Analog Devices Inc. ADM694AN

Overview

ADM694AN from Analog Devices is an 8-pin DIP microprocessor supervisory circuit providing power-on reset, battery backup switchover, watchdog timer, and power-fail warning for +5 V systems. It asserts RESET at 4.65 V threshold with 200 ms pulse width, supports 100 mA VOUT drive, and operates down to 1 V VCC. It is used in industrial controllers and embedded systems requiring reliable brownout protection and nonvolatile memory retention.

For engineers reviewing the ADM694AN datasheet, ADM694AN pinout, ADM694AN application, or ADM694AN equivalent, key selection criteria include its fixed 200 ms reset timeout, 4.65 V reset threshold, battery switchover hysteresis (50 mV power-down / 70 mV power-up), CE gating capability, and compatibility with 5 V ±5% supplies.

Technical Context

The ADM694AN integrates a precision voltage detector (4.65 V ±130 mV), a fixed 1.6 s watchdog timer, and a battery switchover circuit with 1.5 Ω on-resistance in normal mode and 20 Ω in backup mode. Its RESET output remains functional down to 1 V VCC, and it features a 5 ns CEIN-to-CEOUT propagation delay for real-time chip enable gating during supply transients.

It uses an internal oscillator for timing control, with OSC SEL enabling either internal 1.6 s watchdog operation or external clock/capacitor configuration (though ADM694AN lacks adjustable reset timeout - only ADM691/693/695 support that). In battery backup mode, RESET goes low, LOW LINE goes low, BATT ON goes high, and WDI/PFI/CEIN are internally disconnected to minimize leakage.

Key Specifications

Pinout & Package

ADM694AN is supplied in an 8-pin plastic dual in-line package (N-8 DIP), 0.3 inch body width, with through-hole mounting and standard 0.1 inch pin spacing.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with MAX694CPD+ and TPS3823-46DBVR, ADM694AN delivers integrated battery switchover, CE gating, and PFO-based early warning - eliminating four external components and reducing BOM count while improving system-level reliability in memory-critical applications.

Availability

ADM694AN is available at Aetrix Electronics and suitable for industrial controllers, embedded data loggers, automotive body modules, and medical handhelds requiring stable component supply across extended temperature ranges (–40°C to +85°C).

Supply support for ADM694AN 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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The ADM690–ADM695 family was designed specifically for microprocessor system supervision - integrating reset generation, battery backup, watchdog timing, and power-fail warning into single-chip solutions for industrial and automotive embedded applications.

FAQ

What is the reset threshold voltage of the ADM694AN and how tightly is it specified?

The ADM694AN has a nominal reset threshold of 4.65 V, with guaranteed minimum and maximum values of 4.50 V and 4.73 V respectively over temperature and supply conditions. This 230 mV total tolerance ensures robust operation with standard 5 V ±5% power supplies while maintaining immunity to noise-induced false resets.

Does the ADM694AN support adjustable reset timeout or watchdog period?

No - the ADM694AN provides fixed timing: 200 ms reset pulse width and 1.6 s watchdog timeout. Adjustable reset/watchdog periods are exclusive to the 16-pin variants (ADM691/693/695) which include OSC IN and OSC SEL pins. ADM694AN uses internal oscillator only and does not support external timing components.

Can the ADM694AN drive more than 100 mA on the VOUT pin?

The ADM694AN's internal PMOS switch is rated for 100 mA continuous current in normal mode. For higher loads or lower dropout, an external PNP transistor can be driven by the BATT ON signal - though note that ADM694AN lacks BATT ON output (only ADM691/693/695 provide it), so external base drive circuitry is required.

What happens to the ADM694AN outputs when VCC drops below 1 V?

When VCC falls below 1 V, the ADM694AN guarantees RESET remains asserted (low), LOW LINE stays low, and VOUT switches to VBATT (if present and valid). PFO goes low, WDI and CEIN are internally disconnected, and all digital outputs enter high-impedance or defined inactive states per Table II in the datasheet - ensuring fail-safe behavior.

Is the ADM694AN compatible with modern 3.3 V microcontrollers?

The ADM694AN is designed for 5 V systems: its reset threshold (4.65 V), VCC range (4.75–5.5 V), and logic thresholds assume +5 V operation. It is not directly compatible with 3.3 V microcontrollers - use ADM692AN (4.4 V threshold) or newer alternatives like MAX6369 for 3.3 V supervision.