Skyworks Solutions Inc. SI8645BA-AU

Overview

SI8645BA-AU from Skyworks is a quad-channel, unidirectional digital isolator with 4 input channels on VDD1 side and 0 on VDD2 side, rated for 1.0 kV_RMS isolation, 150 Mbps data rate, and –40 to 125 °C operation. It features Schmitt-trigger inputs, tri-state outputs with enable control, selectable fail-safe low-default output, and ultra-low power consumption (1.6 mA/channel @ 1 Mbps, 5 V).

For engineers reviewing the SI8645BA-AU datasheet, SI8645BA-AU pinout, SI8645BA-AU application, or SI8645BA-AU equivalent, this device supports high-noise industrial motor control, isolated ADC/DAC interfaces, and automotive battery management systems where precise timing (<10 ns propagation delay), reinforced insulation compliance, and AEC-Q100 qualification are required.

Technical Context

The SI8645BA-AU implements RF-based on/off keying across a semiconductor isolation barrier-eliminating startup initialization and delivering superior CMTI (≥50 kV/µs) versus optocouplers. Its architecture provides four independent, input-side-only signal paths with no cross-side inputs.

All channels share a single enable input (EN2) on the output side, supporting synchronized tri-state control. The device operates across 2.5–5.5 V supplies on both sides, maintains stable timing over temperature (±0.5 ns channel skew), and uses internal pull-downs to enforce low-fail-safe default output during input-side power loss.

Key Specifications

Pinout & Package

SI8645BA-AU is housed in a RoHS-compliant QSOP-16 package (5.3 mm × 10.2 mm, 1.0 mm height) with 0.635 mm pitch and standard JEDEC land pattern. Creepage and clearance meet IEC 60950-1 requirements for 1.0 kV_RMS working voltage.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SI8645BA-AU, SI8645BB-AU offers higher isolation rating for safety-critical systems, while ADUM140D0BRIZ provides comparable speed and supply range but lacks automotive qualification and configurable fail-safe behavior-making SI8645BA-AU the optimal choice for AEC-Q100-compliant BMS and motor control designs requiring guaranteed low-default outputs.

Availability

SI8645BA-AU is available at Aetrix Electronics and suitable for industrial motor control, automotive battery management systems, and isolated data acquisition requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SI8645BA-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 applications demanding low power, precise timing, and robust noise immunity-enabling next-generation EV powertrains and Industry 4.0 automation systems.

FAQ

What is the isolation rating and safety certification status of SI8645BA-AU?

SI8645BA-AU is rated for 1.0 kV_RMS isolation and certified to UL 1577 (recognized), CSA Component Notice 5A, and basic VDE 0884-10. It meets IEC 60950-1 requirements but does not carry reinforced VDE 0884-10 or IEC 62368-1 certification-those apply only to higher-rated variants like SI8645BB-AU. SI8645BA-AU is AEC-Q100 Grade 1 qualified for automotive use.

Does SI8645BA-AU support bidirectional communication?

No, SI8645BA-AU is a unidirectional isolator with four input channels (A1–A4) on the VDD1 side and four corresponding output channels (B1–B4) on the VDD2 side. It does not support reverse-direction signal flow. For bidirectional isolation, consider SI8642BA-AU (2-channel bidirectional) or separate transmit/receive channel pairing.

What is the function of the EN2 pin on SI8645BA-AU?

The EN2 pin is an active-high enable input located on the VDD2 (output) side. When EN2 is high, B1–B4 outputs follow their respective A1–A4 inputs. When EN2 is low, all four outputs enter high-impedance state-enabling shared bus architectures or safe shutdown sequences. EN2 has internal pull-up and can be left floating if unused, though tying it to VDD2 is recommended in noisy environments.

How does the fail-safe low default operate during power loss on SI8645BA-AU?

When VDD1 is unpowered or drops below UVLO threshold (≈2.2 V), SI8645BA-AU's outputs B1–B4 default to logic low within 12 ns, regardless of prior input state. This behavior is hard-coded via internal 2 µA pull-down resistors on all output pins and is guaranteed across –40 to 125 °C. It ensures safe deactivation of downstream power devices during brownout conditions.

Can SI8645BA-AU operate with mismatched supply voltages on VDD1 and VDD2?

Yes, SI8645BA-AU supports independent 2.5–5.5 V supplies on VDD1 and VDD2. For example, it can interface a 3.3 V MCU (VDD1 = 3.3 V) to a 5 V FPGA I/O bank (VDD2 = 5 V) without external level shifters. Both supplies must remain within specification simultaneously; operation is not guaranteed if either supply falls outside 2.375–5.5 V range.