Application Note Rev. 1.00 / July 2014 ZSC31010/ZSC31014 Interfacing with a Gas Sensor Multi-Market Sensing Platforms Precise and Deliberate ZSC31010/ZSC31014 Application Note – Interfacing with a Gas Sensor Contents 1 2 3 4 5 6 Introduction ....................................................................................................................................................... 3 Digital Interface using the ZSC31014 .............................................................................................................. 3 Analog Interface ............................................................................................................................................... 4 Related Documents .......................................................................................................................................... 5 Glossary ........................................................................................................................................................... 5 Document Revision History .............................................................................................................................. 5 List of Figures Figure 2.1 Figure 3.1 Gas Sensor Connected to ZSC31014 with Digital Interface .............................................................. 3 Gas Sensor Connected to the ZSC31010 with Analog Out ............................................................... 4 For more information, contact ZMDI via [email protected]. Data Sheet July 9, 2014 © 2014 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 2 of 5 ZSC31010/ZSC31014 Application Note – Interfacing with a Gas Sensor 1 Introduction This application note discusses methods for using ZMDI’s ZSC31010 or ZSC31014 Sensor Signal Conditioner ICs (SSCs) to interface with typical gas sensors for the purpose of compensating the sensor signal and outputting the measurement results. Refer to the data sheets for each product for operation details and specifications for the SSCs. The ZSC31014 is a sensor signal conditioner for highly accurate amplification and analog-to-digital conversion of differential full-bridge and half-bridge input signals. Its operating range is -40C to 125C. Measured and corrected 2 * bridge values are provided at the ZSC31014’s digital output pins, which can be configured as I C™ or SPI. Section 2 describes an application using the ZSC31014 to compensate the sensor signal from a typical gas sensor via a digital interface. The ZSC31010 is a sensor signal conditioner for highly accurate amplification and analog-to-digital conversion of differential input signals from a full bridge. It features a wider operating range: -50C to 150C. Its output options include rail-to-rail analog output voltage, absolute analog voltage, and digital ZACwire™* one-wire interface (OWI). Section 3 describes an application using the ZSC31010 to compensate the sensor signal from a typical gas sensor via an analog interface. 2 Digital Interface using the ZSC31014 In this application example, the ZSC31014 is used to interface to an SGX SensorTECH®* gas sensor. The gas sensor consists of a heater and a gas sensor element. The heater current is set through an external 82Ω resistor, which roughly matches the resistance of the heater resistor. The gas sensor requires a load resistor to ground (RL). RL is selected to set the output range of the sensor element. The sensor element changes resistance when exposed to gas and, in combination with RL, forms a half bridge. Figure 2.1 Gas Sensor Connected to ZSC31014 with Digital Interface Vsupply +2.7 to +5.5 V ~82 Ω MICS-5121 3 4 2 1 1 VSS VDD 2 Bsink INT/SS 7 3 VBP SDA/MISO 6 4 VBN SCL/SCLK 5 ZSC31014 8 I2C™ or SPI 0.1 F RL Ground * 2 I C™ is a trademark of NXP. SensorTECH® is a trademark of SGX Sensortech, Ltd. ZACwire™, RBiciLite™, RBicLite™ and Sig™ are trademarks of ZMDI. Data Sheet July 9, 2014 © 2014 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 3 of 5 ZSC31010/ZSC31014 Application Note – Interfacing with a Gas Sensor The ZSC31014 has a differential signal path to support full-bridge measurements into the VBP and VBN pins. There is an option that sets VBN to an internal VDD/2 reference and thus supports a half-bridge measurement through VBP. Figure 2.1 shows how the gas sensor interfaces to the VBP pin. The ZSC31014 has an analog front-end that allows gain adjustment from 1.5 up to 192. A 14-bit ADC converts the signal to the digital domain, and an integrated math engine performs linearization, calibration, and offset correction operations. An onboard temperature sensor can be used to temperature compensate the sensor signal. 2 The digital serial output format is I C™ or SPI. 3 Analog Interface An alternative is to use the ZSC31010 to provide an analog output. This device does not have the option to supply an internal VDD/2 reference; however, the gas sensor already has a ½ supply divider in the heater section. Any variation in the divider voltage over temperature can be compensated via calibration using the on-chip temperature sensor available on the ZSC31010. Figure 3.1shows the circuit configuration. Figure 3.1 Gas Sensor Connected to the ZSC31010 with Analog Output Vsupply +2.7 to +5.5 V ~82 Ω MICS-5121 3 4 2 1 Bsink 2 VBP VSS 8 SIGTM 7 3 N/C VDD 6 4 VBN Vgate 5 1 ZSC31010 Analog Out 0.1 F RL Ground If the gas sensor does not have ½ supply divider available, then a two-resistor divider is required. Typical resistor values would be 10KΩ. The ZSC31010 has an analog front-end that allows gain adjustment from 6 up to 48. A 14-bit ADC converts the signal to the digital domain. An on-board temperature sensor can be used to temperature compensate the sensor signal. The on-chip DSP applies temperature compensation and then the signal is converted back to analog through a DAC converter. A buffer amplifier drives the Sig™* pin. The Sig™ pin also supports a one-wire interface that allows for digital bidirectional communications with the part during calibration. Data Sheet July 9, 2014 © 2014 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 4 of 5 ZSC31010/ZSC31014 Application Note – Interfacing with a Gas Sensor 4 Related Documents Note: X_xy refers to the current revision of the document. Document File Name ZSC31010 RBicLite™ Data Sheet ZSC31010_RBic_Lite_Data_Sheet_Rev_X_xy.pdf ZSC31014 RBiciLite™ Data Sheet ZSC31014_RBic_iLite_Data_Sheet_Rev_X_xy.pdf Visit the following ZSC31010 and ZSC31014 product pages on ZMDI’s website www.zmdi.com or contact your nearest sales office for the latest version of these documents. www.zmdi.com/zsc31010 www.zmdi.com/zsc31014 5 Glossary Term Description ADC Analog-to-Digital Converter DAC Digital-to-Analog Converter DSP Digital Signal Processor 6 Document Revision History Revision 1.00 Date Description July 9, 2014 First release. Sales and Further Information www.zmdi.com [email protected] Zentrum Mikroelektronik Dresden AG Global Headquarters Grenzstrasse 28 01109 Dresden, Germany ZMD America, Inc. 1525 McCarthy Blvd., #212 Milpitas, CA 95035-7453 USA Central Office: Phone +49.351.8822.306 Fax +49.351.8822.337 USA Phone 1.855.275.9634 Phone +1.408.883.6310 Fax +1.408.883.6358 European Technical Support Phone +49.351.8822.7.772 Fax +49.351.8822.87.772 DISCLAIMER: This information applies to a product under development. Its characteristics and specifications are subject to change without notice. Zentrum Mikroelektronik Dresden AG (ZMD AG) assumes no obligation regarding future manufacture unless otherwise agreed to in writing. The information furnished hereby is believed to be true and accurate. However, under no circumstances shall ZMD AG be liable to any customer, licensee, or any other third party for any special, indirect, incidental, or consequential damages of any kind or nature whatsoever arising out of or in any way related to the furnishing, performance, or use of this technical data. ZMD AG hereby expressly disclaims any liability of ZMD AG to any customer, licensee or any other third party, and any such customer, licensee and any other third party hereby waives any liability of ZMD AG for any damages in connection with or arising out of the furnishing, performance or use of this technical data, whether based on contract, warranty, tort (including negligence), strict liability, or otherwise. European Sales (Stuttgart) Phone +49.711.674517.55 Fax +49.711.674517.87955 Data Sheet July 9, 2014 Zentrum Mikroelektronik Dresden AG, Japan Office 2nd Floor, Shinbashi Tokyu Bldg. 4-21-3, Shinbashi, Minato-ku Tokyo, 105-0004 Japan ZMD FAR EAST, Ltd. 3F, No. 51, Sec. 2, Keelung Road 11052 Taipei Taiwan Phone +81.3.6895.7410 Fax +81.3.6895.7301 Phone +886.2.2377.8189 Fax +886.2.2377.8199 Zentrum Mikroelektronik Dresden AG, Korea Office U-space 1 Building 11th Floor, Unit JA-1102 670 Sampyeong-dong Bundang-gu, Seongnam-si Gyeonggi-do, 463-400 Korea Phone +82.31.950.7679 Fax +82.504.841.3026 © 2014 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 5 of 5