Normally closed DIP4-pin economic type with reinforced insulation Modem# Technical Documentation: AQY414EHAX Solid State Relay (SSR)
Manufacturer : NAIS (Panasonic)
Component : AQY414EHAX Photorelay (MOSFET Output Solid State Relay)
Document Version : 1.0
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The AQY414EHAX is a photorelay designed for low-voltage, low-current signal switching applications. Its core function is to provide galvanic isolation between a control circuit and a switched load using an infrared LED optically coupled to a photo-MOSFET.
* Primary Switching Function: It acts as a normally-open (Form A) single-pole single-throw (SPST) switch . When the input LED is energized (typically with an IF of 5-10 mA), the output MOSFET turns on, creating a low-resistance path between its drain (pin 4) and source (pin 3).
* Signal Routing: Commonly used to switch analog or digital signals on data lines, audio paths, or sensor inputs in test equipment, communication devices, and measurement systems.
* Load Control: Suitable for directly driving or controlling very small loads such as other logic-level gates, enabling/disabling sections of a circuit, or interfacing between microcontrollers and higher-voltage sections.
### 1.2 Industry Applications
* Test & Measurement Equipment: Switching between different sensor inputs, signal sources, or calibration paths in multimeters, data acquisition systems, and automatic test equipment (ATE). Its low `RON` (~0.8Ω) minimizes signal attenuation and distortion.
* Communication & Networking: Used in modem banks, PBX systems, and routing equipment for line selection, gain switching, or fault isolation.
* Industrial Automation: Interface between low-voltage PLC output cards and higher-voltage sensor circuits or indicator panels. Provides noise isolation in control systems.
* Medical Electronics: Signal isolation in patient monitoring equipment, where safety and noise immunity are critical (complementary to primary safety isolation).
* Consumer/Professional Audio: Channel switching, input selection, or muting functions in audio mixers and amplifiers, leveraging its low off-state leakage and minimal distortion.
### 1.3 Practical Advantages and Limitations
Advantages:
* High-Speed Switching: Turn-on/off times in the range of 0.2 ms (max) , significantly faster than electromechanical relays, enabling PWM or digital signal switching.
* Long Life & High Reliability: No moving parts or contact arcing, leading to virtually infinite operational life when used within specifications. Excellent for high-cycle applications.
* Excellent Isolation: High input-output isolation voltage ( 1500 Vrms ) protects sensitive control circuits (e.g., microcontrollers) from transients or faults on the load side.
* Low Power Consumption: The control side only requires a few mA of LED current. The output has no holding current requirement.
* Low `RON` & Leakage: Typical on-resistance of 0.8Ω ensures minimal voltage drop. Extremely low off-state output leakage current ( 1 nA max ) prevents signal bleed-through.
* Compact Size: SMD package (SSOP-4) saves board space compared to traditional relays.
Limitations:
* Limited Current/Voltage Rating: Maximum load current is 120 mA continuous . Absolute maximum load voltage is 60 V . Not suitable for mains voltage or power switching.
* `RON` Variation: On-resistance has a positive temperature coefficient and increases with junction temperature. This can lead to higher voltage drop and power dissipation at high ambient temperatures or currents.
* Heat Dissipation: At maximum load current (120 mA), the power dissipation (`I² * RON`) can approach
