Electrocardiogram (ECG) monitors, as precision medical devices directly connected to the patient's body surface to monitor weak bioelectrical signals, are highly susceptible to electrostatic discharge (ESD) and electrical surges. These risks can not only damage the device but also endanger the patient's life.
Analysis of the main electrostatic and surge risks faced by ECG monitors:
1️⃣ Electrostatic Discharge (ESD)
ESD refers to the rapid transfer of charge that occurs when a charged object (such as a human body or clothing) comes into contact with or approaches the device.
For ECG monitors, ESD risks mainly manifest in the following ways:
1. Contact Discharge
- Scenario: When medical personnel or patients touch the monitor's metal casing, buttons, screen, or connectors, if the human body carries static electricity (e.g., after walking in a dry environment), a direct discharge can occur.
- Consequences: High voltage (up to several kilovolts) is injected instantaneously into the device's circuitry, potentially causing damage to the front-end analog chip and data corruption.
2. Air Discharge
- Scenario: When a charged object approaches the device but does not directly contact it, a discharge occurs through the air.
- Consequences: The generated strong electromagnetic field may couple to internal circuit board traces or cables, causing signal noise and waveform distortion.
2️⃣ Electrical Surges and Transients
A surge refers to a brief, high-energy voltage/current pulse appearing on a power line or signal line.
ECG monitors face more complex and higher-energy surge risks:
1. Defibrillator Shock
- Scenario: This is a dangerous surge risk for ECG monitors. During defibrillation, up to 200J-360J of energy is released through the electrodes attached to the patient.
- Risk Path: Because the ECG leads are also connected to the same patient, some of the defibrillation high voltage will couple to the ECG input.
- Consequences: Hardware Damage: Without sufficient high-voltage protection, the front-end circuitry can be instantly burned out.
2. Power Line Surge
- Scenario: Lightning strikes, grid switching, or voltage fluctuations caused by the start-up and shutdown of large medical equipment.
- Consequences: Intrusion through the power cord can damage the power module and subsequently affect low-voltage circuits.
3. Electrical Fast Transient (EFT)
- Scenario: Rapid, high-frequency noise clusters generated by the switching of inductive loads (such as relays and motors).
- Consequences: Although the energy of a single pulse is small, dense pulse clusters can cause malfunctions in digital circuits, communication interruptions, or screen flickering.
Semiware ECG Monitor Protection Design Scheme
To address the aforementioned risks of electrostatic discharge (ESD) and electrical surges, sophisticated circuit protection design is crucial for the reliable operation of ECG monitors.
Below is a specific component solution provided by Semiware, analyzing the protection design for different functional modules of the ECG monitor.
1. Power Input and AC/DC Module Protection
This is the first line of defense against external power grid surges (such as lightning strikes or power switching). This solution employs a combination of gas discharge tubes (GDTs) and varistors (MOVs), achieving both high-voltage isolation and high energy absorption.
| Device Type | Model | Key Parameters | Design Purpose |
| Gas Discharge Tube | SG2R08B600A | 600V, 20KA, 1.5pF | High surge capability for primary lightning protection |
| Gas Discharge Tube | SG2R08B600 | 600V, 10KA, 1.5pF | Backup surge protection |
| MOV | 14D561K | 560V, 4500A, 150J | Fast clamping for transient suppression |
2. DC/DC Power Protection
| Device Type | Model | Key Parameters | Design Purpose |
| TVS Diode | SVB60B6.0（SMBJ6.0CA) | Bidirectional, 6.67–7.37V, 600W | Extremely fast response speed (picosecond level), used for clamping voltage |
3. Battery Protection
| Device Type | Model | Key Parameters | Design Purpose |
| ESD Diode | SE10F55U4.5A | 4.85V, ±30kV, 0.1μA | Prevent ESD from damaging the power management chip during battery replacement or connection |
4. RJ45 / Ethernet Protection
| Device Type | Model | Key Parameters | Design Purpose |
GDT | SG3225B800 | 800V, 1KA, 0.5pF | Common-mode protection: Primary protection for Ethernet interfaces, with low capacitance (0.5pF) to ensure high-speed signal integrity is not affected |
| ESD Diode | SE3D15B3.3MA | 3.3V, 0.6pF, ±30kV | High-speed signal protection |
| ESD Diode | SESRV05-4A | 5V, ±15kV, 0.8pF | Data line protection: Array-type TVS protects differential signal lines, and low capacitance prevents network signal distortion |
| Thyristor | STB100B58(P0640SC) STB100B275(P3100SC) | 58V, 6kV 275V,6kV | Surge crowbar protection |
5. RS485 / RS232 Protection
| Device Type | Model | Key Parameters | Design Purpose |
| GDT | SG3D05B090 | 90V, 5KA | High voltage withstand protection for communication interfaces is provided to prevent induced lightning strikes caused by long-distance cabling |
| TVS Diode | SVB60B15(SMBJ15CA) | 600W, 16.7–18.5V | Extremely fast response speed (picosecond level), used for clamping voltage |
| TVS Array | SE23T40B712B | +7/-12V, ±25KV, SOT-23 | ESD protection for data lines |
| Thyristor 6kV, 100A | STB100B6.0(P0080SC) | 6.0V, 6KV, 100A, SMB | Surge protection |
6. USB Interface Protection
| Device Type | Model | Key Parameters | Design Purpose |
| TVS Array | SE41T06U5.0LB | 5V, ±20kV, 2pF | Designed specifically for USB signal cables, the 2pF capacitor ensures high-speed signal quality while simultaneously discharging static electricity from the human body. |
7. Display Protection
| Device Type | Model | Key Parameters | Design Purpose |
| Bidirectional ESD Diode | SE10F10B3.3A | 3.3V, 12pF, ±30kV,DFN1006 | Protects LCD or touchscreen signal cables, preventing screen flickering, crashes, or touchscreen malfunctions. Bidirectional design accommodates AC signals. |
Summary
Semiware's solution embodies the design philosophy of "multi-level protection and collaborative operation." It uses GDT and MOV at the power input to handle high-energy surges; and low-capacitance TVS and thyristors at the signal and front-end for rapid response and precise clamping. This combination meets the stringent requirements of the IEC 60601 series of medical standards for defibrillation recovery and leakage current control while ensuring the purity of the ECG signal.
About Semiware
In ADAS systems, load transients and electrostatic discharge (ESD) are two common electrical threats. Proper PCB layout, component selection, and interface protection design can effectively improve system reliability and reduce maintenance risks.
Semiware offers a range of AEC-Q101 compliant TVS/ESD protection devices to meet the protection requirements of various interfaces in automotive electronics, helping engineers and purchasing departments quickly select the right devices.
🔗 Explore more medical device protection solutions: https://en.semiware.com/application/medical/
🔹 About Semiware
Semiware is a professional manufacturer of circuit protection and discrete semiconductor devices, headquartered in Shanghai, China.
Founded by experienced engineers in the circuit protection industry, we focus on developing high-reliability TVS diodes, ESD protection devices, GDTs, Triacs, and other discrete components for global OEM and EMS customers.
Our products are widely used in:
- Network & Telecom Equipment
- Automotive Electronics
- Industrial Control Systems
- Security Devices
- New Energy Applications
- Consumer Electronics
We not only supply components, but also provide professional circuit protection design support and EMC technical assistance to help customers improve product reliability.
Stable quality, competitive pricing, and reliable delivery make us a trusted partner for long-term cooperation.
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