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SN74HC540PW Equivalent & Substitute Parts
Part Overview
The SN74HC540PW is a logic buffer IC with inverting functionality, designed for 3-state output applications in 20-TSSOP surface mount packaging. This part is currently discontinued at DiGi Electronics, making equivalent substitutes necessary for ongoing production and maintenance applications. The 74HC540 series provides buffering and inversion of 8-bit data with controlled output impedance suitable for bus driving applications across 2V to 6V supply ranges.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Logic Type | Buffer, Inverting |
| Number of Elements | 1 |
| Number of Bits per Element | 8 |
| Output Type | 3-State |
| Current - Output High, Low | 7.8mA, 7.8mA |
| Voltage - Supply | 2V ~ 6V |
| Operating Temperature | -40°C ~ 85°C (TA) |
| Mounting Type | Surface Mount |
| Package / Case | 20-TSSOP (0.173", 4.40mm Width) |
| Base Product Number | 74HC540 |
| RoHS Status | ROHS3 Compliant |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) |
Substitute Part Grouping Explanation
Substitution of the SN74HC540PW is determined by strict equivalence across the following critical parameters:
- Logic Type: Buffer, Inverting (1 Element, 8 Bit per Element)
- Output Type: 3-State
- Output Current: 7.8mA High and Low
- Supply Voltage Range: 2V ~ 6V
- Mounting Type: Surface Mount
- Base Product Number: 74HC540 series
Substitute parts are grouped into two categories based on package compatibility:
Category 1: 20-TSSOP Package (Direct Pin-Compatible) Parts maintaining the exact 20-TSSOP (0.173", 4.40mm Width) package specification allow direct board-level substitution without layout modification.
Category 2: 20-SSOP Package (Mechanical Variant) Parts using 20-SSOP (0.209", 5.30mm Width) packaging maintain electrical equivalence but require footprint verification due to increased package width.
Parameter Comparison
| Part Number | Manufacturer | Package | Product Status | Operating Temp (°C) | RoHS Status | MSL |
|---|---|---|---|---|---|---|
| SN74HC540PW | Texas Instruments | 20-TSSOP | Discontinued | -40 ~ 85 | ROHS3 Compliant | 1 |
| SN74HC540PWR | Texas Instruments | 20-TSSOP | Active | -40 ~ 85 | ROHS3 Compliant | 1 |
| MM74HC540MTCX | onsemi | 20-TSSOP | Active | -40 ~ 85 | ROHS3 Compliant | 1 |
| MM74HC540MTC | Fairchild Semiconductor | 20-TSSOP | Active | -40 ~ 85 | ROHS3 Compliant | Not specified |
| MC74HC540ADTR2G | onsemi | 20-TSSOP | Active | -55 ~ 125 | ROHS3 Compliant | 1 |
| 74HC540DB,112 | Nexperia USA Inc. | 20-SSOP | Obsolete | -40 ~ 125 | ROHS3 Compliant | 1 |
Engineering Selection Recommendations
Primary Substitutes (20-TSSOP Package)
SN74HC540PWR (Texas Instruments) is the direct functional equivalent with identical package specification and operating temperature range. Active product status ensures long-term availability and supply chain stability.
MM74HC540MTCX (onsemi) provides equivalent electrical performance in 20-TSSOP packaging with active product status and ROHS3 compliance. Higher inventory levels support production volume requirements.
MC74HC540ADTR2G (onsemi) extends operating temperature range to -55°C ~ 125°C while maintaining 20-TSSOP package compatibility. This variant suits applications requiring enhanced thermal performance.
Secondary Substitute (20-SSOP Package)
74HC540DB,112 (Nexperia USA Inc.) maintains electrical equivalence but uses 20-SSOP packaging with 0.209" width versus 0.173" for TSSOP. Extended operating temperature range (-40°C ~ 125°C) provides thermal margin. Obsolete status limits future availability.
MM74HC540MTC (Fairchild Semiconductor) offers 20-TSSOP compatibility with active status but lacks specified MSL rating documentation.
Frequently Asked Questions (FAQ)
Q: Can SN74HC540PWR directly replace SN74HC540PW on existing PCBs?
A: Yes. Both parts use identical 20-TSSOP packaging (0.173", 4.40mm Width) with matching pin assignments, supply voltage (2V ~ 6V), output current (7.8mA), and operating temperature range (-40°C ~ 85°C). No board modification is required.
Q: What is the difference between 20-TSSOP and 20-SSOP packages?
A: Package width differs: TSSOP measures 0.173" (4.40mm) while SSOP measures 0.209" (5.30mm). Electrical function remains identical. PCB footprint verification is required before substituting SSOP variants on TSSOP-designed boards.
Q: Why is MC74HC540ADTR2G listed as a substitute if its operating temperature range differs?
A: MC74HC540ADTR2G maintains all critical electrical parameters (logic type, output type, current ratings, supply voltage) and uses identical 20-TSSOP packaging. The extended temperature range (-55°C ~ 125°C) represents a superset of the original specification (-40°C ~ 85°C), making it functionally compatible for applications within the original temperature window.
Q: Are all substitutes ROHS3 compliant?
A: All listed substitutes carry ROHS3 Compliant status except MM74HC540MTC, which does not specify RoHS status in available documentation.
Q: What inventory considerations apply to these substitutes?
A: SN74HC540PWR (1403 pcs), MM74HC540MTCX (8201 pcs), and MC74HC540ADTR2G (3439 pcs) maintain active stock levels. MM74HC540MTC (2581 pcs) and 74HC540DB,112 (1121 pcs) have lower availability. Original SN74HC540PW (5900 pcs) remains in stock despite discontinued status.
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