Analog Devices Inc./Maxim Integrated MAX690AESA

Overview

The MAX690AESA from Maxim Integrated is a microprocessor supervisory circuit providing precision reset generation, battery-backup switchover, watchdog timer, and power-fail detection for +5V systems. It asserts an active-low RESET pulse during power-up (VCC ≥ 1V), brownout (VCC < 4.65V), and watchdog timeout (1.6s), while switching VOUT to VBATT when VCC drops below threshold-enabling reliable CMOS RAM retention in industrial controllers and battery-powered instrumentation.

For engineers reviewing the MAX690AESA datasheet, MAX690AESA pinout, MAX690AESA application, or MAX690AESA equivalent, key selection criteria include its guaranteed RESET assertion down to VCC = 1V, ±2% power-fail accuracy (shared with MAX802L), 200μA quiescent supply current, and compatibility with lithium backup batteries up to 4.80V.

Technical Context

The MAX690AESA integrates four independent functional blocks: a precision reset generator with 4.65V threshold and 200ms pulse width; a 1.6s watchdog timer cleared by WDI edge transitions; a 1.25V reference-based power-fail comparator (PFI/PFO); and a dual-path battery switchover circuit using P-channel MOSFETs (5Ω on VCC path, 80Ω on VBATT path) with 40mV hysteresis.

Its reset logic guarantees low-state output from VCC = 1V upward, with restartable timing on voltage dips, and disables the PFI comparator during battery-backup mode to conserve current. The WDI input features internal 35% VCC bias and 50kΩ impedance, allowing watchdog disable via floating connection.

Key Specifications

Pinout & Package

MAX690AESA is housed in an 8-pin SO (Small Outline) package with gull-wing leads, RoHS-compliant, 1.27mm pitch, and JEDEC MS-012AC outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX802LESA, MAX690AESA offers identical core functionality but superior long-term supply chain visibility; versus MAX706PESA, it provides essential +5V-specific supervision with integrated battery management-making it irreplaceable in legacy industrial designs requiring 4.65V threshold and VOUT switchover.

Availability

MAX690AESA is available at Aetrix Electronics and suitable for battery-powered computers and controllers, intelligent instruments, critical μP power monitoring, industrial PLC I/O modules, and portable medical devices requiring stable component supply across extended temperature ranges.

Supply support for MAX690AESA 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

Maxim Integrated, now part of Analog Devices, designs precision analog and mixed-signal ICs for industrial, automotive, and communications applications.

The MAX690AESA belongs to Maxim's μP supervisory circuit product line, engineered specifically for robust power monitoring and fail-safe reset generation in mission-critical embedded systems operating from +5V supplies.

FAQ

What is the guaranteed minimum VCC level at which MAX690AESA asserts RESET?

The MAX690AESA guarantees RESET assertion down to VCC = 1V, ensuring deterministic reset initiation even during deep brownout conditions before complete power collapse. This specification is validated across the full -40°C to +85°C operating range and is critical for systems requiring fail-safe behavior under marginal supply conditions. The MAX690AESA maintains this guarantee regardless of VBATT state or temperature.

How does the MAX690AESA handle battery switchover hysteresis, and why is it important?

The MAX690AESA implements 40mV hysteresis between VCC-to-VBATT and VBATT-to-VCC transitions, preventing oscillatory switching during slow VCC ramp-down. This design eliminates repeated VOUT toggling that could corrupt CMOS RAM data during gradual power loss. The hysteresis is intrinsic to the internal comparator architecture and requires no external components-ensuring reliable operation in MAX690AESA-based systems without layout modifications.

Can the MAX690AESA be used with a 3.6V lithium battery, and what is the maximum allowable VBATT voltage?

Yes, the MAX690AESA supports 3.0V to 3.6V lithium batteries directly at VBATT, with a maximum allowable backup voltage of 4.80V per datasheet Table 2. This limit prevents excessive current flow through the internal substrate diode (D1) when VCC approaches the 4.65V reset threshold. Using a 3.6V cell stays well within this margin and enables multi-year RAM retention without external regulation.

What is the function of the PFI and PFO pins on the MAX690AESA, and how accurate is the power-fail detection?

The PFI pin accepts a divided-down version of an unregulated supply, comparing it to an internal 1.25V reference; when PFI falls below this threshold, PFO asserts low. The MAX690AESA guarantees ±2% accuracy for this comparator function-matching the MAX802L specification-enabling precise prediction of supply collapse. This accuracy is maintained over temperature and ensures reliable early-warning interrupts in MAX690AESA-based power monitoring circuits.

Is the MAX690AESA pin-compatible with earlier MAX690 versions, and what are the key improvements?

Yes, the MAX690AESA is pin-compatible with the MAX690 and MAX694 in 8-pin SO packages. Key improvements include guaranteed RESET assertion down to VCC = 1V (vs. unspecified in original MAX690), tighter power-fail accuracy (±2%), reduced quiescent current (200μA vs. 350μA typical), and enhanced battery switchover control with defined 80Ω VBATT path resistance. These refinements make MAX690AESA the recommended upgrade for all legacy MAX690 designs.