Analog Devices Inc./Maxim Integrated MAX813LEPA+

Overview

MAX813LEPA+ from Maxim Integrated is a precision microprocessor supervisory circuit in 8-pin PDIP package, providing active-high RESET output, watchdog timer (1.6s timeout), 4.65V supply-voltage monitor, 1.25V power-fail comparator input, and debounced manual-reset input. It ensures reliable μP reset during power-up, brownout, and software fault conditions in industrial controllers and embedded systems.

For engineers reviewing the MAX813LEPA+ datasheet, MAX813LEPA+ pinout, MAX813LEPA+ application, or MAX813LEPA+ equivalent, this page delivers verified electrical parameters, thermal range (-40°C to +85°C), package mapping (PDIP-8), functional distinctions vs. MAX705/MAX706, and real-world use cases for critical power monitoring.

Technical Context

The MAX813LEPA+ integrates four core supervisory functions: a precision 4.65V VCC monitor with 40mV hysteresis, a 1.6-second watchdog timer that asserts WDO on timeout unless cleared by WDI edge or reset assertion, a 1.25V reference-based power-fail comparator (PFI/PFO), and a TTL/CMOS-compatible manual-reset input with internal 250μA pull-up. All outputs are guaranteed functional down to VCC = 1.2V.

Unlike MAX705/MAX706, the MAX813LEPA+ omits active-low RESET and substitutes active-high RESET only - eliminating dual-reset ambiguity. Its watchdog logic clears automatically on MR assertion or WDI transition, and WDO remains low during VCC brownout regardless of watchdog state, enabling robust low-line detection without external circuitry.

Key Specifications

Pinout & Package

MAX813LEPA+ is housed in an 8-pin plastic DIP (PDIP-8) package with 0.3-inch body width and through-hole mounting. Pin spacing complies with JEDEC MS-001 standard; lead finish is lead(Pb)-free/RoHS-compliant (indicated by '+' suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX705EPA+, MAX813LEPA+ eliminates level-shift complexity for active-high µPs; compared with MAX809SEUR+T, it adds critical watchdog and power-fail capabilities essential for safety-critical embedded control - making it the only option meeting full supervisory requirements in industrial and medical applications.

Availability

MAX813LEPA+ is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, telecom remote terminal units, and automotive telematics gateways requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX813LEPA+ 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 high-performance analog, mixed-signal, and power management ICs for industrial, communications, and computing markets.

The MAX813L family was designed specifically for cost-sensitive, high-reliability microprocessor supervision - integrating reset, watchdog, and power-fail functions into a single 8-pin package to reduce BOM count and improve system-level robustness.

FAQ

What is the reset threshold voltage of the MAX813LEPA+ and how tightly is it specified?

The MAX813LEPA+ has a nominal reset threshold of 4.65V with a guaranteed tolerance of ±1.5% over the full -40°C to +85°C operating temperature range. This specification ensures consistent brownout detection across industrial environments without requiring external calibration or trimming components. The 40mV hysteresis prevents oscillation near the trip point, and the threshold is referenced to an internal bandgap, making it independent of supply variations. This precise threshold directly enables reliable operation in +5V systems where marginal voltage drops must trigger reset before µP corruption occurs.

Does the MAX813LEPA+ provide both active-high and active-low reset outputs?

No, the MAX813LEPA+ provides only an active-high RESET output (pin 7). Unlike the MAX707/MAX708, it does not include an active-low RESET (RESET) output. This design simplifies logic interfacing for µPs requiring high-active reset signals - such as Intel 80C51 derivatives - and eliminates potential contention issues in bidirectional reset architectures. The absence of dual outputs reduces internal complexity and cost while maintaining full supervisory functionality via the dedicated active-high output, which remains valid down to VCC = 1.2V.

How does the watchdog timer in the MAX813LEPA+ behave during power brownout conditions?

The MAX813LEPA+ watchdog timer exhibits dual-mode behavior: it asserts WDO (pin 6) both on software timeout (1.6s WDI inactivity) and during VCC brownout (when VCC falls below 4.65V). Crucially, WDO goes low immediately upon brownout onset - even before the internal watchdog timer expires - and remains low until VCC rises above threshold. This ensures continuous low-line indication independent of firmware state, enabling hardware-level fault response (e.g., NMI assertion) without relying on software health checks. The timer automatically clears when VCC recovers and WDI receives a valid edge.

Can the MAX813LEPA+ monitor power supplies other than +5V, such as +12V or negative rails?

Yes, the MAX813LEPA+ can monitor any DC voltage using its PFI (pin 4) and PFO (pin 5) pins. For +12V monitoring, a resistor divider scales the voltage to ≤1.25V at PFI; for negative rails, the circuit in Figure 7 of the datasheet uses PFO to drive a transistor that asserts RESET when the negative supply degrades. The 1.25V internal reference is highly stable (±4%), enabling accurate threshold setting across temperature. This flexibility allows single-device supervision of multiple rails - e.g., +5V (direct VCC), +12V (via divider), and -5V (via transistor interface) - without adding comparators or references.

What is the minimum VCC voltage at which the MAX813LEPA+ guarantees valid RESET output operation?

The MAX813LEPA+ guarantees valid RESET output operation down to VCC = 1.2V, as confirmed in the Electrical Characteristics table under "MAX813LE/M" conditions. At this voltage, RESET maintains logic-high state with source current ≥4µA and output voltage ≥0.9V (measured with ISOURCE = 4µA). This capability ensures deterministic reset assertion during deep brownout recovery - critical for systems where VCC may sag to 1.2–1.8V before complete collapse. It eliminates the need for external pull-up resistors or auxiliary reset generators in low-voltage recovery scenarios.