Linear Technology LTC2944 User Manual

60V Battery Gas Gauge

2944 TA01b

with Temperature, Voltage

and Current Measurement

FeaTures DescripTion

n

Measures Accumulated Battery Charge
and Discharge

n

3.6V to 60V Operating Range for Multiple Cells

n

14-Bit ADC Measures Voltage, Current
and Temperature

n

1% Voltage, Current and Charge Accuracy

n

±50mV Sense Voltage Range

n

High Side Sense

n

I2C Interface/SMBus Interface

n

General Purpose Measurements for Any Battery
Chemistry and Capacity

n

Configurable Alert Output/Charge Complete Input

n

Quiescent Current Less Than 150µA

n

Small 8-Lead 3mm × 3mm DFN Package

applicaTions

n

Electric and Hybrid Electric Vehicles

n

Power Tools

n

Electric Bicycles, Motorcycles, Scooters

n

High Power Portable Equipment

n

Photo Voltaics

n

Backup Battery Systems

The LT C®2944 measures battery charge state, battery volt-
age, battery current and its own temperature in portable
product

applications. The wide input voltage range allows
use with multicell batteries up to 60V. A precision coulomb
counter integrates current through a sense resistor between
the battery’s positive terminal and the load or charger.
Voltage, current and temperature are measured with an
internal 14-bit No Latency ΔΣ™ ADC. The measurements
are stored in internal registers accessible via the onboard

2

C/SMBus Interface.

I

The LTC2944 features programmable high and low thresh­olds for
threshold

all four measured quantities. If a programmed

is exceeded, the device communicates an alert
using either the SMBus alert protocol or by setting a flag
in the internal status register. The LTC2944 requires only
a single low value sense resistor to set the measured
current range.

All registered trademarks and trademarks are the property of their respective owners.

LTC2944

Typical applicaTion

ALCC

SDA

SCL

CHARGER

LTC2944

SENSE

SENSE

GND

3.3V

2k2k 2k

V

DD

µP

1A
LOAD

1µF

+

R

SENSE

–

50mΩ

+

MULTICELL
Li-ION

2944 TA01a

For more information www.linear.com/LTC2944

Total Charge Error vs

Differential Sense Voltage

3

2

1

0

–1

CHARGE ERROR (%)

–2

–3

0.1

V

SENSE

+

= 3.6V TO 60V

1 10 100

V

(mV)

SENSE

2944fa

1

LTC2944

(Notes 1, 2)

pin conFiguraTionabsoluTe MaxiMuM raTings

Supply Voltage (SENSE+) ........................... –0.3V to 65V

SCL, SDA, ALC C Voltage .............................. –0.3V to 6V

SENSE

–

...............(–0.3V + V

SENSE

+

) to (V

SENSE

+

+ 0.3V)
Operating Ambient Tempera tur e Range

LTC2944C ............................................... 0°C to 70°C

LTC2944I ............................................–40°C to 85°C

GND

GND

SCL

TOP VIEW

+

1SENSE

2

3

4

9

8

7

6

5

SENSE

GND

ALCC

SDA

–

Storage Temperature Range .................. –65°C to 150°C

8-LEAD (3mm × 3mm) PLASTIC DFN

EXPOSED PAD (PIN 9) PCB GND CONNECTION OP

orDer inForMaTion

http://www.linear.com/product/LTC2944#orderinfo

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC2944CDD#PBF LTC2944CDD#TRPBF LGCR 8-Lead (3mm × 3mm) Plastic DFN 0°C to 70°C

LTC2944IDD#PBF LTC2944IDD#TRPBF LGCR 8-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.

DD PACKAGE

= 150°C, θJA = 100°C/W

T

JMAX

TIONAL

elecTrical characTerisTics

The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Power Requirements

+

V

SENSE

I

SUPPLY

I

SENSE

I

SENSE

V

UVLO

Supply Voltage

Supply Current (Note 3) Battery Gas Gauge On, ADC Sleep

+

Pin Current (Note 3) Battery Gas Gauge On, ADC Sleep

–

Pin Current (Note 3) Battery Gas Gauge On, ADC Sleep

Undervoltage Lockout Threshold V

Coulomb Counter

V

SENSE

Sense Voltage Differential Input
Range

R

IDR

Differential Input Resistance Across
SENSE

q

LSB

Charge LSB (Note 4) Prescaler M = 4096(Default), R

+

and SENSE– (Note 8)

Battery Gas Gauge On, ADC On
Shutdown

Battery Gas Gauge On, ADC On
Shutdown

Battery Gas Gauge On, ADC On
Shutdown

+

Falling

SENSE

V

SENSE

+

– V

SENSE

–

= 50mΩ 0.340 mAh

SENSE

l

l
l
l

l

l

3.6 60 V

80

850

15

80

500

15

1

350

1

150
950

30

µA
µA
µA

µA
µA
µA

µA
µA
µA

3.0 3.5 3.6 V

±50 mV

400 kΩ

2944fa

2

For more information www.linear.com/LTC2944

LTC2944

elecTrical characTerisTics

The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

TCE Total Charge Error (Note 5) 10mV ≤ |V

10mV ≤ |V
1mV ≤ |V

V

OSE

Effective Differential Offset Voltage

V

SENSE

≥ 500µV, V

(Note 9)

Voltage Measurement ADC

Resolution (No Missing Codes) (Note 8)

V

ΔV

FS(V)

LSB

Full-Scale Voltage Conversion 70.8 V

Quantization Step of 14-Bit Voltage

(Note 6) 4.32 mV

ADC

TUE

Gain

INL

V

T

CONV(V)

V

V

Voltage Total Unadjusted Error

Voltage Gain Accuracy

Integral Nonlinearity

Voltage Conversion Time

Current Measurement ADC

Resolution (No Missing Codes) (Note 8)

V

FS(I)

V

SENSE

Full-Scale Current Conversion ±64 mV

Sense Voltage Differential Input

V

SENSE

+

– V

Range

ΔI

LSB

Quantization Step of 12-Bit Current

(Note 6) 31.25 µV

ADC

Gain

V

OS(I)

INL

T

CONV(I)

I

I

Current Gain Accuracy

Offset ±1 ±10 LSB

Integral Nonlinearity

Current Conversion Time

Temperature Measurement ADC

Resolution (No Missing Codes) (Note 8)

T

ΔT

FS

LSB

Full-Scale Temperature 510 K

Quantization Step of 11-Bit

(Note 6) 0.25 K

Temperature ADC

TUE

T

Temperature Total Unadjusted Error V

SENSE

+

≥ 5V

(Note 8)

T

CONV(T)

Temperature Conversion Time

Digital Inputs and Digital Outputs

V

ITH(HV)

V

ITH(LV)

V

OL

Logic Input Threshold V

Low Level Output Voltage, ALCC,

+

≥ 5V

SENSE

3.6V < V

SENSE

I = 3mA, V

SDA

I

IN

C

IN

Input Leakage, ALCC, SCL, SDA VIN = 5V
Input Capacitance, , ALCC, SCL,

(Note 8)

SDA

t

PCC

Minimum Charge Complete (CC)
Pulse Width

| ≤ 50mV DC

SENSE

| ≤ 50mV DC

SENSE

| ≤ 10mV DC (Note 8)

SENSE

+ = 30V

SENSE

–

SENSE

+

< 5V 0.5 1.8 V

+

≥ 5V

SENSE

l
l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

±1
±1.5
±3.5

5 10 µV

14 Bits

1

1.3

1.3 %

±1 ±4 LSB

48 ms

12 Bits

±50 mV

1

1.3

±1 ±4 LSB

8 ms

11 Bits

±3

±5

8 ms

0.8 2.2 V

0.4 V

1 µA

10 pF

1 µs

%
%
%

%
%

%
%

K
K

For more information www.linear.com/LTC2944

2944fa

3

LTC2944

The l denotes the specifications which apply over the full operating

elecTrical characTerisTics

temperature range, otherwise specifications are at TA = 25°C.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

2

C Timing Characteristics

I

f

SCL(MAX)

t

BUF(MAX)

t

SU(STA(MIN))

t

HD(STA(MIN))

t

SU(STO(MIN))

t

SU(DAT(MIN))

T

HD(DAT(MIN))

T

HDDATO

T

OF

Maximum SCL Clock Frequency

Bus Free Time Between Stop/Start

Minimum Repeated Start Set-Up
Time

Minimum Hold Time (Repeated)
Start Condition

Minimum Set-Up Time for Stop
Condition

Minimum Data Setup Time Input

Minimum Data Hold Time Input

Data Hold Time Input Output

Data Output Fall Time (Notes 7, 8)

l

400 900 kHz

l

l

l

l

l

l

l

l

0.3 0.9 µs

20 + 0.1 • C

B

1.3 µs

600 ns

600 ns

600 ns

100 ns

50 ns

300 ns

Note 1. Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.

Note 2. All currents into pins are positive, all voltages are referenced to
GND unless otherwise specified.

Note 3. I
flowing in SENSE
SENSE

= I

SUPPLY

–

pin as well. Typically, I

conversion and I

+

SENSE

+

pin. Only during ADC conversions current is flowing in

–

= 20µA during ADC current conversion.

SENSE

+ I

–

. In most operating modes I

SENSE

SENSE

–

= V

–

/150k during ADC voltage

SENSE

SUPPLY

is

Note 4. The equivalent charge of an LSB in the accumulated charge
register depends on the value of R

and the setting of the internal

SENSE

prescaling factor M:
q

= 0.340mAh • (50mΩ/R

LSB

) • (M/4096):

SENSE

TiMing DiagraM

SDA

t

SCL

t

HD(STA)

SU(DAT)

t

HD(DAT0)

t

HD(DAT1)

See Choosing R

and Choosing Coulomb Counter Prescaler M section

SENSE

for more information. 1mAh = 3.6C (Coulombs)
Note 5. Deviation of q

from its nominal value.

LSB

Note 6. The quantization step of the 14-bit ADC in voltage mode, 12-bit
ADC in current mode and 11-bit ADC in temperature mode is not the same
as the LSB of the respective combined 16-bit registers. See the Voltage,
Current

and Temperature Registers section for more information.

Note 7.

C

= Capacitance of one bus line in pF (10pF ≤ CB ≤ 400pF).

B

Note 8. Guaranteed by design, not subject to test.
Note 9. See "Effect of Differential Offset Voltage on Total Charge Error”

section.

t

OF

t

t

SU(STA)

t

HD(STA)

t

SU(STO)

BUF

2944 TD01

START

CONDITION

4

REPEATED START

CONDITION

Figure 1. Definition of Timing on I2C Bus

For more information www.linear.com/LTC2944

STOP

CONDITION

START

CONDITION

2944fa

Typical perForMance characTerisTics

2944 G08

2944 G07

LTC2944

Total Charge Error vs Differential
Sense Voltage

3

2

1

0

–1

CHARGE ERROR (%)

–2

–3

0.1

V

SENSE

+

= 3.6V TO 60V

1 10 100

V

(mV)

SENSE

Supply Current vs Supply Voltage

110

100

90

80

(µA)

70

SUPPLY

I

60

50

TA = 85°C

TA = 25°C

TA = –40°C

2944 G01

Total Charge Error vs Supply
Voltage

1.00

0.75

0.50

0.25

0

–0.25

CHARGE ERROR (%)

–0.50

–0.75

–1.00

0

V

= 10mV

SENSE

V

= 50mV

SENSE

10 70

20 30 40 50 60

V

SENSE

Shutdown Supply Current
vs Supply Voltage

30

25

20

(µA)

15

SIPPLY

I

10

5

–

(V)

TA = 85°C

TA = 25°C

TA = –40°C

2944 G02

Total Charge Error vs
Temperature

1.00

0.75

0.50

0.25

0

–0.25

CHARGE ERROR (%)

–0.50

–0.75

–1.00

–50

V

SENSE

V

SENSE

–25 0

TEMPERATURE (°C)

= 10mV

= 50mV

Voltage Measurement ADC
Total Unadjusted Error

1.0

0.5

0

TUE (%)

–0.5

TA = –45°C

TA = 25°C

25

50

TA = 85°C

75

100

2944 G03

40

0

10 20

40 60 70

30 50

+

V

(V)

SENSE

2944 G04

Voltage Measurement ADC
Integral Nonlinearity

3

2

1

)

LSB

0

INL (V

–1

–2

–3

0

TA = –45°C

10 20 40

30

V

SENSE

–

(V)

TA = 85°C

TA = 25°C

50 60 70

0

0

20

10

30

V

SENSE

40

50

+

(V)

60

2944 G05

Current Measurement ADC
Gain Error

1.0

0.5

0

GAIN ERROR (%)

–0.5

–1.0

10

0

For more information www.linear.com/LTC2944

TA = –45°C

TA = 85°C

20

30 40 50 60

V

SENSE

–

(V)

TA = 25°C

70

–1.0

40

0

10

30

20

V

SENSE

50

–

(V)

60

70

2944 G06

Current Measurement ADC
Integral Nonlinearity

1.0

0.5

)

LSB

0

INL (I

–0.5

–1.0

70

–60 –40 –20 20 40 60

V

SENSE

+

= 30V

V

SENSE

0

(mV)

2943 G09

2944fa

5

LTC2944

2944 G12

2943 G10

Typical perForMance characTerisTics

Temperature Error vs Temperature

3

2

1

0

–1

TEMPERATURE ERROR (°C)

–2

–3

–50 –25

+

V

= 3.6V

SENSE

+

= 5.5V

V

SENSE

+

= 20V

V

SENSE

+

= 60V

V

SENSE

0 755025 100

TEMPERATURE (°C)

Voltage Measurements Noise

900

800

700

600

500

400

COUNTS

300

200

100

0

–2 –1 210

pin FuncTions

SENSE+ (Pin 1): Positive Current Sense Input and Power
Supply. Connect to load/charger side of the sense resistor.

+

V
an input to the ADC during current measurement. Bypass
to GND with a 1µF capacitor located as close to pin 1 and
pin 2 as possible.

GND (Pin 2, Pin 3, Pin 7): Device Ground. Connect directly
to the negative battery terminal.

SCL (Pin 4): Serial Bus Clock Input. SCL is internally pulled
up with 50µA (typ) above its logic input high threshold to
about 2V (typ).

SDA (Pin 5): Serial Bus Data Input and Output. SDA is
internally pulled up with 50µA (typ) above its logic input
high threshold to about 2V (typ).

operating range is 3.6V to 60V. SENSE+ is also

SENSE

Current Measurements Noise

450

800 READINGS

400

350

300

250

200

COUNTS

150

100

50

0

–2 –1 210 3

4.32mV/LSB

2944 G11

–3

31.25µV/LSB

ALCC (Pin 6): Alert Output or Charge Complete Input.
Configured either as an SMBus alert output or charge
complete input by control register bits B[2:1]. At power-up,
the pin defaults to alert mode conforming to the SMBus
alert response protocol. It behaves as an open-drain logic
output that pulls to GND when any threshold register value
is exceeded. When configured as a charge complete input,
connect to the charge complete output from the battery
charger circuit. A low

level at CC sets the value of the

accumulated charge (registers C, D) to FFFFh.

–

SENSE

SENSE
resistor. The voltage between SENSE

(Pin 8): Negative Current Sense Input. Connect

–

to the positive battery terminal side of the sense

–

and SENSE+ must
remain within ±50mV in normal operation. SENSE
an input to the ADC during voltage and current measure­ment.

–

is also

6

Exposed

Pad (Pin 9): Exposed pad may be left open or

connected to device ground (GND).

For more information www.linear.com/LTC2944

2944fa

block DiagraM

2944 BD

LTC2944

1

8

7

2

3

SENSE

SENSE

GND

GND

GND

V

SUPPLY

+

ACCUMULATED

COULOMB COUNTER

REF

TEMPERATURE

SENSOR

–

MUX

REFERENCE

GENERATOR

IN

REF

+

–

CLK

OSCILLATOR

F = 10kHz

CLKREF

ADC

CHARGE

REGISTER

DATA AND

CONTROL

REGISTERS

CC

2

C/

I

SMBUS

LTC2944

AL ALCC

SCL

SDA

6

4

5

For more information www.linear.com/LTC2944

2944fa

7

LTC2944

operaTion

Overview

The LTC2944 is a battery gas gauge designed for use
with multicell batteries with terminal voltages from 3.6V
to 60V. It measures battery charge and discharge, battery
voltage, current and its own temperature.

A precision analog coulomb counter integrates current
through a sense resistor between the battery’s positive
terminal and the load or charger. Battery voltage, battery
current and silicon temperature are measured with an
internal ADC.

Coulomb Counter

Charge is the time integral of current. The LTC2944 mea­sures charge
a sense resistor. The differential voltage between SENSE
and SENSE

by monitoring the voltage developed across

–

is applied to an auto-zeroed differential analog

+

integrator to infer charge.

When the integrator output ramps to REFHI or REFLO
levels, switches S1, S2, S3 and S4 toggle to reverse the
ramp direction (Figure 2). By observing the condition of
the switches and the ramp direction, polarity is determined.
This approach also significantly lowers the impact on offset
of the analog integrator as described in the Differential
Offset Voltage section.

A programmable prescaler effectively increases integration
time by a factor M programmable from 1 to 4096. At each
underflow or overflow of the prescaler, the accumulated
charge register (ACR) value is incremented

or decremented

one count. The value of accumulated charge is read via

2

C interface.

the I

Voltage, Current and Temperature ADC

The LTC2944 includes a 14-bit No Latency ΔΣ analog-to­digital converter, with internal clock and voltage reference
circuits.

The ADC can be used to monitor the battery voltage at
SENSE

–

or the battery current flowing through the sense
resistor or to convert the output of the on-chip tempera­ture sensor.

Conversion of voltage, current and temperature are trig­gered by programming the control register via the I
interface. The LTC2944 includes a scan mode where
voltage, current and temperature conversion measure­ments are executed every 10 seconds. At the end of each
conversion the corresponding registers are updated and
the converter goes to sleep to minimize quiescent current.

The temperature sensor generates a voltage proportional
to temperature with a slope of 2mV/K resulting in a volt­age of 600mV at 27°C.

Power-Up Sequence

When SENSE+ rises above a threshold of approximately

3.3V, the LTC2944 generates an internal power-on reset
(POR) signal and sets all registers to their default state.
In the default state, the coulomb counter is active while
the voltage, current and temperature ADC is switched

The accumulated charge register is set to mid-scale

off.
(7FFFh), all low threshold registers are set to 0000h and all
high threshold registers are set to FFFFh. The alert mode
is enabled and the coulomb counter prescaling factor M
is set to 4096.

2

C

LOADCHARGER

V

CC

+

SENSE

1

R

SENSE

–

SENSE

8

I

BAT

+

BATTERY

GND

2

8

REFHI

+

S1

S2

S3

S4

Figure 2. Coulomb Counter Section of the LTC2944

For more information www.linear.com/LTC2944

–

+

REFLO

–

+

–

CONTROL

LOGIC

POLARITY

DETECTION

M

PRESCALER

ACR

2944 F02

2944fa

applicaTions inForMaTion

LTC2944

Internal Registers

The LTC2944 register map is shown in Table 1. The
LTC2944 integrates current through a sense resistor,
measures battery voltage, current and temperature and
stores the results in internal 16-bit registers accessible

2

C. High and low limits can be programmed for each

via I
measured quantity. The LTC2944 continuously monitors
these limits and sets a flag in the status register when a
limit is exceeded. If the alert mode is enabled, the ALCC
pin pulls low.

Table 1. Register Map

ADDRESS NAME REGISTER DESCRIPTION R/W DEFAULT

00h A Status R See Table 2

01h B Control R/W 3Ch

02h C Accumulated Charge MSB R/W 7Fh

03h D Accumulated Charge LSB R/W FFh

04h E Charge Threshold High MSB R/W FFh

05h F Charge Threshold High LSB R/W FFh

06h G Charge Threshold Low MSB R/W 00h

07h H Charge Threshold Low LSB R/W 00h

08h I Voltage MSB R 00h

09h J Voltage LSB R 00h

0Ah K Voltage Threshold High MSB R/W FFh

0Bh L Voltage Threshold High LSB R/W FFh

0Ch M Voltage Threshold Low MSB R/W 00h

0Dh N Voltage Threshold Low LSB R/W 00h

0Eh O Current MSB R 00h

0Fh P Current LSB R 00h

10h Q Current Threshold High MSB R/W FFh

11h R Current Threshold High LSB R/W FFh

12h S Current Threshold Low MSB R/W 00h

13h T Current Threshold Low LSB R/W 00h

14h U Temperature MSB R 00h

15h V Temperature LSB R 00h

16h W Temperature Threshold High R/W FFh

17h X Temperature Threshold Low R/W 00h

R = Read, W = Write

The status of the charge, voltage, current and temperature
alerts is reported in the status register shown in Table 2.

Table 2. Status Register (A)

BIT NAME OPERATION DEFAULT

A[7] Reserved

A[6] Current Alert

Accumulated

A[5]

A[4]

A[3]

A[2]

A[1] Voltage Alert

A[0]

Charge
Overflow/
Underflow

Temperature
Alert

Charge Alert
High

Charge Alert
Low

Undervoltage
Lockout Alert

Indicates one of the current
limits was exceeded

Indicates that the value of the
ACR hit either top or bottom

Indicates one of the
temperature limits was
exceeded

Indicates that the ACR value
exceeded the charge threshold
high limit

Indicates that the ACR value
exceeded the charge threshold
low limit

Indicates one of the voltage
limits was exceeded

Indicates recovery from
undervoltage. If set to 1, a
UVLO has occurred and the
contents of the registers are
uncertain

0

0

0

0

0

0

1

After each voltage, current or temperature conversion, the
conversion

result is compared to the respective threshold
registers. If a value in the threshold registers is exceeded,
the corresponding bit A[6], A[4] or A[1] is set.

The accumulated charge register (ACR) is compared to
the charge thresholds every time the analog integrator
increments or decrements the prescaler. If the ACR value
exceeds the threshold register values, the corresponding
bit A[3] or A[2] are set. Bit A[5] is set if the accumulated
charge registers (ACR) overflows or underflows. At each
overflow or underflow, the ACR rolls over and resumes
integration.

undervoltage lockout (UVLO) bit of the status register

The
A[0] is set if, during operation, the voltage on the SENSE

+

pin drops below 3.5V without reaching the POR level. The
analog parts of the coulomb counter are switched off while
the digital register values are retained. After recovery of the
supply voltage, the coulomb counter resumes integrating

For more information www.linear.com/LTC2944

2944fa

9

LTC2944

applicaTions inForMaTion

with the stored value in the accumulated charge registers

+

but it has missed any charge flowing while SENSE

< 3.5V.

All status register bits are cleared after being read by the
host, but might be reasserted after the next temperature,
voltage or current conversion or charge integration, if the
corresponding alert condition is still fulfilled.

Control Register (B)

The operation of the LTC2944 is controlled by program

­ming the control register. Table 3 shows the organization
of the 8-bit control register B[7:0].

Table 3. Control Register B

BIT NAME OPERATION DEFAULT

B[7:6] ADC Mode [11] Automatic Mode:

continuously performing
voltage, current and temperature
conversions

[10] Scan Mode: performing
voltage, current and temperature
conversion every 10s

[01] Manual Mode: performing
single conversions of voltage,
current and temperature then
sleep

[00] Sleep

B[5:3] Prescaler M Sets coulomb counter prescaling

factor M between 1 and 4096.
Default is 4096.

Maximum value is limited to 4096

B[5:3] M

000 1

001 4

010 16

011 64

100 256

101 1024

110 4096

111 4096

[00]

[111]

BIT NAME OPERATION DEFAULT

B[2:1] ALCC

Configure

B[0] Shutdown Shut down analog section to

Configures the ALCC pin.
[10] Alert Mode.
Alert functionality enabled. Pin

becomes logic output.
[01] Charge Complete Mode. Pin

becomes logic input and accepts
charge complete inverted signal
(e.g., from a charger) to set
accumulated charge register (C,D)
to FFFFh.

[00] ALCC pin disabled.
[11] Not allowed.

SUPPLY

.

reduce I

[10]

[0]

Power Down B[0]

Setting B[0] to 1 shuts down the analog parts of the
LTC2944, reducing the current consumption to less than

2

15μA (typical). The circuitry managing I

C communica­tion remains operating and the values in the registers are
retained.

Note that any charge flowing while B[0] is 1 is
not measured and any charge information below 1LSB of
the accumulated charge register is lost.

Alert/Charge Complete Configuration B[2:1]

The ALCC pin is a dual function pin configured by the
control register. By setting bits B[2:1] to [10] (default),
the ALCC pin is configured as an alert pin following the
SMBus protocol. In this configuration, the ALCC is pulled
low if one of the four measured quantities (charge, voltage,
current, temperature) exceeds its high or low threshold or
if the value of the accumulated charge register overflows

underflows. An alert response procedure started by the

or
master resets the alert at the ALCC pin. If the configura­tion of

the ALCC

pin is changed while it is pulled low due

to an alert condition, the part will continue to pull ALCC
low until a successful alert response procedure (ARA) has
been issued by the master. For further information see the
Alert Response Protocol section.

10

Setting the control bits B[2:1] to [01] configures the
ALCC pin as a digital input. In this mode, a low input on
the ALCC pin indicates to the LTC2944 that the battery
is full and the accumulated charge register is set to its
maximum, value FFFFh.

2944fa

For more information www.linear.com/LTC2944

50mV

MAX

50mΩ

SENSE

M

50mΩ

SENSE

Q

BAT>IMAX

•22 Hours

BAT

q

LSB

=0.340mAh=1224mC

50mΩ

SENSE

M

applicaTions inForMaTion

LTC2944

If neither the alert nor the charge complete functionality
is desired, bits B[2:1] should be set to [00]. The ALCC
pin is then disabled and should be tied to the supply of

2

C bus with a 10k resistor.

the I

Avoid setting B[2:1] to [11] as it enables the alert and the
charge complete modes simultaneously.

Choosing R

SENSE

To achieve the specified precision of the coulomb counter,

+

the differential voltage between SENSE

and SENSE– must
stay within ±50mV. With input signals up to 300mV the
LTC2944 will remain functional but the precision of the
coulomb counter is not guaranteed.

The required value of the external sense resistor, R
is determined by the maximum input range of V

SENSE

SENSE

and

,

the maximum current of the application:

R

SENSE

≤

I

The choice of the external sense resistor value influences
the gain of the coulomb counter. A larger sense resistor

+

gives a larger differential voltage between SENSE

–

SENSE

for the same current resulting in more precise

and

coulomb counting. The amount of charge represented by
the least significant bit (q

) of the accumulated charge

LSB

(registers C, D) is equal to:

q

=0.340mAh•

LSB

R

•

4096

For such low current applications with a large battery,
choosing R
lead to a q

SENSE

smaller than Q

LSB

mulated charge

according to R

BAT

register may underflow before the battery

SENSE

= 50mV/I

MAX

can

/216 and the 16-bit accu-

is exhausted or overflow during charge. Choose, in this
case, a maximum R

R

SENSE

0.340mAh• 2

≤

Q

SENSE

of:

16

•50mΩ

In an example application where the maximum current is

= 100mA, calculating R

I

MAX

lead to a sense resistor of 500mΩ. This gives a q

SENSE

= 50mV/I

MAX

would

of

LSB

34μAh and the accumulated charge register can represent
a maximum battery capacity of Q
2228mAh. If the battery capacity is larger, R
be lowered. For example, R

SENSE

= 34μAh•65535 =

BAT

must

SENSE

should be reduced to

150mΩ if a battery with a capacity of 7200mAh is used.

Choosing Coulomb Prescaler M B[5:3]

If the battery capacity (Q
maximum current (I

MAX

) is small compared to the

BAT

) the prescaler value M should

be changed from its default value (4096).

In these applications with a small battery but a high maxi
mum current, q

can get quite large with respect to the

LSB

-

battery capacity. For example, if the battery capacity is
100mAh and the maximum current is 1A, the standard
equation leads to choosing a sense resistor value of
50mΩ, resulting in:

or

q

=0.340mAh•

LSB

R

when the prescaler is set to its default value of M = 4096.

Note that 1mAh = 3.6C (coulomb).

Choosing R

SENSE

applications where

= 50mV/I

the battery capacity (Q

is not sufficient in

MAX

compared to the maximum current (I

The battery capacity then corresponds to only 294 q
and less than 0.5% of the accumulated charge register
is utilized.

To preserve digital resolution in this case, the LTC2944
includes a programmable prescaler. Lowering the prescaler
factor M reduces q
charge register to the capacity of the battery. The prescaling
factor M

MAX

BAT

):

) is very large

of 4096. The charge LSB then becomes:

For more information www.linear.com/LTC2944

to better match the accumulated

LSB

can be chosen between 1 and its default value

q

=0.34mAh•

LSB

R

•

4096

LSB

2944fa

11

LTC2944

Q

216•0.340mAh

R

2944 F03

applicaTions inForMaTion

To use as much of the range of the accumulated charge
register as possible the prescaler factor M should be
chosen for a given battery capacity Q
resistor R

M≥ 4096 •

SENSE

as:

BAT

SENSE

•

50mΩ

and a sense

BAT

M can be set to 1, 4, 16, ... 4096 by programming B[5:3]
of the control register as M = 2

2 • (4 • B[5] + 2 • B[4] + B[3])

.

The default value is 4096.

In the above example of a 100mAh battery and an R

SENSE

of 50mΩ, the prescaler should be programmed to
M = 64. The q
corresponds to roughly 18821 q

is then 5.313μAh and the battery capacity

LSB

s.

LSB

Figure 3 illustrates the best choice for prescaler value M
and the sense resistor as function of the ratio between
battery capacity (Q

) and maximum current (I

BAT

MAX

). It
can be seen, that for high current applications with low
battery capacity the prescaler value should be reduced,
whereas in low current applications with a large battery
the sense resistor should be reduced with respect to its
default value of 50mV/I

MAX

.

ADC Mode B[7:6]

The LTC2944 features an ADC which measures either

–

voltage on SENSE
between SENSE

(battery voltage), voltage difference

+

and SENSE– (battery current) or tem­perature via an internal temperature sensor. The reference
voltage and clock for the ADC are generated internally.

ADC has four different modes of operation as shown

The
in Table 3. These modes are controlled by bits B[7:6] of

the control register. At power-up, bits

B[7:6] are set to

[00] and the ADC is in sleep mode.

A single conversion of the three measured quantities
is initiated by setting the bit B[7:6] to [01]. After three
conversions (voltage, current and temperature), the ADC
resets B[7:6] to [00] and goes back to sleep.

The LTC2944 is set to scan mode by setting B[7:6] to
[10]. In scan mode the ADC converts voltage, current,
then temperature, then sleeps for approximately ten
seconds. It then reawakens automatically and repeats the
three conversions. The chip remains in scan mode until
reprogrammed by the host.

Programming B[7:6] to [11] sets the chip into automatic
mode where the ADC continuously performs voltage,
current and temperature conversions. The chip stays in
automatic mode until reprogrammed by the host.

Programming B[7:6] to [00] puts the ADC to sleep. If
control bits B[7:6] change within a conversion, the ADC
will complete the running cycle of conversions before
entering the newly selected mode.

A conversion of voltage requires 33ms (typical), and cur
rent and temperature conversions are completed in 4.5ms
(typical). At the end of each conversion, the corresponding
registers are updated. If the converted quantity exceeds
the values programmed in the threshold registers, a flag
is set in

the status register and the ALCC

pin is pulled low

(if alert mode is enabled).

During ADC conversions additional currents are sunk from

+

SENSE

and SENSE–, refer to the Electrical Characteristics

table for details.

-

M = 1

12

M = 4 M = 16 M = 64 M = 256 M = 1024 M = 4096

0.005h Q

0.02h

0.08h 0.34h 1.4h 5.5h 22h

50mV

R

≤

SENSE

I

MAX

Figure 3. Choice of Sense Resistor and Prescaler as
Function of Battery Capacity and Maximum Current

For more information www.linear.com/LTC2944

R

SENSE

≤

0.34mAh • 2

Q

BAT

16

• 50mΩ

BAT/IMAX

2944fa

RESULT

RESULT

B01C

h

45084





applicaTions inForMaTion

LTC2944

Alert Thresholds Registers (E,F,G,H,K,L,M,N,Q,R,S,
T,W,X)

each of the measured quantities (battery charge,

For
voltage, current and temperature) the LTC2944 features
high and low threshold registers. At power-up, the high
thresholds are set to FFFFh while the low thresholds are set
to 0000h, with the effect of disabling them. All thresholds

2

can be programmed to a desired value via I

C. As soon
as a measured quantity exceeds the high threshold or
falls below the low threshold, the LTC2944 sets the cor

-

responding flag in the status register and pulls the ALCC
pin low if alert mode is enabled via bits B[2:1].

Accumulated Charge Register (C,D)

The coulomb counting circuitry in the LTC2944 integrates
current through the sense resistor. The result of this charge
integration is stored in the 16-bit accumulated charge
register (registers C, D). As the LTC2944 does not know
the actual battery status at power-up, the accumulated
charge register (ACR) is set to mid-scale (7FFFh). If the
host knows the status of the battery, the accumulated
charge (C[7:0]D[7:0]) can be either programmed to the

2

correct value via I

C or it can be set after charging to FFFFh

(full) by pulling the ALCC pin low if charge complete mode
is enabled via bits B[2:1]. Note that before writing to the
accumulated charge registers, the analog section should
be temporarily shut down by setting B[0] to 1. In order to
avoid a change in the accumulated charge registers between
reading MSBs C[7:0] and LSBs D[7:0], it is recommended
to read them sequentially as shown in Figure 11.

Voltage Registers (I,J), and Voltage Threshold
Registers (K,L,M,N)

The result of the 16-bit ADC conversion of the voltage at

–

SENSE

is stored in the voltage registers (I, J).

From the result of the 16-bit voltage registers I[7:0]J[7:0]
the measured voltage can be calculated as:

Example 1: a register value I[7:0] = B0h and J[7:0] = 1Ch

–

corresponds to a voltage on SENSE

V

SENSE

–

=70.8V •

FFFF

h

=70.8V •

of:

65535

DEC

≈ 48.705V

Example 2: To set a low level threshold for the battery
voltage of 31.2V, register M should be programmed to
70h and register N to D0h.

Current Registers (O,P), and Current Threshold
Registers (Q,R,S,T)

The result of the current conversion is stored in the cur

-

rent registers (O,P).

As the ADC resolution is 12 bits in current mode, the
lowest four bits of the combined current registers (O, P)
are always zero.

The ADC measures battery current by converting the volt
age, V

, across the sense resistor R

SENSE

. Depending

SENSE

-

whether the battery is being charged or discharged the
measured voltage drop on R

is positive or negative.

SENSE

The result is stored in registers O and P in excess –32767
representation. O[7:0] = FFh, P[7:0] = F0h corresponds to
the full scale positive voltage 64mV. While O[7:0] = 00h,
P[7:0] = 00h corresponds to the full scale negative volt
age –64mV. The

battery current can be obtained from the

-

two byte register O[7:0]P[7:0] and the value of the chosen
sense resistor R

V

=

SENSE

SENSE

R

SENSE

•



RESULT




I

BAT

64 mV

R

SENSE

=

R

:

64mV

SENSE

DEC

32767

RESULT

•




– 32767

7FFF






– 7FFF

h

h

h

=




Positive current is measured when the battery is charg­ing and negative current is measured when the battery is
discharging.

SENSE

–

=70.8V •

V

FFFF

h

h

=70.8V •

DEC

65535

For more information www.linear.com/LTC2944

2944fa

13

LTC2944





1A •50mΩ





h





2

applicaTions inForMaTion

Example 1: a register value of O[7:0] = A8h P[7:0] = 40h
together with a sense resistor R

= 50mΩ corresponds

SENSE

to a battery current:

I

BAT

64 mV

50mΩ

64mV

=

50mΩ

•






•




A840

– 7FFF

h

7FFF

43072 – 32767

32767

h

=




h



≈ 402.5mA




The positive current result indicates that the battery is
being charged.

The values in the threshold register for the current mode
Q,R,S,T are also expressed in excess –32767 representa

-

tion in the same manner as the current conversion result.

alert after a current measurement is set if the result

The
is higher than the value stored in the high threshold reg

­isters Q,R or lower than the value stored in the low value
registers S,T.

Example 2: In an application, the user wants to get an
alert if the absolute current through the sense resistor,
R
the upper threshold I
lower threshold I
for I

, of 50mΩ exceeds 1A. This is achieved by setting

SENSE

in register [Q,R] to 1A and the

HIGH

in register [S,T] to –1A. The formula

LOW

leads to:

BAT

I

HIGH (DEC)

=




64mV

• 32767

+ 32767= 58366




T = 510K •

RESULT

FFFF

h

=510K •

RESULT

65535

DEC

Example: a register value of U[7:0] = 96h V[7:0] = 96h
corresponds to ~300K or ~27°C

A high temperature limit of 60°C is programmed by setting
register W to A7h. Note that the temperature threshold
register is single byte register and only the eight MSBs of
the 11 bits temperature result are checked.

Effect of Differential Offset Voltage on Total Charge
Error

In battery gas gauges, an important parameter is the
differential offset (V

) of the circuitry monitoring the

OS

battery charge. Many coulomb counter devices perform
an analog to digital conversion of V

SENSE

, where V

SENSE

is the voltage drop across the sense resistor, and ac­cumulate the
an architecture, the differential offset V
charge error of V

conversion results to infer charge. In such

causes relative

OS

OS/VSENSE

. For small V

SENSE

values VOS

can be the main source of error.

The LTC2944 performs the tracking of the charge with an
analog integrator. This approach allows to continuously
monitor the battery charge and significantly lowers the
error due to differential offset. The relative charge error
due to offset (CE

) can be expressed by:

OV



–1A • 50mΩ

I

LOW (DEC)

=



64mV



• 32767

Leading the user to set Q[7:0] = E3h, R[7:0] = FEh for the
high threshold and S[7:0] = 1Bh and T[7:0] = FFh for the
low threshold.

Temperature Registers (U,V) and Temperature
Threshold Registers (W,X)

As the ADC resolution is 11 bits in temperature mode, the
lowest five bits of the combined temperature registers
(U, V) are always zero.

actual temperature can be obtained from the two byte

The
register U[7:0]V[7:0] by:

14



+ 32767= 7168




CEOV=

As example, at a 1mV input signal a differential voltage
offset V
integration, whereas the error is only 0.04% (a factor of
50 times smaller!) using the analog integration approach
of LTC2944.

The reduction of the impact of the offset in LTC2944 can
be explained by its integration scheme depicted in Figure 2.
While positive offset accelerates the up ramping of the
integrator output from REFLO to REFHI, it slows the down
ramping from REFHI to REFLO thus the effect is largely
canceled as depicted in Figure 4.

For more information www.linear.com/LTC2944

V

OS



V



= 20µV results in a 2% error using digital

OS

SENSE




2944fa

applicaTions inForMaTion

LTC2944

INTEGRATOR

OUTPUT

REFHI

REFLO

FASTER
UP RAMPING

Figure 4. Offset Cancellation

WITHOUT OFFSET

WITH OFFSET

SLOWER
DOWN RAMPING

TIME

2944 F04

For input signals with an absolute value smaller than the
offset of the internal op amp the LTC2944 stops integrat­ing and does not integrate its own offset.

2

C/SMBus Interface

I

The LTC2944 communicates with a bus master using

2

a 2-wire interface compatible with I

2

7-bit hard coded I

C address of the LTC2944 is 1100100.

C and SMBus. The

The LTC2944 is a slave only device. The serial clock line
(SCL) is input only while the serial data line (SDA) is

2

bidirectional. The device supports I
mode. For more details refer to the I

C standard and fast

2

C Protocol section.

Each device on the I2C/SMbus is recognized by a unique
address stored in that device and can operate as either a
transmitter or receiver, depending on the function of the
device. In addition to transmitters and receivers, devices
can also be classified as masters or slaves when perform
ing data
data

transfers. A master is the device which initiates a

transfer on the bus and generates the clock signals to

-

permit that transfer. At the same time any device addressed
is considered a slave. The LTC2944 always acts as a slave.

Figure 5 shows an overview of the data transmission on

2

C bus.

the I

Start and Stop Conditions

When the bus is idle, both SCL and SDA must be high. A
bus master signals the beginning of a transmission with
a START condition by transitioning SDA from high to low
while SCL is high. When the master has finished com

­municating with the slave, it issues a STOP condition by
transitioning SDA from low to high while SCL is high. The
bus is then free for another transmission. When the bus
is in use, it stays busy if a repeated START (Sr) is gener

­ated instead of a STOP condition. The repeated START

conditions are functionally identical to the START (S).

(Sr)

2

C Protocol

I

2

The LTC2944 uses an I

C/SMBus-compatible 2-wire
interface supporting multiple devices on a single bus.
Connected devices can only pull the bus lines low and
must never drive the bus high. The bus wires are externally
connected to a positive supply voltage via current sources

pull-up resistors. When the bus is idle, all bus lines

or
are high. Data on the I

2

C bus can be transferred at rates
of up to 100kbit/s in standard mode and up to 400kbit/s
in fast mode.

SDA

SCL

S

START

CONDITION

a6 - a0 b7 - b0 b7 - b0

1 - 7 8 9

ADDRESS R/W ACK DATA ACK DATA ACK

Figure 5. Data Transfer Over I2C or SMBus

1 - 7 8 9 1 - 7 8 9

Write Protocol

The master begins a write operation with a START condition
followed by the seven bit slave address 1100100 and the
R/W bit set to zero, as shown in Figure 6. The LTC2944
acknowledges this by pulling SDA low and the master
sends a command byte which indicates which internal
register the master is to write. The LTC2944 acknowledges
and latches the command byte into its internal register
address pointer. The master delivers the data byte, the
LTC2944 acknowledges once more and latches the data

P

STOP

CONDITION

2944 F05

2944fa

For more information www.linear.com/LTC2944

15

LTC2944

2944 F07

2944 F09

applicaTions inForMaTion

into the desired register. The transmission is ended when
the master sends a STOP condition. If the master contin-

sending a second data byte instead of a stop, the

ues by
LTC2944

acknowledges again, increments its address
pointer and latches the second data byte in the following
register, as shown in Figure 7.

S W

ADDRESS REGISTER DATA

1100100 01h FCh

FROM MASTER TO SLAVE

FROM SLAVE TO MASTER

A A A

0

0 0 0

A: ACKNOWLEDGE (LOW)
A: NOT ACKNOWLEDGE (HIGH)

S: START CONDITION
P: STOP CONDITION

R: READ BIT (HIGH)
W: WRITE BIT (LOW)

Figure 6. Writing FCh to the LTC2944 Control Register (B)

S W

ADDRESS REGISTER DATA

1100100 02h F0h 01h

A A A

0

0 0 0

Figure 7. Writing F001h to the LTC2944 Accumulated Charge
Register (C, D)

2944 F06

DATA

P

P

A

0

Read Protocol

The master begins a read operation with a START condition
followed by the seven bit slave address 1100100 and the
R/W bit set to zero, as shown in Figure 8. The LTC2944
acknowledges and the master sends a command byte
which indicates which internal register the master is to
read. The LTC2944 acknowledges and then latches the

command byte into its internal register address pointer.
The master then sends a repeated START condition fol­lowed by
now

the same seven bit address with the R/W bit

set to one. The LTC2944 acknowledges and sends
the contents of the requested register. The transmission
is ended when the master sends a STOP condition. If
the master acknowledges the transmitted data byte, the
LTC2944 increments its address pointer and sends the
contents of the following register as depicted in Figure 9.

Alert Response Protocol

In a system where several slaves share a common inter

­rupt line, the master can use the alert response address
(ARA) to determine which device initiated the interrupt
(Figure 10).

The master initiates the ARA procedure with a START
condition and the special 7-bit ARA bus address (0001100)
followed by the read bit (R) = 1. If the LTC2944 is as

­serting the ALCC pin in alert mode, it acknowledges and
responds by sending its 7-bit bus address (1100100)
and a 0. While it is sending its address, it monitors the
SDA pin to see if another device is sending an address at

2

the same time using standard I
LTC2944 is sending a 1 and reads a 0

C bus arbitration. If the

on the SDA pin on
the rising edge of SCL, it assumes another device with a
lower address is sending and the LTC2944 immediately
aborts its transfer and waits for the next ARA cycle to try
again. If transfer is successfully completed, the LTC2944
will stop pulling down the ALCC pin and will not respond
to further ARA requests until a new Alert event occurs.

S W

ADDRESS REGISTER Sr

1100100 00h 1

S W

ADDRESS REGISTER Sr

1100100 08h 1

Figure 9. Reading the LTC2944 Voltage Register (I, J)

16

A A ADDRESS

0

0 0 1100100

A

R

DATA

0

01h

Figure 8. Reading the LTC2944 Status Register (A)

A A ADDRESS

0

0 0 1100100

For more information www.linear.com/LTC2944

A

R

0

DATA

F1h

A

0

DATA

24h

P

A

1

2944 F08

P

A

1

2944fa

2944 F10

2944 F11

applicaTions inForMaTion

2944 F13

LTC2944

S R

ALERT RESPONSE ADDRESS DEVICE ADDRESS

0001100 11001000

A

1

0 1

P

A

Figure 10. LTC2944 Serial Bus SDA Alert Response Protocol

S W

ADDRESS REGISTER S

1100100 02h 1

A A ADDRESS

0

0 0 1100100

A

R

A

DATA

0

0

80h

DATA

01h

P

A

1

Figure 11. Reading the LTC2944 Accumulated Charge
Registers (C, D)

S W

ADDRESS REGISTER DATA

1100100 01h 4C

S W

ADDRESS REGISTER S

1100100 08h 1

A A ADDRESS

0

0 0 1100100

A A

0

0 0

40ms

P

A

R

A

DATA

0

0

F1h

DATA

80h

A

1

2944 F12

P

Figure 12. ADC Single Conversion Sequence and Reading
of Voltage Registers (I,J)

PC Board Layout Suggestions

Keep all traces as short as possible to minimize noise and
inaccuracy. Use a 4-wire Kelvin sense connection for the
sense resistor, locating the LTC2944 close to the resistor

+

with short sense-traces to the SENSE

and SENSE– pins.
Use wider traces from the resistor to the battery, load
and/or charger. Put the bypass capacitor close to SENSE

+

and GND.

CHARGER/LOAD

TO

R

SENSE

TO BATTERY

Preventing Violation of Absolute Maximum Ratings

The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the supply
bypass capacitor of LTC2944. However, these capacitors
can cause problems if the LTC2944 is plugged into a live
supply close to its maximum voltage of 65V. The low
loss ceramic capacitor, combined with stray inductance
in series with the power source, forms an under damped

–

tank circuit, and the voltage at the SENSE

pin of the
LTC2944 can ring several tens of volts, possibly exceed­ing the
be
diode to the SENSE

LTC2944 rating and damaging the part. This can

prevented by adding a transient voltage suppression

–

pin as shown in Figure 14.

Also pulling the digital communication pins SCL, SDA and
ALCC below their minimum absolute maximum voltage
of –0.3V—for example, due to differences between the
local GND and the GND of the connected microproces
sor—increases the

supply current of the LTC2944. At
supply voltages above 50V, the power dissipated due
to the increased supply current might damage the part,
which can be prevented by adding Schottky diodes as
shown in Figure 14.

LTC2944

GND

CHARGER

SENSE

SENSE

SMAJ58ACMHSHS-2L

+

R

SENSE

–

50mΩ

+

MULTICELL
Li-ION

3.3V

2k2k 2k

V

DD

µP

ALCC

SDA

SCL

-

1A
LOAD

1µF

2944 F14

1

C

2

LTC2944

3

4

8

7

6

5

Figure 13. Kelvin Connection on Sense Resistor

Figure 14. Preventing Violation of Absolute Maximum Ratings

For more information www.linear.com/LTC2944

2944fa

17

LTC2944

package DescripTion

Please refer to http://www.linear.com/product/LTC2944#packaging for the most recent package drawings.

DD Package

8-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1698 Rev C)

0.70 ±0.05

3.5 ±0.05

1.65 ±0.05
(2 SIDES)2.10 ±0.05

PACKAGE
OUTLINE

0.25 ± 0.05

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

PIN 1

TOP MARK

(NOTE 6)

0.200 REF

NOTE:

1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE

0.50
BSC

2.38 ±0.05

3.00 ±0.10
(4 SIDES)

0.75 ±0.05

0.00 – 0.05

1.65 ± 0.10
(2 SIDES)

R = 0.125

TYP

0.25 ± 0.05

2.38 ±0.10

BOTTOM VIEW—EXPOSED PAD

0.40 ± 0.10

85

14

0.50 BSC

(DD8) DFN 0509 REV C

18

2944fa

For more information www.linear.com/LTC2944

LTC2944

revision hisTory

REV DATE DESCRIPTION PAGE NUMBER

A 10/17 Updated equation for obtaining temperature (T) 15

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa­tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

For more information www.linear.com/LTC2944

2944fa

19

LTC2944

Typical applicaTion

Battery Charger with Gas Gauge

CX

Si7135DP

IGATE

22.1k

CSP

CSN

BGATE

BAT

OFB

FBG

BFB

NTC

1µF0.1µF

1.15M

47k

47k

1.13M

10k

5mΩ

Si7135DP

V

OUT

30.4V, 15A

3.3V

V

DD

µP

C1

R2

R1

2k

2k

LTC2944

R3
2k

ALCC

SDA

SCL

GND

SENSE

SENSE

+

–

1µF

R

SENSE

100mΩ

+

30V
Li-ION
BATTERY

2944 TA02

33V TO 60V

5mΩ

1.10M

100k

10nF

3.0V

LT3845A

IN

SHDN

RST

CLN
IN

1µF

VM

ENC

CHRG
F LT

IIMON

IBMON

10nF

OUT

V

C

14.7k

ITH CC IID

TMR GND BIASCL

100µF

47nF

LTC4000

24.9k

relaTeD parTs

PART NUMBER DESCRIPTION COMMENTS

Battery Gas Gauges

2

LTC2943 I

C Battery Gas Gauge with Voltage, Current and

Temperature ADC

LTC2943-1 1A Multicell Batter

y Gas Gauge with Temperature,

Voltage and Current Measurement

2

LTC2941 I

LTC2941-1 1A I

C Battery Gas Gauge 2.7V to 5.5V Operation, 6-Lead (2mm × 3mm) DFN Package

2

C Battery Gas Gauge with Internal Sense

Resistor

2

LTC2942 I

C Battery Gas Gauge with Temperature, Voltage

Measurement

2

LTC2942-1 1A I

C Battery Gas Gauge with Internal Sense

Resistor and Temperature/Voltage Measurement

LTC4150 Coulomb Counter/Battery Gas Gauge 2.7V to 8.5V Operation, 10-Pin MSOP Package

Battery Chargers

LTC4000 High Voltage High Current Controller for Battery

Charging and Power Management

LTC4009 High Efficiency, Multi-Chemistry Battery Charger 6V to 28V Operation, 20-Lead (4mm × 4mm) QFN Package

LTC4012 High Efficiency, Multi-Chemistr

y Battery Charger

with PowerPath™ Control

®

3652HV Power Tracking 2A Battery Charger Input Supply Voltage Regulation Loop for Peak Power Tracking, 5V to 34V Operation,

LT

3.6V to 20V Operation, 14-Bit Δ∑-ADC, Pin Compatible with LTC2944,
LTC2943-1, 8-Lead (3mm × 3mm) DFN Package

3.6V to 20V Operation, Internal Sense Resistor, 14-Bit Δ∑ ADC, Pin Compatible
with LTC2944 and LTC2943, 8-Lead (3mm × 3mm) DFN Package

2.7V to 5.5V Operation, 6-Lead (2mm × 3mm) DFN Package

2.7V to 5.5V Operation, 14-Bit Δ∑-ADC, 6-Lead (2mm × 3mm) DFN Package

2.7V to 5.5V Operation, 14-Bit Δ∑-ADC, 6-Lead (2mm × 3mm) DFN Package

3V to 60V Operation, 28-Lead (4mm × 5mm) QFN or SSOP Packages

6V to 28V Operation, 20-Lead (4mm × 4mm) QFN Package

1MHz, 2A Charge Current, 3mm × 3mm DFN-12 and MSOP-12 Packages

0.5A
LOAD

20

For more information www.linear.com/LTC2944

2944fa

LT 1017 REV A • PRINTED IN USA

www.linear.com/LTC2944

 LINEAR TECHNOLOGY CORPORATION 2017