PI5A121TEX Equivalent & Substitute Parts

Part Overview

The PI5A121TEX is a single-circuit SPST-NO IC switch manufactured by Diodes Incorporated, designed for low-impedance signal switching applications. This part features a 10Ohm on-state resistance in a SOT-23-5 surface mount package and operates across a 2V to 6V supply range. The product is currently obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. Substitute parts must maintain functional compatibility while meeting the electrical and mechanical requirements of the original application.

Key Parameters

Parameter	PI5A121TEX
Switch Circuit Type	SPST - NO
Number of Circuits	1
Multiplexer/Demultiplexer Circuit	1:1
On-State Resistance (Max)	10Ohm
Channel-to-Channel Matching (ΔRon)	200mOhm
Voltage - Supply, Single (V+)	2V ~ 6V
Switch Time (Ton, Toff) (Max)	15ns, 7ns
-3dB Bandwidth	326MHz
Charge Injection	1.6pC
Channel Capacitance (CS(off), CD(off))	5.5pF, 5.5pF
Current - Leakage (IS(off)) (Max)	200pA (Typ)
Crosstalk	-43dB @ 10MHz
Operating Temperature	-40°C ~ 85°C (TA)
Mounting Type	Surface Mount
Package / Case	SC-74A, SOT-753
Supplier Device Package	SOT-23-5
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the PI5A121TEX is determined by the following critical parameters:

Primary Substitution Criteria:

Switch circuit type: SPST - NO (single pole, single throw, normally open)
Circuit configuration: 1:1 multiplexer/demultiplexer
Number of circuits: 1
Package compatibility: SOT-23-5 or SC-74A footprint
Supply voltage range: Must encompass or overlap with 2V ~ 6V
On-state resistance: 10Ohm nominal (tolerance dependent on application requirements)
Operating temperature: -40°C ~ 85°C minimum

Secondary Compatibility Parameters:

Switch timing characteristics (Ton, Toff)
Bandwidth performance (-3dB Bandwidth)
Leakage current specifications
Charge injection and capacitance values

Substitute parts are grouped into two categories: direct functional equivalents with matching on-state resistance (10Ohm), and alternative resistance values (15Ohm, 22Ohm, 80Ohm, 95Ohm, 280Ohm) suitable for applications where higher impedance is acceptable. All substitutes maintain SPST-NO topology, single-circuit configuration, and surface mount packaging.

Parameter Comparison

Part Number	Manufacturer	On-State Resistance (Max)	Voltage - Supply, Single (V+)	Switch Time Ton/Toff (Max)	-3dB Bandwidth	Operating Temperature	Package	Product Status
PI5A121TEX	Diodes Incorporated	10Ohm	2V ~ 6V	15ns, 7ns	326MHz	-40°C ~ 85°C	SOT-23-5	Obsolete
MAX4594DBVR	Texas Instruments	10Ohm	2.4V ~ 5.5V	35ns, 40ns	300MHz	-40°C ~ 85°C	SOT-23-5	Active
NS5B1G385DTT1G	onsemi	15Ohm	2V ~ 5.5V	6ns, 2ns	330MHz	-40°C ~ 85°C	5-TSOP	Obsolete
74AHC1G66GV,125	Nexperia USA Inc.	22Ohm	2V ~ 5.5V	11ns, 11ns	280MHz	-40°C ~ 125°C	SC-74A	Active
74AHCT1G66GV,125	Nexperia USA Inc.	22Ohm	4.5V ~ 5.5V	11ns, 11ns	280MHz	-40°C ~ 125°C	SC-74A	Active
74HC1G66GV,125	Nexperia USA Inc.	80Ohm	2V ~ 10V	20ns, 20ns	200MHz	-40°C ~ 125°C	SC-74A	Active
74HCT1G66GV,125	Nexperia USA Inc.	95Ohm	4.5V ~ 5.5V	30ns, 44ns	200MHz	-40°C ~ 125°C	SC-74A	Active
74HCT1G66GV-Q100H	Nexperia USA Inc.	95Ohm	4.5V ~ 5.5V	30ns, 44ns	200MHz	-40°C ~ 125°C	SC-74A	Active
74LVC1G66GV,125	Nexperia USA Inc.	10Ohm	1.65V ~ 5.5V	4.2ns, 5ns	500MHz	-40°C ~ 125°C	SC-74A	Active
BU4S66G2-TR	Rohm Semiconductor	280Ohm	3V ~ 18V	Not specified	Not specified	-40°C ~ 85°C	5-SSOP	Active
SN74AUC1G66DBVR	Texas Instruments	15Ohm	0.8V ~ 2.7V	1.4ns, 1.5ns	500MHz	-40°C ~ 85°C	SOT-23-5	Active

Engineering Selection Recommendations

Direct Functional Equivalent (Recommended Primary Substitute):

The MAX4594DBVR from Texas Instruments is the closest functional equivalent to the PI5A121TEX. Both devices feature 10Ohm on-state resistance, SOT-23-5 packaging, and -40°C to 85°C operating temperature range. The MAX4594DBVR is currently in active production status, ensuring long-term availability. Supply voltage range (2.4V ~ 5.5V) overlaps substantially with the original part's 2V ~ 6V specification. Switch timing is slightly slower (35ns/40ns vs. 15ns/7ns), but bandwidth performance remains adequate at 300MHz. This part is ROHS3 compliant and carries identical MSL rating.

Alternative with Matching Resistance (Lower Voltage Operation):

The 74LVC1G66GV,125 from Nexperia USA Inc. provides 10Ohm on-state resistance matching and superior switching speed (4.2ns/5ns). This part extends supply voltage range to 1.65V ~ 5.5V, enabling operation in lower-voltage applications. Bandwidth reaches 500MHz, exceeding the original specification. Operating temperature extends to 125°C. SC-74A package requires PCB footprint verification for compatibility. Active production status ensures availability.

Higher Resistance Alternatives (Application-Dependent):

For applications tolerating increased on-state resistance, the 74AHC1G66GV,125 and 74AHCT1G66GV,125 (22Ohm) from Nexperia provide active production status and extended temperature range to 125°C. The 74AHCT1G66GV,125 operates within narrower supply range (4.5V ~ 5.5V). The 74HCT1G66GV-Q100H variant includes AEC-Q100 automotive qualification for applications requiring automotive-grade components.

Low-Voltage Specialized Substitute:

The SN74AUC1G66DBVR from Texas Instruments operates at ultra-low supply voltages (0.8V ~ 2.7V) with exceptional switching speed (1.4ns/1.5ns) and 500MHz bandwidth. This part is suitable only for applications operating below 2.7V and requiring minimal propagation delay. SOT-23-5 packaging maintains footprint compatibility.

High-Voltage Alternative:

The BU4S66G2-TR from Rohm Semiconductor supports extended supply range (3V ~ 18V) with 280Ohm on-state resistance. This part is appropriate for high-voltage switching applications where impedance is non-critical. 5-SSOP package requires PCB redesign.

All recommended substitutes maintain ROHS3 compliance, MSL-1 rating, and REACH unaffected status, matching the original part's regulatory compliance profile.

Frequently Asked Questions (FAQ)

Q: Can the MAX4594DBVR directly replace the PI5A121TEX without PCB modifications?

A: Yes. Both parts use SOT-23-5 packaging with identical pinout configuration. The MAX4594DBVR is a pin-compatible substitute. Verify supply voltage range compatibility with your application (MAX4594DBVR operates 2.4V ~ 5.5V versus PI5A121TEX 2V ~ 6V). No PCB layout changes are required.

Q: What is the impact of higher on-state resistance in substitute parts?

A: On-state resistance directly affects signal attenuation and power dissipation. The PI5A121TEX specifies 10Ohm maximum. Substitutes with 15Ohm, 22Ohm, or higher resistance will increase insertion loss and heat generation. Select substitutes based on your circuit's impedance requirements and signal integrity margins. For critical analog switching, maintain on-state resistance within 10-15Ohm range.

Q: Are the Nexperia 74-series parts (74AHC1G66GV, 74AHCT1G66GV, etc.) suitable replacements?

A: These parts are functionally compatible SPST-NO switches with SC-74A packaging. They differ in on-state resistance (22Ohm or higher) and supply voltage ranges. The 74AHC1G66GV,125 operates 2V ~ 5.5V and is suitable for general applications. The 74AHCT1G66GV,125 requires 4.5V ~ 5.5V supply. Extended operating temperature to 125°C is an advantage. Verify on-state resistance tolerance for your application before selection.

Q: What is the difference between 74HCT1G66GV,125 and 74HCT1G66GV-Q100H?

A: Both parts are electrically identical with 95Ohm on-state resistance and SC-74A packaging. The -Q100H variant includes AEC-Q100 automotive qualification and is designated for automotive applications. Select the -Q100H variant only if automotive-grade certification is required by your application or supply chain.

Q: Can I use the SN74AUC1G66DBVR in a 5V application?

A: No. The SN74AUC1G66DBVR maximum supply voltage is 2.7V. Operating this part at 5V will cause permanent damage. This part is suitable only for ultra-low-voltage applications (0.8V ~ 2.7V). For 5V applications, select MAX4594DBVR, 74LVC1G66GV,125, or Nexperia 74-series alternatives.

Q: Does package type affect electrical performance?

A: Package type (SOT-23-5 versus SC-74A versus 5-TSOP) does not affect electrical performance specifications. Package selection is determined by PCB layout constraints and manufacturing capabilities. SOT-23-5 and SC-74A are mechanically compatible with identical pinout. 5-TSOP and 5-SSOP packages require PCB redesign and are not pin-compatible with SOT-23-5.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed are ROHS3 compliant with MSL-1 (unlimited) moisture sensitivity rating, matching the original PI5A121TEX compliance profile. REACH status is unaffected for all parts.

Q: What is the significance of the 200mOhm channel-to-channel matching specification on the PI5A121TEX?

A: Channel-to-channel matching (ΔRon) specifies the maximum resistance variation between switching channels in multi-channel devices. The PI5A121TEX is a single-circuit device, so this parameter indicates on-state resistance tolerance. Most substitute parts do not specify this parameter explicitly. For applications requiring tight resistance matching, contact the manufacturer for detailed tolerance specifications.

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