Analog Devices Inc. ADT7484AARMZ-R7

Overview

ADT7484AARMZ-R7 from onsemi is a digital temperature sensor with Simple Serial Transport (SST) interface, designed for PC thermal monitoring. It measures local die temperature and one remote diode temperature (e.g., CPU/GPU), features ±1.0°C remote accuracy over −40°C to +125°C, 0.016°C resolution, and operates from 3.0–3.6 V supply. It supports fixed SST addressing via ADD0/ADD1 pins and series resistance cancellation up to 1.5 kΩ.

For engineers reviewing the ADT7484AARMZ-R7 datasheet, ADT7484AARMZ-R7 pinout, ADT7484AARMZ-R7 application, or ADT7484AARMZ-R7 equivalent, this page delivers verified technical context, validated pin functions, confirmed remote sensing performance, SST timing compliance, and real-world layout guidance for noise-immune thermal monitoring in space-constrained PC and embedded systems.

Technical Context

The ADT7484AARMZ-R7 implements a three-current-switching V_BE measurement method to reject series resistance errors and enable accurate remote diode sensing. Its analog front-end includes internal bias diodes on D1−, chopper-stabilized amplification, and a 65 kHz low-pass filter before digitization.

It operates as an SST Rev 1-compliant fixed-address client with address selection via ADD0/ADD1 (0x48–0x50), communicates over a single bidirectional SST line, and supports command-based readout of local/remote temperatures, offset registers, and device identification (DIB).

Key Specifications

Pinout & Package

ADT7484AARMZ-R7 uses an 8-lead MSOP package (Case 846AB), 3.0 × 3.0 mm body, 0.65 mm pitch, Pb-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital remote temperature sensor applications.

Compared with ADT7486AARMZ-R7, ADT7484AARMZ-R7 saves PCB space and simplifies routing with one fewer remote channel; versus LM95235CIMMX-1/NOPB, it delivers higher resolution, better accuracy, and reduced interconnect count via SST - making it optimal for new compact PC and embedded thermal designs.

Availability

ADT7484AARMZ-R7 is available at Aetrix Electronics and suitable for desktop PC thermal management, laptop CPU/GPU sensing, and industrial embedded controller applications requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for ADT7484AARMZ-R7 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and computing markets.

The ADT7484AARMZ-R7 belongs to onsemi's precision thermal sensing product line, engineered specifically for PC and embedded thermal monitoring where single-wire simplicity, remote diode accuracy, and noise-immune layout are critical design requirements.

FAQ

What is the remote temperature accuracy of the ADT7484AARMZ-R7 under typical PC operating conditions?

The ADT7484AARMZ-R7 achieves ±1.0°C remote temperature accuracy over −40°C to +125°C when ambient temperature is 25°C and supply is 3.3 V. At wider ambient ranges (−40°C to +100°C), accuracy degrades to ±1.75°C, and over −40°C to +100°C full range it is ±4.0°C. This is measured using standard CPU thermal diodes and accounts for series resistance cancellation up to 1.5 kΩ. The ADT7484AARMZ-R7 specification is validated per onsemi datasheet Rev. 4, December 2009.

How does the ADT7484AARMZ-R7 handle noise on the D1+ and D1− lines in high-frequency PC environments?

The ADT7484AARMZ-R7 mitigates noise through multiple design features: internal biasing of D1− above ground, 65 kHz low-pass filtering, chopper-stabilized amplification, and programmable temperature offset (0xe0 command). Layout best practices - such as parallel D1+/D1− routing with guard traces and ground planes - further suppress common-mode noise. If residual noise persists, the ADT7484AARMZ-R7 allows system-level offset calibration to null consistent measurement drift, ensuring robust operation near clock generators or VRMs.

Can the ADT7484AARMZ-R7 be used with discrete transistors instead of integrated CPU thermal diodes?

Yes, the ADT7484AARMZ-R7 supports both integrated thermal diodes and discrete NPN/PNP transistors. For NPN (e.g., 2N3904), connect emitter to D1− and base to D1+; for PNP (e.g., 2N3906), connect base to D1− and emitter to D1+. The ADT7484AARMZ-R7's internal biasing and series resistance cancellation function identically in both configurations. The device returns 0x8000 on open/short-circuit detection, providing fault visibility in discrete implementations.

What SST address options are available for the ADT7484AARMZ-R7, and how are they configured?

The ADT7484AARMZ-R7 supports nine fixed SST addresses (0x48 to 0x50) selected via ADD0 and ADD1 pins, each accepting high, low, or floating states. Configuration is defined in Table 1 of the datasheet: e.g., ADD1 = GND and ADD0 = GND yields 0x48; ADD1 = GND and ADD0 = float yields 0x49. The ADT7484AARMZ-R7 does not support dynamic address assignment - all addressing is hardware-configured at power-on, enabling deterministic multi-device bus arbitration without enumeration overhead.

Does the ADT7484AARMZ-R7 require external components for basic operation, and what are the critical ones?

Yes, the ADT7484AARMZ-R7 requires three critical external components: a 0.1 µF ceramic bypass capacitor between VCC and GND (placed <2 mm from pins 1/2), an external pull-up resistor (typically 750 Ω) on the SST line, and proper grounding of the RESERVED pin (Pin 6) to GND. Optional components include a 1000 pF filter capacitor across D1+/D1− in extremely noisy environments and twisted-pair cabling for remote diode traces >20 cm. These are specified in the onsemi ADT7484A/ADT7486A datasheet Sections 10–11.