FMMT493ATC Equivalent & Substitute Parts

Part Overview

The FMMT493ATC is an NPN bipolar junction transistor manufactured by Diodes Incorporated, rated for 60 V collector-emitter breakdown voltage and 1 A maximum collector current. The device is housed in a SOT-23-3 surface mount package and operates across a temperature range of -55°C to 150°C. This transistor is classified as obsolete, which necessitates identification of equivalent and substitute components for ongoing design requirements and production continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Maximum Collector Current (Ic)	1	A
Collector-Emitter Breakdown Voltage (Max)	60	V
Vce Saturation (Max)	500 mV @ 100 mA, 1 A	—
Maximum Power Dissipation	500	mW
Transition Frequency	150	MHz
DC Current Gain (hFE Min)	300 @ 250 mA, 10 V	—
Operating Temperature Range	-55 to 150	°C
Package Type	SOT-23-3	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the FMMT493ATC is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Collector-emitter breakdown voltage must be greater than or equal to 60 V
Maximum collector current must be greater than or equal to 1 A
Maximum power dissipation must be greater than or equal to 500 mW
Transition frequency must be greater than or equal to 150 MHz
DC current gain (hFE) characteristics must support the intended application

Mechanical Compatibility Criteria:

Surface mount package type (SOT-23-3 or equivalent footprint)
Operating temperature range must encompass -55°C to 150°C or be compatible with application requirements

Compliance Requirements:

RoHS3 compliance
Moisture sensitivity level of 1 (Unlimited)

Substitute parts are grouped into two categories: parametric equivalents (identical electrical specifications with different packaging or product status) and manufacturer-recommended alternatives (enhanced or comparable electrical performance with different package types).

Parameter Comparison

Part Number	Manufacturer	Ic (Max) [A]	Vce(br) [V]	Power [mW]	fT [MHz]	hFE (Min)	Package	Status
FMMT493ATC	Diodes Incorporated	1	60	500	150	300 @ 250mA, 10V	SOT-23-3	Obsolete
FMMT493ATA	Diodes Incorporated	1	60	500	150	300 @ 250mA, 10V	SOT-23-3	Active
2SC5866TLQ	Rohm Semiconductor	2	60	500	200	120 @ 100mA, 2V	TSMT3	Active
2SC5866TLR	Rohm Semiconductor	2	60	500	200	120 @ 100mA, 2V	TSMT3	Active
BC846,215	NXP USA Inc.	0.1	65	250	100	110 @ 2mA, 5V	SOT-23-3	Active
BC846A,215	Nexperia USA Inc.	0.1	65	250	100	110 @ 2mA, 5V	SOT-23-3	Active
BC846ALT1G	onsemi	0.1	65	300	100	110 @ 2mA, 5V	SOT-23-3	Active
BC846B,215	Nexperia USA Inc.	0.1	65	250	100	200 @ 2mA, 5V	SOT-23-3	Active
BC846B,235	Nexperia USA Inc.	0.1	65	250	100	200 @ 2mA, 5V	SOT-23-3	Active
BC846B-TP	Micro Commercial Co	0.1	65	225	100	200 @ 2mA, 5V	SOT-23-3	Active
BC846BLT1G	onsemi	0.1	65	300	100	200 @ 2mA, 5V	SOT-23-3	Active

Engineering Selection Recommendations

Primary Equivalent:

The FMMT493ATA (Diodes Incorporated) is the direct parametric equivalent to the FMMT493ATC. Both devices share identical electrical specifications: 1 A maximum collector current, 60 V breakdown voltage, 500 mW power dissipation, 150 MHz transition frequency, and 300 hFE minimum at 250 mA. The FMMT493ATA is currently in active production status, making it the preferred replacement for obsolete FMMT493ATC applications. Both components are RoHS3 compliant with MSL 1 rating and SOT-23-3 packaging.

Alternative Substitutes:

The 2SC5866TLQ and 2SC5866TLR (Rohm Semiconductor) provide enhanced electrical performance with 2 A maximum collector current and 200 MHz transition frequency, while maintaining 60 V breakdown voltage and 500 mW power dissipation. These devices are suitable for applications requiring higher current capability. Both are active production parts with RoHS3 compliance. Package type is TSMT3 (SC-96), which differs from the SOT-23-3 footprint and requires PCB layout modification.

Limited Substitution Candidates:

The BC846 series transistors (NXP/Nexperia/onsemi/Micro Commercial Co) are small-signal devices with maximum collector current of 100 mA, which is significantly lower than the FMMT493ATC specification of 1 A. These devices are suitable only for applications where the actual current requirement does not exceed 100 mA. All BC846 variants are active production parts with RoHS3 compliance and SOT-23-3 packaging. Voltage ratings of 65 V exceed the 60 V requirement. Transition frequencies of 100 MHz are below the 150 MHz specification.

Compliance Status:

All recommended substitutes maintain RoHS3 compliance and MSL 1 rating, ensuring compatibility with standard manufacturing and storage requirements.

Frequently Asked Questions (FAQ)

Q: Can the FMMT493ATA directly replace the FMMT493ATC without circuit modification?

A: Yes. The FMMT493ATA is a parametric equivalent with identical electrical specifications and SOT-23-3 packaging. No circuit modification is required. The primary difference is product status: FMMT493ATC is obsolete while FMMT493ATA is in active production.

Q: Are the Rohm 2SC5866TLQ and 2SC5866TLR suitable replacements for all FMMT493ATC applications?

A: These devices are electrically compatible for applications operating at or below 1 A collector current. They offer enhanced performance with 2 A maximum current rating and 200 MHz transition frequency. However, the TSMT3 package differs from SOT-23-3, requiring PCB layout redesign. Evaluate application current requirements before selection.

Q: Why are BC846 series transistors listed as substitutes if they have only 100 mA maximum current?

A: BC846 variants are included as limited substitutes for applications where actual collector current does not exceed 100 mA. The FMMT493ATC specification of 1 A maximum current does not necessarily reflect the actual operating current in all designs. BC846 devices are suitable only when circuit analysis confirms current requirements below 100 mA. For applications requiring the full 1 A capability, BC846 series is not appropriate.

Q: What is the significance of the different hFE specifications among substitute parts?

A: DC current gain (hFE) affects transistor biasing and switching characteristics. The FMMT493ATC specifies 300 hFE minimum at 250 mA and 10 V. The FMMT493ATA matches this specification exactly. The 2SC5866 series specifies 120 hFE at different test conditions (100 mA, 2 V), indicating different gain characteristics. BC846 variants specify 110 or 200 hFE at 2 mA and 5 V. Circuit designs relying on specific hFE values must account for these differences through bias network adjustment.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All listed substitute parts are RoHS3 compliant and carry MSL 1 (Unlimited) moisture sensitivity rating, matching the compliance profile of the FMMT493ATC.

Q: What packaging considerations apply when selecting substitutes?

A: The FMMT493ATC and FMMT493ATA both use SOT-23-3 packaging with identical footprints. The 2SC5866 series uses TSMT3 (SC-96) packaging, which has a different footprint and requires PCB redesign. BC846 series devices use SOT-23-3 packaging, maintaining footprint compatibility. Verify PCB layout compatibility before final part selection.

Q: Can I use BC846BLT1G as a direct replacement in a 1 A application?

A: No. The BC846BLT1G has a maximum collector current rating of 100 mA, which is insufficient for applications requiring 1 A operation. Using this device in a 1 A circuit would exceed its absolute maximum ratings and cause device failure. Use BC846 variants only when circuit analysis confirms actual operating current below 100 mA.

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