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FODM121R2 Optoisolator Equivalent & Substitute Parts
Part Overview
The FODM121R2 is an optoisolator with transistor output manufactured by onsemi, rated for 3750Vrms isolation voltage. This single-channel device operates in the DC input category with a 4-SMD gull wing package configuration. The part is currently in active production status with 7600 units in stock inventory.
Equivalent and substitute parts are identified when design requirements permit package format changes, manufacturer substitution, or when supply constraints necessitate alternative sourcing while maintaining electrical performance within specified operating parameters.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Isolation Voltage | 3750Vrms |
| Number of Channels | 1 |
| Output Type | Transistor |
| Input Type | DC |
| Current Transfer Ratio (Min) | 50% @ 5mA |
| Current Transfer Ratio (Max) | 600% @ 5mA |
| Voltage - Output (Max) | 80V |
| Current - Output / Channel | 80mA |
| Vce Saturation (Max) | 400mV |
| Operating Temperature Range | -40°C ~ 110°C |
| Mounting Type | Surface Mount |
| RoHS Status | ROHS3 Compliant |
| Moisture Sensitivity Level | 1 (Unlimited) |
Substitute Part Grouping Explanation
Substitution eligibility is determined by the following core parameters:
- Isolation voltage rating of 3750Vrms
- Single-channel transistor output configuration
- DC input type
- Current transfer ratio range compatibility
- Maximum output voltage of 80V
- Surface mount mounting type
- ROHS3 compliance and MSL 1 rating
Parts are grouped into two categories:
Parametric Equivalents maintain identical electrical specifications and base product number (FODM121 series), with variations limited to packaging format or manufacturer revision codes.
Similar Alternatives share the core isolation voltage, channel count, output type, and input type, but may exhibit variations in current transfer ratio ranges, output current capacity, saturation voltage, or operating temperature limits. These parts require design review when package format differs from the primary specification.
Parameter Comparison
| Part Number | Manufacturer | Isolation Voltage | CTR Min @ 5mA | CTR Max @ 5mA | Output Current | Vce Sat (Max) | Temp Range | Package | Inventory |
|---|---|---|---|---|---|---|---|---|---|
| FODM121R2 | onsemi | 3750Vrms | 50% | 600% | 80mA | 400mV | -40°C ~ 110°C | 4-SMD | 7600 |
| FODM121GR4 | onsemi | 3750Vrms | 50% | 600% | 80mA | 400mV | -40°C ~ 110°C | 4-SMD | 2964 |
| FODM121R2V | onsemi | 3750Vrms | 50% | 600% | 80mA | 400mV | -40°C ~ 110°C | 4-SMD | 23300 |
| EL357N(C)(TA)-VG | Everlight Electronics | 3750Vrms | 200% | 400% | 50mA | 200mV | -55°C ~ 110°C | 4-SOP | 39180 |
| EL357N-G | Everlight Electronics | 3750Vrms | 50% | 600% | 50mA | 200mV | -55°C ~ 110°C | 4-SOP | 1320 |
| HCPL-181-000E | Broadcom Limited | 3750Vrms | 50% | 600% | 50mA | 200mV | -55°C ~ 100°C | 4-SOIC | 47300 |
| HCPL-181-00AE | Broadcom Limited | 3750Vrms | 80% | 160% | 50mA | 200mV | -55°C ~ 100°C | 4-Mini-Flat | 1607 |
| HCPL-181-00BE | Broadcom Limited | 3750Vrms | 130% | 260% | 50mA | 200mV | -55°C ~ 100°C | 4-Mini-Flat | 103100 |
| HCPL-181-00CE | Broadcom Limited | 3750Vrms | 200% | 400% | 50mA | 200mV | -55°C ~ 100°C | 4-Mini-Flat | 1174 |
| HCPL-181-00DE | Broadcom Limited | 3750Vrms | 300% | 600% | 50mA | 200mV | -55°C ~ 100°C | 4-Mini-Flat | 44400 |
| HCPL-181-060E | Broadcom Limited | 3750Vrms | 50% | 600% | 50mA | 200mV | -55°C ~ 100°C | 4-Mini-Flat | 3230 |
Engineering Selection Recommendations
Direct Parametric Equivalents (Recommended for Pin-Compatible Replacement)
FODM121GR4 and FODM121R2V are direct parametric equivalents sharing identical electrical specifications and 4-SMD package format. Both maintain the 80mA output current and 400mV saturation voltage of the primary part. FODM121R2V offers significantly higher inventory availability (23300 units) compared to FODM121GR4 (2964 units). All three onsemi variants are ROHS3 compliant with MSL 1 rating and active product status.
Alternative Manufacturers with Package Format Change
Broadcom HCPL-181 series and Everlight EL357 series provide 3750Vrms isolation with transistor output in alternative package formats (4-SOIC, 4-Mini-Flat, 4-SOP). These alternatives reduce output current capacity to 50mA and lower saturation voltage to 200mV. Operating temperature ranges extend to -55°C minimum for Everlight and Broadcom parts, compared to -40°C for onsemi. All alternatives maintain ROHS3 compliance and MSL 1 rating.
Current Transfer Ratio Considerations
The FODM121R2 specifies 50% to 600% CTR at 5mA. Broadcom HCPL-181-00AE exhibits narrower CTR range (80% to 160%), limiting its use to applications tolerant of higher minimum gain. HCPL-181-00BE (130% to 260%) and HCPL-181-00CE (200% to 400%) provide intermediate CTR ranges. HCPL-181-000E, HCPL-181-060E, EL357N-G, and EL357N(C)(TA)-VG maintain the full 50% to 600% CTR specification.
Temperature Range Limitations
Applications requiring operation below -40°C must select Everlight EL357 or Broadcom HCPL-181 series, which specify -55°C minimum. Applications limited to -55°C to 100°C maximum must avoid FODM121R2 and select Broadcom alternatives. Everlight EL357 series extends to 110°C maximum, matching onsemi specifications.
Frequently Asked Questions (FAQ)
Q: Can FODM121R2 be replaced with FODM121GR4 or FODM121R2V without circuit modification?
A: Yes. FODM121GR4 and FODM121R2V are parametric equivalents with identical electrical specifications and 4-SMD package pinout. No circuit modification is required. FODM121R2V is preferred due to higher inventory availability.
Q: What is the primary limitation when substituting with Broadcom HCPL-181 or Everlight EL357 series?
A: Package format changes from 4-SMD to 4-SOIC, 4-Mini-Flat, or 4-SOP require PCB layout modification and potential footprint redesign. Output current capacity reduces from 80mA to 50mA, requiring circuit current budget review. Saturation voltage improves from 400mV to 200mV.
Q: Which substitute part offers the highest inventory availability?
A: Broadcom HCPL-181-00BE provides 103100 units in stock, the highest among all listed alternatives. This part specifies 130% to 260% CTR at 5mA and 4-Mini-Flat package format.
Q: Are all substitute parts ROHS3 compliant?
A: Yes. All listed parts maintain ROHS3 compliance and MSL 1 (Unlimited) moisture sensitivity rating. All parts are active production status with current availability.
Q: Can HCPL-181-00AE be used in applications requiring full 50% to 600% current transfer ratio range?
A: No. HCPL-181-00AE specifies 80% to 160% CTR at 5mA, which does not cover the full 50% to 600% range. Applications requiring the complete CTR specification must select HCPL-181-000E, HCPL-181-060E, EL357N-G, or EL357N(C)(TA)-VG.
Q: What is the temperature range difference between onsemi and alternative manufacturers?
A: onsemi FODM121 series operates -40°C to 110°C. Broadcom HCPL-181 series operates -55°C to 100°C. Everlight EL357 series operates -55°C to 110°C. Applications requiring -55°C minimum must use Broadcom or Everlight alternatives.
Q: Is the 4-Mini-Flat package compatible with 4-SMD footprints?
A: No. 4-Mini-Flat and 4-SMD are distinct package formats requiring separate PCB footprints. Layout redesign is necessary when transitioning between these formats.
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