Lithium Ion Battery Monitoring System AD7280A FEATURES FUNCTIONAL BLOCK DIAGRAM 12-bit ADC, 1 s per channel conversion time 6 analog input channels, common-mode V DD range 0.5 V to 27.5 V 6 auxiliary ADC inputs DAISY-CHAIN CELL VIN6 1.6 mV cell voltage accuracy INTERFACE BALANCING VIN5 INTERFACE On-chip voltage regulator VIN4 HV VIN3 MUX Cell balancing interface REGULATOR V AD7280A REG VIN2 Daisy-chain interface DGND VIN1 o VIN0 Internal reference: 3 ppm/ C DV CC 12-BIT ADC AUX6 1.8 A power-down current AV CC AUX5 High input impedance V DRIVE AUX4 LV MUX AUX3 Serial interface with alert function CONTROL LOGIC CLOCK AUX2 AND SELF-TEST 1 SPI interface for up to 48 channels AUX1 CRC protection on read and write commands SCLK AUX SDI TERM On-chip registers for channel sequencing SDO LIMIT REG V REF 2.5V V operating range: 8 V to 30 V DD SQN LOGIC ALERT REF C DATA MEMORY CS REF Temperature range: 40C to +105C SPI INTERFACE PD REFGND 48-lead LQFP CNVST MASTER Qualified for automotive applications APPLICATIONS V AGND SDOlo ALERTlo SS Lithium ion battery monitoring Figure 1. Electric and hybrid electric vehicles Power supply backup Power tools GENERAL DESCRIPTION 1 The AD7280A includes on-chip registers that allow a sequence The AD7280A contains all the functions required for general- of channel measurements to be programmed to suit the application purpose monitoring of stacked lithium ion batteries as used in requirements. hybrid electric vehicles, battery backup applications, and power tools. The part has multiplexed cell voltage and auxiliary ADC The AD7280A also includes a dynamic alert function that can measurement channels for up to six cells of battery management. detect whether the cell voltages or auxiliary ADC inputs exceed An internal 3 ppm/C reference is provided that allows a cell an upper or lower limit defined by the user. The AD7280A has voltage accuracy of 1.6 mV. The ADC resolution is 12 bits and cell balancing interface outputs designed to control external FET allows conversion of up to 48 cells within 7 s. transistors to allow discharging of individual cells. The AD7280A operates from a single VDD supply that has a The AD7280A includes a built-in self-test feature that internally range of 8 V to 30 V (with an absolute maximum rating of applies a known voltage to the ADC inputs. 33 V). The part provides six differential analog input channels A daisy-chain interface allows up to eight parts to be stacked to accommodate large common-mode signals across the full without the need for individual device isolation. V range. Each channel allows an input signal range, VIN(+) DD VIN(), of 1 V to 5 V. The input pins assume a series stack of The AD7280A requires only one supply pin that accepts 6.9 mA six cells. In addition, the part includes six auxiliary ADC input under normal operation while converting at 1 MSPS. channels that can be used for temperature measurement or All this functionality is provided in a 48-lead LQFP package system diagnostics. operating over a temperature range of 40C to +105C. 1 Patents pending. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. SCLKhi SDIhi SDOhi ALERThi CShi PDhi CNVSThi CB1 CB2 CB3 CB4 CB5 CB6 09435-001AD7280A TABLE OF CONTENTS Features .............................................................................................. 1 Register Map ................................................................................... 28 Applications ....................................................................................... 1 Cell Voltage Registers ................................................................ 28 Functional Block Diagram .............................................................. 1 Auxiliary ADC Registers ........................................................... 28 General Description ......................................................................... 1 Self-Test Register ........................................................................ 28 Revision History ............................................................................... 2 Control Register ......................................................................... 28 Specif icat ions ..................................................................................... 3 Cell Overvoltage Register .......................................................... 29 Power Specifications .................................................................... 5 Cell Undervoltage Register ....................................................... 30 Timing Specifications .................................................................. 6 AUX ADC Overvoltage Register .............................................. 30 Absolute Maximum Ratings ............................................................ 7 AUX ADC Undervoltage Register ........................................... 30 Thermal Resistance ...................................................................... 7 Alert Register .............................................................................. 30 ESD Caution .................................................................................. 7 Cell Balance Register ................................................................. 30 Pin Configuration and Function Descriptions ............................. 8 CBx Timer Registers .................................................................. 30 Typical Performance Characteristics ........................................... 11 PD Timer Register ...................................................................... 31 Terminology .................................................................................... 14 Read Register .............................................................................. 31 Theory of Operation ...................................................................... 15 CNVST Control Register ........................................................... 31 Circuit Information .................................................................... 15 Serial Interface ................................................................................ 32 Converter Operation .................................................................. 15 Writing to the AD7280A ........................................................... 32 Analog Input Structure .............................................................. 16 Reading from the AD7280A ..................................................... 33 Transfer Function ....................................................................... 16 Daisy-Chain Interface .................................................................... 34 Typical Connection Diagrams .................................................. 17 Addressing the AD7280A While Reading Back Conversion or Register Data .......................................................................... 34 Reference ..................................................................................... 19 Initializing the AD7280A .......................................................... 34 Converting Cell Voltages and Auxiliary ADC Inputs ........... 19 Write Acknowledge .................................................................... 35 Converting Cell Voltages and Auxiliary ADC Inputs in a Chain of AD7280As ............................................................ 21 Cyclic Redundancy Check ........................................................ 35 Conversion Window .................................................................. 22 Examples of Interfacing with the AD7280A ............................... 38 Self-Test Conversion .................................................................. 22 Convert and Readback Routine ............................................... 38 Connection of Fewer Than Six Voltage Cells ............................. 22 Examples ...................................................................................... 38 Auxiliary ADC Inputs ................................................................ 23 EMC Guidelines ............................................................................. 44 Power Requirements .................................................................. 23 Schematic and Layout Guidelines ............................................ 44 Power-Down ............................................................................... 24 Operation in a Noisy Environment ......................................... 44 Power-Up Time ........................................................................... 25 Software Flowchart .................................................................... 45 Cell Balancing Outputs .............................................................. 25 Outline Dimensions ....................................................................... 46 Alert Output ................................................................................ 27 Ordering Guide .......................................................................... 46 Automotive Products ................................................................. 46 REVISION HISTORY 4/11Revision 0: Initial Version Rev. 0 Page 2 of 48