Analog Devices Inc. ADM709RAR

Overview

ADM709RAR from Analog Devices is a precision power supply monitor IC with active-low reset output, 2.63 V reset threshold, 140 ms minimum power-on reset pulse, and operation down to 1 V supply voltage - used for reliable microprocessor reset in industrial embedded systems requiring brownout and power-up supervision.

For engineers reviewing the ADM709RAR datasheet, ADM709RAR pinout, ADM709RAR application, or ADM709RAR equivalent, key selection considerations include reset threshold accuracy (±0.08 V), SO-8 package compatibility, guaranteed RESET functionality at VCC ≥ 1 V, and immunity to sub-20 µs VCC transients in critical control environments.

Technical Context

The ADM709RAR implements a bandgap-based voltage comparator with internal timing circuitry to generate a minimum 140 ms active-low reset pulse after VCC rises above 2.63 V. Its RESET output remains functional down to VCC = 1.0 V, enabling stable shutdown sequencing.

It features glitch immunity against short VCC transients (<20 µs), no external components required for basic operation, and supports bidirectional µP reset lines via optional series resistor - all within an 8-pin SOIC footprint with five NC pins.

Key Specifications

Pinout & Package

ADM709RAR is housed in an 8-pin SOIC (SO-8) package with exposed pad not present; five pins (1, 4, 5, 6, 8) are internally unconnected and must remain floating or grounded per layout best practice.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX709RCSA+ and TPS3808G18DBVR, ADM709RAR offers tighter reset timing control (140 ms vs. 200 ms), lower quiescent current (35 µA vs. 100 µA/1.5 µA), and guaranteed functionality down to 1 V - making it optimal for industrial and battery-backed systems demanding deterministic, low-power reset behavior.

Availability

ADM709RAR is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic equipment, automotive body control modules, and smart energy meters requiring stable component supply and long-term lifecycle support.

Supply support for ADM709RAR 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The ADM709 family was designed specifically for robust, low-cost power supply monitoring in microprocessor-based systems - delivering precision reset generation without external components across wide temperature and voltage ranges.

FAQ

What is the exact reset threshold voltage of the ADM709RAR?

The ADM709RAR has a nominal reset threshold of 2.63 V, with a guaranteed tolerance of ±0.08 V (2.55 V to 2.70 V) over the full –40°C to +85°C operating temperature range. This value is laser-trimmed at wafer test and does not require external calibration. The ADM709RAR's 2.63 V threshold is optimized for monitoring +2.7 V and +3.0 V supply rails in modern low-voltage microprocessor systems.

Does the ADM709RAR support operation below 2.0 V VCC?

Yes, the ADM709RAR guarantees functional RESET output down to VCC = 1.0 V, as confirmed in the Absolute Maximum Ratings and Specifications tables. Below 1.0 V, the RESET output is not guaranteed - if sustained low-state assertion is required below 1 V, a 100 kΩ pull-down resistor between RESET and GND is recommended per the datasheet Figure 5. This behavior makes ADM709RAR uniquely suited for graceful shutdown sequencing in battery-powered devices.

Is the ADM709RAR pin-compatible with the MAX709R?

Yes, the ADM709RAR is a direct pin-compatible upgrade for the MAX709R in SO-8 packages, sharing identical pinout (VCC=2, GND=3, RESET=7, NC=1/4/5/6/8), same 2.63 V threshold, and compatible timing. However, ADM709RAR improves upon MAX709R with lower quiescent current (35 µA vs. 100 µA typ), enhanced glitch immunity, and guaranteed 1 V operation - all without requiring PCB or schematic changes.

What is the minimum power-on reset pulse width for the ADM709RAR?

The ADM709RAR guarantees a minimum power-on reset pulse width of 140 ms after VCC rises above the 2.63 V threshold, with typical duration of 280 ms and maximum of 380 ms. This timing is internally generated and independent of external components. The 140 ms minimum ensures compliance with most microprocessors' reset setup requirements, including ARM Cortex-M and Renesas RL78 families, without additional RC timing networks.

Can the ADM709RAR be used with microcontrollers that have bidirectional reset pins?

Yes, the ADM709RAR can interface safely with bidirectional reset pins (e.g., MC68HC11, some PIC and STM32 variants) by adding a 4.7 kΩ series resistor between its open-drain RESET output and the µP reset line. This prevents signal contention during µP-driven reset assertion while preserving ADM709RAR's ability to force reset during power faults. The resistor value is validated in Analog Devices' Figure 6 and ensures reliable level translation without loading the µP's internal driver.