Medical electronic equipment is an instrument that integrates electronic, computer, communication and other technologies with medical principles. It covers diagnostic equipment (such as X-ray, ultrasound, CT and other imaging equipment for disease detection, ECG, blood pressure, blood oxygen saturation and other monitoring equipment for vital signs monitoring), treatment (electrotherapy equipment such as high-frequency electric knife, low-frequency electrical stimulation therapy device, linear accelerator, cobalt-60 therapy machine and other radiotherapy equipment, and laser therapy equipment) and rehabilitation (physical rehabilitation equipment such as rehabilitation training robots, physiotherapy equipment and hearing aids, cochlear implants and other functional auxiliary equipment). It plays a key role in the entire medical process, promotes the advancement of medical technology, and helps improve medical services and patient health levels.

 Application of MOS tube in wearable ECG signal monitoring equipment

The power charging module uses the battery power management chip BQ21040, and the voltage stabilization circuit uses the TLV70033DCK voltage regulator. The working circuit that controls BQ21040 and TLV70033DCK uses a MOS tube switch circuit.

 This system selects PMOS tube SI2301DS-T1-GE3 as the switching device in the switching circuit, Vds=-20V, Id=5A, small on-resistance, Rdson=43mΩ.

1. Signal processing and amplification: In diagnostic equipment, such as ECG monitors, MOSFET amplifies weak ECG signals (millivolt and microvolt levels) with its high impedance and low noise characteristics, reduces attenuation and noise, provides high-quality signals for subsequent processing, and helps doctors make accurate judgments.

2. Power management and control

Voltage conversion and distribution: The voltage requirements of each module of medical equipment are different. MOSFET in the switching power supply can convert the mains power into different DC voltages (such as 220V to 5V, 3.3V, etc.) to supply each module, and it can also optimize battery life in portable devices.

Circuit on-off control: In imaging (such as X-ray machine exposure control) and ultrasound equipment (probe transceiver switching), MOSFET acts like a switch, turning the circuit on and off according to instructions, and affects the imaging quality frame rate, etc. It can also reduce power consumption and respond quickly when waking up from standby.

3. Function switching and mode selection: For example, the switching of multiple stimulation modes of multifunctional electrotherapy equipment and the switching of imaging modes of ultrasonic diagnostic equipment require the participation of MOSFET in control, and the mode is selected and parameters are adjusted according to needs to assist in diagnosis and treatment.

Selection of MOS tubes in medical electronic equipment

The selection of MOS tubes in medical electronic equipment is based on many factors.

1. Electrical parameters

Withstand voltage value (VDS): Depends on the application scenario. For high voltage applications, choose a high withstand voltage value, and for low voltage applications, choose an adaptive value.

Current carrying capacity (ID): Determined by the maximum current of the circuit. A high current carrying capacity is selected for a high-power circuit, and a small current value is selected for a small signal circuit.

On-resistance (RDS (on)): The power management circuit should select a low on-resistance to improve efficiency, and the requirements can be relaxed for non-sensitive circuits.

Threshold voltage (Vth): For low-voltage and low-power circuits (such as microprocessor peripheral circuits powered by 3.3V or 1.8V), choose low threshold voltage and adapt to the working voltage to ensure reliable conduction under low voltage and reduce design complexity and power consumption.

2. Performance characteristics

Switching speed: For high-frequency switching applications, high-speed switching MOS tubes are selected; for low-frequency circuits, low requirements are required.

Noise characteristics: Select low-noise MOS tubes when processing weak signals or high-precision measurements, and the requirements can be lowered for non-sensitive circuits.

Input impedance: The weak signal amplification circuit should select high input impedance, and other circuits are not critical factors.

3. Reliability and security

Temperature characteristics: Medical equipment generates heat (X-ray machines, etc.), so MOSFETs need to operate over a wide temperature range (such as -40°C to 125°C or even wider) and have small electrical parameter drift at high temperatures to ensure stable operation.

VBsemi's medium and low voltage MOS tubes can become one of the ideal choices for MOS tubes in medical electronic equipment because of their advantages such as being able to efficiently meet the design requirements of single-phase offline uninterruptible power supply circuits, achieve efficient energy conversion and stable output current, and have diverse parameter characteristics to effectively improve system efficiency and reliability. Its different products can be adapted and selected according to different electrical parameters and performance characteristics requirements according to the specific application scenarios of medical equipment (such as high-voltage circuits of imaging equipment, signal processing circuits of monitoring equipment, etc.), to help medical electronic equipment operate stably and accurately.