Countermeasures for ESD Protection

Example of external interface protection against electrostatic discharge
Example of external interface protection against electrostatic discharge

CMOS logic ICs provide electrostatic discharge (ESD) immunity compliant with international standards. Exposure to higher ESD might cause a malfunction or permanent damage to a CMOS logic IC.
Because the oxide film at the input gate of a CMOS logic IC is very thin (hundreds to thousands of angstroms), it could be damaged by an ESD of hundreds to thousands of volts.

To prevent this, each input pin generally provides ESD protection circuitry. However, there is a limit to this protection. Insert external ESD protection diodes for the inputs that might be exposed to excessive ESD (e.g., inputs connected to a board’s external interface).

HBM test circuit
HBM test circuit

There are various ESD models. The following describes one of the major ESD models.

Human body model (HBM)
This model characterizes the susceptibility of a semiconductor device to damage from ESD that might be generated from a human body.
There are numerous discussions on the human body capacitance. For ESD immunity testing, the charged human body is modeled by a 100-pF capacitor and a 1500-Ω discharging resistor. During testing, the capacitor is fully charged and then discharged through a resistor.

The HBM test circuit is shown below.

Usage Considerations of CMOS Logic ICs

Handling of Unused Input Pins
Input Rise and Fall Time Specifications
Multiple Outputs from a General-Purpose CMOS Logic IC Come Into Conflict (Short-Circuiting)
Connecting a Load Capacitance to a CMOS Output Pin
Calculating the Operating Supply Current and Power Dissipation
Level Shifting Using an Input-Tolerant Function
Example of Application of the Power-Down Protection Function (Partial Power-Down)
Input-Tolerant and Output Power-Down Protection Functions Available with Each Series
Types of Noise to be Noted
Countermeasures for Reducing Switching Noise
Countermeasures for Signal Reflection
Countermeasures for Crosstalk
Countermeasures for Hazards
Countermeasures for Metastability
Countermeasures for Latch-Up


Related information