APPLICATION NOTE Measurement of Four Cell Voltages and Temperatures ATA6870 Scope This application note describes how to measure the cell voltage and the temperature in four different cells. Temperature Measurement Description As described in the datasheet, the ATA6870 has two temperature channels. To measure more than two temperatures, it is possible to attach additional temperature sensors at the cell voltage measurement inputs. Figure 1 on page 2 shows the measurement configuration for 4 cell voltages and 4 temperatures. 9170B-AUTO-07/15 Figure 1. Schematic 4 Temperature Sensors and 4 Cell Voltages MBAT7 VDDHV 1kΩ Cell 4 MBAT6 1kΩ ATA6870 Cell 3 VDD MBAT5 1kΩ SPI Cell 2 MBAT4 1kΩ Cell 1 MBAT3 MBAT2 NTC T3 ADC TEMPREF Microcontroller TEMP1 NTC T4 MBAT1 TEMP2 1kΩ GND TEMPVSS NTC T1 NTC T2 GND The temperature voltages for T3 and T4 can be defined according to the formulas below: (1) V(T3) = V(MBAT3-MBAT2) + V(MBAT2-MBAT1). (2) V(T4) = V(MBAT2-MBAT1) To avoid that the TEMPREF output voltage variation causes any issues, the internal ATA6870 temperature measurement ADC is always related to TEMPREF. This, however, does not apply to T3, T4 measurements. In these cases, it is recommended to measure the TEMPREF voltage with the microcontroller’s ADC to eliminate the TEMPREF variation. The cell voltage of cell 1 needs to be calculated as the sum of the voltages of MBAT2, MBAT3 and MBAT4: (3) 2 V(cell1) = V(MAT4-MBAT3) + V(MBAT3-MBAT2) + V(MBAT2-MBAT1) ATA6870 [APPLICATION NOTE] 9170B–AUTO–07/15 1. 2. Restrictions ● Each measurement input pin MBAT(x) is protected with a Zener diode. Hence, the voltage at pin MBAT(x) cannot be higher than the voltage at MBAT(x+1) plus a forward diode. ● ● These voltage inputs cannot be used for simultaneous temperature and cell voltage measurement. For the dimensioning of the temperature measurement resistors, the maximum output current of TEMPREF is 2mA. Revision History Please note that the following page numbers referred to in this section refer to the specific revision mentioned, not to this document. Revision No. History 9170B-AUTO-07/15 Put document in the latest template ATA6870 [APPLICATION NOTE] 9170B–AUTO–07/15 3 XXXXXX Atmel Corporation 1600 Technology Drive, San Jose, CA 95110 USA T: (+1)(408) 441.0311 F: (+1)(408) 436.4200 | www.atmel.com © 2015 Atmel Corporation. / Rev.: 9170B–AUTO–07/15 Atmel®, Atmel logo and combinations thereof, Enabling Unlimited Possibilities®, and others are registered trademarks or trademarks of Atmel Corporation in U.S. and other countries. Other terms and product names may be trademarks of others. DISCLAIMER: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN THE ATMEL TERMS AND CONDITIONS OF SALES LOCATED ON THE ATMEL WEBSITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS AND PROFITS, BUSINESS INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. Atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and products descriptions at any time without notice. Atmel does not make any commitment to update the information contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life. SAFETY-CRITICAL, MILITARY, AND AUTOMOTIVE APPLICATIONS DISCLAIMER: Atmel products are not designed for and will not be used in connection with any applications where the failure of such products would reasonably be expected to result in significant personal injury or death (“Safety-Critical Applications”) without an Atmel officer's specific written consent. Safety-Critical Applications include, without limitation, life support devices and systems, equipment or systems for the operation of nuclear facilities and weapons systems. Atmel products are not designed nor intended for use in military or aerospace applications or environments unless specifically designated by Atmel as military-grade. Atmel products are not designed nor intended for use in automotive applications unless specifically designated by Atmel as automotive-grade.