SGAS707 IDT | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 15
Technical content
Datasheet sections
- 6.1 Constant Voltage Drive
- 6.2 Constant-Current Drive
- 6.3 Pulse-Width Modulation
- 6.4 Operating the Sensor at Temperature Extremes
- 7.1 Sensitivity
- 7.2 Cross-Sensitivity
Features
High sensitivity to a wide range of VOCs Non-specific: responds to many different organic vapors Typical response time < 1 minute to 90% full scale Environmental temperature range: 0°C to 40°C Environmental humidity range: 0% to 90% RH, noncondensing Typical Applications Indoor Air Quality Ventilation Control Air Purification Gas Concentration Detection Examples of Target Gases Formaldehyde Toluene Xylenes Acetone Isobutylene Octane Alcohols Available Support Evaluation Kit – SMOD707 Smart Sensing Module Application Notes Instruction Videos Reference Design
Figure 2. TO-39 (TO4) Pin Assignments for SGAS707 – Top View Table 1. TO-39 (TO4) Pin Descriptions Note: See Figure 2 for the connections described below.
1 Heater + Positive input for the VH heater voltage supply
2 Sensor + High-side of the resistive sensor element; positive input for sensing voltage VC
3 Heater – Negative (ground) input for the VH heater voltage supply
Note: All measurements were made in dry gas at room temperature. Specifications are subject to change. Table 2. Electrical Characteristics
Table 3. Temperature Specifications durations will not will not harm the sensor. orders of magnitude across the sensing range. This shows that log resistance versus log concentration is linear. circuitry exacerbate these challenges and must be understood in order to account for or eliminate these effects.
- Heater Driver Circuits and Control
SGAS707 VOC sensor uses a purely resistive element that is nominally 30Ω at all temperatures.
6.1 Constant Voltage Drive
temperature of the heater (and consequently gas sensitivity), voltage regulation is required. An easily implemented control circuit utilizes a three-terminal voltage regulator, with the LM317 serving as an example as shown in Figure 5. Figure 5. Three-Terminal Voltage Regulator three-terminal voltage regulators are available from component manufacturers. Circuits of this type are relatively efficient, particularly if a switching regulator is used.
6.2 Constant-Current Drive
applications. Additionally, the circuit is “microcontroller friendly” because heater current is directly controllable with by an input voltage signal. R3, and the current through both R3 and RHEATER is thus controlled independently of the load resistance according to the equation in Figure 6. well as the heater. Limiting the supply voltage to several hundred mV above the highest required drive voltage will help increase circuit efficiency. the heater with a variable amplitude. Determination of the heater power or resistance is possible by reading the voltage level at the heater.
Figure 6. Voltage-Controlled Constant-Current Circuit
6.3 Pulse-Width Modulation
sufficient testing at IDT to allow IDT to recommend it for any sensors in the SGAS family. Voltage to the heater should not exceed the maximum voltage allowed for a given heater family. A low-pass filter should be considered as part of the sensor signal circuit path to reduce noise from the heater PWM.
6.4 Operating the Sensor at Temperature Extremes
of the sensing surface with VOC’s. This alters the electrical conduction of the sensor element (the basis of metal-oxide sensor operation). temperature is shown in Figure 7. Figure 7. Recommended Applied Heater Voltage as a Function of Environmental Temperature
The following graphs show the typical responses that are to be expected from the SGAS707 sensors on exposure to a variety of test conditions. For sensor specifications, refer to Table 2.
7.1 Sensitivity
The typical sensitivity of the SGAS707 sensor to a range of organic chemicals is shown in Figure 8. Figure 8. Typical Sensor Response to a Variety of Organic Chemicals
Figure 9. Typical Sensor Sensitivity to a Variety of Organic Chemicals
The typical response of the sensor to changes in humidity is shown in Figure 10. Figure 10. Effect of Different Humidity Levels on the Sensor Signal at Ambient Temperature
7.2 Cross-Sensitivity
The response of the SGAS707 sensors to a range of other common gases is shown in Figure 11. Figure 11. Response of the SGAS707 Sensor to Other Industrial Gases
Table 4. Maximum ESD Ratings
- Mechanical Stress Testing
The qualification of the SGAS707 is based on the JEDEC standard (JESD47). given in this document. For information on constant acceleration test conditions and limits, contact IDT (see contact information on last page). Table 5. Mechanical Stress Test Conditions
- Package Drawing and Dimensions
Figure 12. TO-39 Package (TO4) Outline Drawing PSC-4676
© 2017 Integrated Device Technology, Inc. 15 October 25, 2017 Applications and Use Conditions The SGAS707 sensor is designed for measurement of ppm levels of volatile organic chemicals. The sensor is not intended, recommended, or approved for use in safety or life -protecting applications or in pote ntially explosive environments. IDT disclaims all liability for such use. For sensor storage, IDT strongly recommends a dust-free and VOC-free atmosphere; e.g., in synthetic air. 11. Ordering Information Orderable Part Number Description and Package MSL Rating Shipping Packaging Temperature SGAS707 4-pin TO-39 (TO4) 1 Tray 0°C to +40°C SMOD707KITV1 SMOD707 Evaluation Kit, including the SMOD707 Smart Sensing Module (includes the SGAS707 sensor), and mini-USB cable. The SMOD7xx Application Software is available for download at www.idt.com/SMOD707. 12. Revision History Revision Date Description of Change October 25, 2017 Full revision. November 9, 2016 Changed to IDT branding. Corporate Headquarters
6024 Silver Creek Valley Road
San Jose, CA 95138 www.IDT.com Sales 1-800-345-7015 or 408-284-8200 Fax: 408-284-2775 www.IDT.com/go/sales Tech Support www.IDT.com/go/support DISCLAIMER Integrated Device Technology, Inc. (IDT) and its affiliated companies (herein referred to as “IDT”) reserve the ri ght to modify the products and/or specifications described herein at any time, without notice, at IDT's sole discretion. Performance specifications and operating parameters of the described products are d etermined in an independent state and are not guaranteed to perform the same way when installed in customer pro ducts. The information contained herein is provided without representation or warranty of any kind, whether express or implie d, including, but not limited to, the suitability of IDT's products for any particular purpose, an implied warranty of merchantabil ity, or non-infringement of the intellectual property rights of others. This document is presented only as a guide and does not convey any license under intellectual property rights of IDT or any third parties. IDT's products are not intended for use in applications involving extreme environmental conditions or in life support systems or similar devices where the failure or ma lfunction of an IDT product can be reasonably expected to significantly affect the health or safety of users. Anyone using an IDT p roduct in such a manner does so at their own risk, absent an express, written agreement by IDT. Integrated Device Technology, IDT and the IDT logo are trademarks or registered trademarks of IDT and its subsidiaries in the United States and other countries . Other trademarks used herein are the property of IDT or their respective third party owners. For datasheet type definitions and a glossary of common terms, visit www.idt.com/go/glossary . All contents of this document are copyright of Integrated Device Technology, Inc. All rights reserved.