Analog Devices Inc./Maxim Integrated MAX820REPE+

Overview

MAX820REPE+ from Maxim Integrated is a microprocessor supervisory circuit with ±2% reset and low-line threshold accuracy, 200ms power-up reset delay, and integrated watchdog timer with programmable timeout (1.6s nominal). It provides active-low/high RESET outputs, manual-reset input, chip-enable gating, and overvoltage detection - used in embedded controllers and industrial computing systems for reliable power-on initialization and brownout recovery.

For engineers reviewing the MAX820REPE+ datasheet, MAX820REPE+ pinout, MAX820REPE+ application, or MAX820REPE+ equivalent, this page delivers verified functional identity, exact pin roles, confirmed timing parameters, real-world use cases, and validated alternative parts - all grounded in Maxim's official MAX792/MAX820 datasheet Rev. 4 (11/05).

Technical Context

The MAX820REPE+ implements dual-voltage monitoring via independent reset and low-line comparators, both referenced to a precision 1.30V internal bandgap. Its reset assertion is guaranteed down to VCC = 1V, and low-line output triggers 120mV above the reset threshold with 15mV hysteresis. The device supports both internal threshold mode (factory-set) and external programming mode using resistor dividers on RESET IN/INT and LLIN/REFOUT pins.

Watchdog functionality uses a capacitor-programmable timeout (SWT pin), with WDPO providing a 1.7ms advance pulse preceding WDO assertion by 70ns. Chip-enable gating enforces 10ns max propagation delay and automatic write-cycle completion during power-down, while OVI/OVO form an uncommitted overvoltage comparator with 1.30V threshold.

Key Specifications

Pinout & Package

MAX820REPE+ is housed in a 16-pin plastic DIP (Dual In-line Package) with 0.3-inch body width and through-hole mounting. Pin pitch is 0.1 inch, compatible with standard PCB layouts for legacy and industrial control designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX792REPE+, the MAX820REPE+ offers tighter ±2% threshold accuracy essential for high-reliability systems; compared with TPS3808G33DBVR, it delivers full feature parity including dual reset outputs, NMI signaling, and chip-enable control - making it irreplaceable in designs requiring coordinated memory protection and staged power-fail response.

Availability

MAX820REPE+ is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, telecom base station management units, automotive body control modules, and embedded computing systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX820REPE+ 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 and mixed-signal ICs for demanding industrial, medical, and communications applications - emphasizing reliability, accuracy, and integration density.

The MAX820REPE+ belongs to Maxim's microprocessor supervisory product line, engineered specifically for deterministic power-on reset, brownout recovery, and runtime fault detection in safety-critical embedded systems.

FAQ

What is the guaranteed minimum operating voltage for MAX820REPE+ reset functionality?

The MAX820REPE+ guarantees valid RESET output operation down to VCC = 1V, ensuring reliable reset assertion even during deep brownout conditions. This specification is explicitly confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables of the MAX792/MAX820 datasheet Rev. 4. The internal comparators remain functional at this level, and the 10kΩ external pull-down on RESET (Figure 5) extends validity to GND. This behavior is unique to the MAX820REPE+ and its sibling MAX792REPE+.

How does the low-line output (LOW LINE) relate to the reset threshold in MAX820REPE+?

In internal threshold mode, the LOW LINE output of the MAX820REPE+ asserts 120mV above the programmed reset threshold voltage - for the R-suffix variant, that means LOW LINE triggers at 4.74V when RESET triggers at 4.62V. This staged warning provides a non-maskable interrupt (NMI) to the microprocessor before full reset occurs, enabling graceful shutdown or data save operations. The 15mV hysteresis prevents chatter during slow VCC transitions, and this relationship holds across the full operating temperature range.

Can MAX820REPE+ be used with a 3.3V supply, and what reset threshold options are available?

Yes, the MAX820REPE+ operates from 2.75V to 5.5V, fully supporting 3.3V systems. While the REPE+ suffix denotes the 4.62V reset threshold variant (R-suffix), Maxim offers multiple factory-set thresholds: 4.37V (M), 3.06V (T), 2.91V (S), and 2.61V (L). For 3.3V applications, the MAX820TEPE+ (3.06V) or MAX820SEPE+ (2.91V) are direct alternatives - all share identical pinout, timing, and feature set with the MAX820REPE+, differing only in threshold voltage and accuracy grade.

What is the purpose of the WDPO pin on MAX820REPE+, and how is it timed relative to WDO?

The WDPO (Watchdog Pulse Output) pin on MAX820REPE+ provides a 1.7ms active-low advance warning pulse that precedes WDO assertion by 70ns. This allows external logic (e.g., a D flip-flop in Figure 8) to capture the first watchdog fault and initiate diagnostic actions before hardware shutdown occurs via WDO. WDPO is asserted only once per timeout event and is synchronized to the absence of WDI transitions - making it essential for implementing two-fault latching or pre-shutdown logging in safety-critical firmware.

Does MAX820REPE+ support external programming of reset and low-line thresholds, and how is it configured?

Yes, the MAX820REPE+ supports external programming via the RESET IN/INT and LLIN/REFOUT pins. Pulling RESET IN/INT above 600mV disconnects internal references and connects both comparators to external resistor dividers - enabling custom thresholds such as 4.4V reset and 4.75V low-line (as calculated in the datasheet's Figure 4b example). This mode retains all other functions (watchdog, CE gating, MR), and the ±2% accuracy guarantee applies only to internal mode; external mode accuracy depends on resistor tolerance and reference drift.