CAT9555HT6I-GT2 Equivalent & Substitute Parts

Part Overview

The CAT9555HT6I-GT2 is a 16-bit I/O expander with I2C and SMBus interface operating at 400 kHz, manufactured by onsemi in a 24-TQFN (4x4) package. This component is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. The part provides push-pull output configuration with interrupt output capability and power-on reset (POR) feature, suitable for applications requiring expanded I/O capabilities in space-constrained designs.

Key Parameters

Parameter	Value
Manufacturer Part Number	CAT9555HT6I-GT2
Manufacturer	onsemi
Number of I/O	16
Interface	I2C, SMBus
Clock Frequency	400 kHz
Voltage Supply Range	2.3V ~ 5.5V
Output Type	Push-Pull
Current Output Source/Sink	10mA, 24mA
Operating Temperature	-40°C ~ 85°C
Package Type	24-WFQFN Exposed Pad
Mounting Type	Surface Mount
Interrupt Output	Yes
Features	POR
Product Status	Obsolete
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the CAT9555HT6I-GT2 is determined by the following critical parameters:

I/O Count: 16-bit configuration (non-negotiable)
Interface Protocol: I2C or I2C/SMBus compatibility (non-negotiable)
Clock Frequency: 400 kHz operation (non-negotiable)
Output Configuration: Push-pull output type (non-negotiable)
Interrupt Capability: Interrupt output support (non-negotiable)
Voltage Supply Range: Minimum 2.3V compatibility required
Operating Temperature Range: Minimum -40°C to 85°C coverage required
Package Compatibility: Surface mount packages with similar footprint considerations

Substitute parts are grouped into two categories based on package type: compact QFN/TQFN packages (24-pin variants) and larger SOIC/SSOP packages (28-pin variants). All listed substitutes maintain functional equivalence through identical I/O count, interface protocol, clock frequency, and output characteristics.

Parameter Comparison

Part Number	Manufacturer	I/O Count	Interface	Clock Freq (kHz)	Voltage Supply (V)	Output Current (mA)	Temp Range (°C)	Package	Product Status
CAT9555HT6I-GT2	onsemi	16	I2C, SMBus	400	2.3 ~ 5.5	10, 24	-40 ~ 85	24-WFQFN	Obsolete
MAX7326AEG+T	Analog Devices/Maxim	16	I2C	400	1.71 ~ 5.5	20	-40 ~ 125	24-QSOP	Active
MCP23016-I/ML	Microchip Technology	16	I2C	400	2 ~ 5.5	25	-40 ~ 85	28-QFN	Active
MCP23016-I/SO	Microchip Technology	16	I2C	400	2 ~ 5.5	25	-40 ~ 85	28-SOIC	Active
MCP23016-I/SS	Microchip Technology	16	I2C	400	2 ~ 5.5	25	-40 ~ 85	28-SSOP	Active
MCP23016T-I/ML	Microchip Technology	16	I2C	400	2 ~ 5.5	25	-40 ~ 85	28-QFN	Active
MCP23016T-I/SS	Microchip Technology	16	I2C	400	2 ~ 5.5	25	-40 ~ 85	28-SSOP	Active
TCA6416APWR	Texas Instruments	16	I2C, SMBus	400	1.65 ~ 5.5	10, 25	-40 ~ 85	24-TSSOP	Active
TCA9535DBR	Texas Instruments	16	I2C, SMBus	400	1.65 ~ 5.5	10, 25	-40 ~ 85	24-SSOP	Active
TCA9535PWR	Texas Instruments	16	I2C, SMBus	400	1.65 ~ 5.5	10, 25	-40 ~ 85	24-TSSOP	Active
TCA9535RGER	Texas Instruments	16	I2C, SMBus	400	1.65 ~ 5.5	10, 25	-40 ~ 85	24-VQFN	Active

Engineering Selection Recommendations

All listed substitute parts maintain active product status with full manufacturer support, contrasting with the obsolete CAT9555HT6I-GT2. Selection criteria are based on the following factors:

For 24-pin compact packages matching original footprint:

TCA9535RGER (24-VQFN) provides the closest form factor to the original 24-WFQFN package
TCA6416APWR and TCA9535PWR (24-TSSOP) offer alternative compact configurations
TCA9535DBR (24-SSOP) provides additional compact option
MAX7326AEG+T (24-QSOP) extends operating temperature to 125°C

For 28-pin packages with enhanced current capability:

MCP23016 series (MCP23016-I/ML, MCP23016-I/SO, MCP23016-I/SS) provides 25mA output current
MCP23016T variants offer tape and reel packaging for high-volume applications

Compliance considerations:

All active substitutes maintain RoHS3 compliance and REACH unaffected status
Moisture sensitivity levels range from MSL 1 to MSL 3, with most parts rated MSL 1 (unlimited)

Voltage supply compatibility:

Texas Instruments parts (TCA series) support lower minimum voltage (1.65V) compared to original specification (2.3V)
Microchip MCP23016 series maintains 2V minimum, closest to original specification

Frequently Asked Questions (FAQ)

Q: Can I directly replace CAT9555HT6I-GT2 with any of these substitutes without PCB redesign?

A: Direct replacement without PCB modification is possible only with TCA9535RGER, which uses the same 24-VQFN (4x4) package as the original 24-WFQFN. Other substitutes require PCB layout changes due to different package types (TSSOP, SSOP, QFN, SOIC).

Q: What is the primary difference between 24-pin and 28-pin package options?

A: Both configurations provide 16 I/O lines with identical functional capability. The 28-pin packages (MCP23016 series) offer higher output current (25mA) compared to 24-pin variants (10-25mA range). Package selection depends on PCB space constraints and current delivery requirements.

Q: Are all substitutes compatible with SMBus protocol?

A: No. Texas Instruments TCA series (TCA6416APWR, TCA9535 variants) explicitly support both I2C and SMBus protocols. Microchip MCP23016 series and Analog Devices MAX7326AEG+T support I2C protocol only. Verify SMBus requirement in your application before selection.

Q: Which substitute offers the widest operating temperature range?

A: MAX7326AEG+T extends to 125°C maximum, compared to 85°C for all other options. This is relevant only for applications requiring extended high-temperature operation.

Q: What are the moisture sensitivity implications for long-term storage?

A: Most substitutes are rated MSL 1 (unlimited moisture sensitivity level), identical to the original part. MCP23016T-I/ML is rated MSL 3 (168 hours), requiring controlled storage conditions. Verify storage requirements for your supply chain.

Q: Can I use these parts interchangeably in existing designs?

A: Functional interchangeability is confirmed for all 16-bit, 400 kHz I2C/I2C+SMBus I/O expanders listed. However, package differences require PCB redesign for most substitutes. Address line configuration and interrupt pin functionality must be verified against your specific application schematic.

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