AT90LS8535-4AI Equivalent & Substitute Parts

Part Overview

The AT90LS8535-4AI is an 8-bit AVR microcontroller manufactured by Microchip Technology, featuring 8KB FLASH program memory, 512 bytes EEPROM, and 512 bytes RAM in a 44-TQFP surface mount package. This device operates at 4MHz with a supply voltage range of 2.7V to 6V and includes integrated peripherals such as SPI, UART/USART connectivity, PWM, watchdog timer, and brown-out detection.

The AT90LS8535-4AI is classified as obsolete. Identifying equivalent substitute parts is necessary to support legacy system maintenance, design updates, and procurement continuity when original inventory becomes unavailable.

Key Parameters

Parameter	Value
Core Processor	AVR
Core Size	8-Bit
Program Memory Size	8KB (4K x 16)
Program Memory Type	FLASH
EEPROM Size	512 x 8
RAM Size	512 x 8
Number of I/O	32
Data Converters	A/D 8x10b
Package / Case	44-TQFP (10x10)
Mounting Type	Surface Mount

Substitute Part Grouping Explanation

Substitution of the AT90LS8535-4AI is determined by strict equivalence across core functional parameters: identical AVR processor architecture, 8-bit core size, 8KB FLASH program memory capacity, 512-byte EEPROM and RAM configurations, 32 I/O pins, and 44-TQFP package form factor. The ATMEGA8535-16AU meets all these criteria, providing functional and mechanical compatibility despite differences in operating speed and supply voltage specifications.

Parameter Comparison

Parameter	AT90LS8535-4AI	ATMEGA8535-16AU
Manufacturer	Microchip Technology	Microchip Technology
Core Processor	AVR	AVR
Core Size	8-Bit	8-Bit
Speed	4MHz	16MHz
Program Memory Size	8KB (4K x 16)	8KB (4K x 16)
Program Memory Type	FLASH	FLASH
EEPROM Size	512 x 8	512 x 8
RAM Size	512 x 8	512 x 8
Number of I/O	32	32
Data Converters	A/D 8x10b	A/D 8x10b
Voltage - Supply (Vcc/Vdd)	2.7V ~ 6V	4.5V ~ 5.5V
Connectivity	SPI, UART/USART	I2C, SPI, UART/USART
Operating Temperature	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)
Package / Case	44-TQFP (10x10)	44-TQFP (10x10)
Mounting Type	Surface Mount	Surface Mount
Product Status	Obsolete	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant

Engineering Selection Recommendations

The ATMEGA8535-16AU is the qualified substitute for the AT90LS8535-4AI based on the following engineering criteria:

Functional equivalence is established through identical core architecture, memory configuration, I/O count, and package form factor. Both devices are AVR 8-bit microcontrollers with 8KB FLASH, 512-byte EEPROM, and 512-byte RAM in 44-TQFP packaging.

Product status transition from obsolete to active status supports long-term design continuity and supply chain reliability. The ATMEGA8535-16AU maintains active manufacturing status with verified programmability.

Compliance improvement is achieved through ROHS3 compliance of the substitute part, addressing modern regulatory requirements that the original part does not meet.

Supply voltage specification differences (2.7V–6V versus 4.5V–5.5V) and operating speed differences (4MHz versus 16MHz) require circuit-level evaluation to confirm compatibility within specific application contexts.

Frequently Asked Questions (FAQ)

Q: Can the ATMEGA8535-16AU directly replace the AT90LS8535-4AI in existing designs?

A: Mechanical and functional compatibility is established through identical package form factor (44-TQFP), core architecture, and memory specifications. However, the substitute operates at 16MHz versus 4MHz and requires supply voltage within 4.5V–5.5V versus the original 2.7V–6V range. Circuit-level verification is necessary to confirm compatibility with existing power supply and timing requirements.

Q: What are the key parameters that define substitution eligibility?

A: Substitution is determined by: AVR core processor architecture, 8-bit core size, 8KB FLASH program memory, 512-byte EEPROM and RAM, 32 I/O pins, and 44-TQFP package form factor. These parameters must match exactly between the original and substitute part.

Q: Are there connectivity differences between these parts?

A: The AT90LS8535-4AI provides SPI and UART/USART connectivity. The ATMEGA8535-16AU adds I2C connectivity in addition to SPI and UART/USART. Existing designs utilizing only SPI and UART/USART are unaffected by this addition.

Q: What is the significance of the RoHS compliance difference?

A: The AT90LS8535-4AI is RoHS non-compliant, while the ATMEGA8535-16AU is ROHS3 compliant. For applications subject to RoHS regulations or customer requirements, the substitute part satisfies modern environmental and material restriction standards.

Q: How does the speed difference affect substitution?

A: The ATMEGA8535-16AU operates at 16MHz compared to the original 4MHz. This higher speed does not prevent substitution but requires verification that timing-critical firmware and peripheral configurations remain compatible with the faster clock rate.

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