DC1496A-A - LINEAR TECHNOLOGY

dc1496f

DEMO MANUAL DC1496A-A/B

DESCRIPTION

LTC2941/LTC2942:

Battery Gas Gauge with I2C

Interface [and 14-Bit ADC

(DC1496A-B)]

Demonstration circuit 1496A-A (Figure 1) features the

LT C

2941. Demonstration circuit 1496A-B features the

LTC2942. Both devices measure battery charge state

in handheld PC and portable product applications. The

operating range is perfectly suited for single cell Li-Ion

batteries. A precision analog coulomb counter integrates

current through a sense resistor between the battery’s

positive terminal and the load or charger. The LTC2942 adds

battery voltage and on-chip temperature measurement

with an internal 14-bit No Latency ΔΣ™ ADC. The three

measured quantities (charge, voltage and temperature)

are stored in internal registers accessible via the onboard

SMBus/I2C interface.

The LTC2941 has programmable high and low thresholds

for accumulated charge. The LTC2942 has programmable

high and low thresholds for all three measured quantities.

If a programmed threshold is exceeded, the device reports

an alert using either the SMBus alert protocol or by setting

a ﬂ ag in the internal status register.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and

No Latency ΔΣ is a trademark of Linear Technology Corporation. All other trademarks are

the property of their respective owners.

The LTC2941 and LTC2942 require only a single low value

sense resistor to set the measured current range. The

default value assembled on the DC1496 is 100mΩ for a

maximum current measurement of 500mA. Both parts

have a software-conﬁ gurable charge complete/alert pin.

When the pin is set for charge complete, a jumper con-

nects the pushbutton which simulates a logic high input

to indicate a full battery. When the pin is conﬁ gured for

alert, the same jumper is used to connect a red LED that

indicates an alert is present.

The DC1496A-A/B is a part of the QuikEval system for quick

evaluation with a host controller through a PC.

Design ﬁ les for this circuit board are available at

http://www.linear.com/demo.

Figure 1. DC1496A-A/B

dc1496f

DEMO MANUAL DC1496A-A/B

QUICK START PROCEDURE

Demonstration circuit 1496A is easy to set up to evaluate

the performance of the LTC2941/LTC2942. Refer to Figure

2 for proper measurement equipment setup and follow

the procedure below.

1. Connect a 1-cell Li-Ion battery across V_BAT and

GND.

2. Connect a load across V_CHRG/LD and GND for battery

discharge measurement. Up to 500mA supplied from

the battery can be measured with the board default

100mΩ sense resistor. Use SENSE+ and SENSE– test

points to read voltage across the sense resistor.

3. Connect a 2.7V to 5.5V battery charger supply across

V_CHRG/LD and GND. Up to 500mA supplied to the

battery can be measured with the board default 100mΩ

sense resistor. Use SENSE+ and SENSE– test points to

read voltage across the sense resistor.

4. Connect a DC590 to 14-pin connector J1 for evaluation

with QuikEval, or connect a host controller I2C bus to

the SDA, SCL and GND test turrets.

5. Set JP1 to QuikEval if a DC590 is present. Otherwise

set JP1 to Bat/Chrg for bus pull-up to the battery, or

ﬂ oat JP1 and supply a bus pull-up voltage to VP.

6. Read and write to the LTC2941/LTC2942 through I2C.

7. Through I2C, configure the AL/CC pin. Set JP2

accordingly.

8 If AL/CC is set for charge complete, use pushbutton

switch S1 to simulate a logic high from a controller to

indicate a fully charged battery.

Figure 2. DC1496A-A/B Basic Setup

dc1496f

DEMO MANUAL DC1496A-A/B

QuikEval INTERFACE

The DC1496A-A/B can be connected to a DC590 and used

with the QuikEval software. The DC590 connects to a PC

through USB. QuikEval automatically detects the demo

board and brings up the LTC2941/LTC2942 evaluation

software interface (Figure 3).

Compact and Detailed Form

When the interface is brought up, a compact form is ﬁ rst

shown with a display for the accumulated charge register

(ACR), voltage ADC and temperature ADC. To expand the

form for a more detailed display of the LTC2941/LTC2942

registers and board conﬁ gurations, click on Detail. To go

back to the compact form, click on Hide.

Start/Refresh

Click on Start to begin a polling routine that refreshes the

interface every 1 second. Click on Stop to halt the poll-

ing. For a single update, click on Refresh. Each refresh

scans through the internal I2C registers and updates the

respective displays.

LTC2941 and LTC2942 Display

On a refresh or poll, the software reads Status bit A[7] to

determine communication with an LTC2941 or LTC2942.

When an LTC2941 is detected, the voltage and temperature

ADC and threshold displays are not shown. Control bits

B[7:6] conﬁ gure VBAT Alert for the LTC2941 and ADC

Mode for the LTC2942.

ACR Display

The data in the ACR (registers C and D) is displayed in one

of three selected formats: Counter in coulombs, Counter

in mA • hour, battery gas gauge in mA • hour, and battery

gas gauge in charge percentage of battery. The two gas

gauge displays correspond to the battery gas gauge full

battery conﬁ guration set in the detailed form.

Voltage and Temperature ADC (LTC2942)

Data from the Voltage ADC (registers I and J) and the

Temperature ADC (registers M and N) is displayed here

in Volts and Celsius.

Figure 3. LTC2941/LTC2942 QuikEval Interface

dc1496f

DEMO MANUAL DC1496A-A/B

QuikEval INTERFACE

Address/I2C Status

The write address for the LTC2941/LTC2942 is C8h and the

read address is C9h. The alert response address (ARA) is

19h. If an error occurs while reading from the LTC2941/

LTC2942, the I2C status will read as an error. Otherwise,

the status is good. If the LTC2941/LTC2942 AL/CC pin is

set for alert mode and an alert has been latched, the device

will pull down this pin. Click on ARA to send out an ARA

on to the bus lines and the device will respond with its

address. The Alert pin will then be cleared if the alert is

no longer present.

Status

The individual status bits A[0:7] and their states are shown

here. A red indicator next to bits A[0:5] indicates the re-

spective alert is currently present and will latch the Alert

pin if conﬁ gured for alert. Bit A[7] shows if an LTC2941

or LTC2942 is detected.

Sense Resistor

Enter here the sense resistor value used in the application.

The default for the DC1496A-A/B is a 100mΩ sense resis-

tor. Check LTC2941-1/LTC2942-1 if one of these devices is

used in place of the default IC. This sets the sense resistor

value to 50mΩ, the value of the internal sense resistor

in these devices. The sense resistor can only be changed

when not polling. The software only accepts sense resis-

tors between 0.1mΩ to 5Ω.

Battery Gas Gauge

The battery capacity in the application is entered here. The

ACR full scale (FFFFh) is set to this value and affects the

two Gas Gauge ACR display options. Instead of counting

up from 0 as in the Coulomb Counters, the Gas Gauge

is used to count down from a full battery. The battery

capacity can only be entered when not polling. The data

in the ACR when a battery should be empty is calculated

based off of RSENSE, and pre-scaler M, and displayed in

hexadecimal below the ACR full scale.

Control

Conﬁ gurations done in the Control section write to the

Control register (register B). For the LTC2941, the Control

bits B[7:6] enables a battery monitor to one of three set

voltage thresholds (2.8V, 2.9V, or 3V) or disables this

battery voltage alert. The ADC mode with the LTC2942 is

default to Sleep where both Voltage and Temperature ADCs

(LTC2942) are disabled. Setting ADC Mode to Automatic

Mode enables full-time the Voltage and Temperature ADC.

Selecting Manual Voltage or Temperature mode enables

the respective ADC once and returns the ADC to Sleep

mode.

Select a pre-scaler M value to scale the ACR according

to battery capacity and maximum current. Changing the

pre-scaler will halt the poll. A calculator tool is provided

in the tool bar under Tools to assist in calculating a pre-

scaler value and sense resistor (Figure 4).

The AL#/CC pin can be conﬁ gured for Alert mode, Charge

Complete mode, or disabled. Select the corresponding

settings on the DC1496A-A/B jumper J2.

The Shutdown Analog Section is checked to disable the

Analog portion of the LTC2941/42 and set the device in a

low current state.

Data in the internal registers of the LTC2941/LTC2942 is

displayed here in hexadecimal or appropriate units. Data

can also be entered and written to the write registers.

Enter data to be written in hexadecimal, or select Unit

and enter data in decimal form. Data in decimal scale is

auto corrected if the maximum or minimum full scale is

exceeded. Select the ACR display in Counter (Coulombs)

to be able to write to the ACR and charge thresholds in

Coulombs, or select Counter (mAh) to be able to write

to the ACR and charge thresholds in mA • hour. Voltage

and Temperature High thresholds are rounded down in

the calculations to the nearest lower count, while the

low thresholds are rounded up to nearest higher count.

dc1496f

DEMO MANUAL DC1496A-A/B

Switching back and forth between Hex and Unit can be

used as a conversion tool.

The LSB value for the 16-bit ACR and charge thresholds

is displayed on the bottom. This value is adjusted with the

sense resistor and pre-scaler M. The units are in mAh or

mC depending on the selected ACR display. Shown for

the LTC2942 is the LSB for the 14-bit voltage ADC, 10-bit

temperature ADC, and 8-bit high and low thresholds for

voltage and temperature.

Calculator Tool

A calculator tool is available in the tool bar options under

Tools. In this calculator (Figure 4), enter the maximum cur-

rent passed through the sense and the maximum battery

capacity. Click on Calculate to calculate a recommended

sense resistor and pre-scaler (M) value. The display shows

the battery capacity in comparison to ACR full scale and

provides an LSB value in mAh. Also shown is the recom-

mended equation to use to determine an appropriate sense

resistor as a function of the maximum battery charge and

maximum current.

Figure 4. LTC2941/LTC2942 Pre-Scaler and Sense Resistor Calculator

QuikEval INTERFACE

dc1496f

DEMO MANUAL DC1496A-A/B

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURE/PART NUMBER

1 2 C1, C2 CAP., CHIP X7R, 0.1μF, 25V, 0603 AVX, 06033C104KAT2A

2 4 E1-E4 TURRET, Test Point 0.094" MILL-MAX, 2501-2-00-80-00-00-07-0

3 5 E5-E9 TURRET, Test Point 0.064" MILL-MAX, 2308-2

4 1 E10, E11 TURRET, Test Point 0.037" MILL-MAX, 2309-1

5 0 TP1, TP2 (SMT Pads Only)

6 2 JP1, JP2 HEADER, 3Pin 1 Row 0.079CC SAMTEC, TMM-103-02-L-S

7 2 for (JP1, JP2) SHUNT, 0.079" Center SAMTEC, 2SN-BK-G

8 1 J1 HEADERS, Vertical Dual 2X7 0.079CC MOLEX, 87831-1420

9 1 D1 LED, RED, LIGHT EMITTING DIODES PANASONIC, LN1251CTR

10 1 R1 RES., CHIP, 0.1Ω, 1/8W, 1%, 1206 IRC, LRC-LR1206LF-01-R100-F

11 3 R6, R7, R8 RES., CHIP, 5.10k, 1%, 0603 VISHAY, CRCW06035K10FKEA

12 3 R2, R3, R4 RES., CHIP, 10k, 5%, 0603 VISHAY, CRCW060310K0JNEA

13 1 R5 RES., CHIP, 1k, 5%, 0603 VISHAY, CRCW06031K00JNEA

14 1 R9 RES., CHIP, 100k, 5%, 0603 VISHAY, CRCW0603100KJNEA

15 1 S1 SWITCH, SMT Pushbutton PANASONIC, EVQPE105K

16 1 U2 I.C., Serial EEPROM TSSOP8 MICROCHIP, 24LC025-I/ST

17 1 for (J1) CABLE ASSY., 8" STRIP LINEAR RIBBON CABLE CA-2440

dc1496f

DEMO MANUAL DC1496A-A/B

SCHEMATIC DIAGRAM

A A

B B

C C

D D

NOTES:

Performance Or Reliability. Contact Linear Technology

Circuit Board Layout May Significantly Affect Circuit

Verify Proper And Reliable Operation In The Actual

Linear Technology Has Made A Best EffortTo DesignA

Customer Notice

Supplied For UseWith Linear Technology Parts.

Circuit That Meets Customer-Supplied Specifications;

However, It Remains The Customer's Responsibility To

This Circuit Is Proprietary To Linear Technology And

Applications Engineering ForAssistance.

Application.Comp

onentSubs

titution And Printed

LTCCONFIDENTIAL - FOR CUSTOMER USE ONLY

Quick Eval Demo Only

LTC2941IDCB/LTC

2942IDCBBatteryGas Gauge with I2C

[and 14-Bit ADC (DC1496A-B)]

ASSEMBLY

DC1496A-B

LTC2941IDCB

LTC2942IDCB

DC1496A-A

Bat/Chrg

Pull-U

QuickEval

AL LED

AL / CC

CC PB

Table:1

Demo Circuit 1496A-A/B

Linear Technology Corporation

1630 McCarthy Blvd.

Milpitas, CA. 95035

Phone (408)4

32-1900

Fax (408) 434-0507 www.linear.com

11Tuesday,June 02,2009

Title

Size Document Number Rev.

Date: Sheet of

JP1

GND

0.1uF

0.1

TP2

AL/CC

24LC025-I / ST

SCL

VSS

SDA

VCC

100K

JP2

SDA

TP1

0.1uF

V_BAT

10K

SCL

10K

5.1K

GND

(RED)

2 1

V_CHRG / LD

2.7V - 5.5V

E10

SENSE+

J1HD2X7

V+

GND

SCK

MISO

SDA/MOSI

GND

EESDA

EEVCC

EESCL

EEGND

GND

See Table 1

3 4

VCC / SENSE+ SENSE-

SCL SDA

AL / CC

GND

5.1K

10K

5.1K

E11

SENSE-

dc1496f

DEMO MANUAL DC1496A-A/B

Silkscreen Top Component Side

Inner Layer 2

PCB LAYOUT AND FILM

dc1496f

DEMO MANUAL DC1496A-A/B

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.

PCB LAYOUT AND FILM

Inner Layer 3 Solder Side

SilkScreen Bottom

dc1496f

DEMO MANUAL DC1496A-A/B

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

LT 0510 • PRINTED IN USA

DEMONSTRATION BOARD IMPORTANT NOTICE

Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:

This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT

OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete

in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety

measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union direc-

tive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.

If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date

of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU

OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS

FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR

ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.

The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims

arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all

appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or

agency certified (FCC, UL, CE, etc.).

No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,

customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.

LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.

Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and

observe good laboratory practice standards. Common sense is encouraged.

This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC applica-

tion engineer.

Mailing Address:

Linear Technology

1630 McCarthy Blvd.

Milpitas, CA 95035