T491X686M025AS Equivalent & Substitute Parts Reference

Part Overview

The T491X686M025AS is a 68 µF molded tantalum capacitor manufactured by KEMET, rated for 25 V operation in a 2917 (7343 Metric) surface mount package. This component is classified as obsolete product status. The part features a 700 mOhm equivalent series resistance (ESR) and operates across a temperature range of -55°C to 125°C with general purpose application characteristics.

Due to obsolete product status, direct replacement with active production equivalents is necessary for new designs and ongoing procurement. Substitute parts maintain the core electrical specifications (68 µF capacitance, 25 V rating, ±20% tolerance) while offering improved ESR performance, enhanced reliability ratings, and active manufacturing status.

Key Parameters

Parameter	Value	Unit	Substitution Relevance
Capacitance	68	µF	Critical - must match exactly
Voltage Rating	25	V	Critical - must match or exceed
Tolerance	±20%	%	Critical - defines acceptable variance
Package / Case	2917 (7343 Metric)	-	Critical - PCB footprint compatibility
Mounting Type	Surface Mount	-	Critical - assembly process compatibility
ESR	700	mOhm	Important - affects circuit performance
Operating Temperature	-55 to 125	°C	Important - thermal environment compatibility
Type	Molded	-	Important - construction and reliability
RoHS Status	ROHS3 Compliant	-	Important - regulatory compliance
MSL Rating	1 (Unlimited)	-	Important - moisture handling requirements

Substitute Part Grouping Explanation

Substitution logic for the T491X686M025AS is based on strict electrical and mechanical parameter matching within the tantalum capacitor category. All substitute parts maintain the following critical parameters:

Critical Matching Parameters:

Capacitance: 68 µF (exact match required)
Voltage Rating: 25 V (exact match required)
Tolerance: ±20% (exact match required)
Package: 2917 (7343 Metric) (exact match required)
Mounting: Surface Mount (exact match required)
Operating Temperature Range: -55°C to 125°C (exact match required)

Variable Parameters Allowing Substitution:

ESR (Equivalent Series Resistance): Ranges from 45 mOhm to 900 mOhm across substitute options
Capacitor Type: Molded or Conformal Coated construction
Manufacturer: KEMET, KYOCERA AVX, or Vishay Sprague
Packaging Format: Tape & Reel (TR) or Cut Tape (CT)
Product Status: Active production status preferred over obsolete
RoHS Compliance: ROHS3 Compliant preferred
MSL Rating: Ranges from 1 (Unlimited) to 3 (168 Hours)

Substitutes are grouped by series family (T491, T494, T510 from KEMET; TPM from KYOCERA AVX; 594D/595D from Vishay Sprague) and by ESR performance tier, allowing selection based on circuit requirements and procurement availability.

Parameter Comparison

Part Number	Manufacturer	Series	Capacitance (µF)	Voltage (V)	Tolerance (%)	Type	ESR (mOhm)	Package	Product Status	RoHS	MSL
T491X686M025AS	KEMET	T491	68	25	±20	Molded	700	2917	Obsolete	ROHS3	1
T491X686M025AT	KEMET	T491	68	25	±20	Molded	700	2917	Active	ROHS3	1
T491X686K025AT	KEMET	T491	68	25	±10	Molded	700	2917	Active	ROHS3	1
T494X686M025AT	KEMET	T494	68	25	±20	Molded	300	2917	Active	ROHS3	1
T510X686M025ATE045	KEMET	T510	68	25	±20	Molded	45	2917	Active	ROHS3	1
594D686X0025D2T	Vishay Sprague	594D	68	25	±20	Conformal Coated	200	2917	Active	ROHS3	2A
595D686X0025D2T	Vishay Sprague	595D	68	25	±20	Conformal Coated	260	2917	Active	ROHS3	2A
TAJE686M025RNJ	KYOCERA AVX	TAJ	68	25	±20	Molded	900	2917	Active	ROHS3	1
TPME686M025H0055	KYOCERA AVX	TPM	68	25	±20	Molded	55	2917	Active	Non-compliant	3
TPME686M025R0045	KYOCERA AVX	TPM	68	25	±20	Molded	45	2917	Active	ROHS3	3
TPME686M025R0055	KYOCERA AVX	TPM	68	25	±20	Molded	55	2917	Active	ROHS3	3

Engineering Selection Recommendations

Primary Recommendation: T491X686M025AT

The T491X686M025AT is the direct active production equivalent of the obsolete T491X686M025AS. Both parts share identical electrical specifications (68 µF, 25 V, ±20% tolerance, 700 mOhm ESR) and mechanical packaging (2917 case, surface mount). The T491X686M025AT maintains ROHS3 compliance and MSL 1 rating. This part provides seamless substitution with no circuit redesign required.

Secondary Recommendation: T491X686K025AT

The T491X686K025AT offers improved tolerance specification (±10% versus ±20%) while maintaining all other parameters identical to the main part. This upgrade is suitable for applications requiring tighter capacitance tolerance. Product status is active with ROHS3 compliance.

Performance-Enhanced Options:

For applications sensitive to ESR performance, three options provide significantly lower ESR values:

T510X686M025ATE045 (KEMET, 45 mOhm ESR): Lowest ESR option from KEMET series, active status, ROHS3 compliant
TPME686M025R0045 (KYOCERA AVX, 45 mOhm ESR): Equivalent ESR performance, active status, ROHS3 compliant, MSL 3 rating
TPME686M025R0055 (KYOCERA AVX, 55 mOhm ESR): Low ESR option, active status, ROHS3 compliant, MSL 3 rating

Conformal Coated Options:

For applications requiring conformal coating protection:

594D686X0025D2T (Vishay Sprague, 200 mOhm ESR): Conformal coated construction, active status, ROHS3 compliant, MSL 2A
595D686X0025D2T (Vishay Sprague, 260 mOhm ESR): Conformal coated construction, active status, ROHS3 compliant, MSL 2A

Compliance Considerations:

All recommended substitutes maintain ROHS3 compliance except TPME686M025H0055, which is RoHS non-compliant and should be avoided for new designs subject to RoHS regulations. MSL ratings vary from 1 (Unlimited) to 3 (168 Hours), affecting moisture handling and storage requirements during assembly.

Frequently Asked Questions (FAQ)

Q: Can T491X686M025AT directly replace T491X686M025AS without circuit modification?

A: Yes. The T491X686M025AT is the active production equivalent with identical electrical and mechanical specifications. No circuit redesign is required. The only difference is product status (active versus obsolete) and packaging format availability.

Q: What is the significance of ESR variation among substitute parts?

A: ESR (Equivalent Series Resistance) affects circuit performance in high-frequency applications and ripple current handling. The main part specifies 700 mOhm ESR. Substitutes range from 45 mOhm to 900 mOhm. Lower ESR values improve performance in switching power supplies and high-frequency filtering applications. Higher ESR values (such as TAJE686M025RNJ at 900 mOhm) are acceptable for general purpose applications but may increase noise in sensitive circuits.

Q: Why do some substitutes have ±10% tolerance instead of ±20%?

A: T491X686K025AT offers ±10% tolerance, providing tighter capacitance accuracy. This upgrade is beneficial for precision timing circuits, resonant tank circuits, or applications with strict capacitance requirements. The ±10% tolerance part is fully compatible with designs accepting ±20% tolerance parts.

Q: What is the difference between molded and conformal coated tantalum capacitors?

A: Molded tantalum capacitors (T491, T494, T510, TAJ, TPM series) feature a plastic molded case. Conformal coated capacitors (594D, 595D series) have a conformal coating applied over the component for enhanced moisture and environmental protection. Conformal coated parts are suitable for high-humidity environments or applications requiring additional environmental protection. Both types maintain identical electrical specifications for this part number.

Q: Are KYOCERA AVX TPM series parts compatible with KEMET T491 series?

A: Yes, KYOCERA AVX TPM series parts (TPME686M025R0045, TPME686M025R0055, TPME686M025H0055) are mechanically and electrically compatible. All maintain the 2917 package footprint, 68 µF capacitance, 25 V rating, and ±20% tolerance. Differences exist in ESR performance and MSL ratings. MSL 3 rating for TPM series requires stricter moisture control during assembly compared to MSL 1 rated KEMET parts.

Q: What does MSL rating mean for procurement and assembly?

A: MSL (Moisture Sensitivity Level) indicates moisture handling requirements. MSL 1 (Unlimited) parts like T491X686M025AT require no special moisture control. MSL 2A (4 Weeks) parts like 594D686X0025D2T must be used within 4 weeks of package opening. MSL 3 (168 Hours) parts like TPME686M025R0055 must be used within 168 hours of package opening. Higher MSL ratings require baking before reflow soldering if storage time is exceeded.

Q: Can Vishay Sprague 594D series substitute for KEMET T491 series in all applications?

A: Mechanically and electrically, yes. However, note that 594D series has MSL 2A rating versus MSL 1 for T491 series, requiring stricter moisture control. Additionally, 594D series features conformal coating, which may affect thermal performance in some applications. ESR is lower (200 mOhm) than the main part (700 mOhm), which is generally beneficial but should be verified for applications with specific ESR requirements.

Q: Is RoHS compliance a critical factor for part selection?

A: For applications subject to RoHS regulations (EU, China, and many other markets), ROHS3 compliance is mandatory. TPME686M025H0055 is RoHS non-compliant and must be avoided for regulated applications. All other substitutes listed are ROHS3 compliant and suitable for regulated markets.

Q: What packaging formats are available, and does it affect compatibility?

A: Substitutes are available in Tape & Reel (TR) or Cut Tape (CT) formats. Both formats contain identical components; packaging format affects only procurement and assembly handling. TR format is standard for high-volume automated assembly. CT format is suitable for lower-volume or manual assembly operations. Footprint and electrical performance are identical regardless of packaging format.

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