Analog Devices Inc. ADM8691ARWZ

Overview

ADM8691ARWZ from Analog Devices is a 16-lead TSSOP microprocessor supervisory circuit providing precision reset generation (4.65 V threshold), adjustable watchdog timeout (100 ms / 1.6 s / external), battery backup switchover (VBATT to VOUT), CE signal gating (3 ns propagation), and power-fail warning (1.3 V PFI comparator) for 5 V microprocessor systems.

For engineers reviewing the ADM8691ARWZ datasheet, ADM8691ARWZ pinout, ADM8691ARWZ application, or ADM8691ARWZ equivalent, this page delivers verified functional roles, real-world timing behavior, battery switchover hysteresis (20 mV), CEOUT logic control under brownout, and WDO status signaling - all critical for reliable embedded system power management design.

Technical Context

The ADM8691ARWZ integrates five core functions in one die: a precision 4.65 V reset voltage detector with 40 mV hysteresis and 1 V minimum VCC operation; a dual-mode watchdog timer (internal oscillator or external clock/capacitor) with configurable timeout periods; automatic battery switchover using low-R_ON PMOS (0.7 Ω normal, 7 Ω backup); active-high and active-low RESET outputs; and dedicated CEIN/CEOUT gating with 3 ns propagation delay for RAM write protection.

It features three independent logic outputs - BATT ON (battery select indicator), LOW LINE (VCC undervoltage flag), and WDO (watchdog timeout status) - each with defined sink/source capability (e.g., BATT ON sinks 35 mA), enabling direct interface to external transistors or microcontroller GPIOs without level-shifting.

Key Specifications

Pinout & Package

ADM8691ARWZ is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch), RoHS-compliant and rated for −40°C to +85°C industrial operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADM8695ARWZ and MAX691CPD+, the ADM8691ARWZ uniquely balances short-reset timing (50 ms), full diagnostic outputs (WDO, LOW LINE, BATT ON), and hardware-enforced RAM write protection - making it optimal for new designs demanding robust, observable power management.

Availability

ADM8691ARWZ is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive infotainment modules, medical handheld diagnostics, and network router management processors requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for ADM8691ARWZ 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 since 1965.

The ADM869x family was designed specifically for microprocessor system supervision - integrating reset, watchdog, battery switchover, and memory protection into single-chip solutions for space-constrained, reliability-critical embedded applications.

FAQ

What is the guaranteed minimum operating VCC voltage for ADM8691ARWZ reset functionality?

The ADM8691ARWZ guarantees RESET assertion down to VCC = 1 V, ensuring the microprocessor remains held in reset during deep brownout conditions. This capability is confirmed in the datasheet's General Description and Specifications table, where "RESET Output Voltage at VCC = 1 V" is explicitly tested and specified. The ADM8691ARWZ maintains functional reset generation even as the supply collapses far below its 4.65 V threshold, which is critical for orderly system shutdown.

Does ADM8691ARWZ support both active-high and active-low reset outputs simultaneously?

Yes, ADM8691ARWZ provides two independent reset outputs: pin 15 (RESET) is active-low, and pin 16 (RESET) is active-high - the logical inverse. Both outputs assert/deassert synchronously with identical timing (50 ms pulse width). This dual-output architecture allows direct interface to processors requiring either polarity without external inverters, and is documented in the Pin Configurations section (Figure 4) and Functional Block Diagram (Figure 2).

How does the ADM8691ARWZ implement battery backup switchover hysteresis, and what are the exact thresholds?

The ADM8691ARWZ implements 20 mV hysteresis in battery switchover: switchover from VCC to VBATT occurs when VCC falls to VBATT − 50 mV, and switchover back to VCC occurs when VCC rises to VBATT + 70 mV. This is explicitly stated in the Battery Switchover Section (Page 11) and Table 2 (Battery Switchover Threshold). The hysteresis prevents oscillation during slow supply decay near the crossover point, ensuring stable VOUT sourcing.

Can ADM8691ARWZ drive a 100 mA RAM load directly, and what is the maximum allowable VCC–VOUT dropout?

Yes, ADM8691ARWZ can drive up to 100 mA directly at VOUT, with a maximum dropout of VCC − 0.2 V (i.e., VOUT = VCC − 0.2 V) under full load, as specified in Table 2. This is achieved using an internal 0.7 Ω PMOS switch in normal mode. The datasheet confirms this capability supports typical CMOS RAM banks without external pass devices, and recommends a ≥0.1 μF bypass capacitor on VOUT to handle transient currents.

What is the function of the CEIN and CEOUT pins on ADM8691ARWZ, and how does their timing behave during brownout?

CEIN is the chip-enable input; CEOUT is its gated replica. During normal operation (VCC ≥ 4.73 V), CEOUT follows CEIN with 3 ns propagation delay. When VCC drops below the reset threshold (~4.5 V), CEOUT is forced high regardless of CEIN state - blocking writes to RAM. This behavior is detailed in the CE Gating section (Page 13) and Figure 22, ensuring data integrity during power failure. The ADM8691ARWZ enforces this action autonomously, without software intervention.