DC1812A - Demo Manual

DEMO MANUAL DC1812A
LTC2943/LTC2943-1/LTC2944
Multicell Battery Gas Gauge with Temperature,
Voltage and Current Measurement
Description
Demonstration circuit 1812A-A (Figure 1) features the
LTC®2943. Demonstration circuit 1812A-B features the
LTC2944. Demonstration circuit 1812A-C features the
LTC2943-1. The LTC2943/LTC2943-1 has an operating
range of 3.6V to 20V, while the LTC2944 has an operating
range of 3.6V to 60V, making all three devices perfectly
suited for multicell battery applications. A precision analog
coulomb counter integrates current measured through a
sense resistor between the battery’s positive terminal and
the load or charger. The LTC2943/LTC2943-1 measures
voltage, current and temperature with an internal 14-bit
No Latency ∆∑™ ADC. The LTC2944 measures voltage,
current and temperature with an internal 16-bit No Latency
∆∑ ADC. The measurements are stored in internal registers
accessible via the onboard SMBus/I2C interface.
The LTC2943/LTC2943-1/LTC2944 has programmable
high and low thresholds for all 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 LTC2943 and LTC2944 require only a single low
value sense resistor to set the measured current range.
The LTC2943-1, however, has an integrated sense resistor
of 50mΩ which sets the maximum current measurement
to 1A. The default value assembled on the DC1812A-A and
DC1812A-B is 100mΩ for a maximum current measurement of 500mA. The DC1812A-C which showcases the
LTC2943-1 has the onboard sense resistor omitted in favor
of the integrated 50mΩ sense resistor. All three 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 low input at the
AL/CC pin. This sets the ACR register to FFFFh which
indicates 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.
The DC1812A is a part of the QuikEval™ system for quick
evaluation with a host controller through a PC using the
DC590 or DC2026.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1812A
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No
Latency ∆∑ and QuikEval are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
Figure 1. DC1812A
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DEMO MANUAL DC1812A
Quick Start Procedure
Demonstration circuit 1812A is easy to set up to evaluate
the performance of the LTC2943/LTC2943-1/LTC2944.
Refer to Figure 2 for proper measurement equipment
setup and follow the procedure below.
1.Connect a Li-Ion battery across V_BAT and GND. Multiple Li-Ion batteries can also be used as long as the
total voltage does not exceed the operating voltage of
the device. The LTC2943/LTC2943-1 has a maximum
operating voltage of 20V, so for a 4.2V lithium ion
battery the maximum cell count would be 4 cells. The
LTC2944 has a maximum operating voltage of 60V, so
for a 4.2V lithium-ion battery the maximum cell count
would be 14 cells.
2.Connect a load across V_CHRG/LD and GND for battery
discharge measurement.
3.Connect 3.6V to 20V (LTC2943/LTC2943-1) or
3.6V to 60V (LTC2944) battery charger supply
across V_CHRG/LD and GND for battery charge measurement. Up to 500mA supplied to the battery can
be measured with the board default 100mΩ sense
resistor present on the DC1812A-A and DC1812A-B.
The DC1812A-C can support currents of up to 1A with
its integrated 50mΩ 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.If a host I2C controller is used, then provide a bus pull-up
voltage to the +5V turret, else start QuikEval software
on PC.
6.Read and write to the LTC2943/LTC2943-1/LTC2944
through I2C.
7.Through I2C, configure the AL/CC pin. Set JP1 accordingly.
8 If AL/CC is set for charge complete, use pushbutton
switch S1 to simulate a logic low from a controller to
indicate a fully charged battery.
Figure 2. DC1812A Basic Setup
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DEMO MANUAL DC1812A
QuikEval Interface
Figure 3. DC1812A QuikEval Interface
The DC1812A 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 LTC2943/LTC2944 evaluation
software interface (Figure 3).
is first stored at the start of a scan and then any change
in charge is reported in the ACR text box. This data can
be displayed in one of two formats: coulombs and mAh.
Voltage and Current Display
Info Column
Data from the voltage ADC (registers I and J) and the
current ADC (registers O and P) is displayed here in volts
and amperes, respectively. If the current falls into the mA
range then the interface automatically updates the units
accordingly. The display indicates the current as seen
from the battery. Hence, if a negative value is displayed,
the battery is discharging. If a positive value is displayed,
the battery is charging.
Accumulated Charge Since Start (ACR Display)
Temperature Display
The “Accumulated Charge Since Start” text box displays
the change in accumulated charge since the start of a scan.
The initial data in the ACR registers (registers C and D)
Data from the temperature ADC (register U and V) is displayed here. It can be displayed in two formats: Celsius
and Kelvin.
Interface Design
The QuikEval interface consists of three tabs along with a
column that displays accumulated charge since the start of
the scan, voltage, current and temperature. A start button
allows convenient polling of the registers.
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3
DEMO MANUAL DC1812A
QuikEval Interface
Start Button
Click on start to begin a polling routine that is based on
the selected ADC mode. By default the ADC mode is set to
automatic mode which updates the interface every 60ms.
If the scan ADC mode is selected from the “Registers and
Control” tab, then the interface would update every 10s.
The ADC mode can be switched in real time during a scan
and the interface will respond accordingly.
The interface recognizes when it is scanning and replaces
the start button with a stop button during a polling routine.
Similarly, for a single update, select the manual mode and
click start. The LTC2943/LTC2943-1/LTC2944 will take a
snapshot of the charge, voltage, current and temperature
after which it will immediately go into sleep mode in which
only the charge accumulator is running. For convenience
the GUI will hold the values of the snapshot for 2 seconds
before updating the interface and displaying “ADC Off” in
the current, voltage and temperature text box.
Coulomb Counter Tab
This tab contains time based graphical plots of charge
and current. The charge plot displays the change in accumulated charge since the start of a scan with respect to
time in mAh or coulombs depending on user input. The
current plot displays the change in current with respect
to time in mA. If the current exceeds 1A, then the graph
auto scales to display the current in units of amperes. If
a scan is restarted, the plots start from the beginning. If
manual mode is selected, only the charge plot is active.
Figure 4. Coulomb Counter Tab
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DEMO MANUAL DC1812A
QuikEval Interface
Once the plotted line reaches 300, the x-axis scrolls to
accommodate by 30 second intervals.
Battery Gauge Tab
This tab contains controls to set up the battery gas gauge
and consists of two sections: User Input and Initialization.
User Input
For applications that have low current and a large battery, it
is possible to get a qLSB size smaller than QBAT/216, causing the 16-bit accumulated charge register to underflow
before the battery is exhausted or overflow during charge.
In such cases, RSENSE should be sized according to the
following relationship:
RSENSE ≤
0.340mAh • 216
• 50mΩ
QBAT
where QBAT is in mAh. Similarly, for applications with a small
battery but high maximum current the qLSB can get quite
large with respect to the battery capacity causing a loss
in digital resolution in the accumulated charge register. To
address this, the LTC2943/LTC2943-1/LTC2944 includes
a programmable prescalar. Lowering the prescalar factor
M reduces qLSB to better match the accumulated charge
Figure 5. Battery Gauge Tab
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DEMO MANUAL DC1812A
QuikEval Interface
register to the capacity of the battery. M can be chosen
between 1 and its default value of 4096. The charge LSB
then becomes:
qLSB = 0.34mAh •
50mΩ
M
•
RSENSE 4096
To avoid unnecessary calculation, the interface conveniently
suggests a prescalar value to use based on the entered
battery capacity and sense resistor value. This prescalar
can be overridden by the user with the help of the prescalar
dropdown box. In the case of an override, the prescalar
dropdown box will be colored red giving a visual cue that
the prescalar chosen is not the suggested one.
The interface also warns the user in case the current is
too small with respect to the battery capacity by giving
an error message similar to the one shown in Figure 6.
It is strongly advised to use a characterized battery whose
state of charge is already known and to initialize the ACR
value accordingly.
Battery Gas Gauge
The gas gauge shows the battery’s state of charge. The
upper battery limit is always 0xFFFF while the lower limit
is dependent on the battery capacity and qLSB size. This
lower limit is calculated based off of RSENSE and prescalar
M, and displayed in hexadecimal in the lower right corner
of the gas gauge. Battery charge percentage as well as the
ACR register value is shown alongside the gas gauge. The
amount of charge left is also represented in mAh under
the battery widget.
Figure 6. Low Current Warning
Initializing the Accumulated Charge Register
By default, the ACR register has the initial value of 0x7FFF.
The ACR register can be initialized to full, empty or set to
a user defined level based on battery capacity.
Figure 7. Battery Gas Gauge
The “From Voltage (Li-ion Only)” button gives an estimate
of the initial ACR value by sensing the voltage and ambient
temperature of the battery being used. It compares the
voltage and temperature values to the discharge curves of
a Panasonic CGR18650CG lithium ion battery to estimate
the battery’s state of charge. Due to the fact that the discharge curve for each lithium ion battery is different, the
state of charge calculated this way might not be accurate.
6
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DEMO MANUAL DC1812A
QuikEval Interface
Register and Control Tab
Sense Resistor
The register and control tab provides a detailed view of
the LTC2943/LTC2943-1/LTC2944 device registers as well
as provides convenient means to read and write to them.
By default, the DC1812A-A and DC1812A-B are populated
with a 100mΩ sense resistor to measure a maximum fullscale current of 500mA. If a different full-scale value current
is desired, the sense resistor can be easily replaced and the
corresponding resistor value can be set in the interface.
Every time a new resistor value is entered, the interface will
recalculate a suggested prescalar and qLSB automatically
and display it in the “LSB Information” section.
Address/I2C Status
The write address for the LTC2943/LTC2943-1/LTC2944
is C8h and the read address is C9h. If an error occurs
while reading from the LTC2943/LTC2943-1/LTC2944,
the I2C status will display an error and the corresponding
LED will turn red. Otherwise, the status is good and the
LED remains green.
Figure 8. Register and Control Tab
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DEMO MANUAL DC1812A
QuikEval Interface
LSB Information
LSB information for charge, voltage, current and temperature registers as well as for all threshold registers is
displayed here. The ACR LSB updates depending on the
sense resistor and prescalar value chosen.
Status Register (A)
The individual status bits A[0:7] and their states are shown
here. A red indicator next to bits A[6:0] indicates the respective alert is currently present and will latch the alert
pin if configured for alert. Bit A[7] is reserved.
The demo board alert pin indicator indicates the status of
the AL/CC pin. If the LTC2943/LTC2943-1/LTC2944 AL/
CC pin is set for alert mode and an alert has been latched,
the device will pull down this pin which will light up the
LED indicator on the board as well as on the GUI. Click on
ARA to send out an SMBus alert on to the bus lines and
the device will respond with its address. The LED indicator
on the demo board and GUI alert pin indicator will then
be cleared if the alert is no longer present.
Control Register (B)
Configurations done in the control register section
write to the control register (register B). The control
bits B[7:6] set the LTC2943/LTC2943-1/LTC2944 ADC
mode. The LTC2943/LTC2943-1/LTC2944 defaults
to automatic mode which enables full-time voltage,
current and temperature ADC conversions. Selecting
scan mode enables voltage, current and temperature
conversions cycles every 10s. After each conversion
cycle the ADC goes into sleep mode until it is time for the
next conversion cycle. Selecting manual mode initiates
the ADC for a snapshot of voltage, temperature, current
and charge once after which it returns to sleep mode. In
sleep mode, the LTC2943/LTC2943-1/LTC2944 continues
to accumulate charge while the ADC turns off.
Select a prescalar M value to scale the ACR according
to battery capacity and maximum current. M cannot be
changed during a scan.
The AL/CC pin can be configured for alert mode, charge
complete mode, or disabled. Select the corresponding
settings on the DC1812 jumper JP1.
The shutdown analog section is checked to disable the
analog portion of the LTC2943/LTC2943-1/LTC2944 and
set the device in a low current state. For normal operation
leave unchecked.
Register Read/Write
Data in the internal registers of the LTC2943/LTC2943-1/
LTC2944 is displayed here in hexadecimal format. 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. Then click on the corresponding register
button to write to that register. Data is auto corrected if
the maximum or minimum full-scale is exceeded.
Interfacing with the DC2062B
This board can also interface with the DC2026 Linduino
board which is part of the Linduino Firmware Development
Program. The Linduino Firmware Development Program
provides users with convenient driver code, written in C,
for a wide range of LTC products. Please see the Linduino
page for more details.
The DC2026 comes preloaded with a DC590 emulator
firmware which allows easy interface with QuikEval. With
the emulator firmware, QuikEval will launch the GUI as it
would with the DC590. The DC2026 can also be used as
a development platform, example software along with
drivers can be found on the relevant product landing page:
LTC2943: http://www.linear.com/LTC2943
LTC2943-1: http://www.linear.com/LTC2943-1
LTC2944: http://www.linear.com/LTC2944
8
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DEMO MANUAL DC1812A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
1
1
C2
CAP., CHIP X7R, 0.1µF 0603
AVX, 06033C104KAT2A
2
1
C3
CAP., X7R, 1.0uF, 100V, 10%, 1206
MURATA, GRM31CR72A105KA01
3
1
D1
WL-SMCW SMD CHIP LED WATERCLEAR
WURTH, 150120RS75000
4
1
D2
DIODE, BAT54C SOT23
DIODES INC., BAT54C-7-F
5
4
E1-E4
TURRET, TESTPOINT .094"
MILL-MAX, 2501-2-00-80-00-00-07-0
6
5
E5-E9
TURRET, TESTPOINT .064"
MILL-MAX, 2308-2-00-80-00-00-07-0
7
1
JP1
HEADER, 3 PIN 1 ROW.079CC
WURTH, 62000311121
8
1
XJP1
SHUNT, .079" CENTER
WURTH, 60800213421
9
1
J1
HEADERS, VERTICAL DUAL 2×7 .079CC
MOLEX, 87831-1420
10
3
R6, R7, R8
RES., CHIP, 4.99k, 1%, 0603
NIC, NRC06F4991TRF
11
4
R2, R3, R4, R9
RES., CHIP, 10k, 5%, 0603
NIC, NRC06J103TRF
12
1
R5
RES., CHIP, 1k, 5%, 0603
VISHAY, CRCW06031K00JNEA
13
1
S1
SWITCH, SMT PUSH BUTTON
PANASONIC, EVQPE105K
14
1
U2
I.C., SERIAL EEPROM TSSOP8
MICROCHIP, 24LC025-I/ST
DC1812A-A
1
1
DC1812A GENERAL BOM
2
1
RSENSE
RES., CHIP, 0.1Ω 1/8W 1% 1206
IRC, LRC-LR1206LF-01-R100-F
3
1
U1
I.C., BATTERY GAS GAUGE WITH I2C
LINEAR TECH., LTC2943CDD#PBF
RSENSE
RES., CHIP, 0.1Ω 1/8W 1% 1206
IRC, LRC-LR1206LF-01-R100-F
U1
I.C., BATTERY GAS GAUGE WITH I2C
LINEAR TECH., LTC2944CDD#PBF
DC1812A-B
1
1
2
1
3
1
DC1812A GENERAL BOM
DC1812A-C
1
1
3
1
DC1812A GENERAL BOM
U1
I.C., BATTERY GAS GAUGE WITH I2C
LINEAR TECH., LTC2943CDD-1#PBF
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9
A
B
C
D
1
2
3
E9
E5
E8
1
V+ 2
5V
6
CS 4
SCK/SCL 7
MOSI/SDA 5
MISO
10
EEVCC 9
EESDA 11
EESCL 12
EEGND 14
AUX
LTC2944
LTC2943-1
-B
-C
3.6V-20V
3.6V-60V
4
LTC2943
-A
3-1
3.6V-20V
3
U1
ASSY
SUFFIX
+5V
N/A
0.1
0.1
RSENSE
1. ALL RESISTORS AND CAPACITORS ARE 0603
5
CC
R3
10K
R4
10K
R9
10K
4
D2
1
C3
1uF
1206
CUSTOMER NOTICE
D1
AL
(RED)
R5
1K
3
BAT54C +5V
2
C2
0.1uF
3
5
4
7
1
4
3
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
U1
*
1206
RSENSE
0.1
VCC
WP
SCL
SDA
A0
A1
A2
VSS
SCALE = NONE
S. AFZAL
LT
APPROVALS
4
3
2
1
U2
24LC025-I /ST
SDA
SCL
GND
SENSE+
SEE OPTION TABLE
SENSE+
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES.
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
APP ENG.
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
S1
PANASONIC-EVQPE105K
V-BAT
J1
HD2X7-079-MOLEX
GND
+5V
AL / CC
R2
10K
NOTE: UNLESS OTHERWISE SPECIFIED
*
JP1
E7
E6
E3
E1
AL / CC
AL LED
CC PB
SDA
SCL
GND
V_CHRG/LD
GND
GND
GND
13
8
3
GND
2
EXPAD
9
*
ALCC
6
8
R6
4.99K
TECHNOLOGY
R7
4.99K
GND
*
DATE
8-10-15
DATE:
2
Monday, August 10, 2015
1
SHEET 1
OF 1
MULTICELL BATTERY GAS GAUGE WITH
TEMPERATURE, VOLTAGE AND CURRENT MEASUREMENT
IC NO.
REV.
SIZE
LTC294XCDD
N/A
3
DEMO CIRCUIT 1812A
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
VSS
WP
R8
4.99K
E4
V_BAT
S. AFZAL
PRODUCTION
E2
APPROVED
DESCRIPTION
1
3
REVISION HISTORY
REV
2
TITLE: SCHEMATIC
5
6
7
8
SENSE-
__
ECO
SENSE-
GND
10
3
5
A
B
C
D
DEMO MANUAL DC1812A
Schematic Diagram
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DEMO MANUAL DC1812A
Schematic Diagram
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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.
11
DEMO MANUAL DC1812A
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
12 Linear Technology Corporation
dc1812afa
LT 1215 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 2013
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