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 dc1496fa 1 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 dc1496fa 2 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 dc1496fa 3 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 dc1496fa 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 dc1496fa 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 dc1496fa 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 dc1496fa 7 DEMO MANUAL DC1496B PCB LAYOUT AND FILM Silkscreen Top Component Side Inner Layer 2 dc1496fa 8 DEMO MANUAL DC1496B PCB LAYOUT AND FILM Inner Layer 3 Solder Side SilkScreen Bottom dc1496fa 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