Broadcom Limited ASSR-4128-502E

Overview

ASSR-4128-502E from Broadcom is a dual-channel, normally-off, solid-state photo-MOSFET relay with optically isolated AlGaAs LED input and two discrete high-voltage MOSFET outputs. It delivers 400 V output withstand voltage, 0.1 A DC/AC-rated output current (0.2 A in DC-only mode for ASSR-4119 variants), 25 Ω typical on-resistance, and 3.75 kVRMS input-output isolation. It replaces electromechanical relays in telecom switching and industrial control circuits requiring zero-crossing-free, bounce-free signal routing.

For engineers reviewing the ASSR-4128-502E datasheet, pinout, applications, or equivalent options, key selection criteria include dual SPST Form A functionality, gull-wing DIP-8 surface-mount package compatibility, 3 mA minimum turn-on LED current, 0.8 V maximum turn-off input voltage, and UL1577/CSA-certified insulation for safety-critical isolation.

Technical Context

The ASSR-4128-502E integrates an AlGaAs infrared LED optically coupled to a photovoltaic diode array that drives two independent high-voltage MOSFETs - enabling true bidirectional AC/DC switching without polarity constraints. Its input stage operates at CMOS-compatible low current (≥3 mA), while the output stage sustains 400 V blocking voltage and supports pulsed currents up to 100 mA with ≤5 ms turn-on/turn-off times.

Unlike mechanical relays, it provides galvanic isolation via internal dielectric barrier (3750 VRMS, 1 min), with creepage ≥7.4 mm and clearance ≥7.1 mm between input and output terminals. The device is rated for –40°C to +85°C ambient operation, with junction temperature limited to 125°C and RoHS-compliant lead-free reflow profile (peak 260°C, 10 s).

Key Specifications

Pinout & Package

ASSR-4128-502E uses an 8-pin DIP gull-wing surface-mount package (300-mil width), with pins 1–4 forming the input LED anode/cathode pair and pins 5–8 assigned to two independent output MOSFET terminals (Channel 1: pins 5/6; Channel 2: pins 7/8). The package complies with JEDEC MS-012 and supports reflow soldering per IPC-J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLP3548A and VO615A-3X006, the ASSR-4128-502E uniquely delivers dual SPST functionality in a UL-recognized, gull-wing DIP-8 package - reducing component count, simplifying layout, and ensuring regulatory compliance out-of-box for medical and industrial systems.

Availability

ASSR-4128-502E is available at Aetrix Electronics and suitable for telecom switching, industrial PLC I/O modules, and medical diagnostic equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant surface-mount assembly.

Supply support for ASSR-4128-502E 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

Broadcom Inc. is a global semiconductor leader designing high-performance connectivity, infrastructure, and optoelectronic solutions for enterprise, industrial, and communications markets.

The ASSR-41xx series was developed specifically as solid-state replacements for electromechanical relays - targeting high-reliability, low-maintenance isolation in telecom, medical, and industrial control systems where mechanical wear, EMI, and slow switching are unacceptable.

FAQ

What is the maximum ambient temperature for continuous operation of the ASSR-4128-502E?

The ASSR-4128-502E is rated for continuous operation from –40°C to +85°C ambient temperature. At +85°C, its maximum average output current derates to 0.06 A per channel (per Figure 4 in AV02-0218EN). Exceeding this limit risks junction temperature exceeding 125°C, triggering thermal shutdown or permanent degradation. Derating curves must be applied for designs operating near thermal limits.

Does the ASSR-4128-502E support AC and DC loads on both channels simultaneously?

Yes - the ASSR-4128-502E supports bidirectional AC/DC switching on both channels. Each channel (pins 5–6 and 7–8) functions as an independent SPST switch with no polarity constraints. Unlike ASSR-4119 Connection B (which enables 0.2 A DC-only), ASSR-4128-502E maintains 0.1 A rating for both AC and DC loads across its full operating range.

What is the input LED forward voltage specification for the ASSR-4128-502E at 5 mA drive current?

The ASSR-4128-502E has a typical forward voltage of 1.3 V at 5 mA input current (min 1.1 V, max 1.6 V per AV02-0218EN Table on page 9). This allows direct interfacing with 3.3 V or 5 V logic outputs using a simple current-limiting resistor - e.g., 680 Ω for 5 V supply yields ~5.5 mA drive.

How does the ASSR-4128-502E achieve 3750 VRMS isolation without external barriers?

The ASSR-4128-502E achieves 3750 VRMS isolation via internal molded plastic insulation separating input (pins 1–4) and output (pins 5–8) die stacks, validated per UL1577. Its minimum creepage (7.4 mm) and clearance (7.1 mm) distances are built into the DIP-8 gull-wing package geometry - eliminating need for slotting, conformal coating, or spacing adjustments on the PCB.

Can the ASSR-4128-502E replace two separate ASSR-4118-503E relays in a design?

Yes - the ASSR-4128-502E integrates two independent SPST switches in one package, matching the combined functionality of two ASSR-4118-503E units. It shares identical input characteristics (3 mA turn-on, 0.8 V turn-off) and output specs (400 V, 0.1 A, 25 Ω R(ON)), while reducing footprint by ~40% and eliminating inter-device timing skew in synchronized switching applications.