Texas Instruments ISO7321CD

Overview

ISO7321CD from Texas Instruments is a dual-channel capacitive digital isolator with opposite-direction channel configuration (input→output on Channel A, output←input on Channel B), 3000 VRMS isolation rating, 25 Mbps signaling rate, and integrated noise filtering for industrial bus interfaces. It operates across 3.3 V and 5 V supplies and delivers fail-safe high-level default output during input-side power loss.

For engineers reviewing the ISO7321CD datasheet, ISO7321CD pinout, ISO7321CD application, or ISO7321CD equivalent, key selection criteria include channel directionality, CMTI (65 kV/μs typical at 5 V), propagation delay (33 ns typical), supply current per channel (1.7 mA at 1 Mbps / 5 V), and SOIC-8 package compatibility with reinforced insulation requirements in motor control and isolated power systems.

Technical Context

The ISO7321CD implements a dual-capacitive isolation barrier using silicon dioxide (SiO₂), separating two independent signal paths with distinct voltage domains (VCCI/GNDI and VCCO/GNDO). Its architecture combines a high-frequency channel (100 kbps–25 Mbps) for data transmission and a low-frequency PWM-modulated channel for DC–100 kbps signals, enabling robust operation across wide data-rate ranges without external components.

Each channel features TTL-compatible input thresholds (VIH = 2 V min, VIL = 0.8 V max), hysteresis (460 mV typ), and failsafe logic that forces outputs high when VCCI drops below 2.1 V-critical for safe shutdown in servo drives and battery management systems requiring deterministic state behavior during fault conditions.

Key Specifications

Pinout & Package

Narrow-body SOIC-8 package with creepage/clearance ≥4 mm and CTI ≥400 V per DIN EN 60112, supporting reinforced insulation per IEC 61010-1 and UL 1577.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISO7321FC and ADUM1201BRZ, the ISO7321CD provides superior transient rejection (65 kV/μs vs. 25 kV/μs) and deterministic high-default fail-safe behavior-making it optimal for motor control and high-noise industrial automation where output state predictability during fault conditions is mandatory.

Availability

ISO7321CD is available at Aetrix Electronics and suitable for industrial fieldbus nodes, servo motor controllers, isolated DC-DC feedback loops, and battery management systems requiring stable component supply with long-term lifecycle support.

Supply support for ISO7321CD 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

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in isolation, power management, and signal chain solutions.

The ISO732x family was designed specifically for robust industrial communication and control applications demanding high CMTI, long isolation lifetime (>25 years), and fail-safe operation in harsh electromagnetic environments.

FAQ

What is the default output state of ISO7321CD during input-side power loss?

The ISO7321CD defaults to high-level output on both OUTA and OUTB when VCCI drops below 2.1 V (powered-down condition), ensuring predictable fail-safe behavior in motor control and safety-critical systems. This behavior is inherent to the 'C' suffix variant and does not require external pull-up resistors. The ISO7321CD maintains this state until VCCI recovers above the threshold, making it suitable for applications where open-circuit or floating outputs are unacceptable.

Does ISO7321CD support level translation between 3.3 V and 5 V domains?

Yes, the ISO7321CD supports independent 3.3 V or 5 V operation on each side: VCCI can be 3.3 V while VCCO is 5 V (or vice versa), enabling seamless interfacing between low-voltage microcontrollers and higher-voltage peripherals. Input thresholds remain TTL-compatible across both supply ranges, and output drive strength (VOH/VOL) meets specifications at both voltages-eliminating need for discrete level-shifting circuitry in isolated communication links.

What is the maximum data rate supported by ISO7321CD?

The ISO7321CD supports a maximum signaling rate of 25 Mbps under recommended operating conditions (VCCI/VCCO = 5 V ±10%, TA = 25°C). At 3.3 V supplies, the rated speed remains 25 Mbps, though propagation delay increases slightly to 37 ns typical. This bandwidth accommodates high-speed industrial protocols such as ProfiBus DP, CAN FD physical layer interfaces, and real-time encoder feedback in servo systems without data loss or jitter accumulation.

How does ISO7321CD handle noise on its input pins?

The ISO7321CD incorporates an integrated input noise filter that suppresses pulses shorter than 40 ns, effectively rejecting EFT bursts and switching noise common in factory-floor environments. This feature eliminates the need for external RC filters or Schmitt-trigger buffers while maintaining signal integrity. The filter operates transparently-no configuration or external components required-and preserves full 25 Mbps data throughput without introducing additional latency beyond the specified 33 ns propagation delay.

What safety certifications apply to ISO7321CD?

The ISO7321CD is certified to multiple international safety standards: UL 1577 (3000 VRMS, 1-minute), DIN V VDE V 0884-10 (4242 VPK, reinforced insulation), CSA Component Acceptance Notice 5A, IEC 60950-1, IEC 61010-1, and CQC GB4943.1-2011. These approvals validate its suitability for use in medical equipment, industrial machinery, and energy infrastructure where regulatory compliance and long-term isolation reliability are mandatory.