PCA8574D,512 Equivalent & Substitute Parts

Part Overview

The PCA8574D,512 is an 8-bit I/O Expander with I2C interface operating at 400 kHz, manufactured by NXP USA Inc. in a 16-SOIC package. This part is classified as Obsolete, making substitute components necessary for new designs and ongoing production requirements. The device provides 8 I/O lines with push-pull output configuration, interrupt output capability, and power-on reset (POR) feature, suitable for applications requiring I2C-based port expansion in embedded systems.

Key Parameters

Parameter	Value
Number of I/O	8
Interface	I2C
Clock Frequency	400 kHz
Voltage Supply Range	2.3V ~ 5.5V
Output Type	Push-Pull
Current Output Source/Sink	100µA, 25mA
Operating Temperature	-40°C ~ 85°C
Package Type	16-SOIC (0.295", 7.50mm Width)
Interrupt Output	Yes
Features	POR
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the PCA8574D,512 is determined by the following critical parameters:

I/O Count: Must provide 8 I/O lines
Interface Protocol: Must support I2C communication
Clock Frequency: 400 kHz operation required for direct replacement; 100 kHz alternatives acceptable for lower-speed applications
Voltage Supply Range: Must encompass or be compatible with 2.3V ~ 5.5V
Output Configuration: Push-pull output type required
Package Compatibility: 16-pin surface mount packages (16-SOIC, 16-TSSOP, 16-VQFN acceptable with PCB layout adjustment)
Interrupt Output: Must include interrupt output capability
Product Status: Active or Last Time Buy status preferred over Obsolete

Substitute parts are grouped into two categories: direct pin-compatible replacements in 16-SOIC packaging, and functional equivalents in alternative packages requiring layout modification.

Parameter Comparison

Part Number	Manufacturer	I/O Count	Interface	Clock Frequency	Voltage Supply	Output Current (Source/Sink)	Operating Temp	Package	Product Status
PCA8574D,512	NXP USA Inc.	8	I2C	400 kHz	2.3V ~ 5.5V	100µA, 25mA	-40°C ~ 85°C	16-SOIC	Obsolete
PCF8574T/3,518	NXP USA Inc.	8	I2C	100 kHz	2.5V ~ 6V	300µA, 25mA	-40°C ~ 85°C	16-SOIC	Active
MAX7324AEG+T	Analog Devices Inc./Maxim Integrated	8	I2C	400 kHz	1.71V ~ 5.5V	20mA	-40°C ~ 125°C	24-SSOP	Active
MAX7324ATG+T	Analog Devices Inc./Maxim Integrated	8	I2C	400 kHz	1.71V ~ 5.5V	20mA	-40°C ~ 125°C	24-TQFN (4x4)	Active
PCA9554ADWR	Texas Instruments	8	I2C, SMBus	400 kHz	2.3V ~ 5.5V	10mA, 25mA	-40°C ~ 85°C	16-SOIC	Last Time Buy
PCF8574DW	Texas Instruments	8	I2C	100 kHz	2.5V ~ 6V	1mA, 25mA	-40°C ~ 85°C	16-SOIC	Obsolete
PCF8574DWR	Texas Instruments	8	I2C	100 kHz	2.5V ~ 6V	1mA, 25mA	-40°C ~ 85°C	16-SOIC	Active
TCA6408APWR	Texas Instruments	8	I2C, SMBus	400 kHz	1.65V ~ 5.5V	10mA, 25mA	-40°C ~ 85°C	16-TSSOP	Active
TCA6408AQPWRQ1	Texas Instruments	8	I2C, SMBus	400 kHz	1.65V ~ 3.6V	10mA, 25mA	-40°C ~ 125°C	16-TSSOP	Active
TCA6408ARGTR	Texas Instruments	8	I2C, SMBus	400 kHz	1.65V ~ 5.5V	10mA, 25mA	-40°C ~ 85°C	16-VQFN (3x3)	Active

Engineering Selection Recommendations

Direct Pin-Compatible Replacements (16-SOIC Package)

PCA9554ADWR is the primary substitute for the PCA8574D,512. It maintains identical package geometry, voltage supply range (2.3V ~ 5.5V), operating temperature (-40°C ~ 85°C), and 400 kHz clock frequency. The part includes SMBus compatibility in addition to I2C, providing enhanced protocol support. Product status is Last Time Buy, indicating continued availability for transition periods.

PCF8574DWR provides an alternative with Active product status and identical 16-SOIC packaging. This part operates at 100 kHz instead of 400 kHz, suitable for applications where reduced clock frequency is acceptable. Voltage supply range (2.5V ~ 6V) and operating temperature remain compatible.

Alternative Package Options (Requires PCB Layout Modification)

MAX7324AEG+T and MAX7324ATG+T offer 400 kHz operation with extended operating temperature range (-40°C ~ 125°C) and lower minimum supply voltage (1.71V). These parts require PCB redesign due to 24-pin packaging (SSOP and TQFN formats). Product status is Active with unlimited moisture sensitivity level.

TCA6408APWR, TCA6408AQPWRQ1, and TCA6408ARGTR provide 400 kHz operation in 16-pin packages (TSSOP and VQFN) with SMBus support. These require PCB layout modification but maintain 8-bit I/O functionality. TCA6408AQPWRQ1 includes automotive qualification (AEC-Q100) for applications requiring automotive-grade components.

Compliance and Certification

All substitute parts maintain ROHS3 compliance and REACH Unaffected status, matching the original part's environmental certifications. Moisture sensitivity levels vary; parts with MSL 1 (Unlimited) provide superior shelf-life characteristics compared to MSL 2 (1 Year).

Frequently Asked Questions (FAQ)

Q: Can PCF8574DWR directly replace PCA8574D,512 in existing designs?

A: Yes, PCF8574DWR provides direct pin-compatible replacement in 16-SOIC packaging with identical footprint. The primary difference is 100 kHz clock frequency versus 400 kHz. Applications operating at lower I2C speeds will function identically. Voltage supply range and operating temperature are compatible.

Q: What is the key difference between 400 kHz and 100 kHz I2C operation?

A: Clock frequency determines maximum I2C bus speed. The PCA8574D,512 operates at 400 kHz (Fast mode), while PCF8574 variants operate at 100 kHz (Standard mode). Substituting a 100 kHz part into a 400 kHz system will limit bus speed to 100 kHz. This is acceptable if the application does not require higher-speed communication.

Q: Are MAX7324 parts suitable replacements despite different packaging?

A: MAX7324 variants provide functional equivalence with 400 kHz operation and extended temperature range. However, 24-pin packaging (SSOP or TQFN) differs from the original 16-SOIC, requiring PCB redesign. Pin assignments differ; direct socket replacement is not possible.

Q: What does "Last Time Buy" product status mean for PCA9554ADWR?

A: Last Time Buy indicates the manufacturer has announced end-of-life with a final purchase window. PCA9554ADWR remains available for transition periods but will eventually become obsolete. For new long-term designs, Active status parts (PCF8574DWR, TCA6408 variants, MAX7324 variants) are recommended.

Q: Can I use TCA6408AQPWRQ1 in non-automotive applications?

A: Yes. TCA6408AQPWRQ1 is automotive-qualified (AEC-Q100) but functions in standard industrial and consumer applications. The automotive qualification indicates enhanced reliability testing and stricter manufacturing controls. Voltage supply range is limited to 1.65V ~ 3.6V compared to standard TCA6408APWR (1.65V ~ 5.5V).

Q: What is the impact of different output current ratings?

A: Output current (source/sink) determines maximum load-driving capability per I/O pin. PCA8574D,512 provides 100µA source and 25mA sink. Substitutes vary: PCF8574 variants provide 1mA source and 25mA sink; MAX7324 provides 20mA; TCA6408 provides 10mA source and 25mA sink. Lower source current may limit direct LED driving capability; verify application requirements before substitution.

Q: Is SMBus compatibility important for I2C-only applications?

A: SMBus is a superset of I2C with additional protocol features. Parts with SMBus support (PCA9554ADWR, TCA6408 variants) are backward-compatible with I2C-only systems. SMBus compatibility provides no disadvantage in I2C applications and enables future protocol flexibility.

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