FM75M8 Temperature Sensor – Equivalent & Substitute Parts

Part Overview

The FM75M8 is a digital local temperature sensor manufactured by onsemi, designed for applications requiring temperature monitoring across the -40°C to 125°C range. This component features 11-bit resolution, SMBus output, and programmable functionality including output switching and limit configuration. The FM75M8 is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	FM75M8 Specification
Sensor Type	Digital, Local
Sensing Temperature Range	-40°C ~ 125°C
Resolution	11 bit
Output Type	SMBus
Supply Voltage	2.7V ~ 5.5V
Accuracy (Best/Worst)	±2°C / ±4°C
Package	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Features	Output Switch, Programmable Limit, Programmable Resolution

Substitute Part Grouping Explanation

Substitution for the FM75M8 is determined by the following critical parameters:

Package Compatibility: All substitutes must use 8-SOIC surface mount packaging with identical 0.154" (3.90mm) width
Supply Voltage Range: Minimum 2.7V support required for direct replacement
Resolution: 11-bit resolution preferred for functional equivalence
Output Protocol: SMBus or I2C compatibility (I2C is backward compatible with SMBus)
Temperature Range: Minimum -40°C to 125°C operating range
Accuracy: ±2°C or better at nominal conditions
Product Status: Active status preferred due to obsolescence of FM75M8

Substitute parts are grouped into two categories:

Upgrade Substitutes (Direct functional replacement with extended capabilities):

DS75S+ and DS75S+T&R: Extended temperature range (-55°C to 125°C), I2C output, additional power management features

Similar Substitutes (Compatible alternatives with parameter variations):

DS1621S+ / DS1621S+T&R: 9-bit resolution, enhanced accuracy
DS1631Z+ / DS1631Z+T&R: 11-bit resolution, enhanced accuracy
DS1721S+ / DS1721S+T&R: 11-bit resolution, enhanced accuracy
DS75LVS+ / DS75LVS+T&R: Low-voltage variant (1.7V minimum)

Parameter Comparison

Part Number	Manufacturer	Temperature Range	Resolution	Output Type	Supply Voltage	Accuracy (Best/Worst)	Package	Status
FM75M8	onsemi	-40°C ~ 125°C	11 bit	SMBus	2.7V ~ 5.5V	±2°C / ±4°C	8-SOIC	Obsolete
DS75S+	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	2.7V ~ 5.5V	±2°C / ±3°C	8-SOIC	Active
DS75S+T&R	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	2.7V ~ 5.5V	±2°C / ±3°C	8-SOIC	Active
DS1621S+	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	9 bit	I2C	2.7V ~ 5.5V	±0.5°C / ±2°C	8-SOIC	Active
DS1621S+T&R	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	9 bit	I2C	2.7V ~ 5.5V	±0.5°C / ±2°C	8-SOIC	Active
DS1631Z+	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	2.7V ~ 5.5V	±0.5°C / ±2°C	8-SOIC	Active
DS1631Z+T&R	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	2.7V ~ 5.5V	±0.5°C / ±2°C	8-SOIC	Active
DS1721S+	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	2.7V ~ 5.5V	±1°C / ±2°C	8-SOIC	Active
DS1721S+T&R	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	2.7V ~ 5.5V	±1°C / ±2°C	8-SOIC	Active
DS75LVS+	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	1.7V ~ 3.7V	±2°C / ±3°C	8-SOIC	Active
DS75LVS+T&R	Analog Devices Inc./Maxim Integrated	-55°C ~ 125°C	11 bit	I2C	1.7V ~ 3.7V	±2°C / ±3°C	8-SOIC	Active

Engineering Selection Recommendations

Primary Upgrade Path: DS75S+ or DS75S+T&R

The DS75S+ series provides direct functional replacement with extended operating temperature range (-55°C to 125°C versus -40°C to 125°C). Both variants maintain 11-bit resolution, 2.7V–5.5V supply compatibility, and identical 8-SOIC packaging. The I2C output is protocol-compatible with SMBus applications. DS75S+T&R offers tape and reel packaging for high-volume procurement. Both parts are ROHS3 compliant and carry active product status.

Alternative with Enhanced Accuracy: DS1631Z+ or DS1631Z+T&R

The DS1631Z+ series matches the FM75M8 in 11-bit resolution and package form factor while providing superior accuracy (±0.5°C best case versus ±2°C). Extended temperature range and I2C output maintain compatibility. ROHS3 compliance and active status support long-term availability.

Low-Voltage Applications: DS75LVS+ or DS75LVS+T&R

For designs requiring operation below 2.7V, the DS75LVS+ series operates from 1.7V minimum while maintaining 11-bit resolution and identical packaging. Accuracy and temperature range match DS75S+ specifications. Use only when supply voltage constraints require this variant.

Resolution Trade-off Option: DS1621S+ or DS1621S+T&R

The DS1621S+ series reduces resolution to 9 bits but delivers enhanced accuracy (±0.5°C best case). Select only when application requirements permit reduced resolution in exchange for improved measurement precision.

All substitute parts carry REACH Unaffected and EAR99 ECCN classifications matching the FM75M8.

Frequently Asked Questions (FAQ)

Q: Can DS75S+ directly replace FM75M8 without firmware changes?

A: DS75S+ uses I2C protocol while FM75M8 uses SMBus. I2C is a subset of SMBus, making DS75S+ compatible with SMBus host controllers. However, verify that your SMBus implementation supports I2C devices. Both parts use identical 8-SOIC packaging and pin configuration.

Q: What is the difference between DS75S+ and DS75S+T&R?

A: Both parts are electrically identical. DS75S+ ships in tube packaging; DS75S+T&R ships in cut tape and Digi-Reel format. Select based on procurement volume and assembly line requirements. DS75S+T&R offers higher inventory availability (48,300 pcs versus 6,172 pcs).

Q: Why does DS1631Z+ show better accuracy than FM75M8?

A: DS1631Z+ achieves ±0.5°C accuracy at nominal conditions compared to FM75M8's ±2°C. This reflects improved sensor design in the DS1631 architecture. Both maintain ±2°C worst-case accuracy across the full operating range.

Q: Is DS75LVS+ suitable for 5V systems?

A: DS75LVS+ operates from 1.7V to 3.7V maximum. It is not suitable for 5V systems. Use DS75S+ or DS1631Z+ for 2.7V–5.5V supply compatibility.

Q: Do all substitutes support programmable resolution like FM75M8?

A: DS75S+, DS1631Z+, DS1721S+, and DS75LVS+ all support programmable resolution. DS1621S+ does not offer this feature. Verify firmware compatibility with your application's resolution requirements.

Q: What is the moisture sensitivity level for substitute parts?

A: All substitute parts carry MSL 1 (Unlimited), matching FM75M8 specifications. No special moisture handling is required during storage or assembly.

Q: Are substitute parts RoHS compliant?

A: All Analog Devices Inc./Maxim Integrated substitutes are ROHS3 compliant. FM75M8 REACH status is unaffected; all substitutes maintain identical REACH Unaffected classification.

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