C122F1G Equivalent & Substitute Parts

Part Overview

The C122F1G is a Silicon Controlled Rectifier (SCR) manufactured by Littelfuse Inc., rated for 50V off-state voltage and 8A RMS on-state current in a TO-220AB through-hole package. This component is Active status and ROHS3 compliant. Substitute parts are identified when equivalent functional performance is required within the constraints of application voltage and current specifications, or when the primary part becomes unavailable.

Key Parameters

Parameter	C122F1G
Voltage - Off State	50 V
Voltage - Gate Trigger (Vgt) (Max)	1.5 V
Current - Gate Trigger (Igt) (Max)	25 mA
Voltage - On State (Vtm) (Max)	1.83 V
Current - On State (It (RMS)) (Max)	8 A
Current - Hold (Ih) (Max)	30 mA
Current - Off State (Max)	10 µA
Current - Non Rep. Surge 50, 60Hz (Itsm)	90A @ 60Hz
Operating Temperature	-40°C ~ 125°C
Mounting Type	Through Hole
Package / Case	TO-220-3
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the C122F1G SCR are identified based on the following criteria:

Critical Parameters for Substitution:

SCR Type: Standard Recovery (all substitutes must match)
Mounting Type: Through Hole (all substitutes must match)
Package / Case: TO-220-3 (all substitutes must match)
Current - On State (It (RMS)) (Max): 8 A (all substitutes must match or exceed)
Operating Temperature Range: -40°C ~ 125°C (all substitutes must match or exceed)
RoHS Status: ROHS3 Compliant (all substitutes must match)

Voltage Rating Consideration: Substitute parts may have higher off-state voltage ratings than the C122F1G (50V). A higher voltage rating does not prevent substitution in applications designed for lower voltages, as the component will operate within its safe operating area. However, substitution with lower voltage ratings is not permitted.

Gate Trigger Parameters: Gate trigger voltage and current specifications must be compatible with the application's gate drive circuit. Variations within the provided specifications are acceptable.

Parameter Comparison

Parameter	C122F1G	S4008RTP	TYN608RG
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	STMicroelectronics
Voltage - Off State	50 V	400 V	600 V
Voltage - Gate Trigger (Vgt) (Max)	1.5 V	1.5 V	1.3 V
Current - Gate Trigger (Igt) (Max)	25 mA	15 mA	15 mA
Voltage - On State (Vtm) (Max)	1.83 V	1.6 V	1.6 V
Current - On State (It (RMS)) (Max)	8 A	8 A	8 A
Current - Hold (Ih) (Max)	30 mA	30 mA	30 mA
Current - Off State (Max)	10 µA	10 µA	5 µA
SCR Type	Standard Recovery	Standard Recovery	Standard Recovery
Operating Temperature	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	TO-220-3	TO-220-3	TO-220-3
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Both S4008RTP and TYN608RG are valid substitutes for the C122F1G based on compliance and product status criteria.

S4008RTP (Littelfuse Inc.): This substitute maintains manufacturer continuity with the primary part. It provides 400V off-state voltage rating, higher than the C122F1G, and is suitable for applications where the C122F1G is specified but higher voltage margin is acceptable. Gate trigger current is reduced to 15 mA, which may require gate drive circuit verification. Product status is Active with ROHS3 compliance.

TYN608RG (STMicroelectronics): This substitute provides 600V off-state voltage rating and is manufactured by an alternative qualified supplier. Gate trigger voltage is lower at 1.3V maximum, and off-state leakage current is reduced to 5 µA. Product status is Active with ROHS3 compliance. This part introduces a manufacturer change and should be evaluated for supply chain and qualification requirements.

Selection between substitutes depends on application voltage requirements, gate drive circuit compatibility, and supplier qualification status.

Frequently Asked Questions (FAQ)

Q: Can the C122F1G be replaced with a lower voltage-rated SCR? A: No. Substitute parts must maintain or exceed the 8A RMS current rating and operating temperature range. Lower voltage ratings are not acceptable substitutes.

Q: Are the S4008RTP and TYN608RG interchangeable with the C122F1G? A: Both parts meet the core substitution criteria: Standard Recovery SCR type, TO-220-3 package, 8A RMS current rating, -40°C to 125°C operating temperature, and ROHS3 compliance. However, the higher voltage ratings (400V and 600V respectively) and different gate trigger parameters require verification that the application circuit can accommodate these specifications.

Q: What is the impact of higher off-state voltage ratings? A: Higher voltage ratings do not negatively impact operation in lower-voltage applications. The component will function within its safe operating area. However, the application circuit design must be verified to ensure compatibility with the substitute part's electrical characteristics.

Q: Does the TO-220AB packaging differ from TO-220AB-R or TO-220? A: All three variants (TO-220AB, TO-220AB-R, TO-220) are classified as TO-220-3 package type and are mechanically compatible for through-hole mounting. Packaging designation variations reflect supplier or manufacturing process differences but do not affect functional interchangeability.

Q: What should be verified before implementing a substitute part? A: Gate trigger voltage and current specifications must be compatible with the application's gate drive circuit. Off-state voltage rating must be adequate for the application. Thermal management and PCB layout should be re-evaluated if switching to a different manufacturer.

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