Analog Devices Inc./Maxim Integrated MAX794EPE

Overview

MAX794EPE from Maxim Integrated is a 3.0V/3.3V adjustable microprocessor supervisory circuit featuring externally programmable reset threshold, backup-battery switchover (VBATT > VCC), independent watchdog timer (1.6s timeout), and chip-enable signal gating with ≤7ns propagation delay. It operates across –40°C to +85°C and supports battery-freshness sealing for long-term storage in portable controllers and embedded systems.

For engineers reviewing the MAX794EPE datasheet, MAX794EPE pinout, MAX794EPE application, or MAX794EPE equivalent, key selection criteria include adjustable reset threshold via resistor divider, guaranteed reset assertion down to VCC = 1V, battery-switching hysteresis (15mV typical), and CE IN-to-CE OUT timing compatibility with high-speed µPs.

Technical Context

The MAX794EPE implements an external resistor-divider–based reset comparator with VRST IN threshold of 1.212V to 1.287V (typical), enabling precise reset voltage programming from VSW (2.55V) to 5.5V. Its battery switchover logic uses dual comparators with 15mV hysteresis to prevent oscillation during VCC transitions near VSW.

It integrates a non-disableable 1.6s watchdog timer monitored via WDI, with WDO output capable of driving MR directly to generate system resets. The CE gating path employs a low-on-resistance transmission gate (≤46Ω at VRST max) and guarantees <10µs hold time when CE IN is low at reset assertion.

Key Specifications

Pinout & Package

MAX794EPE is housed in a 16-pin plastic DIP package (0.300" wide), with through-hole mounting and industry-standard 0.1" pin pitch. Pin 1 is marked by a notch or dot; pin numbering follows standard counter-clockwise layout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX793EPE and MAX795EPE, the MAX794EPE uniquely supports external reset threshold programming, retains full watchdog functionality, and provides both LOWLINE and BATT ON outputs-making it the only option among the three for designs requiring adaptive voltage supervision and robust fault recovery.

Availability

MAX794EPE is available at Aetrix Electronics and suitable for battery-powered portable controllers, industrial embedded controllers, and critical µP power monitoring applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX794EPE 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) is a semiconductor company specializing in analog, mixed-signal, and power-management ICs for industrial, computing, and communications markets.

The MAX793/MAX794/MAX795 product line was designed specifically for 3.0V/3.3V microprocessor supervision-delivering integrated reset, watchdog, battery switchover, and memory protection in single-chip solutions for space- and power-constrained systems.

FAQ

What is the reset threshold adjustment range for the MAX794EPE?

The MAX794EPE reset threshold is externally adjustable from 2.55V to 5.5V using a resistor divider on the RESET IN pin. The internal reference is 1.212V to 1.287V (typ), and VRST = VRST_IN × (R1/R2 + 1). This allows precise alignment with system supply tolerances, unlike fixed-threshold variants such as the MAX793EPE or MAX795EPE.

Does the MAX794EPE support battery-freshness sealing, and how is it enabled?

Yes, the MAX794EPE supports battery-freshness sealing to minimize BATT leakage (<1nA typ) until first use. To enable it: connect battery to BATT, ground PFO, bring VCC above VRST, wait for reset deassertion (~200ms), then cycle VCC low and high. Once enabled, the seal remains active until VCC exceeds VRST again - a key feature distinguishing MAX794EPE from MAX795EPE.

Can the watchdog timer on the MAX794EPE be disabled?

No, the MAX794EPE watchdog timer cannot be disabled. It operates continuously with a 1.6s timeout, clearing only on WDI transitions or reset assertion. This design ensures fail-safe recovery even if firmware malfunctions - a deliberate safety feature not present in some competing supervisors like the MAX690 family.

What is the maximum load current supported by the MAX794EPE's OUT pin in battery-backup mode?

The MAX794EPE's OUT pin supports up to 250µA continuous load in battery-backup mode (VCC = 0V, VBATT = 2.3V). For higher currents (>75mA), the BATT ON output must drive an external PMOS transistor, as the internal p-MOSFET is rated for ≤75mA in normal mode and significantly less in backup. This limitation is documented in the Absolute Maximum Ratings table.

How does the CE IN-to-CE OUT propagation delay behave under varying load conditions?

The MAX794EPE guarantees ≤7ns CE IN-to-CE OUT propagation delay under test conditions (50Ω source, 50pF load). In practice, delay increases with capacitive loading on CE OUT or high source impedance on CE IN. To maintain timing integrity, minimize CE OUT capacitance and use low-impedance drivers - critical for µPs with sub-10ns bus cycle times.