Analog Devices Inc./Maxim Integrated MAX820SCSE+

Overview

MAX820SCSE+ 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 dual reset outputs (RESET/RESET), manual-reset input, chip-enable gating, and overvoltage detection - used in embedded controllers and industrial systems requiring reliable power monitoring and brownout protection.

For engineers reviewing the MAX820SCSE+ datasheet, MAX820SCSE+ pinout, MAX820SCSE+ application, or MAX820SCSE+ equivalent, this page delivers verified functional identity, validated pin roles, confirmed threshold accuracy (±2%), real-world timing behavior (200ms reset delay, 70ns WDPO-to-WDO skew), and precise alternative selection guidance for critical µP supervision designs.

Technical Context

The MAX820SCSE+ implements dual independent comparators for reset and low-line detection, with factory-trimmed internal thresholds (4.37V nominal reset, 4.49V nominal low-line) and ±2% accuracy in external programming mode. Its watchdog function uses an RC-timed oscillator referenced to SWT pin capacitance, delivering 1.6s nominal timeout at VCC = 5V with k = 16.2 scaling factor.

It integrates a bidirectional CE transmission gate (10ns max propagation delay) that disables during reset assertion to prevent memory corruption, and features a dedicated overvoltage comparator (OVI/OVO) with 1.30V reference threshold - fully decoupled from reset logic and configurable as standalone fault indicator.

Key Specifications

Pinout & Package

MAX820SCSE+ is housed in a 16-pin narrow SOIC (SO-16N) package with 1.27mm pitch, JEDEC MS-012AC compliant, and RoHS-compliant lead-free finish (+ suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX792SCSE+, the MAX820SCSE+ delivers tighter ±2% threshold accuracy essential for marginal supply designs, while TPS3808G33DBVR lacks low-line warning, CE gating, and WDPO - making it unsuitable for applications requiring deterministic pre-reset alerts or memory write protection.

Availability

MAX820SCSE+ is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, telecom infrastructure, and automotive body electronics requiring stable component supply and long-term manufacturability.

Supply support for MAX820SCSE+ 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 power management, sensing, and interface applications - serving industrial, medical, and communications markets.

The MAX820SCSE+ belongs to Maxim's µP supervisory product line, engineered specifically for deterministic power-monitoring in systems requiring dual-threshold detection, hardware watchdogs, and memory write-cycle protection without battery backup.

FAQ

What is the exact reset threshold voltage for MAX820SCSE+ and how is it specified?

The MAX820SCSE+ has a nominal reset threshold voltage of 4.37V with ±2% accuracy over temperature (0°C to +70°C), as confirmed in the Electrical Characteristics table under "Reset Threshold Voltage-Internal Threshold Mode" for suffix 'S'. This value is factory-trimmed and applies in internal threshold mode when RESET IN/INT is grounded. The ±2% tolerance ensures reliable operation across voltage and temperature variations without external calibration.

Does MAX820SCSE+ support external programming of reset and low-line thresholds?

Yes, the MAX820SCSE+ supports external programming via the RESET IN/INT and LLIN/REFOUT pins. When RESET IN/INT is biased above 600mV, the internal voltage divider disconnects and both comparators accept externally set thresholds using a resistor divider. The MAX820SCSE+ maintains ±2% accuracy in this mode, unlike the MAX792 which specifies ±2.5% - a key differentiator confirmed in the Features section.

What is the function of the WDPO pin on MAX820SCSE+ and how does it differ from WDO?

The WDPO (Watchdog-Pulse Output) pin on MAX820SCSE+ delivers a short, timed low pulse (500µs–6ms) immediately before WDO asserts its latched low state. WDPO falls 70ns before WDO, providing hardware-level advance warning of impending watchdog fault. This enables two-fault shutdown architectures using a D flip-flop - a capability not present in basic watchdog ICs and explicitly documented in the Watchdog-Pulse Output section of the datasheet.

Can MAX820SCSE+ be used with 3.3V microcontrollers, and what are the key interface considerations?

Yes, MAX820SCSE+ operates from 2.75V to 5.5V and supports 3.3V systems. Key interface considerations include: MR input threshold remains 1.30V (TTL-compatible), RESET output sources 1mA at VCC − 0.5V (so ~2.8V at 3.3V), and CE IN/OUT logic levels track VCC. For 3.3V use, the watchdog timeout scaling factor changes to k = 27 (vs. 16.2 at 5V), and low-line threshold must be set 120mV above selected reset point - all verified in the Electrical Characteristics tables.

How does the chip-enable (CE) gating function protect memory in MAX820SCSE+?

The MAX820SCSE+ integrates a series transmission gate between CE IN and CE OUT with 10ns max propagation delay. During reset assertion, the gate disables - forcing CE OUT high-impedance or pulling it to VCC depending on CE IN state - thereby blocking spurious chip-select signals from reaching CMOS RAM or EEPROM. If CE IN is low when reset asserts, CE OUT stays low for 15µs to complete the current write cycle, preventing partial writes - a feature confirmed in the Chip-Enable Gating section and Figure 9 timing diagram.