LM77CIM-3 Temperature Sensor Equivalent & Substitute Parts

Part Overview

The LM77CIM-3 is a digital temperature sensor manufactured by Texas Instruments, designed for local temperature measurement across the -55°C to 125°C range with 9-bit resolution and I2C output interface. The device operates on supply voltages between 3V and 5.5V and includes programmable limit switches and shutdown mode functionality. This part is classified as "Not For New Designs," indicating it has been superseded in the product lifecycle. Finding equivalent substitute parts is necessary for ongoing system support, maintenance applications, and designs requiring compatible thermal monitoring solutions.

Key Parameters

Parameter	Value
Sensor Type	Digital, Local
Sensing Temperature Range	-55°C ~ 125°C
Resolution	9 bits
Output Type	I2C
Supply Voltage	3V ~ 5.5V
Accuracy	±1.5°C (-10°C ~ 65°C) / ±3°C (-55°C ~ 125°C)
Package	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Features	Output Switch, Programmable Limit, Shutdown Mode

Substitute Part Grouping Explanation

Substitution eligibility for the LM77CIM-3 is determined by the following critical parameters:

Output Interface: I2C protocol compatibility
Temperature Range: Minimum coverage of -55°C to 125°C operating window
Resolution: 9-bit or higher digital output
Supply Voltage: Compatibility with 3V to 5.5V range
Sensor Type: Digital local temperature measurement capability
Package Compatibility: Surface mount form factor suitable for PCB integration

The substitute parts identified (LM77CIM-3/NOPB and MCP9844T-BE variants) meet these core electrical and functional requirements. Variations in packaging format (Tube, Cut Tape, Tape & Reel) and product status do not affect functional equivalence but may impact procurement and inventory considerations.

Parameter Comparison

Parameter	LM77CIM-3	LM77CIM-3/NOPB	MCP9844T-BE/MNY	MCP9844T-BE/MNYAA	MCP9844T-BE/MNYAB
Manufacturer	Texas Instruments	Texas Instruments	Microchip Technology	Microchip Technology	Microchip Technology
Sensor Type	Digital, Local	Digital, Local	Internal	Internal	Internal
Temperature Range	-55°C ~ 125°C	-55°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C
Resolution	9 bits	9 bits	Not specified	Not specified	Not specified
Output Type	I2C	I2C	2-Wire Serial, I2C	2-Wire Serial, I2C	2-Wire Serial, I2C
Supply Voltage	3V ~ 5.5V	3V ~ 5.5V	1.7V ~ 3.6V	1.7V ~ 3.6V	1.7V ~ 3.6V
Accuracy	±1.5°C / ±3°C	±1.5°C / ±3°C	±3°C (Max)	±3°C (Max)	±3°C (Max)
Package	8-SOIC	8-SOIC	8-TDFN (2x3)	8-TDFN (2x3)	8-TDFN (2x3)
Product Status	Not For New Designs	Obsolete	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Equivalent (Same Manufacturer): The LM77CIM-3/NOPB is the direct equivalent from Texas Instruments, maintaining identical electrical specifications and package format. This part is classified as Obsolete but remains functionally equivalent. Selection of this substitute is appropriate when maintaining design continuity with the original LM77 architecture is prioritized.

Cross-Manufacturer Alternatives (Microchip MCP9844T-BE variants): The MCP9844T-BE/MNY, MCP9844T-BE/MNYAA, and MCP9844T-BE/MNYAB are active products from Microchip Technology offering I2C-compatible temperature monitoring. These parts feature ROHS3 compliance and REACH unaffected status, providing superior regulatory positioning compared to the original LM77CIM-3. The MCP9844 series operates at lower supply voltages (1.7V ~ 3.6V) and uses a different package format (8-TDFN versus 8-SOIC), requiring PCB layout and schematic modifications. The temperature range extends to -40°C minimum (versus -55°C for LM77CIM-3), which may be acceptable depending on application requirements.

Compliance Considerations: The LM77CIM-3 is RoHS non-compliant and REACH affected. All substitute options provide improved compliance status, with LM77CIM-3/NOPB offering ROHS3 compliance and the Microchip variants offering both ROHS3 compliance and REACH unaffected designation.

Frequently Asked Questions (FAQ)

Q: Can the MCP9844T-BE variants directly replace the LM77CIM-3 without PCB modifications?

A: No. The MCP9844T-BE uses an 8-TDFN (2x3) package, while the LM77CIM-3 uses 8-SOIC. Package footprints are incompatible, requiring PCB layout redesign. Additionally, the supply voltage range differs (1.7V ~ 3.6V for MCP9844 versus 3V ~ 5.5V for LM77CIM-3), necessitating power supply circuit evaluation.

Q: What is the minimum temperature difference between the LM77CIM-3 and MCP9844T-BE variants?

A: The LM77CIM-3 operates down to -55°C, while MCP9844T-BE variants operate down to -40°C. Applications requiring operation below -40°C must use the LM77CIM-3 or LM77CIM-3/NOPB.

Q: Are all substitute parts I2C compatible with the original LM77CIM-3?

A: Yes. All listed substitutes support I2C protocol (2-Wire Serial interface), ensuring software and firmware compatibility at the communication protocol level. However, register maps and command structures may differ between manufacturers and require firmware validation.

Q: What is the difference between LM77CIM-3/NOPB and the Microchip MCP9844T-BE options?

A: LM77CIM-3/NOPB is the direct Texas Instruments equivalent with identical electrical specifications and 8-SOIC packaging. MCP9844T-BE variants are cross-manufacturer alternatives with different packaging (8-TDFN), lower supply voltage range, and active product status. LM77CIM-3/NOPB is classified as Obsolete.

Q: Which substitute offers the best regulatory compliance?

A: All Microchip MCP9844T-BE variants (MCP9844T-BE/MNY, MCP9844T-BE/MNYAA, MCP9844T-BE/MNYAB) offer ROHS3 compliance and REACH unaffected status. The LM77CIM-3/NOPB provides ROHS3 compliance but remains REACH affected.

Q: Do packaging differences (Tube, Cut Tape, Tape & Reel) affect functional performance?

A: No. Packaging format differences (Tube for LM77CIM-3/NOPB, Cut Tape for MCP9844T-BE/MNY, Tape & Reel for MCP9844T-BE/MNYAA and MCP9844T-BE/MNYAB) affect only procurement, handling, and inventory management. Electrical and functional performance remains identical within each part number.

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