FMMT549ATC Equivalent & Substitute Parts

Part Overview

The FMMT549ATC is a PNP bipolar junction transistor manufactured by Diodes Incorporated, designed for surface mount applications in the SOT-23-3 package. This device operates at 30 V collector-emitter breakdown voltage with a maximum collector current of 1 A and 500 mW power dissipation. The FMMT549ATC is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and production continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Collector Current (Max)	1	A
Collector-Emitter Breakdown Voltage (Max)	30	V
Power Dissipation (Max)	500	mW
Transition Frequency	100	MHz
Operating Temperature Range	−55 to 150	°C
Package Type	SOT-23-3	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the FMMT549ATC is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor type must be PNP
Collector-emitter breakdown voltage must be ≥ 30 V
Maximum collector current must be ≥ 1 A
Power dissipation must be ≥ 500 mW
Package must be SOT-23-3 or mechanically compatible surface mount variant
Mounting type must be surface mount
RoHS3 compliance required

Parametric Equivalent: FMMT549ATA (Diodes Incorporated) is an exact parametric match with identical electrical specifications and differs only in packaging format (Tape & Reel versus Cut Tape).

Direct Manufacturer Equivalent: FMMT549 (onsemi) provides identical electrical performance with the same SOT-23-3 package, though with minor variations in saturation voltage characteristics.

Manufacturer Recommended Substitutes: Parts including 2SB1695KT146, 2SB1695TL, 2STR2230, and BC858 series devices meet or exceed the primary electrical requirements. These parts feature enhanced specifications such as higher collector current ratings (1.5 A) or improved frequency response (280 MHz), making them suitable for applications requiring the FMMT549ATC performance envelope.

Current-Limited Alternatives: BC858ALT1G, BC858B,215, BC858B,235, BC858BLT1G, and BC858CLT1G are lower current-rated devices (100 mA maximum) and are suitable only for applications where collector current does not exceed 100 mA.

Parameter Comparison

Part Number	Manufacturer	Ic (Max) [A]	Vce(br) [V]	Power [mW]	Freq [MHz]	Package	Status
FMMT549ATC	Diodes Inc.	1	30	500	100	SOT-23-3	Obsolete
FMMT549ATA	Diodes Inc.	1	30	500	100	SOT-23-3	Active
FMMT549	onsemi	1	30	500	100	SOT-23-3	Active
2SB1695KT146	Rohm Semi.	1.5	30	200	280	SMT3	Active
2SB1695TL	Rohm Semi.	1.5	30	500	280	TSMT3	Active
2STR2230	STMicroelectronics	1.5	30	500	100	SOT-23-3	Active
BC858ALT1G	onsemi	0.1	30	300	100	SOT-23-3	Active
BC858B,215	Nexperia USA	0.1	30	250	100	TO-236AB	Active
BC858B,235	Nexperia USA	0.1	30	250	100	TO-236AB	Active
BC858BLT1G	onsemi	0.1	30	300	100	SOT-23-3	Active
BC858CLT1G	onsemi	0.1	30	300	100	SOT-23-3	Active

Engineering Selection Recommendations

Tier 1 – Direct Replacement (Identical Specifications):

FMMT549ATA and FMMT549 are the primary recommended substitutes. Both devices maintain full electrical and mechanical compatibility with the FMMT549ATC. FMMT549ATA is sourced from the original manufacturer (Diodes Incorporated) and is available in active production status with 2403 units in stock. FMMT549 from onsemi provides equivalent performance with 5432 units available. Both are RoHS3 compliant and carry identical operating temperature ranges and package specifications.

Tier 2 – Enhanced Performance Substitutes (Higher Current Rating):

2STR2230 (STMicroelectronics) and 2SB1695TL (Rohm Semiconductor) are suitable for applications where the 1 A collector current specification is adequate but enhanced performance margins are beneficial. The 2STR2230 maintains the 100 MHz transition frequency and 500 mW power rating while supporting 1.5 A collector current. The 2SB1695TL provides 280 MHz transition frequency with 1.5 A current capability, offering superior frequency response for high-speed switching applications. Both are active products with substantial inventory availability.

Tier 3 – Current-Limited Applications:

BC858 series devices (BC858ALT1G, BC858BLT1G, BC858CLT1G, BC858B,215, BC858B,235) are applicable only for circuits where collector current does not exceed 100 mA. These devices share the 30 V breakdown voltage and SOT-23-3 package but are not suitable for 1 A applications. Selection within this series depends on specific DC current gain requirements and automotive qualification needs (BC858B,215 and BC858B,235 carry AEC-Q101 qualification).

Compliance and Availability:

All recommended substitutes maintain RoHS3 compliance and REACH unaffected status. Moisture sensitivity level is uniformly rated at MSL 1 (Unlimited) across all alternatives. Product status verification confirms that FMMT549ATA, FMMT549, 2SB1695KT146, 2SB1695TL, 2STR2230, and all BC858 variants are in active production.

Frequently Asked Questions (FAQ)

Q: Can FMMT549ATA directly replace FMMT549ATC in existing designs?

A: Yes. FMMT549ATA is a parametric equivalent with identical electrical specifications (1 A collector current, 30 V breakdown voltage, 500 mW power, 100 MHz transition frequency) and the same SOT-23-3 package. The only difference is packaging format (Tape & Reel versus Cut Tape). No circuit modifications are required.

Q: What is the difference between FMMT549ATA and FMMT549?

A: Both devices are electrically equivalent with identical maximum ratings and operating characteristics. FMMT549ATA is manufactured by Diodes Incorporated, while FMMT549 is manufactured by onsemi. Minor differences exist in saturation voltage specifications (300 mV versus 750 mV at different test conditions) and DC current gain (150 versus 100 at 500 mA, 2V). Both are suitable direct replacements.

Q: Can 2STR2230 be used instead of FMMT549ATC?

A: Yes, for applications within the 1 A collector current specification. The 2STR2230 supports 1.5 A maximum collector current, providing additional design margin. It maintains the 30 V breakdown voltage, 500 mW power rating, and 100 MHz transition frequency. The SOT-23-3 package is mechanically identical. Saturation voltage is higher (800 mV at 200 mA, 2A), which may affect switching speed in some circuits.

Q: Are BC858 series devices suitable replacements?

A: BC858 series devices are not suitable for applications requiring 1 A collector current. These devices are rated for maximum 100 mA collector current. They share the 30 V breakdown voltage and SOT-23-3 package but are limited to low-current signal switching applications. Use BC858 variants only when collector current does not exceed 100 mA.

Q: What is the significance of the 2SB1695 series higher transition frequency?

A: The 2SB1695KT146 and 2SB1695TL devices operate at 280 MHz transition frequency compared to 100 MHz for the FMMT549ATC. This higher frequency response enables faster switching transitions and is beneficial for high-frequency applications. However, the 2SB1695KT146 is rated for only 200 mW power dissipation, which is lower than the FMMT549ATC specification. The 2SB1695TL maintains 500 mW power rating and is the preferred option if enhanced frequency response is required.

Q: Do all substitute parts have the same package dimensions?

A: Most substitutes use SOT-23-3 or mechanically equivalent packages (TO-236-3, SC-59). The 2SB1695KT146 uses SMT3 package and 2SB1695TL uses TSMT3 package. While these are surface mount variants, physical dimensions may differ. Verify PCB footprint compatibility before selection. BC858B,215 and BC858B,235 use TO-236AB package, which is mechanically compatible with SOT-23-3.

Q: Which substitute offers the best inventory availability?

A: FMMT549 (onsemi) has the highest inventory with 5432 units in stock. FMMT549ATA (Diodes Incorporated) has 2403 units available. 2STR2230 (STMicroelectronics) has 209,400 units in stock, providing the largest supply buffer for high-volume applications.

Q: Are automotive-grade alternatives available?

A: Yes. BC858B,215 and BC858B,235 (Nexperia USA Inc.) carry AEC-Q101 automotive qualification and Grade designation. However, these are limited to 100 mA collector current. For 1 A automotive applications, consult manufacturer datasheets for automotive-qualified variants of FMMT549ATA, FMMT549, or 2STR2230.

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