the programmable threshold
and to the other cells in the pack.

The MAX1666 protects the battery pack in an overcurrent
condition by disconnecting the pack from the load at a pro­grammable limit. On-chip power MOSFET drivers control
external P-channel MOSFETs to disconnect the cells from
external terminals when faults occur.

The MAX1666 employs a unique timing scheme that allows
three modes of operation, for optimal performance and bat­tery power conservation. The MAX1666 can operate in a
stand-alone configuration or in conjunction with a micro­controller. It is available in three versions: the “S” version
monitors two Li-Ion cells, the “V” version monitors three
cells, and the “X” version monitors four cells.

Applications

2/3/4-Cell Lithium-Ion Battery Pack

Features

♦ Overvoltage Protection

Programmable Limits from +4.0V to +4.4V
Accurate to ±0.5%

♦ Undervoltage Protection

Programmable Limits from +2.0V to +3.0V
Accurate to ±2.5%

♦ Cell Mismatch Protection

Programmable Limits from 0 to 500mV
Accurate to ±10%

♦ Overcharge Current Protection
♦ Overdischarge Current Protection
♦ Low Operating Supply Current: 30µA typ
♦ Low Standby Current: 1µA max
♦ +28V max Input Voltage
♦ Available in Small 16-Pin QSOP (MAX1666S) and

20-Pin QSOP (MAX1666V/X) Packages

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

________________________________________________________________

Maxim Integrated Products

1

TOP VIEW

20

19

18

17

16

15

14

13

1

2

3

4

5

6

7

8

UVO

V

CC

REF

OVACGO

TKO

DSO

SRC

UVA

MMA

WRN

PKFB1P

B2P

B3P

B3P

12

11

9

10

CGI

DSIPKN

GND

MAX1666V

20

19

18

17

16

15

14

13

1

2

3

4

5

6

7

8

UVO

V

CC

REF

OVACGO

TKO

DSO

SRC

UVA

MMA

WRN

PKFB1P

B2P

B3P

B4P

12

11

9

10

CGI

DSIPKN

GND

MAX1666X

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

SRC V

CC

REF

OVA

UVA

MMA

PKF

CGI

DSI

MAX1666S

DSO

TKO

BIP

CGO

B2P

GND

PKN

QSOP

QSOP QSOP

19-1465; Rev 1; 7/99

PART

MAX1666SEEE
MAX1666VEEP
MAX1666XEEP -40°C to +85°C

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

16 QSOP
20 QSOP
20 QSOP

Pin Configurations

Ordering Information

Selector Guide

Typical Operating Circuits appear at end of data sheet.

NUMBER OF LI-ION CELLSPART

MAX1666S 2

3
4MAX1666X

MAX1666V

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

SRC

= 16V, each cell voltage V

CELL

= 3.6V, 330kΩ load at REF, TA= 0°C to +85°C, unless otherwise noted. Typical values are at

T

A

= +25°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.

SRC, DSO, TKO, CGO, UVO, PKF, WRN to GND ...-0.3V to +28V

V

CC

, REF, OVA, UVA, MMA to GND ........................-0.3V to +6V

B4P to B3P ...............................................................-0.3V to +6V

B3P to B2P ...............................................................-0.3V to +6V

B2P to B1P ...............................................................-0.3V to +6V

B1P to GND..............................................................-0.3V to +6V

PKN to GND...........................................................................±2V

V

CC

, CGI, DSI to PKN...............................................-0.3V to +6V

Continuous Power Dissipation (T

A

= +70°C)

16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW

20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10sec) .............................+300°C

No faults, long time average current from
the top battery terminal B_P

V

SRC

- V

B_P

= 1V

V

SRC

- V

B_P

R

LOAD

≥ 665Ω, 2V < V

CELL

< 4.4V

Pulse on

CONDITIONS

µA

30 45

I

SUP

Supply Current

µA

210

V

1

Charge Mode Detection Threshold
SRC Input Current Range

µA1I

SHDN

Shutdown Supply Current

V3.09 3.25 3.41V

CC

VCCOutput Voltage

V2.7 2.85 3

VCCUndervoltage Lockout
Threshold

V1.221V

REF

Reference Output Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

Cell voltage rising

Cell voltage falling

4.378 4.400 4.422

V4.2

3.980 4.000 4.020

Overvoltage Threshold

mV200Overvoltage Threshold Hysteresis

V

1.950 2.000 2.050

Undervoltage Threshold 2.500

2.925 3.000 3.075

OVA, UVA, MMA = REF

Above undervoltage threshold,
cell voltage falling

mV

All cells > 2V

-220 -200 -180

PKN to GND Overcharge Current
Threshold

nA0.1 20OVA, UVA, MMA Input Current

mV100

mV100Undervoltage Threshold Hysteresis

WRN Early Warning Threshold

mV

±0

Cell Mismatch Threshold

±250

±450 ±500 ±550

mV270 300 330

PKN to GND Overdischarge
Current Threshold

OVA = GND
V

OVA

= V

REF

/ 2

OVA = REF

UVA = GND
V

UVA

= V

REF

/ 2

UVA = REF

MMA = GND
V

MMA

= V

REF

/ 2

MMA = REF

mV200

WRN Early Warning Threshold
Hysteresis

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

_______________________________________________________________________________________ 3

No faults, long time average current from the
top battery terminal B_P

V

SRC

- V

B_P

= 1V to 4V

V

SRC

- V

B_P

4.373 4.427

R

LOAD

≥ 665Ω, 2V < V

CELL

< 4.4V

3.975 4.025

CONDITIONS

Overvoltage Threshold

OVA, UVA, MMA = REF

µA

45

I

SUP

Supply Current

µA

10

V

1

Charge Mode Detection
Threshold

SRC Input Current Range

nA20OVA, UVA, MMA Leakage

µA1I

SHDN

Shutdown Supply Current

V3.09 3.41V

CC

VCCOutput Voltage

V2.7 3

VCCUndervoltage Lockout
Threshold

UNITSMIN TYP MAXSYMBOLPARAMETER

OVA = GND
OVA = REF

V

V

2.925 3.075

1.950 2.050

Undervoltage Threshold

UVA = GND
UVA = REF

CONDITIONS

No faults, V

DSO

= V

CGO=VUVO

= 1V to 27V

V

DSO

= V

SRC

- 4V and V

CGO

= V

SRC

- 4V,

fault condition

V

DSO

= V

CGO

= V

UVO

= 27V, fault condition

ms1.6 2.4 3.2t

I-DELAY

Overdischarge/Overcharge
Current Fault Blanking Time

ms330 550 770t

P-DELAY

Overcurrent Fault Timer Delay

µA20 30 40

DSO, CGO, UVO Output Sink
Current

mA210

DSO, CGO Output Source
Current

µA0.2

DSO, CGO, UVO Leakage
Current

UNITSMIN TYP MAXSYMBOLPARAMETER

V

DSI

, V

CGI

= 5V

Referenced to PKN

Referenced to PKN

Fault condition, V

WRN

= 0.4V

Fault condition, V

PKF

= 0.4V

V

PKF

= V

WRN

= 27V

µA1

DSI, CGI Input Current

V0.45

V2

TKO = GND
DSI, CGI Input High Voltage
DSI, CGI Input Low Voltage

mA24

WRN Sink Current

mA48

PKF Sink Current

µA0.2

PKF, WRN Leakage Current

kΩ100 200

TKO Pull-Down Resistance

mA18

TKO Source Current

Fault persistent for 4 consecutive sample

periods

ms180 320 460t

F-DELAY

Undervoltage, Overvoltage, or
Mismatch Fault, to DSO, CGO,
TKO Transition Delay

ELECTRICAL CHARACTERISTICS (continued)

(V

SRC

= 16V, each cell voltage V

CELL

= 3.6V, 330kΩ load at REF, TA= 0°C to +85°C, unless otherwise noted. Typical values are at

T

A

= +25°C.)

ELECTRICAL CHARACTERISTICS

(V

SRC

= 16V, each cell voltage V

CELL

= 3.6V, 330kΩ load at REF, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

4 _______________________________________________________________________________________

CONDITIONS

No faults; V

DSO

, V

CGO

, V

UVO

= 1V to 27V

V

DSO

= V

SRC

- 4V and V

CGO

= V

SRC

- 4V,

fault condition

V

DSO

= V

CGO

= V

UVO

= 27V, fault condition

ms1.6 3.2t

I-DELAY

Overdischarge/Overcharge
Current Fault Blanking Time

ms330 770t

P-DELAY

mV

All cells > 2V, MMA = REF

-220 -180

PKN to GND Overcharge
Current Threshold

Overcurrent Fault Timer Delay

µA20 40

DSO, CGO UVO Output Sink
Current

mA2

DSO, CGO Output Source
Current

µA0.2

DSO, CGO, UVO Leakage
Current

UNITSMIN TYP MAXSYMBOLPARAMETER

mV±450 ±550Cell Mismatch Threshold

mV270 330

PKN to GND Overdischarge
Current Threshold

V

DSI

= V

CGI

= 5V

Referenced to PKN

Referenced to PKN

Fault condition, V

WRN

= 0.4V

Fault condition, V

PKF

= 0.4V

V

PKF

= V

WRN

= 27V

µA1

DSI, CGI Input Current

V0.45

V2

TKO = GND
DSI, CGI Input High Voltage
DSI, CGI Input Low Voltage

mA2

WRN Sink Current

mA4

PKF Sink Current

µA0.2

PKF, WRN Leakage Current

kΩ100

TKO Pull-Down Resistance

mA1

TKO Source Current

Fault persistent for 4 consecutive sample

periods

ms180 460t

F-DELAY

Undervoltage, Overvoltage, or
Mismatch Fault, to DSO, CGO,
TKO Transition Delay

Note 1: Specifications to -40°C are guaranteed by design, not production tested.

ELECTRICAL CHARACTERISTICS

(V

SRC

= 16V, each cell voltage V

CELL

= 3.6V, 330kΩ load at REF, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

_______________________________________________________________________________________

5

700

720

710

740

730

760

750

770

-40 0 20-20 40 60 80 100

SHUTDOWN SUPPLY CURRENT

vs. TEMPERATURE

MAX1666toc01

TEMPERATURE (°C)

SUPPLY CURRENT (nA)

V

CELL

= 3.6V

25

27

31

29

33

35

-40 0 20-20 40 60 80 100

SUPPLY CURRENT

vs. TEMPERATURE

MAX1666toc02

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

V

CELL

= 3.6V

3.0000

3.0005

3.0010

3.0015

UNDERVOLTAGE THRESHOLD

vs. TEMPERATURE

MAX1666toc03

TEMPERATURE (°C)

UNDERVOLTAGE THRESHOLD (V)

-40 20 40-20 0 60 80 100

UVA = REF

4.385

4.390

4.395

4.400

OVERVOLTAGE THRESHOLD

vs. TEMPERATURE

MAX1666toc04

TEMPERATURE (°C)

UNDERVOLTAGE THRESHOLD (V)

-40 20 40-20 0 60 80 100

OVA = REF

295

297

296

299

298

301

300

302

-40 0 20-20 40 60 80 100

OVERDISCHARGE THRESHOLD

vs. TEMPERATURE

MAX1666toc07

TEMPERATURE (°C)

OVERDISCHARGE THRESHOLD (mV)

495

497

496

499

498

500

501

-40 20 40-20 0 60 80 100

MISMATCH VOLTAGE THRESHOLD

vs. TEMPERATURE

MAX1666toc05

TEMPERATURE (°C)

MISMATCH VOLTAGE THRESHOLD (mV)

MMA = REF

199

200

201

202

203

OVERCHARGE THRESHOLD

vs. TEMPERATURE

MAX1666toc06

TEMPERATURE (°C)

OVERCHARGE THRESHOLD (mV)

-40 20 40-20 0 60 80 100

1ms/div

OVERDISCHARGE PROTECTION

PKN

(0.5V/div)

DSO

(10V/div)

MAX1666toc08

t

I-DELAY

100ms/div

OVERDISCHARGE RECOVERY TIME

(0.5V/div)

(10V/div)

PKN

DSO

MAX1666toc09

t

P

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

6 _______________________________________________________________________________________

100ms/div

OVERCHARGE

(0.5V/div)

(10V/div)

PKN

CGO

MAX1666toc10

t

P-DELAY

Typical Operating Characteristics (continued)

(TA= +25°C, unless otherwise noted.)

100ms/div

OVERVOLTAGE FAULT

4.1V

(1V/div)

4.5V

123 4 123 4

REF

B1P

MAX1666toc11

(10V/div)

CGO

t

F-DELAY

t

F-DELAY

V

CELL2

= V

CELL3

= V

CELL4

= 4.15V,

OVERVOLTAGE THRESHOLD = 4.4V

100ms/div

UNDERVOLTAGE FAULT

3.4V

2.9V

(10V/div)

(1V/div)

(10V/div)

REF

B1P

DSO

MAX1666toc12

WRN

t

F-DELAY

t

F-DELAY

V

CELL2

= V

CELL3 = VCELL4

= 3.35V,
UNDERVOLTAGE THRESHOLD = 3.0V,
UVA = REF

1234 1234

100ms/div

CELL MISMATCH FAULT

3.4V

2.9V
32141234

(10V/div)

(1V/div)

(10V/div)

REF

B1P

DSO

MAX1666toc13

PKF

t

F-DELAY

t

F-DELAY

V

CELL2

= V

CELL3 = VCELL4

= 3.6V,

CELL MISMATCH THRESHOLD = 0.5V,

100ms/div

UNDERVOLTAGE FAULT WITHOUT

CHARGE SOURCE (V

SRC

< V

B4P

+ 1V)

V

CELL2

= V

CELL3 = VCELL4

= 3.35V,
UNDERVOLTAGE THRESHOLD = 3.0V,
UVA = REF

3.4V

2.9V

(1V/div)

(10V/div)

(2V/div)

REF

B1P

V

CC

DSO

MAX1666toc14

Pin Description

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

_______________________________________________________________________________________ 7

Cell 1 Positive Input88

Ground99
Battery Pack Negative Terminal. Connect to bottom of current sense

resistor. Ground reference for logic inputs DSI and CGI.

1010

Discharge Control Input 1111

Charge Control Input 1212

Fast-Charge Driver Output. Drives external P-channel MOSFET to
control fast charge.

44

Cell 4 Positive Input. Power supply input for MAX1666X.

—

5

Cell 3 Positive Input. Power supply input for MAX1666V.5, 6 6

Cell 2 Positive Input. Power supply input for MAX1666S.77

Trickle-Charge Driver Output. Drives external P-channel MOSFET to
control trickle-charge current. Internally grounded when inactive.

3 3

Discharge Driver Output. Drives external P-channel MOSFET to con­trol discharge.

22

Charge Source Input. Provides current for gate drivers DSO, TKO,
CGO, and UVO.

11

MAX1666VMAX1666X

FUNCTION

Pack Fail Output. PKF goes low when any cell voltage exceeds the
mismatch threshold or when a shorted cell is detected.

1313

Undervoltage/Overvoltage Warning Output1414

6

7

8

9

10

4

—

—

5

3

2

1

MAX1666S

11

—

B1P

GND

PKN

DSI

CGI

CGO

B4P

B3P

B2P

TKO

DSO

SRC

NAME

PKF

WRN

Undervoltage Adjust Input. Set the undervoltage threshold with a
resistor-divider from REF to GND.

1616

Overvoltage Adjust Input. Set the overvoltage threshold with a
resistor-divider from REF to GND.

1717

Reference Voltage Output. Minimize PCB stray capacitance on this
node.

1818

3.3V Linear Regulator Output. Bypass with a 0.47µF min capacitor
to GND.

1919

Undervoltage Fault Output2020

Mismatch Adjust Input. Set the mismatch threshold by a resistor­divider from REF to GND.

1515

13

14

15

16

—

12

UVA

OVA

REF

V

CC

UVO

MMA

PIN

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

8 _______________________________________________________________________________________

BIAS

B4P

CQI_FAULT

550ms
TIMER

SET/RESET

WARNING

OV-FAULT

UV-FAULT

CM-FAULT

PKF

WRN

V

CC

DQI_FAULT

TKO

N

SRC

SRC

SRC

SHUTDOWN

CHARGE

DQI_HI

CQI_HI

OV_FAULT

UV_FAULT

CM_FAULT

UV_FAULT

WARNING

UV_FAULT

CGI

OV_FAULT

CM_FAULT

OV_FAULT

CM_FAULT

UV_FAULT

Q

D

RB

30µA

CGO

B4P

B3P

B2P

BIP

GND

CMP_P

CMP_N

LATCH_CM

LATCH_UV

LATCH_OV

LATCH_WRN

CMP

OVA

UVA

MMA

GND

GND

PKN

SRC

B4P

200mV

300mV

30µA

N

N

N

1V

REF

1.221V

CK

CQI_FAULT

CGI

3.3V

LINEAR

REG.

THRESHOLD

VOLTAGE

SELECTOR

CELL

VOLTAGE

SELECTOR

STATE

MACHINE

50kHZ

OSC

OSC

"1"

CM_FAULT

UV_FAULT

Q

D

RB

30µA

N

N

N

N

GND

DSO

CK

DQY_FAULT

DSI

"1"

REG

EARLY

WARNING

REG

OVER-

VOLTAGE

REG

UNDER-

VOLTAGE

REG

CELL

MISMATCH

UVO

GND

GND

MAX1666

Figure 1. Functional Diagram

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

_______________________________________________________________________________________ 9

YES

YES

NO

NO

STANDBY

80ms

SAMPLE

2.5ms

CHECK V

REF

LATCH UVW = ‘1’

V

REF >

1.1V

V

CELL

<

UNDERVOLTAGE

WARNING

THRESHOLD

YES

NO

V

CELL

<

UNDERVOLTAGE

THRESHOLD

LATCH UVF = ‘1’

YES

NO

V

CELL

>

OVERVOLTAGE

THRESHOLD

LATCH OVF = ‘1’

YES

YES

NO

CELL MISMATCH

LATCH MMF = ‘1’

NO

UVF = ‘1’

AND

V

SRC

< V

B4P

+ 1V

GO TO

TABLE 3

YES

YES

NO

VCC > 2.85V

V

SRC

< V

B4P + 1V

V

SRC

> V

B4P + 1V

SHUTDOWN

BATTERY

CONNECTED

CHARGE
CURRENT
MONITOR

OVERCHARGE

CGO = H

OVER-

DISCHARGE

DSO = H

(DISCHARGE CURRENT

· R

CS

)

300mV

(>2.4ms)

(CHARGE CURRENT

· R

CS

)

200mV

(>2.4ms)

550ms DELAY

RESET

DS0 = L

RESET
CGO = L

Figure 2. Cell Fault Monitor

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

10 ______________________________________________________________________________________

Detailed Description

The MAX1666 battery-pack protectors supervise the
charging and discharging processes of Lithium-Ion
battery cells. Designed for 2, 3, and 4-cell applications,
these devices monitor the voltage across each cell to
provide protection against undervoltage, overvoltage,
and overcurrent damage.

Control pins CGO, TKO, and DSO allow control of
external MOSFET gates. This allows fast charging,
trickle charging, and discharging processes (see

Typical Operating Circuit

). The voltage of each cell is
measured individually. Also, each cell is measured dif­ferentially between every other cell of the pack.

The MAX1666 contains a state machine, a voltage reg­ulator, an oscillator, and other logic functions to selec­tively drive CGO, UVO, TKO, DSO, WRN, and PKF
(Figure 1).

Modes of Operation

Shutdown Mode

The MAX1666 goes into shutdown mode when a bat­tery pack is first connected. The quiescent current is
less than 1µA. All circuitry is inactive except the com-

parator monitoring V

SRC

and the top-cell voltage. The

MAX1666 remains in shutdown mode as long as V

SRC

is less than the top-cell voltage. When SRC is connect­ed to an external charger and V

SRC

is 1V above the

top-cell voltage, the device goes into standby mode.
The MAX1666 returns to shutdown mode under two

conditions: the battery is disconnected and then re­connected, or the device detects an undervoltage fault

and

no charge source.

Normal Mode

The standby state activates the bias circuitry, overcur­rent comparator, and timer. The standby state lasts
80ms, then the MAX1666 goes into the sample state for

2.5ms.
Within the 2.5ms, the MAX1666 checks for overvoltage,

undervoltage, and mismatch between cells sequential­ly, and it stores the results in internal latches. The
MAX1666 drives the outputs according to the faults (if
any) detected by reading the latches (Figure 2) at the
end of the sample state. Then the MAX1666 returns to
the standby state.

Overvoltage Protection

The MAX1666 provides overvoltage protection to avoid
overcharging of any cell. When any cell is at overvolt­age, CGO and TKO go high, turning off the external MOS­FETs and stopping the charging process (

Typical

Operating Circuits

). WRN goes low. Overvoltage is set
when any cell voltage exceeds the overvoltage thresh­old.

Overvoltage threshold is linearly adjustable through an
external 1% resistor-divider (Figure 3) from REF.
Determine the overvoltage threshold (V

OVT

) required.

V

OVT

must be between 4V and 4.4V. Set R

TOTAL

= R1

+ R2 = 1MΩ. Calculate R1 and R2 as follows:

R2 = [(V

OVT

- 4V) / (4.4V- 4V)] · R

TOTAL

R1 = R

TOTAL

- R2

MODE TIME

TYPICAL

QUIESCENT

CURRENT (µA)

CONDITION

80ms 24 Only bias circuitry, overcurrent comparator, and timer are active.

Normal

2.5ms 250 All circuitry active.

Shutdown — 0.7

All circuitry inactive. Device enters shutdown when it detects an undervolt­age fault and V

SRC

< V

TOP-CELL

+ 1V (no charge source).

Table 1. Operating Modes

R1 R3

REF

OVA

R5

R2 R4 R6

UVA

MMA

GND

MAX1666

Figure 3. Using an External Resistor-Divider to Adjust
Overvoltage Threshold

STATE

Standby

Sample

—

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

______________________________________________________________________________________ 11

Maximum mismatch of 1% external resistor-dividers is
±2%. The external adjusted overvoltage threshold accu­racy includes the internal overvoltage threshold accuracy
(±0.5%) and the error due to the external resistor-divider
multiplied by maximum adjustment.

The total external adjusted overvoltage threshold (V

OVT

)

accuracy is ±0.7%.

Undervoltage Protection

The MAX1666 provides undervoltage protection to
avoid overdischarging the cells. When any cell is under
voltage, UVO, DSO, and CGO go high, turning off the
external charging and discharging MOSFETs. TKO
remains low to keep the trickle charge current on.
Undervoltage threshold is linearly adjustable through
an external resistor-divider (Figure 3) from REF.
Determine the undervoltage threshold (V

UVT

) required.

V

UVT

must be between 2V and 3V. Set R

TOTAL

= R3 +

R4 = 1MΩ. Calculate R3 and R4 as follows:

R4 = [(V

UVT

- 2V) / (3V - 2V)] R

TOTAL

R3 = R

TOTAL

- R4

Maximum mismatch of 1% external resistor-dividers is
±2.0%, and the error due to the external resistor-divider
multiplied by maximum adjustment is ±2% (3V - 2V) / 3V
= ±0.7%. The total external adjusted undervoltage

threshold (V

UVT

) accuracy including the internal under-

voltage threshold accuracy (±2.5%) is ±3.2%.

Undervoltage Warning

When any cell drops to 100mV above the undervoltage
threshold, WRN goes low. WRN returns high when all
cells are 300mV above the undervoltage threshold.

Cell-Mismatch Protection

The MAX1666 disables charging or discharging when
mismatch occurs. When any two cells are mismatched,
TKO, CGO, UVO, and DSO go high, turning off the
external MOSFETs. PKF goes low. PKF has a strong
pull-down current (>4mA), and can be used to control
an external thermal fuse. The cell-mismatch threshold is
linearly adjustable through an external resistor-divider
(Figure 3) from REF. Determine the cell-mismatch
threshold (V

CMT

) required. V

CMT

has to be between 0

and 500mV. Set R

TOTAL

= R5 + R6 = 1MΩ. Calculate

R5 and R6:

R6 = (V

CMT

/ 500mV) R

TOTAL

R5 = R

TOTAL

- R6

Maximum mismatch of 1% external resistor-divider is
±2%. The total external adjusted cell-mismatch thresh­old accuracy, including the internal cell-mismatch
threshold accuracy (±10%), is ±12%.

Cell Voltage Sampling

The MAX1666 does not introduce cell mismatch. When
the battery cells are matched, the MAX1666 draws
close to zero current from the intermediate cells.
Figure 4 shows a simplified diagram of the voltage
sampling scheme.

B4P: I4= 3ICB+ V4/ R = 4V4/ R = BAT4 Current
B3P: I3= I3P+ I4= BAT3 Current

I3P+ ICB= V3 / R ⇒ I3P= V3/ R - V4/ R
I3= I4+ (V3- V4) / R = (3V4+ V3) / R

B2P: I2= I2P+ I3= BAT2 Current

I2P+ ICB= V2/ R ⇒ I2P= V2/ R - V4/ R
I2= I3+ V2/ R - V4/ R = I4+ (V3 - V4) / R +

(V2- V4) / R = (2V4+ V3+ V2) / R

B1P: I1= I1P+ I2= BAT1 Current

I1P+ ICB= V1/ R ⇒ I1P= V1/ R - V4/ R
I1= I2+ V1/ R - V4/ R = I4+ (V3- V4) / R +

(V2- V4) / R + (V1- V4) / R
= (V4+ V3+ V2+ V1) / R

When V1= V2= V3= V4, I1P= I2P= I3P= 0, and

I1= I2= I3= I4= 4V4/ R

±

−
=±2

44 40

44

02%

. .

.

.%

VV

V

+

V4

-

B3P

B2P

B1P

B4P

+

V3

-

I

3

I

4

I

3P

I

2P

I

1P

I

2

I

1

+

V2

-

+

V2

-

+

V1-RR R R

+

V1

-

I

CB =

V4

R

I

CB =

V4

R

I

CB =

V4

R

V1

R

V2

R

+

V3

-

V3

R

+

V4

-

V4

R

Figure 4. Cell Voltage Sampling

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

12 ______________________________________________________________________________________

Overcharge/Overdischarge

Current Protection

The MAX1666 checks for overcharge or overdischarge
current in standby and sample states. The thresholds
are factory preset to 200mV and 300mV, respectively.
A charge current makes PKN go below GND. A dis­charge current makes PKN go above GND. When PKN
exceeds the threshold, a fault is acknowledged. CGO
goes high when the overcharge threshold is exceeded.
DSO goes high when the overdischarge threshold is
exceeded. An internal 550ms timer starts. At the end of
550ms, DSO or CGO goes low, while the MAX1666
rechecks for an overcharge/overdischarge fault. A per­sistent fault causes DSO and CGO to return high and
restarts the 550ms timer again.

Truth Table

The MAX1666 has a total of eight signal inputs and six
outputs. Table 2 lists all the possible states.

Applications Information

Choosing an External MOSFET

The external P-channel MOSFETs act as a gated switch
to enable or disable the charging/discharging process.
CGO controls the MOSFET for normal charging of the
battery. TKO controls the MOSFET for trickle charge of
the cells. DSO controls the discharging MOSFET. Use
different MOSFETs to optimize each function depending
on the maximum charge and discharge rates. Table 3
lists some suitable MOSFETs in a small SO-8 package.

Layout Considerations and Bypassing

As with all printed circuit board designs, a careful lay­out is suggested. Minimize lead lengths to reduce loss­es in the traces.

P-CHANNEL MOSFETs MAXIMUM DRAIN CURRENT (A)

IRF7406 4.7

IRF7404 5.3

Si4431 4.5

Si4947 (dual) 2.5 EA

Table 3. MOSFET Selection

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

______________________________________________________________________________________ 13

Table 2. Truth Table

Control Inputs Control Outputs Notes

UVW UVF OVF MMF CGI DSI OCC ODC DSO CGO TKO WRN PKF UVO

00000000 LLLHHLNormal operation

00000001PSLLHHLOverdischarge current fault

00000010 LPSLHHLOvercharge current fault

00000100 HLLHHLDisable dischar

g

e

p

ath

00000110 HPSLHHLDisable discharge path, overcharge current fault

00001000 LHHHHLDisable charge path

00001001PSHHHHLDisable charge path, overdischarge current fault

00001100 HHHHH LDisable charge and discharge path

00010000 HHHH LHMismatch fault

00010100 HHHH LHMismatch fault, disable discharge path

00011000 HHHH LHMismatch fault, disable charge path

00011100 HHHH LHMismatch fault, disable charge and discharge path

00100000 LHHLHLOvervoltage fault

00100001PSHHLHLOvervoltage fault, overdischarge current fault

00100100 HHHLHLOvervoltage fault, disable discharge path

00101000 LHHLHLOvervoltage fault, disable charge path

00101001PSHHLHLOvervoltage fault, disable charge path, overdischarge current fault

00101100 HHHLHLOvervoltage fault, disable charge and discharge path

00110000 HHHLLHOvervoltage fault, mismatch fault

00110100 HHHLLHOvervoltage fault, mismatch fault, disable discharge path

00111000 HHHLLHOvervoltage fault, mismatch fault, disable charge path

00111100 HHHLLHOvervoltage fault, mismatch fault, disable charge and discharge path

11000000 HHLLHHUndervoltage fault

11000100 HHLLHHUndervoltage fault, disable discharge path

11001000 HHHLHHUndervoltage fault, disable charge path

11001100 HHHLHHUndervoltage fault, disable charge and discharge path

11010000 HHHLLHUndervoltage fault, mismatch fault

11010100 HHHLLHUndervoltage fault, mismatch fault, disable discharge path

11011000 HHHLLHUndervoltage fault, mismatch fault, disable charge path

11011100 HHHLLHUndervoltage fault, mismatch fault, disable charge and discharge path

11110000 HHHLLHUndervoltage fault, overvoltage fault, mismatch fault

11110100 HHHLLHUndervoltage fault, overvoltage fault, mismatch fault, disable discharge path

11111000 HHHLLHUndervoltage fault, overvoltage fault, mismatch fault, disable charge path

11111100 HHHLLHUndervoltage fault, overvoltage fault, mismatch fault, disable charge and discharge path

10000000 LLLLHLUndervoltage fault early warning

10000001PSLLLHLUndervoltage fault early warning, overdischarge current fault

10000010 LPSLLHLUndervoltage fault early warning, overcharge current fault

10000100 HLLLHLUndervoltage fault early warning, disable discharge path

10000110 HPSLLHLUndervoltage fault early warning, disable discharge path, overcharge current fault

10001000 LHHLHLUndervoltage fault early warning, disable charge path

10001001PSHHLHLUndervoltage fault early warning, disable charge path, overdischarge current fault

10001100 HHHLHLUndervoltage fault early warning, disable charge and discharge path

10010000 HHHLLHUndervoltage fault early warning, mismatch fault

10010100 HHHLLHUndervoltage fault early warning, mismatch fault, disable discharge path

10011000 HHHLLHUndervoltage fault early warning, mismatch fault, disable charge path

10011100 HHHLLHUndervoltage fault early warning, mismatch fault, disable charge and discharge path

10110000 HHHLLHUndervoltage fault early warning, overvoltage fault, mismatch fault

10110100 HHHLLHUndervoltage fault early warning, overvoltage fault, mismatch fault, disable discharge path

10111000 HHHLLHUndervoltage fault early warning, overvoltage fault, mismatch fault, disable charge path

10111100 HHHLLHUndervoltage fault early warning, overvoltage fault, mismatch fault, disable charge and discharge path

PS: Overcurrent fault pulse sampling. (Output goes high for 500ms then resets low to monitor charge/discharge current. Output goes high again if fault persists.)

UVW: Undervoltage fault early warning UVF: Undervolta

g

e fault OVF: Overvoltage fault MMF: Mismatch fault

OCC: Overcharge current fault ODC: Overdischarge current fault

CGI: Charge control input DSI: Discharge control input

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

14 ______________________________________________________________________________________

DSI

CGI

WRN

PKF

UVO

V

CC

REF

17

18

20

13

14

12

11

19

0.47µF

16
15

10

9

8

7

6

5

3

4

2

1

OVA

499k1%499k1%499k

1%

499k
1%

499k1%499k

1%

+3.3V
5mA

0.05Ω

UVA

MMA

PKN

GND

R

SENSE

B1P

B2P

B3P

B4P

CGO

DSO

SRC

P

PACK+

OVERDISCHARGE
PROTECTION

PACK-

TRICKLE
CHARGE

OVERCHARGE
PROTECTION

470k 470k270Ω

MAX1666X

TKO

P

P

Typical Operating Circuits

MAX1666S/V/X

Advanced Lithium-Ion

Battery-Pack Protector

______________________________________________________________________________________ 15

Typical Operating Circuits (continued)

DSI

CGI

WRN

PKF

UVO

V

CC

V

CC

REF

17

18

100k 100k 220k

20

13

14

11

12

19

1µF

16
15

10

9

8

7

6

5

3

4

2

1

OVA

499k1%499k1%499k

1%

499k
1%

499k1%499k

1%

+3.3V
5mA

0.05Ω

UVA

MMA

PKN

GND

GND

PACK

CONTROLLER

R

SENSE

B1P

B2P

OUT1

OUT2

IN1

IN2

IN3

B3P

B4P

CGO

DSO

SRC

P

PACK+

OVERDISCHARGE
PROTECTION

PACK-

TRICKLE
CHARGE

OVERCHARGE
PROTECTION

470k 470k270Ω

MAX1666X

TKO

P

P

___________________Chip Information

TRANSISTOR COUNT: 4835

MAX1666S/V/X

Advanced Lithium-Ion
Battery-Pack Protector

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.

16

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© 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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________________________________________________________Package Information