![]() The ACK/NACK signal must be valid after a configuration time (tVD ACK) that varies between 3,45µs in Standard mode (100 kHz) and 0,45µs in Fast Plus mode (1 MHz). One aspect is the ACK/NACK response from the destination device to the controller. They must also be able to meet the timing requirements set for I2C. In addition, the chosen devices must have open collector outputs to allow adequate control of the bus. One of them is the bidirectional nature of the SDA and SCL lines, while optocouplers are usually unidirectional. While easy to use, they can be expensive and leave the user with no workarounds or second provider to protect against potential supply problems.Īn isolated connection can be obtained using conventional optocouplers, although this can create some complications. Commercially available digital isolation ICs allow all isolation circuitry to be implemented in a single device. These situations require a suitable means of isolating I2C connections. I2C is also used to communicate circuits that cannot share a ground reference, such as industrial automation and drives, motor controls, solar panel microinverters, and medical systems that require protective isolation between I2C control signals and the network. In addition, critical device values, such as the maximum negative I/O voltage, may be exceeded. In these cases it is quite common that there are differences in the local ground potential between the connected devices that can affect the noise margins of the system. I2C has grown in popularity and its use has spread to situations that require longer communication distances. This signal is typically unidirectional, although a target device may take longer to respond to a request, if necessary, by keeping SCL and SDA low while generating an ACK. The SCL line controls the speed of data communication on the bus. The destination devices also use the SDA line to confirm the correct receipt of the request (ACK) by holding SDA low or by denying correct reception (NACK) by letting SDA go high. The controller uses the SDA line to select the destination device and register access to that device, which sends the requested data over the SDA line itself. ![]() The controller has open collector I/O that can pull the data (SDA) and clock (SCL) lines low and require a pull-up resistor that allows multiple controllers and target devices to coexist without causing conflicts on the bus. The I2C bus typically has a controller, such as a microcontroller or SoC, and one or more destination devices. The simplicity and efficiency of I2C have led to its communication principles being included in standards such as SMBbus and PMBus. The standard establishes a two-wire connection for bidirectional data and clock lines that can be implemented inexpensively. Originally intended for short distance communication within the board, its success has multiplied the number of applications and the maximum data handling capacity has been expanded to include Standard (100 kHz), Fast (400 kHz), Fast Plus (1 MHz), High-Speed (3,4 MHz) and Ultra-Fast Plus (5 MHz). ![]() ![]() The I2C (Inter-Integrated Circuit) bus was introduced in the 1980s to allow communication between a central CPU and peripheral devices for configuration, monitoring, and control. A solution with discrete optical isolators is easily implemented and can offer flexibility and cost savings, for example, in industrial applications. Torsten Siems, Field Applications Engineer, Toshiba Electronics Europe GmbHĪpplications based on the I2C bus sometimes require high voltage isolation to ensure protection and reliability.
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