HMA121A Optoisolator Equivalent & Substitute Parts

Part Overview

The HMA121A is a 3750Vrms optoisolator with transistor output manufactured by onsemi in a 4-SMD package. This component is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support. The HMA121A provides single-channel isolation suitable for DC input applications with 80V maximum output voltage and 80mA output current capability.

Key Parameters

Parameter	Value
Voltage - Isolation	3750Vrms
Number of Channels	1
Output Type	Transistor
Voltage - Output (Max)	80V
Current - Output / Channel	80mA
Current Transfer Ratio (Min)	100% @ 5mA
Current Transfer Ratio (Max)	300% @ 5mA
Input Type	DC
Operating Temperature	-40°C ~ 100°C
Mounting Type	Surface Mount
Package / Case	4-SMD, Gull Wing

Substitute Part Grouping Explanation

Substitution for the HMA121A is determined by strict equivalence across the following critical parameters:

Voltage isolation rating: 3750Vrms (mandatory match)
Single channel configuration
Transistor output topology
Maximum output voltage: 80V
DC input type
Surface mount technology

Substitute parts are grouped into two categories:

Direct Functional Equivalent: FODM121A (onsemi) maintains identical electrical specifications with active product status and extended operating temperature range (-40°C ~ 110°C). This part is the primary substitute for HMA121A applications.

Compatible Alternatives: HCPL-181 series (Broadcom), EL357ND(TA)-G (Everlight), and LTV-356T (Lite-On) meet the core isolation voltage, output type, and channel requirements. These parts feature different package configurations and current transfer ratio grades, requiring verification of specific application requirements.

Parameter Comparison

Parameter	HMA121A	FODM121A	EL357ND(TA)-G	HCPL-181-000E	HCPL-181-00BE	HCPL-181-00CE	HCPL-181-00DE	LTV-356T
Manufacturer	onsemi	onsemi	Everlight	Broadcom	Broadcom	Broadcom	Broadcom	Lite-On
Voltage - Isolation	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms	3750Vrms
Number of Channels	1	1	1	1	1	1	1	1
Output Type	Transistor	Transistor	Transistor	Transistor	Transistor	Transistor	Transistor	Transistor
Voltage - Output (Max)	80V	80V	80V	80V	80V	80V	80V	80V
Current - Output / Channel	80mA	80mA	50mA	50mA	50mA	50mA	50mA	50mA
Current Transfer Ratio (Min)	100% @ 5mA	100% @ 5mA	300% @ 5mA	50% @ 5mA	130% @ 5mA	200% @ 5mA	300% @ 5mA	50% @ 5mA
Current Transfer Ratio (Max)	300% @ 5mA	300% @ 5mA	600% @ 5mA	600% @ 5mA	260% @ 5mA	400% @ 5mA	600% @ 5mA	600% @ 5mA
Input Type	DC	DC	DC	DC	DC	DC	DC	DC
Vce Saturation (Max)	400mV	400mV	200mV	200mV	200mV	200mV	200mV	200mV
Operating Temperature	-40°C ~ 100°C	-40°C ~ 110°C	-55°C ~ 110°C	-55°C ~ 100°C	-55°C ~ 100°C	-55°C ~ 100°C	-55°C ~ 100°C	-55°C ~ 110°C
Package / Case	4-SMD, Gull Wing	4-SMD, Gull Wing	4-SMD, Gull Wing	4-SOIC (0.209", 5.30mm Width)	4-SMD, Gull Wing	4-SMD, Gull Wing	4-SMD, Gull Wing	4-SMD, Gull Wing
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Primary Substitute: FODM121A is the recommended replacement for HMA121A. This onsemi part maintains identical electrical specifications and package configuration while offering active product status and extended temperature range. FODM121A is available in tube packaging with 1496 units in stock.

Secondary Substitutes: The HCPL-181 series from Broadcom provides multiple current transfer ratio grades (HCPL-181-00BE, HCPL-181-00CE, HCPL-181-00DE) with extended temperature range (-55°C ~ 100°C) and ROHS3 compliance. These parts are available in 4-Mini-Flat package configuration with high inventory levels. HCPL-181-00CE matches the HMA121A current transfer ratio range (200% ~ 400% @ 5mA) most closely.

Alternative Options: EL357ND(TA)-G (Everlight) and LTV-356T (Lite-On) are functionally compatible with 3750Vrms isolation and transistor output. Both support extended temperature ranges and ROHS3 compliance. Note that these alternatives feature 50mA maximum output current versus the HMA121A's 80mA specification, and lower Vce saturation (200mV versus 400mV).

All substitute parts maintain REACH compliance and EAR99 export classification consistent with the original HMA121A.

Frequently Asked Questions (FAQ)

Q: Can FODM121A directly replace HMA121A in existing designs?

A: Yes. FODM121A is electrically and mechanically equivalent to HMA121A with identical isolation voltage (3750Vrms), output current (80mA), and package configuration (4-SMD, Gull Wing). The extended operating temperature range (-40°C ~ 110°C) provides additional margin over the original specification.

Q: What is the difference between HCPL-181-00BE, HCPL-181-00CE, and HCPL-181-00DE?

A: These Broadcom parts differ only in current transfer ratio grade at 5mA input current. HCPL-181-00BE specifies 130% ~ 260%, HCPL-181-00CE specifies 200% ~ 400%, and HCPL-181-00DE specifies 300% ~ 600%. All three maintain identical isolation voltage, output voltage, and saturation voltage specifications. Selection depends on the required current transfer ratio for your application.

Q: Why does EL357ND(TA)-G have lower output current (50mA) than HMA121A (80mA)?

A: EL357ND(TA)-G is a different device variant optimized for different application requirements. While it meets the 3750Vrms isolation and transistor output requirements, the 50mA output current limit must be verified against your circuit's current demands before substitution.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All active substitute parts listed (FODM121A, EL357ND(TA)-G, HCPL-181 series, and LTV-356T) are ROHS3 compliant. The original HMA121A does not specify RoHS status due to its obsolete classification.

Q: What is the difference between 4-SMD and 4-Mini-Flat packages?

A: Both are surface mount configurations with four leads. The 4-Mini-Flat package used by HCPL-181 series is a compact variant of the standard 4-SMD Gull Wing package. PCB footprint compatibility must be verified before substitution, as these packages have different physical dimensions despite similar electrical function.

Q: Can I use HCPL-181-000E as a substitute if my design requires the 4-SOIC package?

A: HCPL-181-000E uses a 4-SOIC (0.209", 5.30mm Width) package, which differs from the HMA121A's 4-SMD Gull Wing configuration. This substitution requires PCB redesign and is not a direct mechanical replacement. Other HCPL-181 variants maintain the 4-SMD Gull Wing package for direct substitution.

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