PIC18F4539-I/PT Equivalent & Substitute Parts

Part Overview

The PIC18F4539-I/PT is an 8-bit microcontroller from Microchip Technology's PIC® 18F series, featuring 24KB of FLASH program memory and operating at 40MHz. This device is actively produced and widely used in embedded applications requiring moderate memory capacity and integrated peripherals including I2C, SPI, and UART/USART connectivity. Finding equivalent or substitute parts may be necessary due to inventory constraints, design optimization, or application-specific requirements where alternative memory configurations or I/O counts are acceptable.

Key Parameters

Parameter	Value
Manufacturer	Microchip Technology
Series	PIC® 18F
Core Processor	PIC
Core Size	8-Bit
Speed	40MHz
Program Memory Size	24KB (12K x 16)
Program Memory Type	FLASH
EEPROM Size	256 x 8
RAM Size	1408 x 8
Number of I/O	32
Connectivity	I2C, SPI, UART/USART
Voltage Supply (Vcc/Vdd)	4.2V ~ 5.5V
Data Converters	A/D 8x10b
Package / Case	44-TQFP (10x10)
Operating Temperature	-40°C ~ 85°C (TA)
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	3 (168 Hours)

Substitute Part Grouping Explanation

Substitution of the PIC18F4539-I/PT is evaluated based on strict compatibility criteria within the PIC® 18F microcontroller family. The primary substitution candidate, PIC18F4431-I/PT, maintains compatibility through the following key parameters:

Compatibility Criteria:

Identical manufacturer (Microchip Technology)
Same series (PIC® 18F)
Identical core processor (PIC) and core size (8-Bit)
Identical operating speed (40MHz)
Identical package type (44-TQFP 10x10)
Identical voltage supply range (4.2V ~ 5.5V)
Identical connectivity interfaces (I2C, SPI, UART/USART)
Identical EEPROM size (256 x 8)
Identical operating temperature range (-40°C ~ 85°C)
Identical RoHS and MSL compliance

Differences Requiring Evaluation:

Program memory reduced from 24KB to 16KB
RAM reduced from 1408 x 8 to 768 x 8
I/O count increased from 32 to 36
A/D converter channels increased from 8x10b to 9x10b
Additional peripherals (Power Control PWM, QEI)

Parameter Comparison

Parameter	PIC18F4539-I/PT (Main)	PIC18F4431-I/PT (Substitute)
Manufacturer	Microchip Technology	Microchip Technology
Series	PIC® 18F	PIC® 18F
Core Processor	PIC	PIC
Core Size	8-Bit	8-Bit
Speed	40MHz	40MHz
Program Memory Size	24KB (12K x 16)	16KB (8K x 16)
Program Memory Type	FLASH	FLASH
EEPROM Size	256 x 8	256 x 8
RAM Size	1408 x 8	768 x 8
Number of I/O	32	36
Connectivity	I2C, SPI, UART/USART	I2C, SPI, UART/USART
Voltage Supply (Vcc/Vdd)	4.2V ~ 5.5V	4.2V ~ 5.5V
Data Converters	A/D 8x10b	A/D 9x10b
Oscillator Type	Internal	Internal
Operating Temperature	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)
Mounting Type	Surface Mount	Surface Mount
Package / Case	44-TQFP (10x10)	44-TQFP (10x10)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	3 (168 Hours)	3 (168 Hours)
REACH Status	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

The PIC18F4431-I/PT qualifies as a substitute for the PIC18F4539-I/PT based on electrical and mechanical compatibility within the PIC® 18F family. Both devices maintain identical core specifications, voltage supply ranges, operating temperature ranges, and compliance certifications (ROHS3, REACH Unaffected).

Selection of the PIC18F4431-I/PT as a substitute is appropriate when:

Application firmware requires 16KB or less of FLASH program memory
Application requires 768 x 8 bytes or less of RAM
Additional I/O pins (36 versus 32) are beneficial or neutral to the design
Additional A/D converter channels (9 versus 8) are beneficial or neutral to the design
Additional peripherals (Power Control PWM, QEI) are beneficial or neutral to the design

Selection of the original PIC18F4539-I/PT is required when:

Application firmware exceeds 16KB of FLASH program memory
Application requires more than 768 x 8 bytes of RAM
Design is constrained to exactly 32 I/O pins
Design requires exactly 8 A/D converter channels

Both devices are actively produced with verified inventory availability and carry identical compliance and reliability certifications.

Frequently Asked Questions (FAQ)

Q: Can PIC18F4431-I/PT be used as a direct replacement for PIC18F4539-I/PT?

A: Direct replacement is possible only if the application firmware fits within 16KB of FLASH memory and uses 768 x 8 bytes or less of RAM. The identical 44-TQFP package and pinout support physical interchangeability, but firmware validation is required to confirm memory and peripheral requirements are met.

Q: What are the main differences between these two microcontrollers?

A: The PIC18F4431-I/PT has reduced FLASH memory (16KB versus 24KB) and reduced RAM (768 x 8 versus 1408 x 8), but offers increased I/O count (36 versus 32 pins) and additional A/D converter channels (9 versus 8). Both operate at identical speed (40MHz) and voltage ranges (4.2V ~ 5.5V).

Q: Are the packages identical?

A: Yes, both devices use the 44-TQFP (10x10) package with identical pinout and mounting type (Surface Mount). Physical board compatibility is maintained.

Q: What compliance certifications apply to both parts?

A: Both the PIC18F4539-I/PT and PIC18F4431-I/PT are ROHS3 Compliant, REACH Unaffected, with identical Moisture Sensitivity Level (MSL) of 3 (168 Hours). Both carry identical ECCN and HTSUS classifications.

Q: Which device should be selected for new designs?

A: Selection depends on application memory requirements. If firmware fits within 16KB FLASH and 768 x 8 bytes RAM, the PIC18F4431-I/PT offers additional I/O and A/D channels. If greater memory capacity is required, the PIC18F4539-I/PT is necessary.

Q: Are both devices actively manufactured?

A: Yes, both devices carry Active product status from Microchip Technology with verified inventory availability.

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