Skyworks Solutions Inc. SI8641BB-AU

Overview

SI8641BB-AU from Skyworks is a quad-channel digital isolator with 3 input channels on VDD1 side and 1 output channel on VDD2 side, rated for 2.5 kVRMS isolation and supporting up to 150 Mbps data rate. It features Schmitt-trigger inputs, tri-state outputs with dedicated enable control, selectable fail-safe low-default output state, and operates across –40 to 125 °C in QSOP-16 package - used in isolated motor control feedback loops and battery management system signal conditioning.

For engineers reviewing the SI8641BB-AU datasheet, SI8641BB-AU pinout, SI8641BB-AU application, or SI8641BB-AU equivalent, key selection criteria include channel asymmetry (3:1), fail-safe low default mode, 2.5 kV reinforced isolation rating, QSOP-16 footprint compatibility, and ultra-low power consumption at 100 Mbps (7.3 mA per side typical).

Technical Context

The SI8641BB-AU implements RF-based on/off keying across a silicon dioxide isolation barrier, eliminating startup initialization and enabling robust noise immunity without optical degradation. Its architecture supports independent undervoltage lockout (UVLO) on both sides, with VDDUV+ = 2.24 V (typ) and hysteresis of 70 mV (typ), ensuring clean power-up sequencing in multi-rail systems.

It integrates dual enable inputs (EN1 on VDD1 side for A4; EN2 on VDD2 side for B1–B3), allowing independent tri-state control of input and output groups. The device uses internal 2 µA pull-downs on all channels to enforce low-default behavior during power loss - confirmed by ordering code "BB" (low default) and "2.5 kV" isolation rating per Table 1.1.

Key Specifications

Pinout & Package

SI8641BB-AU is housed in a RoHS-compliant QSOP-16 package (5.3 mm × 10.2 mm, 1.0 mm height), optimized for high-density PCB layouts with 0.635 mm pitch and creepage >5.5 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital isolator applications.

Compared with ADUM1401BRWZ and ISO6741QDWR, SI8641BB-AU uniquely delivers 150 Mbps speed with 3:1 channel asymmetry and guaranteed low-default fail-safe behavior - making it optimal for next-generation motor control and automotive BMS where timing precision and power-loss safety are co-critical.

Availability

SI8641BB-AU is available at Aetrix Electronics and suitable for industrial motor drives, battery management systems, and isolated data acquisition requiring stable component supply and long-term lifecycle support.

Supply support for SI8641BB-AU 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

Skyworks Solutions is a global semiconductor company specializing in analog and mixed-signal connectivity solutions, with leadership in RF, timing, and isolation technologies.

The Si864x family was designed specifically for high-reliability industrial and automotive isolation needs - delivering ultra-low power, high-speed, and safety-certified digital signal transfer across galvanic barriers.

FAQ

What is the default output state of SI8641BB-AU during power loss on the input side?

The SI8641BB-AU has a factory-configured fail-safe low-default output mode. When VDD1 is unpowered but VDD2 remains active, all outputs (B1–B3) are actively pulled low via internal 2 µA pull-down resistors - a critical safety feature preventing unintended activation in isolated gate driver circuits. This behavior is fixed by the "BB" ordering code and does not require external components.

Does SI8641BB-AU require external bypass capacitors, and where should they be placed?

Yes, SI8641BB-AU requires a 0.1 µF ceramic bypass capacitor between VDD1 and GND1, and another between VDD2 and GND2. These must be placed within 3 mm of their respective pins to suppress high-frequency switching noise and ensure stable UVLO operation. Additional bulk capacitance (e.g., 1–10 µF tantalum) is recommended near the QSOP-16 footprint for motor drive applications with pulsed loads.

Can SI8641BB-AU operate with different supply voltages on each side, such as 3.3 V on VDD1 and 5 V on VDD2?

Yes, SI8641BB-AU supports independent supply rails: VDD1 and VDD2 each operate from 2.5 V to 5.5 V. This allows direct interfacing between 3.3 V microcontrollers (VDD1) and 5 V analog front-ends or gate drivers (VDD2) without level-shifting circuitry - verified across –40 to 125 °C per Table 4.1 operating conditions.

What is the maximum achievable data rate for SI8641BB-AU, and what layout practices support it?

SI8641BB-AU supports up to 150 Mbps per channel. To achieve this, use controlled-impedance PCB traces (50 Ω ±10%) for all B1–B3 outputs, minimize stub lengths, place series termination resistors (33–56 Ω) close to the receiver, and maintain solid ground planes beneath signal layers. Eye diagram testing per Figure 2.3 confirms integrity at full rate with <350 ps peak jitter.

Is SI8641BB-AU qualified for automotive applications, and what certifications does it hold?

No, SI8641BB-AU is an industrial-grade part (suffix "-AU" denotes automotive-compatible packaging and marking, but not full AEC-Q100 qualification). For automotive use, select SI8641BB-AU's automotive-grade counterpart SI8641BB-AU (with "-A" suffix), which undergoes full AEC-Q100 stress testing and includes AIAG PPAP documentation. SI8641BB-AU itself holds UL 1577, CSA 5A, and basic VDE 0884-10 certifications.