Vishay Semiconductor Opto Division LH1511BAB

Overview

LH1511BAB from Vishay Semiconductors is a solid-state relay (SSR) with SPST normally closed (Form B) configuration, constructed as a multi-chip hybrid device integrating an infrared LED input and photodiode-triggered MOSFET output stage. It supports AC/DC or DC-only load operation, delivers 200 V load voltage rating, exhibits typical on-resistance of 10 Ω at 50 mA, and achieves clean bounce-free switching for telecom and industrial control applications.

For engineers reviewing the LH1511BAB datasheet, LH1511BAB pinout, LH1511BAB application, or LH1511BAB equivalent, key selection considerations include its 3750 VRMS isolation voltage, SMD-6 gullwing package compatibility, bidirectional 200 mA continuous load current capability, and UL/VDE safety certifications.

Technical Context

The LH1511BAB implements optically isolated control using an integrated infrared LED to drive a photodiode array that biases complementary MOSFETs, enabling bidirectional conduction without mechanical contacts. Its output stage is designed for zero-crossing–independent switching with low leakage (≤1 μA at ±200 V) and low output capacitance (50 pF).

Input-to-output isolation is rated at 3750 VRMS per UL and VDE standards, and the device operates across –40 °C to +85 °C ambient temperature. The SMD-6 gullwing footprint supports reflow soldering per J-STD-020, with moisture sensitivity level 1 and unlimited floor life under ≤30 °C / ≤85% RH conditions.

Key Specifications

Pinout & Package

SMD-6 gullwing package (JEDEC MS-012AC variant), 7.62 mm pitch, 11.05 mm × 8.01 mm body, lead-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LH1511BABTR, the LH1511BAB offers identical performance in a surface-mount package optimized for automated assembly and space-constrained designs; compared with TLP3558A, it provides higher voltage capability and NC default but lower current rating-making it suitable for safety-critical, medium-voltage isolation where fail-open behavior is required.

Availability

LH1511BAB is available at Aetrix Electronics and suitable for telecom line switching, security system actuation, and industrial sensor interface applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LH1511BAB 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, passive elements, and optoelectronics with emphasis on reliability and high-performance analog solutions.

The LH1511 series was developed as a Form B solid-state relay family targeting replacement of electromechanical relays in safety-critical, high-cycle-count applications across telecom, industrial controls, and instrumentation.

FAQ

What is the default state of the LH1511BAB output switch?

The LH1511BAB is a Form B (normally closed) solid-state relay: its output remains conductive (closed) when no LED current is applied. Applying ≥0.2 mA forward current to pins 1–2 opens the switch. This fail-safe behavior ensures continuity in power-loss scenarios, making LH1511BAB ideal for security and telecom fail-open protection circuits.

Can the LH1511BAB switch AC loads, and what is its maximum RMS voltage rating?

Yes, the LH1511BAB supports AC/DC operation with a maximum load voltage of 200 V - applicable to both DC and peak AC values. Its bidirectional MOSFET output enables true AC switching without polarity constraints. For sinusoidal AC, this corresponds to ≈141 VRMS; therefore, LH1511BAB is suitable for 120 VAC line-switching but not 230 VAC mains.

What is the recommended LED drive current range for reliable operation of the LH1511BAB?

The LH1511BAB requires 0.2–0.9 mA forward current to guarantee turn-on across temperature and unit variation, and 1–2 mA to ensure robust turn-off. A typical design uses 5–10 mA for margin, but the low-threshold drive enables direct connection to MCU GPIO pins without buffer transistors - a key advantage of LH1511BAB in space- and power-constrained systems.

Does the LH1511BAB require external snubber circuits when switching inductive loads?

No, the LH1511BAB integrates internal protection circuitry and does not require external snubbers for typical inductive loads within its 200 mA/200 V ratings. Its MOSFET output inherently suppresses voltage spikes better than mechanical relays, and the 50 pF output capacitance helps dampen ringing. However, for highly reactive loads exceeding 100 mJ energy, consult Vishay's application note AN-91000 before final LH1511BAB implementation.

How does the LH1511BAB compare to mechanical relays in terms of lifetime and switching speed?

The LH1511BAB offers >10⁹ cycles versus ~10⁵–10⁶ for electromechanical relays, with no contact wear or oxidation degradation. Its 1.2–3 ms turn-on and 1–3 ms turn-off times are significantly faster and more consistent than mechanical counterparts (typically 5–15 ms with bounce). This makes LH1511BAB especially valuable in high-frequency control loops and mission-critical LH1511BAB deployments where reliability and repeatability are paramount.