SPVA018 August   2025 LM2904B

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2ESD Overview
    1. 2.1 What is Electrostatic Discharge?
      1. 2.1.1 ESD Cell Robustness in Semiconductors
  6. 3Types of ESD Cells
    1. 3.1 Dual Diode Configuration
      1. 3.1.1 Why Not Always Use Dual Diode Configuration?
    2. 3.2 Bootstrapped Diodes
    3. 3.3 Absorption Devices
      1. 3.3.1 Active Clamps
      2. 3.3.2 GCNMOS Clamps
    4. 3.4 Silicon Controlled Rectifiers
    5. 3.5 CER and ECR NPN Diodes
      1. 3.5.1 Measuring the Response of an ECR and CER ESD Cell
    6. 3.6 Comparison of ESD Cells
  7. 4How to Determine the ESD Structure of the Device from the Data Sheet
  8. 5How to Protect The System from In Circuit ESD/EOS Events
    1. 5.1 Using TVS Diodes and Series Resistance for Circuit Protection
    2. 5.2 Using Schottky Diodes for Circuit Protection
  9. 6How to Test an Op Amp in a System Level Circuit
    1. 6.1 ESD Protection Cell Advancements Over the Years
  10. 7Summary
  11. 8References

3.5 CER and ECR NPN Diodes

The CER/ECR NPN ESD protection structure is another common option, particularly for higher voltages. This behaves similarly to a snapback diode, in that the voltage reaches a certain level before dropping back to the threshold voltage. Figure 3-9 shows the general layout.

CER Diode Structure Figure 3-9 CER Diode Structure

The protection structure raises the base potential to lower the NPN trigger voltage. These are preferred when the device is tolerant to a high trigger or clamping voltage. Note that one pad is connected to ground through a diode. The other pad is voltage triggered. This offers ESD protection while taking up a relatively small area, albeit not as small as an SCR structure. These structures are also advantageous because the structures are generally considered to be a latch-up free design unlike SCRs, which are more prone to latch-up.