Analog Devices Inc./Maxim Integrated MAX815LEPA+

Overview

MAX815LEPA+ from Maxim Integrated is a high-accuracy, low-power microprocessor supervisory circuit with integrated watchdog timer, power-fail monitor, and manual reset input. It provides active-low RESET output, 4.7V fixed reset threshold (±1% worst-case accuracy), 200ms reset timeout, and guaranteed RESET validity down to VCC = 1V. Designed for +5V systems, it supports critical µP power monitoring in portable and medical equipment.

For engineers reviewing the MAX815LEPA+ datasheet, MAX815LEPA+ pinout, MAX815LEPA+ application, or MAX815LEPA+ equivalent, this device delivers verified ±1% reset threshold accuracy, independent watchdog with 1.56s timeout, 75µA max supply current, glitch-immune reset comparator, and dual-supply compatibility (VCC = 4.75V to 5.5V).

Technical Context

The MAX815LEPA+ implements a dedicated watchdog timer with 1.56s timeout, triggered by transitions on WDI - not VCC - enabling robust software execution monitoring independent of supply stability. Its reset generator uses a precision bandgap reference and hysteresis-free comparator to assert RESET when VCC falls below 4.7V (±1%), holding low for ≥200ms after recovery.

Power-fail detection is handled by a separate 2.50V PFI comparator (K/L/N suffixes), with PFO providing an open-drain output that sinks ≥1.2mA. The manual reset input (MR) features a 150µA internal pullup and accepts TTL/CMOS logic, asserting RESET immediately upon MR low and maintaining it for 200ms after MR release.

Key Specifications

Pinout & Package

MAX815LEPA+ is housed in an 8-pin plastic DIP (PDIP) package with 0.3-inch body width, RoHS-compliant lead-free finish (+ suffix). Pin spacing is 0.1 inch, compatible with standard through-hole PCB layouts and socketing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX815LEPA+, MAX814LEPA+ removes watchdog capability but adds low-line detection for NMI-based brownout response, while TPS3808G33DBVR trades reset accuracy and feature set for extreme low-power and small footprint in +3.3V-only systems.

Availability

MAX815LEPA+ is available at Aetrix Electronics and suitable for medical equipment, portable/battery-powered equipment, controllers, and set-top boxes requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.

Supply support for MAX815LEPA+ 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, automotive, and computing applications.

The MAX814/MAX815/MAX816 family was designed specifically for high-reliability microprocessor supervision in systems demanding ±1% reset accuracy, low quiescent current, and integrated watchdog or power-fail warning functions.

FAQ

What is the reset threshold voltage of the MAX815LEPA+ and how is it specified?

The MAX815LEPA+ has a factory-trimmed fixed reset threshold of 4.70V with ±1% worst-case accuracy over temperature, voltage, and process variation. This value is denoted by the "L" suffix in the part number and is guaranteed across the full operating range of VCC = 4.75V to 5.5V and TA = -40°C to +85°C. The threshold is referenced to an internal bandgap and does not require external components.

Does the MAX815LEPA+ include a watchdog timer, and how does it operate?

Yes, the MAX815LEPA+ integrates an independent watchdog timer with a nominal timeout period of 1.56 seconds. It monitors transitions on the WDI pin - not VCC - and asserts WDO low if WDI remains static (high or low) beyond that interval. The timer resets on every WDI edge, enabling robust detection of software hangs regardless of supply stability.

Can the MAX815LEPA+ monitor voltages other than VCC, and how is this implemented?

Yes, the MAX815LEPA+ can monitor auxiliary voltages using its PFI pin. By connecting a resistor divider from the target voltage to PFI and ground, the device compares the divided voltage against its internal 2.50V reference. When the monitored voltage drops below the corresponding PFI threshold, PFO asserts low - enabling early warning before VCC-related reset occurs.

What is the function of the WDO pin on the MAX815LEPA+, and how does it differ from RESET?

The WDO pin on the MAX815LEPA+ is an active-low watchdog output that goes low during watchdog timeout or when VCC falls below the 4.70V reset threshold. Unlike RESET, WDO has no minimum pulse width and responds immediately to VCC recovery. It is commonly connected to a µP's NMI input or looped back to MR to convert watchdog timeouts into full system resets.

Is the MAX815LEPA+ compatible with 3.3V microcontrollers, and what are the interface considerations?

The MAX815LEPA+ operates from a +5V supply (4.75V–5.5V) and its RESET and WDO outputs are push-pull with VOH ≥ VCC – 1.5V and VOL ≤ 0.4V, making them fully compatible with 3.3V-tolerant µP reset inputs. However, MR and WDI inputs require 5V-compatible logic thresholds; level-shifting is needed if driven directly by 3.3V GPIOs.