DC1496B - Demo Manual

DEMO MANUAL DC1496B
LTC2941/LTC2942:
Battery Gas Gauge with I2C
Interface and 14-Bit ADC
DESCRIPTION
Demonstration circuit 1496B-A (Figure 1) features the
LTC®2941. Demonstration circuit 1496B-B features the
LTC2942. Demonstration circuit 1496B-C features the
LTC2941-1. Demonstration circuit 1496B-D features the
LTC2942-1. The C, D options have parts that use an internal
sense resistor while the A, B options rely on an external
precision sense resistor. All four 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 ∆Σ™
ADC. The three measured quantities (charge, voltage and
temperature) are stored in internal registers accessible via
the onboard SMBus/I2C interface.
The LTC2941/LTC2941-1 has programmable high and
low thresholds for accumulated charge. The LTC2942/
LTC2942-1 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 flag in the internal
status register.
The LTC2941 and LTC2942 require only a single low value
sense resistor to set the measured current range. The
LTC2941-1 and the LTC2942-1 have their own 50mΩ internal resistor. The default value assembled on the DC1496 is
100mΩ for a maximum current measurement of 500mA.
Both parts have a software-configurable charge complete/
alert pin. When the pin is set for charge complete, a jumper
connects the pushbutton which simulates a logic high input
to indicate a full battery. When the pin is configured for
alert, the same jumper is used to connect a red LED that
indicates an alert is present. A change was made between
DC1496A and DC1496B to float the exposed pad under
the LTC2941/LTC2942 in accordance with the data sheet
recommendations.
The DC1496B is a part of the QuikEval system for quick
evaluation with a host controller through a PC.
Design files for this circuit board are available at
http://www.linear.com/demo.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No Latency ∆Σ is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners.
Figure 1. DC1496B
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DEMO MANUAL DC1496B
QUICK START PROCEDURE
Demonstration circuit 1496B is easy to set up to evaluate
the performance of the LTC2941/LTC2942/LTC2941-1/
LTC2942-1. 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 or 50mΩ internal 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
float 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.
VSENSE
+
CHARGER
+
–
LOAD
–
BATTERY
1-CELL
Li-Ion
BUS PULL-UP
VOLTAGE
TO QuikEval
TO MICROCONTROLLER
Figure 2. DC1496B Basic Setup
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DEMO MANUAL DC1496B
QuikEval INTERFACE
The DC1496B 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 first
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/
LTC2941-1/LTC2942-1 registers and board configurations,
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 polling. 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, LTC2942,
LTC2941-1 or LTC2942-1. When an LTC2941 is detected,
the voltage and temperature ADC and threshold displays
are not shown. Control bits B[7:6] configure 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 configuration set in the detailed form.
Voltage and Temperature ADC (LTC2942, LTC2942-1)
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
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DEMO MANUAL DC1496B
QuikEval INTERFACE
Address/I2C Status
Control
The write address for the LTC2941/LTC2942/LTC2941-1/
LTC2942-1 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/LTC2941-1/
LTC2942-1, the I2C status will read as an error. Otherwise,
the status is good. If the LTC2941/LTC2942/LTC2941-1/
LTC2942-1 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.
Configurations 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.
Status
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 prescaler value and sense resistor (Figure 4).
The individual status bits A[0:7] and their states are shown
here. A red indicator next to bits A[0:5] indicates the respective alert is currently present and will latch the Alert
pin if configured for alert. Bit A[7] shows if an LTC2941,
LTC2942, LTC2941-1 or LTC2942-1 is detected.
Sense Resistor
Enter here the sense resistor value used in the application.
The default for the DC1496B is a 100mΩ sense resistor.
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 resistors 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.
The AL#/CC pin can be configured for Alert mode, Charge
Complete mode, or disabled. Select the corresponding
settings on the DC1496B jumper J2.
The Shutdown Analog Section is checked to disable the
Analog portion of the LTC2941/42/41-1/42-1 and set the
device in a low current state.
Register Read/Write
Data in the internal registers of the LTC2941/LTC2942/
LTC2941-1/LTC2942-1 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
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4
DEMO MANUAL DC1496B
QuikEval INTERFACE
count, while the low thresholds are rounded up to nearest
higher count. 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/LTC2942-1 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 current 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 recommended 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
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5
DEMO MANUAL DC1496B
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURE/PART NUMBER
1
2
C1, C2
CAP., CHIP X7R, 0.1μF, 25V, 0603
AVX, 06033C104KAT2A
2
3
4
E1-E4
TURRET, Test Point 0.094"
MILL-MAX, 2501-2-00-80-00-00-07-0
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
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6
D
C
B
A
GND
NOTES:
CC PB
R9
100K
OPEN
OPEN
LTC2941IDCB-1
LTC2942IDCB-1
DC1496B-C
DC1496B-D
0.1
R1
0.1
2
3
3
D1
AL
(RED)
R5
1K
LTC2942IDCB
LTC2941IDCB
R4
10K
DC1496B-B
DC1496B-A
S1
CC
R3
10K
ASSEMBLY
VERSION TABLE
1
2
3
E9
E8
E7
E6
R2
10K
U1
*
1
2
3
E5
AL / CC
JP2
AL / CC
SDA
SCL
VP
AL LED
1
JP1
E3
E1
Pull - Up
Quick Eval
Bat/Chrg
GND
2.7V - 5.5V
V_CHRG / LD
1
2
2
C1
0.1uF
3
2
1
SDA
SCL
EESDA
EESCL
EEVCC
MISO
NC
SDA/MOSI
SCK EEGND
CS
5V
V+
14
12
9
11
10
4
5
Linear Technology Has Made A Best Effort To Design A
Circuit That Meets Customer-Supplied Specifications;
However, It Remains The Customer's Responsibility To
Verify Proper And Reliable Operation In The Actual
Application. Component Substitution And Printed
Circuit Board Layout May Significantly Affect Circuit
Performance Or Reliability. Contact Linear Technology
Applications Engineering For Assistance.
This Circuit Is Proprietary To Linear Technology And
Supplied For Use With Linear Technology Parts.
Customer Notice
LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY
5
7
4
6
2
J1 HD2X7
7
DNC
4
5
6
A0
A1
A2
WP
SDA
SCL
1
2
3
7
5
6
U2
24LC025-I / ST
7
R6
5.1K
E4
E2
R7
5.1K
GND
V_BAT
Date:
Size
Title
www.linear.com
6
7
Sheet
1
Demo Circuit 1496B
Wednesday, March 02, 2011
Document Number
LTC294XIDCB
Battery Gas Gauge with I2C
1630 McCarthy Blvd.
Milpitas, CA. 95035
Phone (408) 432-1900
Fax (408) 434-0507
Linear Technology Corporation
C2
0.1uF
EX PAD
AL / CC
E11
GND
*
*
SENSE-
SENSE-
U1
R1
6
VCC / SENSE+
E10
SENSE+
5
Quick Eval Demo Only
1
4
GND
3
GND
8
GND
13
8
VCC
VSS
4
1
of
TP2
TP1
R8
5.1K
8
8
1
Rev.
B
D
C
B
A
DEMO MANUAL DC1496B
SCHEMATIC DIAGRAM
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7
DEMO MANUAL DC1496B
PCB LAYOUT AND FILM
Silkscreen Top
Component Side
Inner Layer 2
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8
DEMO MANUAL DC1496B
PCB LAYOUT AND FILM
Inner Layer 3
Solder Side
SilkScreen Bottom
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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.
9
DEMO MANUAL DC1496B
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 directive 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 application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1496fa
10 Linear Technology Corporation
LT 0711 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2010
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