Analog Devices Inc. ADM709SAR

Overview

ADM709SAR from Analog Devices is a precision power supply monitor IC with active-low reset output, 2.93 V threshold, 140 ms minimum power-on reset pulse, and operation down to 1 V supply voltage - used for reliable microprocessor reset in +3 V systems.

For engineers reviewing the ADM709SAR datasheet, ADM709SAR pinout, ADM709SAR application, or ADM709SAR equivalent, key selection considerations include reset threshold accuracy, guaranteed reset assertion at VCC ≥ 1 V, glitch immunity on VCC, SO-8 package compatibility, and direct upgrade path from MAX709-series supervisors.

Technical Context

The ADM709SAR integrates a precision voltage comparator and internal 140 ms reset timer to generate a clean, debounced active-low RESET signal during power-up, brownout, and power-down events. Its reset generator remains functional even as VCC drops to 1 V, ensuring controlled µP shutdown.

It features no-connect pins (1,4,5,6,8), single-supply operation (1.2–5.5 V), and guaranteed reset hold time over –40°C to +85°C. The device uses internal hysteresis and is immune to short VCC transients without external filtering.

Key Specifications

Pinout & Package

ADM709SAR is housed in an 8-lead SOIC (SO-8) package with standard 1.27 mm pitch, JEDEC MS-012 compliant outline, and exposed pad not present. Pin 1 is marked by notch or dot; device is surface-mount compatible.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power supply monitor applications.

Compared with MAX709SASA+ and TPS3808G18DBVR, the ADM709SAR delivers guaranteed 1 V operation and lower supply current than MAX709, while avoiding external component dependency unlike TPS3808 - making it optimal for cost-sensitive, robust +3 V industrial reset applications.

Availability

ADM709SAR is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, medical point-of-care devices, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADM709SAR 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, founded in 1965 and headquartered in Wilmington, MA.

The ADM709 belongs to Analog Devices' precision voltage supervisor product line, engineered specifically for deterministic, low-power, and glitch-immune microprocessor reset in industrial and automotive power management systems.

FAQ

What is the exact reset threshold voltage of the ADM709SAR?

The ADM709SAR has a nominal reset threshold of 2.93 V, with a guaranteed range of 2.85 V to 3.00 V across –40°C to +85°C. This value is laser-trimmed at wafer test and specified in the Absolute Maximum Ratings table of the official Analog Devices datasheet Rev. 0. It is designed to accurately supervise +3 V power rails without external calibration.

Does the ADM709SAR support operation below 1.2 V VCC?

Yes - the ADM709SAR RESET output is guaranteed functional down to VCC = 1.0 V, as explicitly stated in the "Circuit Information" section and confirmed in Figure 5 of the datasheet. Below 1 V, a 100 kΩ pull-down resistor is recommended to maintain low state. This capability ensures fail-safe reset assertion during deep brownouts where other supervisors cease operation.

Is the ADM709SAR pin-compatible with the MAX709S?

No - while both are SO-8 voltage supervisors with 2.93 V thresholds, the ADM709SAR has five no-connect pins (1,4,5,6,8), whereas MAX709S uses all eight pins functionally. Pin 1 on ADM709SAR is NC, but on MAX709S it is RESET. Direct replacement requires PCB redesign; however, the ADM709SAR is positioned as an upgrade with improved 1 V operation and lower quiescent current.

What is the minimum power-on reset pulse width for the ADM709SAR?

The ADM709SAR guarantees a minimum power-on reset pulse width of 140 ms after VCC rises above the 2.93 V threshold, as specified in the "RESET Active Time-Out Period" row of the Electrical Characteristics table. Typical duration is 280 ms, and maximum is 380 ms. This timing allows ample margin for microprocessor core and peripheral stabilization before release from reset.

Can the ADM709SAR be used with microcontrollers having bidirectional reset lines?

Yes - the ADM709SAR RESET output is active-low and compatible with bidirectional µP reset lines such as those found on MC68HC11. Analog Devices recommends adding a 4.7 kΩ series resistor between ADM709SAR pin 7 and the µP reset pin to prevent signal contention, as illustrated in Figure 6 of the datasheet. This preserves safe bidirectional operation without latch-up risk.