Analog Devices Inc./Maxim Integrated MAX815NCSA+T

Overview

MAX815NCSA+T from Maxim Integrated is a ±1% accurate, low-power microprocessor supervisory circuit with integrated watchdog timer, power-fail monitor, and manual reset input. It provides active-low RESET output, 4.55V fixed reset threshold (N-suffix), 200ms reset timeout, and guaranteed RESET validity down to VCC = 1V. It is used in portable/battery-powered equipment for reliable power-on reset and brownout protection.

For engineers reviewing the MAX815NCSA+T datasheet, MAX815NCSA+T pinout, MAX815NCSA+T application, or MAX815NCSA+T equivalent, this page delivers verified functional identity, confirmed pin roles, exact reset and watchdog timing values, real-world power-fail comparator behavior, and validated alternative options for 5V µP supervision with watchdog capability.

Technical Context

The MAX815NCSA+T implements a dedicated watchdog timer with 1.56s timeout, independent of the reset comparator - WDI transitions reset the timer, and WDO asserts low on timeout or during VCC reset conditions. Its reset comparator features ±1% worst-case accuracy over temperature and supply variation, with hysteresis-free trip point at 4.55V (N-suffix) and guaranteed operation down to VCC = 1V.

It integrates a 2.50V power-fail comparator (PFI/PFO) referenced to internal bandgap, enabling early warning of +5V rail collapse; PFO sinks ≥1.2mA when asserted. The manual reset input (MR) includes 150µA internal pullup and supports TTL/CMOS logic drive, with 200ms minimum reset pulse width after MR release.

Key Specifications

Pinout & Package

MAX815NCSA+T is housed in an 8-pin SO (Small Outline) package, RoHS-compliant and lead-free (+T suffix). Pin functions are electrically and physically distinct from MAX814/MAX816 variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX815NCSA+T, MAX815LCSA+T offers higher reset voltage for tighter 5V rail control but same watchdog capability, while TPS3808G33DBVR trades watchdog and power-fail features for nanoamp-level current draw in pure 3.3V applications - neither is pin-compatible, and both require PCB layout changes.

Availability

MAX815NCSA+T is available at Aetrix Electronics and suitable for medical instrumentation, industrial controllers, set-top boxes, and intelligent sensor nodes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX815NCSA+T 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.

The MAX814/MAX815/MAX816 family was engineered specifically for high-reliability microprocessor supervision in portable and critical embedded systems, combining accuracy, low power, and multiple fault-detection functions in compact packages.

FAQ

What is the exact reset threshold voltage for MAX815NCSA+T?

The MAX815NCSA+T has a factory-set reset threshold of 4.55V ±1%, specified over temperature and supply variation. This value is fixed by the 'N' suffix and applies to VCC monitoring - it ensures reset assertion when the +5V rail drops below 4.55V, supporting systems with ±10% power supply tolerance. The threshold remains stable across the full operating temperature range (0°C to +70°C).

Does MAX815NCSA+T include a watchdog timer, and how does it operate?

Yes, MAX815NCSA+T integrates a dedicated watchdog timer with a 1.56s timeout period. It monitors the WDI pin: any transition (high→low or low→high) resets the timer, while static high or low states longer than 1.56s cause WDO to assert low. WDO also goes low during VCC reset conditions. This dual-trigger behavior ensures robust firmware supervision independent of the main reset function.

Can MAX815NCSA+T monitor voltages other than VCC?

Yes - the PFI pin accepts externally divided voltages, enabling monitoring of +12V, +3.3V, or negative rails. For example, connecting a resistor divider to PFI allows detection of +12V collapse before the +5V rail fails. The internal 2.50V comparator reference remains fixed, so the divider ratio sets the trip point. PFO then signals the event to the µP or triggers reset via MR connection.

What is the purpose of the LOW LINE output, and is it present on MAX815NCSA+T?

The LOW LINE output is exclusive to the MAX814 variant and is not present on MAX815NCSA+T. MAX815NCSA+T substitutes this function with WDO (watchdog output) and relies on PFO for early power-fail warning. LOW LINE appears only on MAX814 and MAX816 devices; its absence on MAX815NCSA+T reflects the product's focus on watchdog-driven reliability rather than dual-threshold brownout detection.

How does the manual reset (MR) input behave on MAX815NCSA+T?

The MR input on MAX815NCSA+T is active-low with an internal 150µA pullup to VCC. Pulling MR below 1.10V asserts RESET immediately; RESET remains low for at least 200ms after MR returns high. MR accepts TTL/CMOS logic levels and requires no external components - a momentary switch to GND suffices. In noisy environments, a 0.1µF capacitor from MR to GND improves immunity.