APPLICATION NOTE Calculation of ADC Output for Measurement of Cell Temperature with the ATA6870 ATA6870 ADC Concept of ATA6870 To measure cell voltage and cell temperature, the ATA6870 uses a 12-bit incremental analog-to-digital conversion (ADC) concept. The circuit diagram for this ADC is shown in Figure 1. Figure 1. Incremental ADC, as Realized in the ATA6870 R3 R2 VREF qn R1 VIN R1 + + d - y Counter 12-bit q qn CLK CLK R2 VREF q R3 VREF The general formula for the ADC output is: Q = 212 0.5 (1 + VIN / VREF R2/R1 – R2/R3) With the realized resistor values: R1 = 1500k R2 = 800k R3 = 1000k The formula for the output results in: Q = 212 0.5 (1 + VIN / VREF 8/15 – 8/10) 9179B-AUTO-07/15 VIN and VREF of the ADC for Measurement of Temperature The temperature sensors are based on a resistor divider, using a standard resistor and an NTC resistor. The resistor divider is connected to the temperature reference input of the ADC (see Figure 2). Figure 2. Temperature Sensor Based on Voltage Divider TEMPREF RES_REF ATA6870 VREF TEMP RES_NTC VIN TEMPVSS With the ratio VIN / VREF = RES_NTC / (RES_NTC + RES_REF) and the formula Q = 212 0.5 (1 + Vin / VRef 8/15 – 8/10) the output of the ADC for measuring temperature is equal to: Q = 2048 [1 + (RES_NTC / (RES_NTC + RES_REF) 8/15) – 8/10] 2 ATA6870 [APPLICATION NOTE] 9179B–AUTO–07/15 1. 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 9179B-AUTO-07/15 Put document in the latest template ATA6870 [APPLICATION NOTE] 9179B–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.: 9179B–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.