Name: BAT54S
Brand: Onsemi
SKU: BAT54S

🛠️ Typical Application Scenarios

1. I/O Pin Overvoltage & ESD Protection (Dual-Voltage Clamping) —— The Most Classic Application

BAT54S is widely used for voltage clamping protection on the General Purpose Input/Output (I/O) pins of microcontrollers (MCUs, DSPs, FPGAs), key inputs, or external communication interfaces:

Circuit Connection: Pin 1 connects to Ground (GND), Pin 2 connects to the Power Supply (VCC), and Pin 3 connects to the protected signal line.
Positive Clamping: When an external voltage spike (ESD or surge) drives the signal line above

, the upper diode instantly conducts, clamping the overvoltage and discharging the excess energy into the VCC plane to prevent MCU damage.
Negative Clamping: When the signal line drops below

due to negative spikes or ringing, the lower diode conducts, clamping the negative voltage to a safe level.

2. Communication Bus Protection (High-Speed Data Line Isolation)

It is commonly deployed on USB, CAN bus, LIN bus, I2C, and SPI interfaces. Because of its exceptionally low parasitic capacitance, it delivers robust transient overvoltage protection without compromising signal integrity.

3. Reverse Polarity Protection & Battery Power Switching

Leveraging its ultra-low forward voltage drop, the BAT54S is ideal for reverse polarity protection in portable and wearable micro-power electronics. It also serves as a low-loss automatic switch and isolation diode between multiple power sources (e.g., switching between USB power and a lithium battery).

4. High-Frequency Signal Detection & Ultra-Fast Switching

With its nanosecond-level reverse recovery time (

), it is frequently used as a high-frequency detector, AM demodulator, or logic-level translation switch in radio frequency (RF) circuits, microwave receivers, and clock distribution systems.

🚀 Key Features

Ultra-Low Forward Voltage Drop (

):
- Drops below 0.24 V at micro-ampere levels (
  
  ) [1].
- Stays around 0.40 V at low currents (
  
  ) [1].
- Advantage: Conducts much earlier than standard silicon diodes (~0.7V) to divert overvoltage quickly.
Ultra-Fast Switching Speed (

):
- Reverse recovery time is a maximum of 5 ns [1].
- Advantage: Perfectly handles high-frequency signals, fast-rising pulses, and high-speed switching circuits [1].
Extremely Low Parasitic Capacitance (

):
- Diode capacitance is typically only 10 pF at a frequency of
  
  [1].
- Advantage: Minimizes signal attenuation and distortion on high-speed data communication buses (such as I2C, SPI, CAN).
200mA Continuous Forward Current (

):
- Supports a continuous forward current up to 200mA [1], with a non-repetitive peak forward surge current (
  
  ) up to 600mA [1].
High Integration & Reliability:
- Dual diodes in a single SOT-23 package save PCB space and simplify layout [1].
- Automotive-grade versions meeting AEC-Q101 standards are widely available from major manufacturers.