Analog Devices Inc./Maxim Integrated MAX691CWE-T

Overview

The MAX691CWE-T from Maxim Integrated is a 16-pin microprocessor supervisory circuit providing reset generation, battery backup switchover, watchdog timer, power-fail detection, and CE gating for CMOS RAM/EEPROM. It features a 4.65V reset threshold, 200ms reset timeout, adjustable watchdog (100ms/1.6s), 1.3V PFI comparator, and VOUT switching between VCC and VBATT. It is used in industrial controllers and automotive ECUs requiring reliable power monitoring and data retention during brownouts.

For engineers reviewing the MAX691CWE-T datasheet, MAX691CWE-T pinout, MAX691CWE-T application, or MAX691CWE-T equivalent, key selection criteria include its 16-pin SOIC package, dual reset outputs (RESET and RESET), BATT ON and WDO signals, CE IN/CE OUT write protection logic, and compatibility with 2.0–4.25V backup batteries and 4.75–5.5V main supplies.

Technical Context

The MAX691CWE-T integrates five core supervisory functions in a single IC: precision voltage monitoring (4.65V ±150mV threshold), battery switchover with 70mV rise/50mV fall hysteresis, dual-mode watchdog (internal oscillator or external clock input via OSC IN/OSC SEL), 1.3V power-fail comparator with PFO output, and active-high CE gating with 50ns propagation delay. Its internal architecture includes separate comparators for reset and PFI, a prescaled oscillator-based timeout counter, and MOSFET-based VOUT switching.

It operates across 0°C to +70°C (C-suffix), supports manual reset assertion via WDI transitions, and provides two independent reset outputs: open-drain active-low RESET and active-high RESET. The CE OUT signal forces high when VCC drops below 4.65V, preventing erroneous writes to memory-critical for systems where data integrity must survive power transients.

Key Specifications

Pinout & Package

MAX691CWE-T is housed in a 16-pin wide-body SOIC (SOIC-W) package, 7.5mm body width, 1.27mm pitch, RoHS-compliant, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACWE+T, the MAX691CWE-T trades tighter voltage tolerance and wider temperature range for lower cost and qualification level; versus TPS3823MPWPT, it delivers full feature integration-including VOUT switching and CE gating-at the expense of footprint and bill-of-material simplicity.

Availability

MAX691CWE-T is available at Aetrix Electronics and suitable for industrial controllers, automotive body electronics, medical infusion pumps, and smart energy meters requiring stable component supply over multi-year production cycles.

Supply support for MAX691CWE-T 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, mixed-signal, and power management ICs for industrial, automotive, and computing applications.

The MAX690–MAX695 family was engineered specifically for microprocessor-based systems needing integrated power supervision, battery backup, and memory protection-replacing discrete reset generators, voltage monitors, and watchdog timers with a single 16-pin solution.

FAQ

What is the operating temperature range of the MAX691CWE-T?

The MAX691CWE-T is specified for 0°C to +70°C (C-suffix grade). This commercial temperature range suits indoor industrial equipment, consumer electronics, and non-under-hood automotive modules. For extended environments such as engine compartments or outdoor enclosures, the MAX691ACWE+T (−40°C to +85°C) is the qualified alternative. The MAX691CWE-T's thermal performance is validated per JEDEC JESD22-A104, with no derating required within its rated range.

Does the MAX691CWE-T support adjustable reset timeout delay?

Yes, the MAX691CWE-T supports configurable reset timeout delay via the OSC SEL and OSC IN pins. With OSC SEL floating and OSC IN low, reset delay is 50ms; with OSC SEL floating and OSC IN floating, it is 200ms-the default for MAX691/MAX695 variants. External clock or capacitor on OSC IN enables further customization per Table 1 in the datasheet. This adjustability allows alignment with specific microprocessor oscillator startup times without external RC networks.

Can the MAX691CWE-T directly drive a PNP transistor for higher VOUT current?

Yes, the MAX691CWE-T's BATT ON pin is designed to directly drive the base of an external PNP transistor. It sinks up to 25mA and has logic-compatible voltage levels (0.4V low, >3.5V high), enabling direct connection to transistors like the MMBT3906. This extends VOUT capability beyond the internal 50mA limit-critical for powering larger RAM arrays or RTCs. No series resistor is needed unless base current limiting is required for specific transistor gain characteristics.

How does the CE OUT pin protect CMOS RAM during power failure?

The CE OUT pin of the MAX691CWE-T forces high within 50ns when VCC drops below 4.65V, regardless of CE IN state. This immediately disables chip select to battery-backed RAM, preventing partial or corrupted writes during brownout. Unlike simple reset assertion, CE gating acts faster and independently of reset timing-ensuring memory integrity even during sub-50ms voltage dips that may not trigger RESET. It is especially effective when paired with low-power RAMs drawing <1µA in standby.

Is the MAX691CWE-T pin-compatible with other devices in the MAX690 family?

The MAX691CWE-T is pin-compatible with MAX691, MAX693, and MAX695 in the 16-pin SOIC package, but not with 8-pin variants (MAX690/MAX692/MAX694). Differences exist in reset threshold (4.65V vs. 4.4V for MAX693), watchdog behavior, and CE gating logic. Substituting MAX693CWE-T requires validation of 4.4V reset compatibility and CE OUT timing. Always verify electrical specifications and functional behavior against the target application's voltage and timing margins before interchange.