SLLS984I June 2009 – July 2015 ISO7420 , ISO7420M , ISO7421
UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.
- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
-
6 Specifications
- 6.1 Absolute Maximum Ratings
- 6.2 ESD Ratings
- 6.3 Recommended Operating Conditions
- 6.4 Thermal Information
- 6.5 Electrical Characteristics: VCC1 and VCC2 at 5 V ±5%
- 6.6 Electrical Characteristics: VCC1 at 5 V ±5%, VCC2 at 3.3 V ±5%
- 6.7 Electrical Characteristics: VCC1 at 3.3 V ±5%, VCC2 at 5 V ±5%
- 6.8 Electrical Characteristics: VCC1 and VCC2 at 3.3 V ±5%
- 6.9 Power Dissipation Characteristics
- 6.10 Switching Characteristics: VCC1 and VCC2 at 5 V ±5%
- 6.11 Switching Characteristics: VCC1 at 5 V ±5%, VCC2 at 3.3 V ±5%
- 6.12 Switching Characteristics: VCC1 at 3.3 V ±5%, VCC2 at 5 V ±5%
- 6.13 Switching Characteristics: VCC1 and VCC2 at 3.3 V ±5%
- 6.14 Typical Characteristics
- 7 Parameter Measurement Information
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
9.1 Application Information
ISO742x utilize single-ended TTL-logic switching technology. Its supply voltage range is from 3.15 V to 5.25 V for both supplies, VCC1 and VCC2. When designing with digital isolators, it is important to keep in mind that due to the single-ended design structure, digital isolators do not conform to any specific interface standard and are only intended for isolating single-ended CMOS or TTL digital signal lines. The isolator is typically placed between the data controller (i.e. μC or UART), and a data converter or a line transceiver, regardless of the interface type or standard.
9.2 Typical Application
ISO7421 can be used with Texas Instruments' mixed signal micro-controller, digital-to-analog converter, transformer driver, and voltage regulator to create an isolated 4-20 mA current loop.
Figure 12. Isolated 4-20 mA Current Loop
9.2.1 Design Requirements
Unlike optocouplers, which require external components to improve performance, provide bias, or limit current, the ISO742x only require two external bypass capacitors to operate.
9.2.2 Detailed Design Procedure
Figure 13. Typical ISO7420 and ISO7421 Circuit Hookup
9.2.3 Application Curve
Figure 14. Life Expectancy vs Working Voltage