ISO643x/ISO643x-Q1 Triple-Channel Digital Isolators

Introduction

Texas Instruments’ ISO643x and ISO643x-Q1 are triple-channel digital isolators designed to transfer CMOS or LVCMOS signals across galvanic isolation barriers. Each channel combines a logic input and output buffer separated by a silicon-dioxide (SiO₂) insulation barrier, providing isolation while supporting digital interfaces operating at up to 150 Mbps.

The family is notable for combining three isolated channels with isolation ratings up to 5000 VRMS, working voltage capability up to 1061 VRMS and 1500 VDC, and common-mode transient immunity up to ±200 kV/µs. ISO643x-Q1 variants add AEC-Q100 qualification for automotive applications.

What it does

The ISO643x family provides isolated digital signal paths between circuits that require separate electrical domains. It is intended for general-purpose digital isolation of CMOS and LVCMOS I/O, with three channels available in each device.

Devices operate from supplies between 2.25 V and 5.5 V and support ambient temperatures from -40°C to +125°C. Maximum propagation delay is specified as 10 ns at 5 V or 12 ns at 3.3 V, while maximum pulse-width distortion is 1.8 ns at 5 V and 2.2 ns at 3.3 V, respectively.

For serial communications, the family supports SPI operation up to 25 MHz with a 5 V supply and up to 20.8 MHz at 3.3 V. Default-high and default-low output options are available, allowing designers to select the intended output state for an input-side power-loss or unpowered condition.

Applications

Potential uses that follow directly from the devices’ isolated digital-channel architecture include:

• Isolating three CMOS or LVCMOS control and status signals between separate electrical domains
• SPI links requiring isolated clock, data, and control paths
• Digital interfaces in systems operating from 2.25 V, 3.3 V, or 5 V logic supplies
• Automotive electronic systems using AEC-Q100-qualified ISO643x-Q1 variants
• Digital control circuitry exposed to substantial common-mode voltage transients

Design considerations

The three-channel configuration should be matched to the required signal direction and the selected default-output behavior. Designers should also account for the specified propagation delay and pulse-width distortion, particularly where timing margins are tight or SPI timing is used near the stated operating limits.

Supply voltage affects the specified timing and SPI capability: the listed maximum SPI rate is 25 MHz at 5 V and 20.8 MHz at 3.3 V. The device family supports a 2.25 V to 5.5 V supply range, but timing requirements should be evaluated for the selected operating voltage.

Package selection is also an integration consideration. The family is offered in Wide-SSOP (DFP-16) and SSOP (DBQ-16) packages. Isolation, working-voltage, and surge requirements should be considered alongside the package option and the system’s intended electrical environment.

Availability and further information

The source/distributor and datasheet links on this page provide further information on the ISO643x and ISO643x-Q1 triple-channel digital isolator family, including individual device variants and technical documentation.