The **PVT422** is a high-performance, dual-pole, normally open (1-Form-A) Photovoltaic Relay (PVR). It is essentially a solid-state replacement for electromechanical reed relays, designed to switch AC or DC loads with high reliability. --- ## 1. Core Technical Specifications The following table summarizes the primary electrical characteristics of the PVT422: | Parameter | Specification | Note | |:---|:---|:---| | **Contact Configuration** | Dual 1-Pole, Normally Open | 2 independent channels | | **Operating Voltage** | 0 to ± 400V | Peak AC or DC | | **Max Load Current** | 120mA (AC/DC) | Per channel | | **Max On-Resistance** | 35 $\Omega$ | At 120mA load | | **Control Current (LED)** | 2mA to 25mA | Typical trigger at 5mA | | **Isolation Voltage** | 4000 $V_{rms}$ | Input to Output | | **Package Type** | 8-pin DIP / SMD | Through-hole or surface mount | --- ## 2. Internal Components & Operation The PVT422 operates through **optical isolation**, which means there is no physical electrical connection between the control signal and the load. It consists of three main internal parts: 1. **Input LED (Gallium Aluminum Arsenide):** When current flows through the input pins, the LED emits infrared light. 2. **Photovoltaic Generator:** A silicon-based cell captures the light and converts it into a small voltage. 3. **Power MOSFETs:** This voltage triggers the gate of two HEXFET power MOSFETs, allowing current to flow through the output pins. ### Schematic Representation ```text Input (LED) Side Output (MOSFET) Side Pin 1 (+) ----[LED]---- Pin 2 (-) | Pin 8 (Drain) ---- [Switch] ---- Pin 7 (Source) Pin 3 (+) ----[LED]---- Pin 4 (-) | Pin 6 (Drain) ---- [Switch] ---- Pin 5 (Source) ``` --- ## 3. Key Advantages * **Longevity:** Since there are no moving parts, it does not suffer from contact bounce, arcing, or mechanical wear. * **Sensitivity:** It can be driven directly by CMOS or TTL logic levels (low power consumption). * **High Isolation:** The 4000V isolation protects sensitive microcontrollers from high-voltage spikes on the load side. * **Dual Channel:** Having two independent switches in one small package saves PCB space. --- ## 4. Typical Applications * **Telecommunications:** Ideal for "on-hook/off-hook" switching and ring injection. * **Instrumentation:** Used in automated test equipment (ATE) for signal routing. * **Industrial Controls:** Replacing small reed relays in PLC (Programmable Logic Controller) outputs. * **Data Acquisition:** Switching sensors where low offset voltage is required. ---