MSP430™ System-Level ESD Troubleshooting Guide

System-level electrostatic discharge (ESD) immunity, as one part of electromagnetic compatibility (EMC), has become more and more important in our daily lives with most electrical products. The MSP430™ microcontroller (MCU) portfolio offers a wide variety of 16-bit MCUs with ultra-low-power and integrated analog and digital peripherals for sensing and measurement applications. This application report introduces the concepts of system-level ESD immunity tests, troubleshooting guidelines, and a failure analysis procedure when encountering system-level ESD problems with MSP430 devices.

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1 Overview of System-Level ESD and EMC Test Standards

Electrostatic discharge (ESD) is the transient static electricity flow between two objects with different electrical potentials when they come into contact or close enough.

ESD is one example of electromagnetic interference (EMI), which is the generic term describing a situation in which an electrical disturbance generated by a certain electronic or electrical equipment causes an undesirable response in another equipment. Electromagnetic compatibility (EMC) is just the opposite; it is the discipline of analyzing and preventing or fixing interference problems.

IEC 61000-4-x standards define the test and measurement techniques for EMC immunity tests of electronic equipment. The most common test standards follow:

IEC 61000-4-2: System-level ESD immunity test
IEC 61000-4-3: Radiated radio-frequency, electromagnetic field immunity test
IEC 61000-4-4: Electrical fast transient/burst immunity test
IEC 61000-4-5: Surge immunity test
IEC 61000-4-6: Conducted RF immunity test
IEC 61000-4-8,9,10: Magnetic field immunity test
IEC 61000-4-11, and -12 to -35: additional tests

IEC 61000-4-2 is an International Electrotechnical Commission (IEC) immunity standard on system-level ESD. It defines the typical discharge current waveforms, test levels, test setup, and test procedure. For quick reference of ESD waveform, test levels, and test bench setup, see IEC 61000-4-2, IEC 61000-4-4 and IEC 61000-4-5 tests for TI's protection devices. For more detailed description about the system-level ESD test, see the IEC 61000-4-2 standard.

Many products specify the system-level ESD immunity requirement for end customers and define which levels are needed to comply with IEC 61000-4-2 standard. To achieve the system-level ESD immunity performance and pass the IEC 61000-4-2 tests, system designers need to follow specific guidelines during development. To understand the difference between component-level and system-level ESD, and for detailed guidelines related to MSP430 MCUs, see MSP430 System-Level ESD Considerations.

2 System-Level ESD Failure Scenarios

A product designed with an MSP430 microcontroller (MCU) uses firmware programmed in the MSP430 MCU to work with power supply circuits, external components (for example, sensors and parallel or serial communication devices) and electrical actuators that are connected to the MSP430 MCU. When there is system-level ESD failure in the system, the failure scenarios will be diverse and depend on the system design and the noise immunity performance of the components. The following behaviors are examples of ESD failures:

System reset when ESD applies and resume after the ESD
System reset and cannot resume after the ESD
LCD display failed (can be restored or cannot be restored after ESD test)
Serial communication failed – UART, I²C, or SPI
System hang-up
Abnormal power consumption
Memory corruption
ADC sampling incorrect, Speaker or buzzer noise
Device damage

System-level ESD failure can be caused by normal operations such as lighting, occasional zap when reaching for a door knob, cable plug, BGM (blood glucose meter) test strip plug, and more. So the system-level ESD test is widely used to evaluate the ESD immunity performance for most products before mass production.

Figure 1. System-Level ESD Failure Example

Figure 1 shows an example of the system-level ESD test that failed on a water meter MCU board. The green LED blinks several times after power on and turns off. When ESD simulator discharges onto the metal plate of the test platform, the LED blinks again which means the water meter board resets, showing that the test failed.

ESD failure scenarios can be summarized in two categories:

Soft failure
- A failure that can be corrected in the system
- A failure requiring intervention to resume (for example, reboot, power cycle, or a hardware reset)
Physical failure
- Catastrophic failures that cause permanent damage. The board will work abnormally.
- Latent defects that cause partially degraded performance. The board can still work functionally but life cycle will be impacted.

The debug and troubleshooting of soft failure scenarios are discussed in Section 3 from system application point of view. Regarding the physical failure scenarios, a failure analysis process can be applied which is discussed in Section 4.