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Why engineers need IC ESD and TLP data

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Design Engineers need ESD and TLP characterization data to make informed decisions to design robust circuits and systems.

Engineers often review semiconductor data among several manufacturers when designing a circuit or system. While two or more ICs may perform satisfactorily under normal operating conditions, they may not perform the same under extreme conditions, such as when hit with an electrostatic discharge (ESD) event. System designers need to optimize the ESD robustness of their system design with an industry-standard methodology but may not have the data they need to make informed decisions.

Semiconductor companies must provide circuit and system designers with the information necessary to optimize ESD protection and ensure robust designs. One key piece of information that can help customers achieve this goal is Transmission Line Pulse (TLP) characterization data. Supplying TLP test data can make the difference between a robust design and one that fails in the field.

With IEC, HBM, and CDM, why do we need TLP and SEED?
ESD is a significant concern in the design and manufacture of electronic systems. An ESD hit damages ICs and disrupts system functionality. To mitigate this risk, various ESD testing standards have been developed, including the Human Body Model (HBM) and Charged Device Model (CDM). The HBM standard, defined by ANSI/ESDA/JEDEC JS-001, simulates the discharge of a human body to a device, while the CDM standard, defined by ANSI/ESDA/JEDEC JS-002, simulates the discharge of a charged device. The International Electrotechnical Commission (IEC) also provides standards for ESD testing systems, including IEC 61000-4-2, which defines the electrostatic discharge immunity test.

ESC in semiconductors
Figure 1. SEED Modeling of TVS Protection Shunt Current (red) and Residual Pulse applied to ASIC/DUP (yellow).

The System Efficient ESD Design (SEED) methodology is an industry-standard approach for designing ESD-robust systems. It involves characterizing the ESD behavior of ICs and using this information to optimize system-level ESD protection. Figure 1 shows the SEED methodology considers the current sharing between the protection device and the device under protection (DUP), the residual pulse applied to the failure criteria of the individual devices to predict and verify the robustness level that the system will pass in qualification. By following the SEED methodology, designers can create systems that are more robust and reliable, reducing the risk of ESD-related failures.

Without SEED, designers are simply left with a trial-and-error approach that consumes enormous amounts of time, produces destroyed systems in the lab, and results in product qualification and field failures.

What is TLP, anyway?
TLP is a standard test method, defined by ANSI/ESD STM5.5.1, and is a powerful tool for characterizing an IC’s ESD behavior. It involves applying a high-current, short-duration pulse to the device and measuring the resulting voltage and current waveforms. TLP can provide valuable insights into the ESD properties of ICs, including its trigger voltage, snapback voltage, and second breakdown current. This information is essential for designing effective ESD protection circuits.

I-V curve
Figure 2: Typical I-V Curve provided in a TVS protection device datasheet, to be used in conjunction with the ASIC DUP’s curve in SEED simulation. Image: Littelfuse SP3522 TVS datasheet.

TLP systems typically consist of a transmission line, a pulse generator, and a measurement system. The transmission line is charged to a high voltage, and then the pulse generator is triggered, releasing the stored energy into the IC. The measurement system captures accurate and very repeatable voltage and current waveforms, which are then used to successively create a TLP I-V curve. The TLP I-V curve in Figure 2 provides a detailed characterization of the IC’s ESD behavior, including the voltages and currents at which the IC triggers, snaps back and/or clamps, and fails.

There are several types of TLP systems, commonly distinguished as TLP and very fast TLP (VF-TLP). TLP systems that use a 50 ns, 100 ns, or longer pulse length are used to accurately characterize HBM and IEC energy and power correlations. In comparison, VF-TLP systems use a 10 ns or shorter pulse length in conjunction with fast risetimes in the picosecond range to simulate the fast rise times of CDM and IEC ESD events.

Why provide TLP characterization data?
Providing TLP characterization data to circuit and system designers can help them optimize ESD protection for your ICs, reducing the risk of field failures and returns. Engineers can design more robust systems that meet the required ESD standards by understanding an IC’s ESD behavior. This, in turn, enhances a product’s overall value, increasing customer satisfaction.

Some semiconductor companies may hesitate to provide TLP characterization data because of concerns about revealing proprietary information or creating unrealistic expectations about their IC’s ESD robustness. The benefits of providing this information, however, far outweigh the risks. By working closely with engineers and providing the necessary data, IC manufacturers can help design more reliable and robust systems, ultimately reducing the risk of field failures and returns.

Semiconductor companies often possess expensive TLP equipment to evaluate their own and competitors’ devices. System designers, who operate on thinner margins, usually lack access to such equipment. Withholding TLP data to protect “proprietary secrets” from competitors is an unfounded concern, especially when weighed against the benefits of supporting customers.

But we already have IBIS, SPICE, and S-Parameter models
Small-signal models, signal integrity IBIS models, SPICE models, and S-parameter models let engineers analyze and simulate the behavior of electronic circuits under normal operating conditions. These models focus on small-signal behavior and are typically valid below operating voltage ranges.

Small-signal models are linear representations of a circuit’s behavior around a specific operating point. They are useful for analyzing the circuit’s response to small variations in input signals. These models typically include parameters such as passive parasitics and are commonly used in linear circuit analysis. On the other hand, high-current, high-energy TLP characterization and SEED models are designed to analyze circuit behavior during high-current, short-duration (ESD) events.

The problem of extrapolating milliamp I-V curves into the ESD regime arises from the fact that the behavior of electronic devices during ESD events is significantly different from their behavior under small-signal conditions. Extrapolating small-signal I-V curves, which are typically measured in the milliamp range, to the high-current ESD regime will lead to inaccurate predictions of device behavior and inadequate ESD protection.

ESD waveform
Figure 3. An 8 kV ESD waveform from IEC 61000-4-2 has a 30 A spike with a rise time of 0.7 ns to 1 ns, where 8kV for HBM is much lower current and slower. Image: IEC 61000-4-2

ESD events involve fast-rising currents from milliamps to over 100 A peak in the extreme for a 30 kV IEC 61000-4-2 pulse (Figure 3), which can cause nonlinear effects, localized heating, and device breakdown. Small-signal models and measurements are not suitable nor intended to capture these effects accurately. TLP and SEED models, which are specifically designed for high-current, high-energy ESD events, provide a more realistic representation of device behavior and enable accurate optimization of ESD protection strategies.

The Downside of not providing TLP characterization data
Not providing TLP characterization data to customers can have significant consequences, including:

  • SEED relies on TLP data from both the Protection Devices and the ASIC I/O pins to be protected. Without both sets of data from suppliers, the system designer cannot perform a SEED analysis.
  • Increased risk of field failures: Without TLP data, a system designer’s customers may be unable to design effective ESD protection circuits, leading to an increased risk of field failures and returns.
  • Reduced customer satisfaction: Engineers unable to obtain the necessary information to design robust systems may become frustrated and dissatisfied, leading to then choosing other suppliers, resulting in lost business and lowered reputation.
  • Competitive disadvantage: Companies that do not provide TLP data may be at a competitive disadvantage compared to those that do, as engineers may prefer to work with companies that provide the necessary information to design reliable and robust systems. If the engineers must create their own model for the IC with estimated datasheet parameters, then it may not perform as well as an accurate TLP model would.
  • Increased support costs: Without TLP data, engineers may require more support and assistance from IC manufacturers, leading to increased support costs and a greater burden on your resources.
  • Missed opportunities: By not providing TLP data, IC manufacturers may miss opportunities to work closely with customers and help engineers design more reliable and robust systems, which can lead to increased sales and revenue.

In addition, not providing TLP characterization data can also lead to a lack of trust and confidence between your company and your customers. Customers may view your company as uncooperative or unhelpful, which can damage your reputation and relationships with them.

Benefits of providing TLP characterization data
There are several benefits to providing TLP data to engineers designing with ICs, including:

  • Improved system reliability: By providing engineers with detailed information about the ESD behavior of your ICs, IC manufacturers can help them design systems that are more robust and reliable.
  • Reduced field failures and returns: When design engineers have access to detailed information about the ESD behavior of your ICs, they can design systems that are better equipped to handle ESD events, reducing the number of failures and returns.
  • Enhanced product value: By providing designers with the information they need to design robust systems, semiconductor manufacturers can increase customer satisfaction and loyalty, leading to increased sales and revenue.
  • Increased customer satisfaction: Providing TLP characterization data can help engineers design systems that meet their specific needs and requirements, leading to increased customer satisfaction and loyalty.
  • Competitive advantage: By providing TLP characterization data, you can differentiate your company from competitors and establish yourself as a leader in the industry.

Conclusion
As technology continues to advance, the increasing complexity and susceptibility of ICs make the risk of ESD-related failures and damage higher than ever. While it may not be feasible or necessary for semiconductor manufacturers to provide TLP characterization data for every pin and every chip, it is essential to establish a process for system designers to request and access this critical information. At a minimum, semiconductor manufacturers should provide a clear conduit for system providers to submit requests for TLP data, allowing for a dialogue to take place about the specific ESD protection needs of their application. This does not require a commitment to provide data for every request, but rather a willingness to engage with customers and consider their needs on a case-by-case basis. By establishing this process, semiconductor manufacturers can demonstrate their commitment to supporting the development of robust and reliable systems, while also managing their own resources and priorities.

You can argue that the costs of not prioritizing ESD protection and robust system design fall more heavily on the system manufacturer and the consumer society. System manufacturers, with thinner profit margins and greater exposure to the costs of field failures and returns, bear the brunt of the financial burden. Furthermore, there are broader societal considerations of less reliable and less robust systems, including electronic waste, safety risks, increased maintenance, and further stress to weak supply chains. In contrast, semiconductor suppliers, with higher margins and lower costs of returns, may be less directly impacted by the costs of poor ESD protection. Think of an ambulance being towed to an OEM for repairs for a failed Engine Control Module (ECM), versus a CPU shipped in a box to an IC supplier for a failed ECM failure analysis.

Providing a process for sharing TLP characterization data with customers is essential for helping them optimize ESD protection for your ICs.  Moreover, robust systems contribute to a more reliable and efficient overall global infrastructure, which has far-reaching benefits for society. While generating, sharing, and properly utilizing TLP data requires significant resources and effort, the benefits to your customers, your business, and the industry at large make it a worthwhile and competitive investment.

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