Vishay Semiconductor Opto Division LH1546ADF

Overview

LH1546ADF from Vishay Semiconductors is a single-channel, normally open solid-state relay (SSR) in an SMD-4 package, integrating a GaAlAs LED input and MOSFET output stage. It delivers 350 V load voltage handling, 120 mA continuous bidirectional load current, and 22 Ω typical on-resistance - enabling electromechanical relay replacement in telecom switching, metering, and industrial control circuits.

For engineers reviewing the LH1546ADF datasheet, LH1546ADF pinout, LH1546ADF application, or LH1546ADF equivalent, key selection criteria include isolation voltage (5300 VRMS), turn-on/off timing (0.13 ms / 0.05 ms typ.), safety-rated insulation (VIORM = 890 Vpeak), and SMD-4 footprint compatibility with automated assembly.

Technical Context

The LH1546ADF implements optically isolated control via a GaAlAs infrared LED driving complementary MOSFETs to form a bidirectional, bounce-free SPST (Form A) switch. Its input-output isolation meets UL, cUL, and DIN EN 60747-5-5 (VDE 0884-5) standards with 8 mm creepage/clearance and ≥0.4 mm insulation thickness.

Electrical operation relies on low-input-current activation (0.25 mA typical IFon at 100 mA load), sub-1 μA off-state leakage at ±100 V, and stable RON up to 85 °C ambient. Safety power dissipation (PSO = 600 mW) and input safety current (ISI = 240 mA) are thermally derated per Fig. 2 and Fig. 3.

Key Specifications

Pinout & Package

SMD-4 surface-mount package (JEDEC MS-012AC variant), 9.80 × 6.65 mm body, 2.54 mm pin pitch, lead (Pb)-free, MSL 1, compliant with J-STD-020 reflow profile.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar solid-state relay applications.

Compared with LH1546AEF and CPC1976Y, the LH1546ADF offers optimal balance of 350 V capability, VDE-certified isolation, and low 22 Ω RON - making it preferred for metering, telecom, and industrial controls where safety compliance and thermal efficiency are jointly critical.

Availability

LH1546ADF is available at Aetrix Electronics and suitable for telecom switching, smart metering, and industrial PLC I/O modules requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LH1546ADF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Vishay Intertechnology is a global semiconductor manufacturer specializing in discrete components, optoelectronics, and passive devices with emphasis on reliability, precision, and safety certification.

The LH1546ADF belongs to Vishay's LH1546 family of optically coupled solid-state relays, designed specifically for replacing electromechanical relays in safety-isolated, low-power control applications across industrial, energy, and communications infrastructure.

FAQ

What is the maximum ambient temperature for continuous operation of the LH1546ADF?

The LH1546ADF supports continuous operation from –40 °C to +85 °C ambient temperature. At 85 °C, its maximum load current derates to approximately 80 mA (per Fig. 4), and output safety power drops to ~300 mW (per Fig. 2). Thermal design must account for PCB copper area and airflow to maintain junction temperature below 125 °C under full 120 mA load.

Does the LH1546ADF require an external current-limiting resistor on the LED input?

Yes, the LH1546ADF requires an external series resistor on the LED anode (Pin 1) to limit forward current to ≤50 mA absolute maximum. For typical 3.3 V MCU GPIO drive, a 1.0 kΩ resistor sets IF ≈ 1.9 mA - well within the 0.25–2 mA turn-on range and ensuring reliable activation without overstressing the GaAlAs LED.

Can the LH1546ADF switch AC loads, and what is its zero-crossing behavior?

The LH1546ADF is a random-turn-on SSR and does not incorporate zero-crossing detection. It can switch AC loads up to 350 V peak, but turn-on occurs at any point in the AC cycle - potentially causing inrush current and EMI. For zero-crossing operation, consider Vishay's LH1546AC series instead; the LH1546ADF is intended for DC or non-zero-crossing AC control where timing precision matters more than EMI suppression.

What safety certifications apply to the LH1546ADF, and are test reports available?

The LH1546ADF carries UL 1577 and cUL recognition (file E152670) and complies with DIN EN 60747-5-5 (VDE 0884-5) for reinforced insulation when ordered with Option 1. Full safety test reports - including partial discharge, VIOTM = 8000 Vpeak, and RIO ≥ 10¹² Ω - are published in Vishay document 83836 and accessible via the official product page.

How does the LH1546ADF compare to mechanical relays in terms of lifetime and reliability?

The LH1546ADF provides >10⁹ operations versus ~10⁵–10⁶ cycles for typical electromechanical relays, with no contact wear, oxidation, or bounce. Its MTTF exceeds 1 million hours at 25 °C (per Vishay reliability data), and it withstands vibration/shock immunity far beyond mechanical counterparts - making the LH1546ADF ideal for high-cycle, maintenance-free deployments in automatic test equipment and security systems.