Analog Devices Inc. ADM708AN

Overview

ADM708AN from Analog Devices is a precision microprocessor supervisory circuit with active-high reset output, 4.40 V supply voltage monitor threshold, 200 ms reset pulse width, 190 μA quiescent current, and power-fail comparator (PFI/PFO) for low-battery or preregulator monitoring in 5 V systems.

For engineers reviewing the ADM708AN datasheet, ADM708AN pinout, ADM708AN application, or ADM708AN equivalent, this device serves as a drop-in replacement for legacy MAX708-style supervision in industrial controllers, embedded instrumentation, and battery-backed computing where guaranteed RESET validity down to 1 V VCC and debounced manual reset are required.

Technical Context

The ADM708AN implements a precision bandgap-based voltage reference (1.25 V) for PFI comparison and a separate 4.40 V reset threshold detector with 40 mV hysteresis. Its internal reset generator ensures monotonic assertion/deassertion timing independent of VCC ramp rate.

No watchdog timer is present - unlike ADM705/ADM706 - and the device provides dual reset outputs: active-low RESET and active-high RESET, enabling direct interface with processors requiring either polarity without external inversion logic.

Key Specifications

Pinout & Package

ADM708AN is supplied in an 8-lead narrow-body plastic dual-in-line package (PDIP, N-8), with 0.3-inch body width and through-hole mounting. Pin 1 is marked by a notch or dot; leads are tin-lead plated per JEDEC MS-001-BA.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX708CSA+ and TPS3808G33DBVR, the ADM708AN uniquely combines 5 V supply supervision, dual-polarity reset, and integrated power-fail monitoring in a single PDIP-8 package - making it irreplaceable in legacy industrial systems requiring all three features without layout changes.

Availability

ADM708AN is available at Aetrix Electronics and suitable for industrial motor controllers, medical diagnostic instruments, programmable logic controllers, smart energy meters, and battery-backed embedded systems requiring stable component supply across extended product lifecycles.

Supply support for ADM708AN 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, with design centers and manufacturing facilities worldwide.

The ADM70x family was designed specifically for robust, low-power microprocessor supervision in industrial, medical, and communications equipment - emphasizing guaranteed operation down to 1 V, precise voltage thresholds, and integrated fault-detection features.

FAQ

What is the reset threshold voltage of the ADM708AN?

The ADM708AN has a nominal reset threshold of 4.40 V, with a tolerance of ±0.15 V (4.25 V to 4.50 V) over temperature and supply range. This value is factory-trimmed and specified in Table 1 of the Rev. H datasheet. The ADM708AN uses this threshold to detect brownout conditions on 5 V systems and assert RESET until VCC rises above the threshold plus 40 mV hysteresis. The ADM708AN's 4.40 V setting distinguishes it from the 4.65 V ADM707AN and makes it suitable for systems with tighter 5 V regulation margins.

Does the ADM708AN include a watchdog timer function?

No, the ADM708AN does not include a watchdog timer. Unlike the ADM705/ADM706 variants, the ADM708AN omits the WDI and WDO pins and associated timing circuitry. Its functional block diagram (Figure 2 in the datasheet) confirms the absence of watchdog logic. Instead, the ADM708AN focuses on precision voltage supervision and power-fail detection via PFI/PFO. If watchdog functionality is required, the ADM706AN - which shares the same 4.40 V threshold but adds watchdog capability - must be selected.

Can the ADM708AN monitor a 12 V supply using the PFI input?

Yes, the ADM708AN can monitor a 12 V supply using the PFI input with an external resistive divider. The PFI pin accepts voltages up to VCC + 0.3 V (5.8 V max), so a 12 V rail must be scaled to ≤1.25 V using two resistors. For example, R1 = 86.6 kΩ and R2 = 10 kΩ yields 1.25 V at PFI when VIN = 12 V. The datasheet Figure 18 shows this configuration, and the PFI input bias current is <±25 nA - negligible for standard 1% metal-film dividers. This enables early warning of 12 V supply collapse before the 5 V regulator fails.

What is the purpose of the NC pin on the ADM708AN?

Pin 6 on the ADM708AN is designated NC (No Connect) and is internally unconnected. It must remain electrically floating - no external component or trace should be attached. This pin exists due to shared die/package architecture with the ADM705/ADM706 (which use pin 6 for WDI). Leaving it unconnected avoids parasitic coupling or ESD path issues. The datasheet explicitly states "NC = NO CONNECT" in Figure 4 and Table 3, and violation risks latch-up or degraded noise immunity. The ADM708AN's functionality is fully realized using only pins 1–5 and 7–8.

Is the ADM708AN RoHS compliant?

The base part number ADM708AN is not RoHS compliant; it uses leaded solder finish and contains Pb in the package leads. RoHS-compliant versions are identified by the "Z" suffix (e.g., ADM708ANZ), which denotes lead-free termination and full compliance with EU Directive 2011/65/EU. The ordering guide on page 12 of the Rev. H datasheet confirms ADM708ANZ as the RoHS-compliant variant. For new designs targeting CE marking or export to regulated markets, ADM708ANZ - not ADM708AN - must be specified and procured.