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 in a single 8-pin SO package. It asserts an active-low RESET pulse (200ms width) when VCC drops below 4.65V, switches VOUT to VBATT during brownout, monitors PFI against a 1.25V reference, and triggers reset if WDI remains static for 1.6s - all critical for reliable operation in battery-powered industrial controllers.

For engineers reviewing the MAX690AESA+ datasheet, MAX690AESA+ pinout, MAX690AESA+ application, or MAX690AESA+ equivalent, this page delivers verified functional identity, exact pin roles, confirmed timing and voltage thresholds, real-world use cases in μP systems with backup RAM, and two validated alternative parts with documented technical and application differences.

Technical Context

The MAX690AESA+ integrates four independent monitoring functions: a precision reset generator with 4.65V threshold and 200ms delay, a 1.6s watchdog timer cleared by WDI edges, a 1.25V reference-based power-fail comparator driving PFO, and a dual-source power switch routing VCC or VBATT to VOUT based on voltage comparison and hysteresis (±20mV). All logic operates down to VCC = 1.0V, with guaranteed RESET assertion at 1V.

Its internal architecture separates the reset generator, watchdog, PFI comparator, and battery switchover circuits - enabling simultaneous but independent operation. The VOUT switch uses a 5Ω PMOS when VCC is valid and an 80Ω PMOS only when VCC < 4.65V and VBATT > VCC, minimizing backup current to <1μA when VCC is >1V below VBATT.

Key Specifications

Pinout & Package

MAX690AESA+ is housed in an 8-pin SOIC package (SO, 150mil width, RoHS-compliant lead-free finish denoted by '+' suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX802LESA+, MAX690AESA+ omits guaranteed PFI accuracy but retains identical reset, watchdog, and switchover performance - making it optimal for cost-sensitive industrial controllers where absolute comparator tolerance is non-critical. Against MAX706TESA+, MAX690AESA+ provides essential battery switchover and power-fail warning missing in the latter, disqualifying it for RAM backup use cases.

Availability

MAX690AESA+ is available at Aetrix Electronics and suitable for industrial data loggers, battery-powered medical monitors, programmable logic controller modules, smart energy meters, and embedded telemetry systems 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 high-performance analog and mixed-signal ICs for industrial, communications, and computing applications.

The MAX690AESA+ belongs to Maxim's microprocessor supervisory circuit family, engineered specifically to replace discrete reset generators, battery switches, and watchdog timers in space-constrained μP systems demanding high reliability under brownout and power-fail conditions.

FAQ

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

The MAX690AESA+ guarantees RESET assertion down to VCC = 1.0V. This is explicitly specified in the Electrical Characteristics table under "RESET Output Voltage" for MAX69_AE/M grade parts at VCC = 1.2V, and confirmed in the Detailed Description section stating "On power-up, once VCC reaches 1V, RESET is guaranteed to be a logic low." This ensures robust reset behavior during severe brownouts where other supervisors may release reset prematurely.

Does MAX690AESA+ support active-high reset output?

No, MAX690AESA+ provides only active-low RESET output. The datasheet clearly distinguishes MAX690A/MAX692A/MAX802L/MAX802M as having RESET (active-low), while MAX805L provides RESET (active-high) as an alternative variant. The MAX690AESA+ pin description, block diagram, and timing diagrams all reference only the active-low RESET signal - no internal inversion or alternate output is available in this part number.

What is the maximum allowable voltage on the VBATT pin of MAX690AESA+?

The absolute maximum rating for VBATT is +6.0V, but the recommended operational maximum is 4.80V as stated in Table 2 ("Allowable Backup-Battery Voltages"). Exceeding 4.80V risks forward-biasing the internal substrate diode (D1 in Figure 3) when VCC approaches the 4.65V reset threshold, causing unintended current flow from VBATT to VCC and potential latch-up or accelerated battery drain.

Can MAX690AESA+ monitor a negative supply rail?

Yes, MAX690AESA+ can monitor a negative rail using the external resistor network shown in Figure 7. The PFI input compares against the internal 1.25V reference, so connecting the negative rail through a voltage divider that presents a positive voltage to PFI (e.g., referencing PFI to VCC instead of GND) allows detection of negative rail degradation. The datasheet confirms this in the "Monitoring a Negative Voltage" section on page 8.

Is MAX690AESA+ pin-compatible with the legacy MAX690?

Yes, MAX690AESA+ is pin-compatible with MAX690 and MAX694 as stated in the General Description: "The MAX690A/MAX802L are pin compatible with the MAX690 and MAX694." This compatibility extends to identical pin functions (VOUT, VCC, GND, PFI, PFO, WDI, RESET, VBATT), same 8-pin SO footprint, and matching electrical behavior - enabling drop-in replacement in existing designs without PCB modification.