## ADT7485AARMZ-R7: Technical Overview The **ADT7485AARMZ-R7** is a high-precision digital temperature sensor and voltage monitor manufactured by **onsemi**. It is primarily designed for thermal management in computers, servers, and embedded systems. --- ### 1. Key Features and Functions The device acts as a "system monitor" by measuring external and internal temperatures and monitoring power supply rails. | Feature | Specification / Description | | :--- | :--- | | **Interface** | Simple Serial Transport (SST) 1.1 bus | | **Temp Channels** | 1 Internal sensor, 1 Remote thermal diode (external) | | **Supply Voltage** | 3.0V to 3.6V | | **Temp Accuracy** | ±1°C (External), ±3°C (Internal) | | **Voltage Monitoring** | Monitors $V_{CCP}$ (CPU Core Voltage) | | **Package** | 10-Lead MSOP (Micro Small Outline Package) | --- ### 2. Core Electronic Components & Architecture #### A. Thermal Sensors * **Internal Sensor:** An on-chip bandgap temperature sensor that monitors the ambient temperature of the PCB where the IC is mounted. * **Remote Channel:** Differential inputs ($D+$ and $D-$) connect to a discrete transistor (like a 2N3904) or a thermal diode integrated into a CPU/GPU to measure "hot spot" temperatures. #### B. Analog-to-Digital Converter (ADC) The chip contains a high-resolution Sigma-Delta ADC. It converts the analog voltage levels from the thermal diodes and the $V_{CCP}$ input into 10-bit digital data. #### C. SST Interface Unlike standard $I^2C$ or SMBus, this part uses the **SST (Simple Serial Transport)** protocol. * **One-wire interface:** Provides high-speed communication. * **Deterministic:** Designed for real-time thermal data transfer to the Southbridge or Baseboard Management Controller (BMC). #### D. Voltage Monitoring ($V_{CCP}$) The device includes a specific input to monitor the CPU core voltage. It compares the measured voltage against programmed limits and can trigger alerts if the voltage fluctuates outside the safe range. --- ### 3. Pin Configuration (10-Lead MSOP) | Pin No. | Name | Function | | :--- | :--- | :--- | | 1 | $V_{CCP}$ | CPU Core Voltage Monitor Input | | 2 | $V_{DD}$ | Positive Supply (3.3V) | | 3 | GND | Ground | | 4 | $D1+$ | Positive Connection to Remote Diode | | 5 | $D1-$ | Negative Connection to Remote Diode | | 6-9 | SST/ADDR | SST Data Line and Address Select pins | | 10 | ALERT | Interrupt output for over-limit events | --- ### 4. Applications * **Enterprise Servers:** Monitoring processor temperatures to control fan speeds. * **Desktop PCs:** High-performance gaming rigs requiring precise thermal throttling. * **Embedded Systems:** Industrial PC hardware where environmental conditions vary. ---