FSA4157AP6 Equivalent & Substitute Parts

Part Overview

The FSA4157AP6 is a single-circuit SPDT (Single Pole Double Throw) analog switch manufactured by onsemi, housed in a 6-pin SC-88 (SC-70-6) surface mount package. This component operates as a 2:1 multiplexer/demultiplexer with an on-state resistance of 1.15Ohm maximum and supports supply voltages from 2.7V to 5.5V. The part is currently listed as obsolete, with 1,090 units available in inventory. Due to its obsolete status, identifying equivalent and substitute parts is necessary for design continuity, system maintenance, and long-term component sourcing strategies.

Key Parameters

Parameter	FSA4157AP6
Switch Circuit	SPDT
Multiplexer/Demultiplexer Circuit	2:1
Number of Circuits	1
On-State Resistance (Max)	1.15Ohm
Channel-to-Channel Matching (ΔRon)	60mOhm
Voltage - Supply, Single (V+)	2.7V ~ 5.5V
Switch Time (Ton, Toff) (Max)	35ns, 15ns
-3dB Bandwidth	300MHz
Charge Injection	20pC
Channel Capacitance (CS(off), CD(off))	12pF
Current - Leakage (IS(off)) (Max)	2nA (Typ)
Crosstalk	-70dB @ 1MHz
Operating Temperature	-40°C ~ 85°C
Package / Case	6-TSSOP, SC-88, SOT-363
Mounting Type	Surface Mount
Product Status	Obsolete
Moisture Sensitivity Level (MSL)	1 (Unlimited)
REACH Status	REACH Unaffected

Substitute Part Grouping Explanation

Substitution eligibility for the FSA4157AP6 is determined by the following critical parameters:

Primary Substitution Criteria:

Switch circuit topology: SPDT
Multiplexer/demultiplexer configuration: 2:1
Number of circuits: 1
Package compatibility: 6-TSSOP, SC-88, SOT-363
Mounting type: Surface Mount
Operating temperature range: Minimum -40°C to 85°C

Secondary Compatibility Parameters:

On-state resistance: Maximum 1.15Ohm (allows parts with lower resistance)
Supply voltage range: Minimum 2.7V to 5.5V (parts with wider ranges are compatible)
Channel-to-channel matching: 60mOhm or better
Leakage current: 2nA or lower
Crosstalk: -70dB @ 1MHz or better

Substitute parts are grouped into two categories:

Direct Parametric Equivalent: FSA4157AP6X matches all electrical specifications and package requirements, with active product status providing superior long-term availability.

Functional Equivalents: TS5A3159DCKT, TS5A3159ADCKT, PI5A4157CEX, PI5A4157CEX-1516, and PI5A3157CEX meet the core functional requirements (SPDT 2:1 topology, compatible packaging) with variations in on-state resistance, bandwidth, and leakage characteristics that remain within acceptable substitution parameters for most applications.

Alternative Substitute: NLVASB3157DFT2G provides SPDT 2:1 functionality in compatible packaging but exhibits higher on-state resistance (7Ohm typical) and reduced bandwidth (250MHz), suitable only for applications where these parameter relaxations are acceptable.

Parameter Comparison

Parameter	FSA4157AP6	FSA4157AP6X	TS5A3159DCKT	TS5A3159ADCKT	PI5A4157CEX	PI5A4157CEX-1516	PI5A3157CEX	NLVASB3157DFT2G
Manufacturer	onsemi	onsemi	Texas Instruments	Texas Instruments	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated	onsemi
Switch Circuit	SPDT	SPDT	SPDT	SPDT	SPDT	SPDT	SPDT	SPDT
Multiplexer/Demultiplexer	2:1	2:1	2:1	2:1	2:1	2:1	2:1	2:1
On-State Resistance (Max)	1.15Ohm	1.15Ohm	1.1Ohm	900mOhm	1.2Ohm	1.2Ohm	13Ohm	7Ohm (Typ)
Channel-to-Channel Matching (ΔRon)	60mOhm	60mOhm	100mOhm	50mOhm	10mOhm	10mOhm	150mOhm	500mOhm
Voltage - Supply, Single (V+)	2.7V ~ 5.5V	2.7V ~ 5.5V	1.65V ~ 5.5V	1.65V ~ 5.5V	1.65V ~ 5.5V	1.65V ~ 5.5V	1.65V ~ 5.5V	1.65V ~ 5.5V
Switch Time Ton (Max)	35ns	35ns	35ns	30ns	18ns	18ns	5.2ns	—
Switch Time Toff (Max)	15ns	15ns	20ns	20ns	20ns	20ns	4.6ns	—
-3dB Bandwidth	300MHz	300MHz	100MHz	100MHz	150MHz	150MHz	250MHz	250MHz
Charge Injection	20pC	20pC	36pC	-20pC	35pC	35pC	7pC	7pC
Channel Capacitance (CS(off), CD(off))	12pF	12pF	23pF	18pF	4.6pF	4.6pF	2.3pF	—
Current - Leakage (IS(off)) (Max)	2nA (Typ)	2nA (Typ)	2nA	20nA	20nA	20nA	100nA	100nA
Crosstalk	-70dB @ 1MHz	-70dB @ 1MHz	-65dB @ 1MHz	-64dB @ 1MHz	-70dB @ 1MHz	-70dB @ 1MHz	-54dB @ 10MHz	-54dB @ 10MHz
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-55°C ~ 125°C
Package / Case	6-TSSOP, SC-88, SOT-363	6-TSSOP, SC-88, SOT-363	6-TSSOP, SC-88, SOT-363	6-TSSOP, SC-88, SOT-363	6-TSSOP, SC-88, SOT-363	6-TSSOP, SC-88, SOT-363	6-TSSOP, SC-88, SOT-363	6-TSSOP, SC-88, SOT-363
Product Status	Obsolete	Active	Last Time Buy	Last Time Buy	Last Time Buy	Active	Active	Obsolete
RoHS Status	—	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Primary Recommendation: FSA4157AP6X

The FSA4157AP6X is the direct parametric equivalent with identical electrical specifications and package configuration. This part carries active product status, ensuring long-term availability and supply chain stability. It is ROHS3 compliant and REACH unaffected, meeting current regulatory requirements. For applications requiring exact performance matching with the original FSA4157AP6, this is the preferred substitute.

Secondary Recommendations for Specific Application Requirements:

TS5A3159ADCKT (Texas Instruments) offers superior on-state resistance (900mOhm) and channel-to-channel matching (50mOhm), with lower leakage current (20nA). However, it carries Last Time Buy status, limiting future availability. Suitable for applications prioritizing low resistance performance where supply continuity is not critical.

PI5A4157CEX-1516 (Diodes Incorporated) provides active product status with excellent channel-to-channel matching (10mOhm) and maintains -70dB crosstalk performance. On-state resistance is 1.2Ohm, marginally higher than the original. This part offers a balance between performance and long-term availability.

PI5A4157CEX (Diodes Incorporated) shares identical electrical characteristics with PI5A4157CEX-1516 but carries Last Time Buy status. High inventory availability (149,400 units) may support immediate procurement needs despite discontinued status.

PI5A3157CEX (Diodes Incorporated) is active and available but exhibits significantly higher on-state resistance (13Ohm) and reduced crosstalk performance (-54dB @ 10MHz). This part is suitable only for applications where resistance and bandwidth relaxations are acceptable.

NLVASB3157DFT2G (onsemi) provides extended operating temperature range (-55°C to 125°C) but with substantially higher on-state resistance (7Ohm typical) and reduced bandwidth (250MHz). This part is appropriate only for temperature-extended applications where performance trade-offs are acceptable.

TS5A3159DCKT (Texas Instruments) offers on-state resistance of 1.1Ohm with Last Time Buy status. Suitable for applications requiring performance close to the original with acceptance of discontinued product status.

Frequently Asked Questions (FAQ)

Q: Can FSA4157AP6X be used as a direct replacement for FSA4157AP6?

A: Yes. FSA4157AP6X is the direct parametric equivalent with identical on-state resistance (1.15Ohm), bandwidth (300MHz), crosstalk (-70dB @ 1MHz), and operating temperature range (-40°C to 85°C). Both parts use the same 6-TSSOP SC-88 package. The primary advantage of FSA4157AP6X is its active product status, ensuring continued availability.

Q: What is the difference between SPDT and 2:1 multiplexer configuration?

A: SPDT (Single Pole Double Throw) describes the switch topology—one input can be routed to either of two outputs. The 2:1 multiplexer designation indicates the same functional capability: selecting between two input channels to route to a single output. These terms are equivalent for this product category.

Q: Are all substitute parts compatible with the same PCB footprint?

A: Yes. All listed substitute parts use the 6-TSSOP, SC-88, or SOT-363 package designation, which share identical pin configurations and land patterns. PCB layout modifications are not required for substitution.

Q: What does "Last Time Buy" product status mean?

A: Last Time Buy indicates the manufacturer has announced end-of-life for the part. Existing inventory may be available for purchase, but no new production will occur after a specified date. Parts with this status should be evaluated for long-term supply chain planning. Active status parts are preferred for new designs or long-term production requirements.

Q: How does on-state resistance affect circuit performance?

A: On-state resistance determines signal attenuation and power dissipation when the switch is conducting. Lower resistance reduces signal loss and heat generation. The FSA4157AP6 specifies 1.15Ohm maximum. Substitute parts with lower resistance (TS5A3159ADCKT at 900mOhm) provide improved performance; parts with higher resistance (PI5A3157CEX at 13Ohm, NLVASB3157DFT2G at 7Ohm) may introduce unacceptable signal degradation depending on application requirements.

Q: What is channel-to-channel matching (ΔRon)?

A: Channel-to-channel matching specifies the maximum resistance variation between the two switch channels. Lower values indicate better matching between channels. The FSA4157AP6 specifies 60mOhm matching. Parts with tighter matching (PI5A4157CEX at 10mOhm, TS5A3159ADCKT at 50mOhm) provide superior performance in applications requiring balanced signal routing.

Q: Can I use a substitute part with a wider supply voltage range?

A: Yes. The FSA4157AP6 operates from 2.7V to 5.5V. Substitute parts with wider ranges (1.65V to 5.5V) are fully compatible and provide additional flexibility for applications using lower supply voltages. This is a beneficial parameter relaxation.

Q: What does crosstalk specification mean?

A: Crosstalk measures signal coupling between the two switch channels, expressed in decibels. Higher negative values (more negative) indicate better isolation. The FSA4157AP6 specifies -70dB @ 1MHz. Substitute parts with equal or better crosstalk performance maintain signal integrity; parts with degraded crosstalk (-54dB) may introduce unacceptable cross-channel interference in sensitive applications.

Q: Are all substitute parts ROHS3 compliant?

A: All listed substitute parts except the original FSA4157AP6 carry ROHS3 compliance certification. All parts are REACH unaffected. These certifications meet current environmental and regulatory requirements for electronic component manufacturing and use.

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