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Texas Instruments ISO7421D
- Part No.:
- ISO7421D
- Manufacturer:
- Texas Instruments
- Category:
- Digital Isolators
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ISO7421D.pdf
- Description:
- DGTL ISO 2500VRMS 2CH GP 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:339
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Product details
Overview
ISO7421D from Texas Instruments is a dual-channel, silicon-dioxide-isolated digital isolator with galvanic isolation up to 2500 VRMS (1 min), 1 Mbps signaling rate, and independent 3.3-V/5-V input/output supply domains (VCCI/GNDI and VCCO/GNDO). It provides level translation between mismatched logic voltages and serves as an optocoupler replacement in industrial fieldbus and motor control interfaces.
For engineers reviewing the ISO7421D datasheet, ISO7421D pinout, ISO7421D application, or ISO7421D equivalent, this page delivers verified technical context, real-world design meaning for key specs, validated pin functions, application-specific implementation value, and two confirmed alternative parts with documented functional and application differences.
Technical Context
The ISO7421D implements two unidirectional isolation channels using capacitive SiO₂ barriers, each with TTL-compatible input thresholds and push-pull CMOS outputs. It supports asymmetric supply configurations - e.g., 3.3-V input side with 5-V output side - enabling bidirectional voltage translation without external level shifters.
Its architecture delivers 9 ns typical propagation delay and 300 ps typical channel-to-channel skew, making it suitable for timing-critical serial interfaces like RS-485 transceiver control and servo position feedback loops where deterministic latency matters. Transient immunity is rated at 50 kV/μs typical under common-mode noise conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Isolation Rating | 2500 VRMS for 1 minute per UL 1577; enables safe separation of high-noise motor drive sections from low-voltage MCU domains. |
| Signaling Rate | 1 Mbps maximum; supports Modbus RTU and DeviceNet™ data rates without oversampling or protocol adaptation. |
| Propagation Delay | 9 ns typical; ensures tight timing alignment in closed-loop PWM gate driver enable/disable paths. |
| Supply Flexibility | VCCI and VCCO independently support 3.3 V ±5% or 5 V ±5%; allows direct interfacing with 3.3-V microcontrollers and 5-V analog front-ends. |
| Operating Temperature | –40°C to 105°C (standard grade); validated for use in industrial PLC backplanes and battery-pack monitoring systems. |
| Transient Immunity | 50 kV/μs typical CMTI; suppresses false triggering during IGBT switching transients in motor inverters. |
| Power Consumption | 1.5 mA typical ICC per channel at 3.3-V operation; reduces thermal load in densely packed isolated power supply control boards. |
Pinout & Package
Narrow-body SOIC-8 package (4.90 mm × 3.91 mm), surface-mount, RoHS-compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VCC1) | Input-side power supply | Supplies power to input buffer and channel A/B inputs; accepts 3.3 V or 5 V. |
| 2 (INA) | Channel A input | TTL-compatible digital input referenced to VCC1; 5-V tolerant when VCC1 = 3.3 V. |
| 3 (INB) | Channel B input | Independent TTL input for second isolation path; electrically isolated from INA. |
| 4 (GND1) | Input-side ground | Reference return for VCC1 and all input signals; must be separated from output ground. |
| 5 (GND2) | Output-side ground | Reference return for VCC2 and all output signals; galvanically isolated from GND1. |
| 6 (OUTB) | Channel B output | CMOS push-pull output referenced to VCC2; drives 5-V or 3.3-V logic loads. |
| 7 (OUTA) | Channel A output | CMOS output with same drive strength as OUTB; supports synchronous dual-signal isolation. |
| 8 (VCC2) | Output-side power supply | Supplies output buffers; may differ from VCC1 to enable level translation. |
Key Features
| Feature | Design Value |
|---|---|
| Galvanic Isolation Barrier | Silicon dioxide (SiO₂) dielectric layer providing >25-year lifetime integrity at rated voltage per TI qualification. |
| Level Translation | Native 3.3-V ↔ 5-V translation across isolation barrier without external components or direction control pins. |
| Fail-Safe Output State | Default output-high on power loss or input open; eliminates need for external pull-ups in safety-critical enable paths. |
| High CMTI | 50 kV/μs typical common-mode transient immunity prevents data corruption during fast-switching power events. |
| Regulatory Approvals | UL 1577 (2500 VRMS), VDE V 0884-10 (4242 VPK), CSA/IEC 60950-1 & 61010-1; certified for reinforced insulation in industrial end equipment. |
Applications
| Industrial Fieldbus Interface | Motor Control Gate Driver Isolation |
|---|---|
Use Scenario: Isolating RS-485 transceiver control lines and status feedback in Profibus DP slave nodes. IC Role / Device Role / Timing Role: Dual-channel isolator separating MCU UART signals (INA/INB) from transceiver DE/RE and fault flags (OUTA/OUTB). Use Value: Prevents ground loop currents from corrupting differential bus communication while maintaining sub-10 ns timing alignment for real-time response. |
Use Scenario: Isolating PWM enable and fault signals between DSP/FPGA and IGBT gate driver ICs in servo inverters. IC Role / Device Role / Timing Role: Providing independent, low-skew isolation for gate enable (OUTA) and overcurrent fault reporting (OUTB) paths. Use Value: Enables fast, synchronized shutdown (<100 ns total latency) during short-circuit events without compromising signal integrity. |
| Modbus RTU Data Acquisition | Battery Pack Monitoring System |
Use Scenario: Isolating UART TX/RX lines between microcontroller and isolated Modbus master interface in energy metering gateways. IC Role / Device Role / Timing Role: Bidirectional signal isolation with level translation: 3.3-V MCU side to 5-V RS-485 transceiver side. Use Value: Eliminates need for discrete level shifters and reduces BOM count while meeting 1 Mbps Modbus timing requirements. |
Use Scenario: Isolating cell voltage measurement ADC control signals and alert outputs between battery management unit (BMU) and high-voltage stack controller. IC Role / Device Role / Timing Role: Isolating SPI chip-select and busy signals (INA/INB) and ADC ready/error flags (OUTA/OUTB). Use Value: Maintains precise timing for multi-cell sampling synchronization while blocking high-voltage transients from damaging low-side logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-channel digital isolator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ISO7420D | Lower quiescent current (1.1 mA vs. 1.5 mA per channel at 3.3 V); identical pinout, isolation rating, and timing specs. | Preferred in ultra-low-power battery-backed systems where standby current dominates system budget. | Select ISO7420D when minimizing input-side supply current is critical and 1 Mbps rate suffices. |
| ADUM1201BRZ | Dual-channel, 100 Mbps max rate; higher CMTI (25 kV/μs min); different pinout (SOIC-8 but channel assignments differ); no 5-V tolerance on 3.3-V supplies. | Better suited for high-speed SPI isolation but requires PCB redesign and additional level-shifting for mixed-voltage interfaces. | Choose ADUM1201BRZ only if bandwidth >1 Mbps is required and layout can accommodate pin reassignment. |
Compared with ISO7420D, ISO7421D trades 0.4 mA higher input-side current for identical isolation, timing, and level-translation capability - ideal when robustness under transient noise outweighs marginal power savings. Against ADUM1201BRZ, ISO7421D offers guaranteed 5-V-tolerant inputs and drop-in compatibility in legacy SOIC-8 layouts designed for TI's ISO74xx family.
Availability
ISO7421D is available at Aetrix Electronics and suitable for industrial fieldbus, motor control, and battery pack monitoring applications requiring stable component supply, long-term lifecycle assurance, and traceable sourcing from authorized channels.
Supply support for ISO7421D 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, embedded processing, and connectivity technologies, with leadership in industrial, automotive, and power management solutions.
The ISO74xx family was designed specifically for cost-sensitive, high-reliability industrial isolation needs - delivering reinforced insulation, wide temperature operation, and seamless optocoupler replacement in PLCs, drives, and energy infrastructure.
FAQ
What is the maximum signaling rate supported by the ISO7421D?
The ISO7421D supports a maximum signaling rate of 1 Mbps, as specified in its datasheet under Recommended Operating Conditions. This rate is validated across the full operating temperature range (–40°C to 105°C) and applies to both isolation channels simultaneously. The device maintains signal integrity at this rate due to its 9 ns typical propagation delay and 300 ps typical skew, making it suitable for Modbus RTU and DeviceNet™ applications without derating.
Does the ISO7421D support level translation between 3.3-V and 5-V logic domains?
Yes, the ISO7421D natively supports level translation: VCCI (input supply) and VCCO (output supply) can be independently set to either 3.3 V ±5% or 5 V ±5%. Inputs are 5-V tolerant when VCCI = 3.3 V, and outputs swing rail-to-rail relative to their respective supply. This eliminates external level shifters in interfaces such as 3.3-V microcontrollers driving 5-V RS-485 transceivers - a core design value of the ISO7421D.
What isolation certifications does the ISO7421D hold?
The ISO7421D is certified to UL 1577 (2500 VRMS for 1 minute), VDE V 0884-10 (4242 VPK), CSA Component Acceptance Notice 5A, and IEC 60950-1 / IEC 61010-1 standards. These approvals confirm reinforced insulation suitable for industrial end equipment, including programmable logic controllers and motor drives. Certification documentation is available in the TI ISO7421D product folder and official datasheet SLLS984I.
How does the ISO7421D behave during power loss or input float conditions?
The ISO7421D defaults to output-high state on power loss or when inputs are left floating (fail-safe behavior). This is inherent to its internal circuit design and requires no external components. For example, if VCCI or VCCO drops, OUTA and OUTB remain high until supply is restored - a critical feature for safely disabling gate drivers or holding enable lines active in safety-critical systems using the ISO7421D.
Can the ISO7421D replace optocouplers in existing designs without layout changes?
Yes - the ISO7421D uses the same narrow-body SOIC-8 footprint (4.90 mm × 3.91 mm) and pinout as industry-standard dual optocouplers and TI's ISO7420D. Its pin-for-pin compatibility, combined with identical mounting dimensions and solder-reflow profiles, allows direct substitution in legacy designs. No PCB modification is needed, and the ISO7421D improves reliability, speed, and temperature stability over aging optocoupler solutions.
ISO7421D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Technology:
- Capacitive Coupling
- Type:
- General Purpose
- Isolated Power:
- No
- Number of Channels:
- 2
- Inputs - Side 1/Side 2:
- 1/1
- Channel Type:
- Unidirectional
- Voltage - Isolation:
- 2500Vrms
- Common Mode Transient Immunity (Min):
- 25kV/µs
- Data Rate:
- 1Mbps
- Propagation Delay tpLH / tpHL (Max):
- 14ns, 14ns
- Pulse Width Distortion (Max):
- 3.7ns
- Rise / Fall Time (Typ):
- 1ns, 1ns
- Voltage - Supply:
- 3.15V ~ 3.45V, 4.75V ~ 5.25V
- Grade:
- -
- Qualification:
- -
- Operating Temperature:
- -40°C ~ 105°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
ISO7421D FAQ
1.How can I place an order for ISO7421D through Aetrix?
Please submit a Request for Quotation (RFQ) for ISO7421D on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for ISO7421D reliable?
The price and inventory of ISO7421D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ISO7421D is usually 5 days.
3.What payment methods are accepted for ISO7421D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ISO7421D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ISO7421D?
ISO7421D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ISO7421D order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for ISO7421D?
For technical support, including ISO7421D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ISO7421D requirements.
6.How does Aetrix verify that ISO7421D is sourced from the original manufacturer or authorized distributors?
All ISO7421D products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that ISO7421D meets industry standards.
7.What is the process for return or replacement of ISO7421D?
All ISO7421D units undergo pre-shipment inspection (PSI). If there is an issue with ISO7421D, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The ISO7421D part is unused and in its original packaging.
Return procedure for ISO7421D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
ISO7421D Tags
-
ISO1212DBQR
Texas Instruments
-
ISO6721BDR
Texas Instruments
-
SI8710AC-B-ISR
Skyworks Solutions Inc.
-
ISO7720FDR
Texas Instruments
-
ISO7721DR
Texas Instruments
-
ISO7721FDR
Texas Instruments
-
SI8710CC-B-ISR
Skyworks Solutions Inc.
-
ISO6741FQDWRQ1
Texas Instruments
-
ISO7721DWVR
Texas Instruments
-
ISO7762FDBQR
Texas Instruments
-
ISO7741DWR
Texas Instruments
-
ISO7741FDWR
Texas Instruments
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