ADT7421ARMZ-2RL7

Overview

The ADT7421ARMZ-2RL7 is a dual-channel digital thermometer and under/overtemperature alarm manufactured by onsemi. It features Beta Cancellation Technology for accurate measurement of small geometry CPU processes. The device includes an on-chip local sensor with 1°C resolution and a remote channel with 0.25°C resolution. It operates via a 2-Wire SMBus interface with a default address of 0x4C, while the -2 suffix indicates an SMBus address of 0x4D. Supply voltage ranges from 3.0 V to 3.6 V. Local accuracy is ±2.75°C (0°C to +125°C), and remote accuracy varies between ±1.75°C and ±3.25°C depending on temperature conditions. Measurement ranges are switchable between 0°C to +125°C and -40°C to +125°C.

Feature Summary

• Beta Cancellation Technology automatically compensates for thermal transistor variations in small geometry processors.
• Series Resistance Cancellation removes up to 50 Ohms of parasitic resistance from remote sensor readings.
• Configurable ALERT output supports interrupt signaling or can be reconfigured as a second THERM comparator output.
• Pin and register compatible with ADM1032, ADT7461, and ADT7461A devices.

Applications

• Desktop and notebook computer thermal management
• Industrial controllers
• Smart batteries
• Automotive systems
• Embedded systems and instrumentation

Procurement Notes

Verify the specific ordering suffix matches the required SMBus address configuration. The -2 suffix designates an I2C address of 0x4D, distinct from the standard 0x4C. Confirm package type requirements against the MSOP-8 specification. Check current availability status as distribution may vary. Ensure compatibility with existing system power rails within the 3.0 V to 3.6 V operating range.

Selection Notes

Select this component when beta variation cancellation is required for modern CPU architectures. Choose the -2 suffix variant if multiple sensors share the same SMBus line to prevent address conflicts. Verify that the remote sensing path does not exceed the series resistance cancellation limits. Ensure the application environment stays within the specified junction temperature and supply voltage constraints.

Part Context

This part belongs to the ADT7421 family of precision temperature sensors. It is designed as a drop-in replacement for legacy components like the ADM1032. The device integrates both local and remote sensing capabilities into a single compact package. It serves as a critical monitoring element in complex electronic systems requiring precise thermal regulation.

Replacement Considerations

Compatible replacements include ADM1032, ADT7461, and ADT7461A due to pin and register compatibility. When substituting, verify that the target device supports Beta Cancellation if used with small geometry CPUs. Ensure the replacement supports the required SMBus address configuration for multi-device bus topologies.

FAQ

What is the function of the Beta Cancellation feature?

It automatically cancels errors induced by variations in the Beta factor of embedded thermal transistors found in small geometry (e.g., <45 nm) CPU processes.

How does the Series Resistance Cancellation work?

It automatically removes the temperature offset caused by parasitic resistance in the D+ and D- traces, typically canceling up to 50 Ohms without user characterization.

What is the difference between the ADT7421 and ADT7421-2?

The primary difference is the SMBus address; the standard ADT7421 uses 0x4C, while the ADT7421-2 uses 0x4D, allowing multiple devices on the same bus.

Can the ALERT output be used for purposes other than interrupts?

Yes, the ALERT output (Pin 6) can be reconfigured via the Configuration Register to function as a second THERM output for fan control or clock throttling.