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CZRT55C18-G Zener Diode 18V 350mW SOT-23-3 Equivalent & Substitute Parts
Part Overview
The CZRT55C18-G is an 18V 350mW Zener diode manufactured by Comchip Technology in SOT-23-3 surface mount packaging. This component is classified as Active product status with ROHS3 compliance and unlimited moisture sensitivity level (MSL 1). The part operates across a temperature range of -65°C to 150°C with ±6% voltage tolerance. Equivalent and substitute parts are identified based on matching electrical specifications, package compatibility, and regulatory compliance to support design flexibility and supply chain continuity.
Substiute Parts
Key Parameters
| Parameter | Value | Unit |
|---|---|---|
| Voltage - Zener (Nom) | 18 | V |
| Power - Max | 350 | mW |
| Tolerance | ±6% | - |
| Impedance (Max) | 45 | Ohms |
| Current - Reverse Leakage @ Vr | 100 | nA @ 12.6V |
| Voltage - Forward (Max) @ If | 900 | mV @ 10mA |
| Operating Temperature | -65 to 150 | °C |
| Package / Case | SOT-23-3 | - |
| Mounting Type | Surface Mount | - |
| RoHS Status | ROHS3 Compliant | - |
Substitute Part Grouping Explanation
Substitute parts for the CZRT55C18-G are classified based on the following electrical and mechanical compatibility criteria:
Primary Substitution Criteria:
- Zener voltage: 18V nominal
- Package: SOT-23-3 (TO-236-3, SC-59)
- Mounting type: Surface Mount
- Operating temperature range: -65°C to 150°C minimum
- RoHS3 compliance required
Secondary Compatibility Parameters:
- Power dissipation: 300mW to 350mW acceptable
- Voltage tolerance: ±2% to ±6% acceptable
- Impedance (Max): 21 to 45 Ohms acceptable
- Reverse leakage current: 50 to 100 nA acceptable
- Forward voltage: 900mV @ 10mA maximum
Substitution Categories:
Category 1 - Direct Electrical & Mechanical Match (350mW, ±5-6% tolerance): Parts matching the original 350mW power rating with compatible tolerance specifications.
Category 2 - Reduced Power Rating (300mW, ±2-6% tolerance): Parts with 300mW maximum power dissipation, suitable where thermal constraints permit lower power ratings while maintaining electrical function.
Category 3 - Enhanced Performance (300mW, ±3% tolerance, lower impedance): Parts with tighter tolerance and lower impedance characteristics for applications requiring improved voltage regulation.
Category 4 - Automotive Grade (AEC-Q101 qualified): Parts meeting automotive qualification standards for applications requiring automotive-grade reliability.
Parameter Comparison
| Manufacturer Part Number | Manufacturer | Vz (Nom) | Power (Max) | Tolerance | Zzt (Max) | Ir @ Vr | Vf (Max) | Temp Range | Grade | Inventory |
|---|---|---|---|---|---|---|---|---|---|---|
| CZRT55C18-G | Comchip Technology | 18V | 350mW | ±6% | 45Ω | [email protected] | 900mV@10mA | -65 to 150°C | Commercial | 974 Pcs |
| BZX84B18-7-F | Diodes Incorporated | 18V | 300mW | ±2% | 45Ω | [email protected] | 900mV@10mA | -65 to 150°C | Commercial | 7535 Pcs |
| BZX84B18Q-7-F | Diodes Incorporated | 18V | 300mW | ±2% | 45Ω | [email protected] | 900mV@10mA | -65 to 150°C | Automotive | 1865 Pcs |
| BZX84C18-7-F | Diodes Incorporated | 18V | 300mW | ±6% | 45Ω | [email protected] | 900mV@10mA | -65 to 150°C | Automotive | 104300 Pcs |
| BZX84C18-TP | Micro Commercial Co | 18V | 350mW | ±5% | 45Ω | [email protected] | 900mV@10mA | -55 to 150°C | Commercial | 5563 Pcs |
| DDZX18C-13 | Diodes Incorporated | 18V | 300mW | ±3% | 23Ω | 50nA@14V | 900mV@10mA | -65 to 150°C | Commercial | 40300 Pcs |
| MMBZ5248B-7-F | Diodes Incorporated | 18V | 350mW | ±5% | 21Ω | 100nA@14V | 900mV@10mA | -65 to 150°C | Commercial | 35838 Pcs |
| MMBZ5248B-TP | Micro Commercial Co | 18V | 350mW | ±5% | 21Ω | 100nA@14V | 900mV@10mA | -55 to 150°C | Commercial | 3400 Pcs |
| MMBZ5248BQ-7-F | Diodes Incorporated | 18V | 350mW | ±5% | 21Ω | 100nA@14V | 900mV@10mA | -65 to 150°C | Automotive | 3700 Pcs |
| BZX84C18 TR PBFREE | Central Semiconductor Corp | 18V | 350mW | ±5% | 45Ω | [email protected] | 900mV@10mA | -65 to 150°C | Commercial | 27060 Pcs |
Engineering Selection Recommendations
Highest Compatibility - Direct Substitutes (350mW Power Rating):
BZX84C18-TP (Micro Commercial Co) and MMBZ5248B-7-F (Diodes Incorporated) provide direct electrical equivalence to CZRT55C18-G with matching 350mW power dissipation. Both maintain 18V nominal zener voltage, SOT-23-3 package compatibility, and ROHS3 compliance. BZX84C18-TP operates at -55°C minimum temperature versus -65°C for the original part. MMBZ5248B-7-F maintains full -65°C to 150°C operating range with lower impedance (21Ω vs 45Ω), providing improved voltage regulation characteristics.
Automotive-Grade Alternatives:
BZX84C18-7-F (Diodes Incorporated) and MMBZ5248BQ-7-F (Diodes Incorporated) both carry AEC-Q101 automotive qualification with ROHS3 compliance. BZX84C18-7-F operates at 300mW with ±6% tolerance matching the original specification tolerance. MMBZ5248BQ-7-F provides 350mW power rating with ±5% tolerance and lower impedance (21Ω), suitable for automotive applications requiring enhanced voltage regulation.
High-Availability Commercial Options:
BZX84C18-7-F maintains the largest inventory (104,300 Pcs) with ±6% tolerance matching CZRT55C18-G tolerance specification, though at reduced 300mW power rating. This part is suitable for applications where thermal constraints permit lower power dissipation. DDZX18C-13 (Diodes Incorporated) offers 40,300 Pcs inventory with enhanced performance characteristics: ±3% tolerance, 23Ω impedance, and 50nA reverse leakage current, providing superior voltage regulation for precision applications.
Parametric Equivalent:
BZX84C18 TR PBFREE (Central Semiconductor Corp) provides 27,060 Pcs inventory with 350mW power rating, ±5% tolerance, and full -65°C to 150°C operating range. This part maintains 45Ω impedance matching the original specification with reduced reverse leakage (50nA vs 100nA).
All substitute parts maintain SOT-23-3 surface mount package compatibility, ROHS3 compliance, and MSL 1 (unlimited) moisture sensitivity rating. Selection should be based on thermal design requirements (300mW vs 350mW), tolerance specifications (±2% to ±6%), and supply chain availability.
Frequently Asked Questions (FAQ)
Q: Can BZX84C18-7-F replace CZRT55C18-G in all applications?
A: BZX84C18-7-F is electrically compatible with matching 18V zener voltage, SOT-23-3 package, and -65°C to 150°C operating range. The primary difference is reduced power dissipation (300mW vs 350mW). Substitution is valid where circuit thermal design accommodates 300mW maximum power. The ±6% tolerance matches the original specification exactly.
Q: What is the difference between 300mW and 350mW power ratings?
A: Power rating indicates maximum continuous power dissipation capability. The 350mW original part permits higher current handling at the zener voltage. Substitution with 300mW parts requires verification that circuit design does not exceed 300mW dissipation under worst-case conditions. Both ratings are suitable for typical voltage regulation applications.
Q: Are automotive-grade parts (AEC-Q101) required for non-automotive applications?
A: AEC-Q101 qualification is not required for commercial applications. Automotive-grade parts (BZX84C18-7-F, BZX84B18Q-7-F, MMBZ5248BQ-7-F) provide additional reliability screening and are optional for commercial designs. Selection should be based on application requirements and supply chain strategy.
Q: What does impedance (Zzt) specification mean for zener diode selection?
A: Impedance (Zzt) represents dynamic impedance at the zener voltage and affects voltage regulation quality. Lower impedance (21Ω in MMBZ5248B-7-F vs 45Ω in CZRT55C18-G) provides better voltage regulation with reduced voltage variation across load changes. Both values are acceptable; selection depends on regulation precision requirements.
Q: Can parts with different tolerance specifications be interchanged?
A: Parts with ±2%, ±3%, ±5%, and ±6% tolerances are electrically interchangeable in the 18V zener function. Tighter tolerance parts (±2%, ±3%) provide more precise voltage regulation. Selection should match circuit tolerance requirements. All listed parts maintain 18V nominal zener voltage within their specified tolerance bands.
Q: Is the operating temperature range difference (-55°C vs -65°C minimum) significant?
A: BZX84C18-TP and MMBZ5248B-TP operate at -55°C minimum versus -65°C for other parts. Substitution is valid where application minimum operating temperature is -55°C or higher. For applications requiring -65°C operation, select parts with -65°C minimum specification.
Q: What is the significance of reverse leakage current (Ir) specification?
A: Reverse leakage current indicates leakage in the reverse-biased condition. Lower leakage (50nA in DDZX18C-13 and BZX84C18 TR PBFREE vs 100nA in CZRT55C18-G) reduces standby power consumption. Both values are acceptable; selection depends on low-power application requirements.
Q: Are all substitute parts ROHS3 compliant?
A: Yes, all listed substitute parts carry ROHS3 compliance certification matching CZRT55C18-G. All parts also maintain MSL 1 (unlimited) moisture sensitivity level and are suitable for standard PCB assembly processes without special moisture handling requirements.
Q: Which substitute offers the best inventory availability?
A: BZX84C18-7-F (Diodes Incorporated) provides the highest inventory at 104,300 Pcs. This part is suitable for high-volume production with ±6% tolerance matching the original specification, though at 300mW power rating. DDZX18C-13 offers 40,300 Pcs with enhanced performance characteristics.
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