ISO721DG4 General Purpose Digital Isolator Equivalent & Substitute Parts

Part Overview

The ISO721DG4 is a general purpose digital isolator manufactured by Texas Instruments, featuring 2500Vrms isolation voltage, 1 channel unidirectional configuration, and 100Mbps data rate in an 8-SOIC surface mount package. This part is classified as Obsolete, necessitating identification of equivalent and substitute components for ongoing design support and procurement continuity. The device utilizes capacitive coupling technology and operates across the -40°C to 125°C temperature range with 3V to 5.5V supply voltage compatibility.

Key Parameters

Parameter	ISO721DG4 Value
Manufacturer	Texas Instruments
Technology	Capacitive Coupling
Type	General Purpose
Number of Channels	1
Channel Type	Unidirectional
Voltage - Isolation	2500Vrms
Common Mode Transient Immunity (Min)	25kV/µs
Data Rate	100Mbps
Propagation Delay tpLH / tpHL (Max)	24ns / 24ns
Pulse Width Distortion (Max)	2ns
Voltage - Supply	3V ~ 5.5V
Operating Temperature	-40°C ~ 125°C
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the ISO721DG4 is determined by strict parameter matching across the following critical criteria:

Primary Substitution Parameters:

Isolation voltage: 2500Vrms minimum
Channel configuration: 1 channel, unidirectional
Package type: 8-SOIC (0.154", 3.90mm Width)
Data rate: 100Mbps or higher
Supply voltage range: 3V ~ 5.5V compatible
Operating temperature: -40°C ~ 125°C
Technology: Capacitive coupling

Substitute Categories:

Category 1 - Texas Instruments Direct Equivalents (Same Base Product ISO721): ISO721D and ISO721DR maintain identical electrical specifications and package configuration. These parts differ only in product status and packaging format (Tube vs. Tape & Reel), making them direct functional replacements.

Category 2 - Texas Instruments Parametric Equivalent (ISO722D): ISO722D shares all critical electrical parameters with ISO721DG4 but carries a different base product number. Parametric equivalence is confirmed through matching isolation voltage, channel count, data rate, and package specifications.

Category 3 - Skyworks Solutions Alternatives (SI8610 Series): SI8610AB-B-IS, SI8610AB-B-ISR, and SI8610BB-B-ISR provide functional substitution with modified performance characteristics. These parts maintain 2500Vrms isolation, 1-channel unidirectional configuration, and 8-SOIC packaging. Data rate variations (1Mbps to 150Mbps) and CMTI differences (35kV/µs vs. 25kV/µs) represent performance enhancements suitable for applications requiring higher speed operation.

Category 4 - Enhanced Isolation Voltage Alternatives: SI8610EC-B-ISR provides 3750Vrms isolation with 150Mbps data rate, offering increased isolation margin while maintaining package and channel compatibility.

Category 5 - Higher Isolation Voltage Alternative: SI8710CD-B-ISR delivers 5000Vrms isolation but operates at 1Mbps data rate and requires 6-SOIC packaging, representing a trade-off between isolation performance and package footprint.

Parameter Comparison

Part Number	Manufacturer	Isolation Voltage	Data Rate	CMTI (Min)	Package	Supply Voltage	Propagation Delay (Max)	Product Status
ISO721DG4	Texas Instruments	2500Vrms	100Mbps	25kV/µs	8-SOIC	3V ~ 5.5V	24ns	Obsolete
ISO721D	Texas Instruments	2500Vrms	100Mbps	25kV/µs	8-SOIC	3V ~ 5.5V	24ns	Last Time Buy
ISO721DR	Texas Instruments	2500Vrms	100Mbps	25kV/µs	8-SOIC	3V ~ 5.5V	24ns	Active
ISO722D	Texas Instruments	2500Vrms	100Mbps	25kV/µs	8-SOIC	3V ~ 5.5V	24ns	Last Time Buy
SI8610AB-B-IS	Skyworks Solutions	2500Vrms	1Mbps	35kV/µs	8-SOIC	2.5V ~ 5.5V	35ns	Active
SI8610AB-B-ISR	Skyworks Solutions	2500Vrms	1Mbps	35kV/µs	8-SOIC	2.5V ~ 5.5V	35ns	Active
SI8610BB-B-ISR	Skyworks Solutions	2500Vrms	150Mbps	35kV/µs	8-SOIC	2.5V ~ 5.5V	13ns	Active
SI8610EC-B-ISR	Skyworks Solutions	3750Vrms	150Mbps	35kV/µs	8-SOIC	2.5V ~ 5.5V	13ns	Active
SI8710CD-B-ISR	Skyworks Solutions	5000Vrms	1Mbps	20kV/µs	6-SOIC	3V ~ 30V	60ns	Active
SI8715BC-A-IS	Skyworks Solutions	3750Vrms	15Mbps	35kV/µs	8-SOIC	2.5V ~ 5.5V	50ns	Active
SI8717BC-A-IS	Skyworks Solutions	3750Vrms	15Mbps	35kV/µs	8-SOIC	2.5V ~ 5.5V	50ns	Active

Engineering Selection Recommendations

Primary Recommendation - ISO721DR: ISO721DR is the preferred substitute for ISO721DG4. This Texas Instruments part maintains complete electrical and mechanical compatibility with identical specifications across all critical parameters. ISO721DR carries Active product status with 25,100 units in stock, ensuring long-term availability. Packaging format is Tape & Reel (TR), standard for high-volume production environments. RoHS3 compliance and MSL 1 rating match the original part exactly.

Secondary Recommendation - ISO721D: ISO721D provides identical electrical performance and 8-SOIC packaging in Tube format. With 5,354 units available and Last Time Buy status, this part serves as an alternative for applications where Tube packaging is acceptable. Electrical specifications remain fully compatible with ISO721DG4.

Tertiary Recommendation - ISO722D: ISO722D offers parametric equivalence with identical electrical characteristics and 8-SOIC packaging. Last Time Buy status and 5,425 units in stock support near-term procurement. This part functions as a direct substitute where base product number variation is acceptable.

Skyworks Solutions Alternatives: SI8610BB-B-ISR provides enhanced performance with 150Mbps data rate and 13ns propagation delay, suitable for applications requiring higher speed operation while maintaining 2500Vrms isolation and 8-SOIC packaging. Active product status and 8,129 units in stock ensure availability. Supply voltage range extends to 2.5V minimum, providing additional design flexibility.

SI8610EC-B-ISR offers increased isolation voltage (3750Vrms) with 150Mbps capability, appropriate for designs requiring enhanced isolation margins. Active status and 7,998 units support production requirements.

Package Constraint Consideration: SI8710CD-B-ISR requires 6-SOIC packaging, incompatible with 8-SOIC board layouts. This part is suitable only for new designs where package footprint can be modified.

Frequently Asked Questions (FAQ)

Q: Can ISO721DR directly replace ISO721DG4 in existing designs? A: Yes. ISO721DR maintains identical electrical specifications, package configuration (8-SOIC), and operating parameters. No circuit modifications are required. The only difference is product status (Active vs. Obsolete) and packaging format (Tape & Reel vs. Tube).

Q: What is the difference between ISO721D and ISO721DR? A: Both parts are electrically identical. ISO721D is supplied in Tube packaging with Last Time Buy status. ISO721DR is supplied in Tape & Reel format with Active status. Selection depends on packaging requirements and procurement timeline.

Q: Are Skyworks SI8610 series parts compatible with ISO721DG4 designs? A: SI8610AB-B-ISR and SI8610AB-B-IS maintain 2500Vrms isolation, 1-channel configuration, and 8-SOIC packaging. However, data rate is reduced to 1Mbps and propagation delay increases to 35ns. These parts are compatible only if application data rates do not exceed 1Mbps. SI8610BB-B-ISR offers 150Mbps operation, exceeding ISO721DG4 performance, and is suitable for designs requiring higher speed.

Q: What does "Last Time Buy" status mean? A: Last Time Buy indicates the manufacturer will accept orders for a limited period before discontinuing the part. Existing inventory may be available, but future procurement is not guaranteed. Parts with Active status (ISO721DR, SI8610 series) are recommended for new designs.

Q: Can SI8710CD-B-ISR replace ISO721DG4? A: SI8710CD-B-ISR provides 5000Vrms isolation but requires 6-SOIC packaging, incompatible with 8-SOIC board layouts. Data rate is limited to 1Mbps. This part is suitable only for new designs where package footprint modification is feasible and lower data rates are acceptable.

Q: What is the significance of CMTI (Common Mode Transient Immunity)? A: CMTI measures the isolator's ability to maintain signal integrity during rapid voltage transitions across the isolation barrier. ISO721DG4 specifies 25kV/µs minimum. Skyworks SI8610 series parts offer 35kV/µs, providing superior noise immunity in high-noise environments. Both values are acceptable for standard applications.

Q: Are all substitute parts RoHS3 compliant? A: Yes. ISO721D, ISO721DR, ISO722D, and all Skyworks SI8610 series parts listed carry RoHS3 compliance certification, matching ISO721DG4 environmental standards.

Q: What is the difference between SI8610AB-B-IS and SI8610AB-B-ISR? A: Both parts are electrically identical. SI8610AB-B-IS is supplied in Tube packaging. SI8610AB-B-ISR is supplied in Tape & Reel format. Selection depends on packaging requirements for assembly processes.

Q: Can I use SI8610EC-B-ISR if my design only requires 2500Vrms isolation? A: Yes. SI8610EC-B-ISR provides 3750Vrms isolation, exceeding the 2500Vrms requirement. The higher isolation voltage does not create compatibility issues and provides additional design margin. This part is suitable for applications where enhanced isolation performance is beneficial.

Q: What is MSL (Moisture Sensitivity Level) and why does it matter? A: MSL indicates the component's sensitivity to moisture absorption during storage and handling. ISO721DG4 specifies MSL 1 (Unlimited), meaning no moisture precautions are required. Skyworks SI8610 series parts specify MSL 2A (4 Weeks) or MSL 3 (168 Hours), requiring controlled storage conditions. This affects handling procedures but does not impact electrical performance.

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