CS218I-50PB Equivalent & Substitute Parts

Part Overview

The CS218I-50PB is a Silicon Controlled Rectifier (SCR) rated for 1.2 kV off-state voltage with 50 A RMS on-state current capability in a TO-218-3 through-hole package. Manufactured by Central Semiconductor Corp, this component is classified as obsolete. Due to its obsolete status and limited availability from the original manufacturer, identifying equivalent substitute parts is essential for system maintenance, repair, and redesign applications where this thyristor function is required.

Key Parameters

Parameter	Value	Unit
Voltage - Off State	1.2	kV
Current - On State (It (RMS)) (Max)	50	A
Voltage - Gate Trigger (Vgt) (Max)	1.5	V
Current - Gate Trigger (Igt) (Max)	80	mA
Voltage - On State (Vtm) (Max)	1.9	V
Current - Hold (Ih) (Max)	80	mA
Operating Temperature Range	-40 to 125	°C
SCR Type	Standard Recovery	—
Mounting Type	Through Hole	—

Substitute Part Grouping Explanation

Substitution of the CS218I-50PB is determined by matching the following critical electrical and mechanical parameters:

Voltage Rating (Off State): 1.2 kV minimum
Current Rating (RMS): 50 A minimum
Gate Trigger Voltage (Vgt): 1.5 V or lower
Gate Trigger Current (Igt): 80 mA or lower
On-State Voltage (Vtm): 1.9 V or lower
Hold Current (Ih): Must be compatible with circuit requirements
SCR Type: Standard Recovery
Mounting: Through-hole configuration
Operating Temperature: -40°C to 125°C

The BTW69-1200RG meets all critical electrical specifications and maintains through-hole mounting compatibility, though in a different package form factor (TOP-3 versus TO-218-3).

Parameter Comparison

Parameter	CS218I-50PB	BTW69-1200RG	Match Status
Manufacturer	Central Semiconductor Corp	STMicroelectronics	Different
Voltage - Off State	1.2 kV	1.2 kV	Match
Current - On State (It (RMS)) (Max)	50 A	50 A	Match
Voltage - Gate Trigger (Vgt) (Max)	1.5 V	1.3 V	Compatible
Current - Gate Trigger (Igt) (Max)	80 mA	80 mA	Match
Voltage - On State (Vtm) (Max)	1.9 V	1.9 V	Match
Current - Hold (Ih) (Max)	80 mA	150 mA	Compatible
Current - Off State (Max)	20 µA	10 µA	Compatible
SCR Type	Standard Recovery	Standard Recovery	Match
Operating Temperature	-40 to 125°C	-40 to 125°C	Match
Mounting Type	Through Hole	Through Hole	Match
Package / Case	TO-218-3	TOP-3	Different
Product Status	Obsolete	Active	Substitute is Active
RoHS Status	Non-compliant	ROHS3 Compliant	Substitute is Compliant

Engineering Selection Recommendations

The BTW69-1200RG is the manufacturer-recommended substitute for the CS218I-50PB. Selection of this substitute is supported by the following factors:

Electrical Equivalence: All critical voltage and current ratings match or exceed the original part specifications.
Active Product Status: The BTW69-1200RG is an active product with current manufacturing and availability, eliminating obsolescence risk.
Regulatory Compliance: The substitute is ROHS3 compliant, whereas the original part is non-compliant. This is advantageous for new designs and systems requiring regulatory adherence.
Through-Hole Compatibility: Both parts maintain through-hole mounting, enabling direct circuit integration.
Package Consideration: The BTW69-1200RG uses a TOP-3 package instead of TO-218-3. Physical dimensions and pin configurations differ; PCB layout and mechanical mounting must be verified before implementation.

Frequently Asked Questions (FAQ)

Q: Can the BTW69-1200RG directly replace the CS218I-50PB without circuit modification?

A: Electrical substitution is valid based on matching voltage and current ratings. However, the different package form factor (TOP-3 versus TO-218-3) requires PCB layout verification and mechanical mounting adjustment. Pin configuration and thermal characteristics must be confirmed against the respective datasheets.

Q: What is the significance of the different hold current (Ih) values?

A: The BTW69-1200RG specifies a maximum hold current of 150 mA compared to 80 mA for the CS218I-50PB. This parameter defines the minimum current required to maintain SCR conduction after gate signal removal. The higher value in the substitute is compatible with applications designed for the original part, as it represents a less stringent requirement.

Q: Why is RoHS compliance important for this substitution?

A: RoHS3 compliance in the BTW69-1200RG ensures the part meets current environmental and regulatory standards for lead-free manufacturing. The original CS218I-50PB is non-compliant. For systems requiring regulatory adherence or integration into modern supply chains, the compliant substitute is preferable.

Q: Are there any thermal or reliability differences between these parts?

A: Both parts are rated for the same operating temperature range (-40°C to 125°C) and are classified as Standard Recovery SCRs. Thermal performance depends on package design and mounting method. The TOP-3 package of the substitute may have different thermal characteristics than the TO-218-3; thermal analysis specific to your application is necessary.

Q: What should be verified before implementing the BTW69-1200RG as a substitute?

A: Verify PCB footprint compatibility with the TOP-3 package, confirm pin assignment alignment, validate thermal management adequacy for the new package form, and test gate drive circuit compatibility with the slightly lower gate trigger voltage (1.3 V versus 1.5 V).

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