SLVAFO2 august 2023 ESD1LIN24-Q1 , ESD751-Q1 , TSM24CA-Q1
Local Interconnect Network (LIN) is a communication protocol commonly used in automotive applications. As with other exposed connectors, the LIN interface can experience electrostatic discharge (ESD). Designing a LIN interface with a protection diode protects the LIN transceiver itself and the respective downstream bus components. To increase system-level robustness from ESD strikes, the characteristics of the LIN interface must be considered for correct ESD diode selection.
LIN is a single wire communications interface that is low-cost and space-efficient. Developed where speed is not critical, LIN data lines operate at a maximum of 20 Kbit/s. A LIN cluster is composed of a leader node and up to 15 follower nodes attached along the single LIN line, which is standardized by ISO 17897. The LIN bus is biased to the battery of the car, which is typically 12 V. Figure 1 shows a LIN transceiver node that is supplied by the car battery and connected to the single LIN line.
ESD can be prevalent in any environment where exposed connectors are present, particularly the LIN bus. When the LIN bus is in contact with the outside world, the bus is at risk of a high voltage strike. This high voltage strike or transient can cause damage to the LIN transceiver and subsequent components downstream.
When a product moves through an assembly line in a factory, the cabling can build up excess charge. Once the cabling is connected to the LIN bus, the excess charge flows into the downstream circuitry which can cause permanent damage.
Maintenance on a car where cabling is disconnected and reconnected can also allow ESD to occur. Additionally, ESD strikes can take place due to the proximity of multiple electronic control units (ECUs) nearby. Overall, the LIN bus can encounter ESD in a variety of situations and must be considered.
To protect the LIN system, use the list of key parameters.
IEC 61000-4-2 Rating:
Table 1 lists devices that support these specifications.
TI offers several ESD diodes with robust specifications for a myriad of LIN use cases. Figure 3 shows the block diagram of TLIN1029A-Q1 paired with ESD1LIN24-Q1, demonstrating how the system provides system-level ESD immunity in an automotive environment.
In Figure 3, the diode is connected directly to the LIN data line of the LIN transceiver. To properly protect the circuit, place the diode as close to the ESD source or connector side as design rules allow. The clamping voltage of the ESD1LIN24-Q1 (valued at 37 V) is within the absolute maximum value of the TLIN1029A-Q1 (45 V). The IEC 61000-4-2 30-kV rating of the diode provides the maximum level of protection against unprecedented ESD strikes across the LIN bus.
For more information on ESD protection layouts, see the ESD Packaging and Layout Guide.
The LIN interface requires robust ESD protection to survive real-world ESD strikes. The selection of the correct diode is critical for proper system coverage in the event of high voltage transients, while allowing full function of the LIN transmission with low capacitance. The ESD7xx and ESD1LINxx device lines have low clamping voltages and high ESD ratings, providing ESD protection for the LIN bus interfaces. Table 1 lists these device suggestions.
LIN Device | IEC 61000-4-2 (kV) | VRWM(V) | Line Capacitance (pF) | Clamping Voltage (V) | Package Size (mm) |
---|---|---|---|---|---|
ESD1LIN24-Q1 | 30 | 24 | 3 | 37 | SOT-323 (2.50 × 1.20) |
ESD751-Q1 | 22 | 24 | 1.6 | 36.5 | SOT-523 (1.60 × 0.80) |
ESD761-Q1 | 15 | 24 | 1.1 | 36.3 | DFN1006 (1.00 × 0.60) |