HCPL2731SD Equivalent & Substitute Parts

Part Overview

The HCPL2731SD is a 2-channel optoisolator with Darlington output manufactured by onsemi, rated for 2500Vrms isolation voltage. This component is classified as obsolete, which necessitates identification of equivalent and substitute parts for ongoing design support and procurement continuity. The HCPL2731SD operates as a DC input optoisolator with dual Darlington output stages, suitable for applications requiring galvanic isolation in industrial and consumer electronics.

Key Parameters

Parameter	HCPL2731SD Value
Number of Channels	2
Voltage - Isolation	2500Vrms
Current Transfer Ratio (Min)	500% @ 1.6mA
Output Type	Darlington
Voltage - Output (Max)	18V
Current - Output / Channel	60mA
Voltage - Forward (Vf) (Typ)	1.3V
Current - DC Forward (If) (Max)	20mA
Operating Temperature	-40°C ~ 85°C
Package / Case	8-SMD, Gull Wing
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the HCPL2731SD is determined by the following critical parameters: number of channels (2), output type (Darlington), maximum output voltage (18V), output current per channel (60mA), input type (DC), and package configuration (8-SMD, Gull Wing). Substitute parts must maintain these core electrical and mechanical specifications to ensure functional compatibility.

The identified substitute parts fall into two categories based on isolation voltage rating:

Category 1: Enhanced Isolation Voltage (3750Vrms) Parts HCPL-2731#300, HCPL-2731#500, HCPL-273L-500E, HCPL-4731#300, HCPL-4731-300E, and HCPL-4731-500E provide higher isolation voltage than the original HCPL2731SD, offering improved safety margins in high-voltage isolation applications.

Category 2: Maximum Isolation Voltage (5000Vrms) Parts HCPL-4731-320E and HCPL-4731-520E provide the highest isolation voltage rating, suitable for applications requiring maximum galvanic separation.

All substitute parts maintain the 2-channel Darlington output configuration, 60mA per-channel output current, and 8-SMD Gull Wing package format.

Parameter Comparison

Parameter	HCPL2731SD	HCPL-2731#300	HCPL-2731#500	HCPL-273L-500E	HCPL-4731#300	HCPL-4731-300E	HCPL-4731-320E	HCPL-4731-500E	HCPL-4731-520E
Manufacturer	onsemi	Broadcom Limited	Broadcom Limited	Broadcom Limited	Broadcom Limited	Broadcom Limited	Broadcom Limited	Broadcom Limited	Broadcom Limited
Number of Channels	2	2	2	2	2	2	2	2	2
Voltage - Isolation	2500Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms	5000Vrms	3750Vrms	5000Vrms
Current Transfer Ratio (Min)	500% @ 1.6mA	500% @ 1.6mA	500% @ 1.6mA	300% @ 1.6mA	600% @ 500µA	600% @ 500µA	600% @ 500µA	600% @ 500µA	600% @ 500µA
Output Type	Darlington	Darlington	Darlington	Darlington	Darlington	Darlington	Darlington	Darlington	Darlington
Voltage - Output (Max)	18V	18V	18V	7V	18V	18V	18V	18V	18V
Current - Output / Channel	60mA	60mA	60mA	60mA	60mA	60mA	60mA	60mA	60mA
Voltage - Forward (Vf) (Typ)	1.3V	1.4V	1.4V	1.5V	1.25V	1.25V	1.25V	1.25V	1.25V
Current - DC Forward (If) (Max)	20mA	12mA	12mA	20mA	10mA	10mA	10mA	10mA	10mA
Operating Temperature	-40°C ~ 85°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C	0°C ~ 70°C
Package / Case	8-SMD, Gull Wing	8-SMD, Gull Wing	8-SMD, Gull Wing	8-SMD, Gull Wing	8-SMD, Gull Wing	8-SMD, Gull Wing	8-SMD, Gull Wing	8-SMD, Gull Wing	8-SMD, Gull Wing
RoHS Status	ROHS3 Compliant	RoHS non-compliant	RoHS non-compliant	ROHS3 Compliant	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active

Engineering Selection Recommendations

Direct Functional Equivalents (Preferred for Retrofit)

HCPL-2731#300 and HCPL-2731#500 are direct functional equivalents of the HCPL2731SD, maintaining identical channel count, output type, maximum output voltage, and per-channel current specifications. Both parts are manufactured by Broadcom Limited and carry active product status. However, both are RoHS non-compliant, which may present procurement constraints in regulated markets. These parts provide 50% higher isolation voltage (3750Vrms vs. 2500Vrms), offering improved safety margins without circuit modification.

Enhanced Performance Alternatives (Higher Current Transfer Ratio)

HCPL-4731#300, HCPL-4731-300E, HCPL-4731-500E, HCPL-4731-320E, and HCPL-4731-520E offer superior current transfer ratio specifications (600% minimum @ 500µA vs. 500% @ 1.6mA), enabling operation with lower input drive currents. These parts maintain the 2-channel Darlington output configuration and 60mA per-channel current rating. HCPL-4731-300E, HCPL-4731-320E, HCPL-4731-500E, and HCPL-4731-520E are ROHS3 compliant, supporting regulatory compliance requirements. HCPL-4731-320E and HCPL-4731-520E provide maximum isolation voltage at 5000Vrms.

Constrained Voltage Application Alternative

HCPL-273L-500E is suitable only for applications where maximum output voltage of 7V is acceptable, as it is rated for 7V maximum output versus 18V for the HCPL2731SD. This part is ROHS3 compliant and carries active product status.

Temperature Range Consideration

All substitute parts operate within 0°C to 70°C, which is narrower than the HCPL2731SD range of -40°C to 85°C. Applications requiring extended low-temperature operation below 0°C or high-temperature operation above 70°C cannot use these substitutes without thermal management modifications.

Frequently Asked Questions (FAQ)

Q: Can HCPL-2731#300 or HCPL-2731#500 be used as direct replacements for HCPL2731SD?

A: Yes, both parts maintain identical electrical specifications for channel count, output type, maximum output voltage, and per-channel current. The primary differences are higher isolation voltage (3750Vrms vs. 2500Vrms), narrower operating temperature range (0°C to 70°C vs. -40°C to 85°C), and RoHS non-compliance status. Circuit-level compatibility is maintained without modification.

Q: What is the advantage of HCPL-4731 series parts over HCPL-2731 equivalents?

A: HCPL-4731 series parts feature higher current transfer ratio (600% minimum @ 500µA) compared to HCPL-2731 series (500% @ 1.6mA), allowing operation with reduced input drive current. This reduces input LED power dissipation and improves noise immunity in low-signal applications. Output specifications remain identical.

Q: Are all substitute parts ROHS3 compliant?

A: No. HCPL-2731#300 and HCPL-2731#500 are RoHS non-compliant. HCPL-273L-500E, HCPL-4731-300E, HCPL-4731-320E, HCPL-4731-500E, and HCPL-4731-520E are ROHS3 compliant. HCPL-4731#300 is RoHS non-compliant. Compliance requirements should be verified against procurement specifications.

Q: Can HCPL-273L-500E be used in applications requiring 18V output?

A: No. HCPL-273L-500E is rated for maximum output voltage of 7V, making it unsuitable for circuits designed for 18V output operation. This part is restricted to applications with output voltage requirements of 7V or lower.

Q: What is the impact of operating temperature range differences?

A: The HCPL2731SD operates from -40°C to 85°C, while all substitute parts operate from 0°C to 70°C. Applications requiring operation below 0°C or above 70°C cannot use these substitutes without external thermal management or circuit redesign to maintain component temperature within specified limits.

Q: Do all parts use the same 8-SMD Gull Wing package?

A: Yes. All substitute parts maintain the 8-SMD Gull Wing package configuration, ensuring PCB footprint and reflow soldering process compatibility with the HCPL2731SD.

Q: What isolation voltage should be selected for new designs?

A: Selection depends on application requirements. HCPL-2731#300 and HCPL-2731#500 provide 3750Vrms isolation. HCPL-4731-320E and HCPL-4731-520E provide maximum isolation at 5000Vrms. Higher isolation voltage provides greater safety margin but does not affect circuit functionality if the original 2500Vrms specification is adequate.

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