Analog Devices Inc. AD7818AR-REEL

Overview

AD7818AR-REEL from Analog Devices is a 10-bit, single-channel analog-to-digital converter with integrated temperature sensor, 9 μs conversion time, on-chip 2.5 V reference (±1%), and overtemperature indicator output - used in battery-powered industrial monitoring systems for ambient temperature and voltage sensing.

For engineers reviewing the AD7818AR-REEL datasheet, AD7818AR-REEL pinout, AD7818AR-REEL application, or AD7818AR-REEL equivalent, key selection criteria include its single-ended VIN input, 2.7–5.5 V supply range, automatic power-down at 4 μW (10 SPS), and compatibility with SPI/QSPI/MICROWIRE serial interfaces.

Technical Context

The AD7818AR-REEL implements a successive approximation ADC architecture with capacitor DAC, inherent track-and-hold functionality, and an internal clock oscillator - eliminating need for external timing components. Its temperature sensor is accessed via Channel 0 and delivers 0.25°C resolution with ±2°C accuracy from −40°C to +85°C.

It uses a flexible 3-wire serial interface (DIN/OUT, SCLK, RD/WR) with Intel 8051, Motorola SPI, and National MICROWIRE protocol support. The OTI pin provides asynchronous overtemperature alerting by comparing Channel 0's ADC result against an 8-bit register value.

Key Specifications

Pinout & Package

AD7818AR-REEL is housed in an 8-lead SOIC package (width 3.9 mm, body height 1.75 mm, lead pitch 1.27 mm), RoHS-compliant and rated for industrial temperature operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 10-bit temperature-sensing ADC applications.

Compared with MAX1270BCPP+ and ADS7822U, AD7818AR-REEL uniquely combines 10-bit precision, on-chip temperature sensing, and ultra-low 4 μW power at 10 SPS - making it optimal for space- and energy-constrained thermal-aware systems where integration reduces design risk and bill-of-materials complexity.

Availability

AD7818AR-REEL is available at Aetrix Electronics and suitable for industrial process monitoring, battery management systems, and automotive cabin sensors requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7818AR-REEL 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

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD7817/AD7818 product line was designed specifically for embedded thermal-aware data acquisition - delivering integrated temperature sensing, low-power operation, and robust serial interfacing in minimal footprint packages.

FAQ

What is the maximum sampling rate supported by the AD7818AR-REEL?

The AD7818AR-REEL achieves a 9 μs conversion time for its single analog input channel, enabling a theoretical maximum sampling rate of approximately 111 kSPS. However, practical throughput is limited by serial interface speed, CONVST timing, and bus turnaround - typical sustained rates are ≤100 kSPS in optimized SPI configurations. The AD7818AR-REEL does not specify dynamic performance above 100 kSPS in its Rev. E datasheet.

Does the AD7818AR-REEL require an external reference voltage?

No, the AD7818AR-REEL includes a factory-trimmed 2.5 V on-chip reference with ±1% initial accuracy and 30 ppm/°C temperature coefficient - fully sufficient for most industrial temperature and voltage monitoring applications. An external reference is neither required nor supported; the REFIN pin is absent in the AD7818AR-REEL's 8-lead SOIC package.

How is the temperature sensor accessed on the AD7818AR-REEL?

The temperature sensor in the AD7818AR-REEL is accessed exclusively through Channel 0. When CONVST is asserted, the internal multiplexer routes the sensor output to the ADC core. A completed conversion yields a 10-bit code corresponding to ambient temperature with 0.25°C resolution - no external connections or configuration registers are needed beyond standard serial readout of Channel 0 data.

What is the function of the OTI pin on the AD7818AR-REEL?

The OTI (Overtemperature Indicator) pin on the AD7818AR-REEL is an active-low, open-drain output that asserts logic low when the digitized temperature reading from Channel 0 exceeds the value stored in the internal 8-bit overtemperature register (OTR). It resets automatically after each serial read operation - enabling direct connection to MCU interrupt inputs for immediate thermal event handling without polling.

Can the AD7818AR-REEL operate from a 3.3 V supply?

Yes, the AD7818AR-REEL is fully specified for operation from 2.7 V to 5.5 V, including standard 3.3 V rails. At VDD = 3.3 V, it maintains ±2°C temperature accuracy, 9 μs conversion time, and 1.3 mA typical supply current in normal mode. Logic thresholds scale with VDD, ensuring compatibility with 3.3 V microcontrollers without level-shifting.