Analog Devices Inc./Maxim Integrated MAX804SCSA

Overview

MAX804SCSA from Maxim Integrated is a 3.3V/3.0V microprocessor supervisory circuit with active-high open-drain RESET output, precision 2.925V reset threshold (±2%), 200ms reset timeout, 1.6s watchdog timer, and battery-backup switchover capability. It monitors VCC for brownout detection, asserts reset during power-up/down, and supports CMOS RAM backup in portable controllers and embedded systems.

For engineers reviewing the MAX804SCSA datasheet, MAX804SCSA pinout, MAX804SCSA application, or MAX804SCSA equivalent, this page delivers verified electrical specs, thermal behavior across -40°C to +85°C, battery-switching hysteresis, PFI comparator accuracy (±75mV), and design-critical timing margins for reliable µP reset sequencing.

Technical Context

The MAX804SCSA integrates a precision voltage monitor with 2.925V rising/falling reset threshold (±2% tolerance), a 1.6s watchdog timer cleared only by WDI edge transitions, and dual-path power switching: VCC-to-VOUT via 3Ω PMOS and VBATT-to-VOUT via 140Ω switch. Its PFI input compares against 1.237V reference with ±75mV accuracy and 10mV hysteresis.

Reset assertion is guaranteed down to VCC = 1.0V; RESET remains low for 200ms after VCC rises above threshold or MR release. Battery switchover occurs at VSW = 2.40V (VBATT > VCC) on power-down and defers to VRST on recovery-ensuring stable VOUT reconnection only after supply stabilization.

Key Specifications

Pinout & Package

MAX804SCSA is housed in an 8-pin SO (Small Outline) package with gull-wing leads, RoHS-compliant, 3.9mm x 4.9mm body size, 1.27mm pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX804TCSA and MAX804RCSA, the MAX804SCSA offers optimal reset margin for 3.3V systems with ±10% tolerance-asserting reset before VCC drops to 2.85V while avoiding nuisance trips above 3.00V, making it the preferred choice for robust portable and industrial µP supervision.

Availability

MAX804SCSA is available at Aetrix Electronics and suitable for battery-powered computers and controllers, embedded industrial controllers, and intelligent instrumentation requiring stable component supply and long-term lifecycle support.

Supply support for MAX804SCSA 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 industrial, computing, and communications applications.

The MAX804 series belongs to Maxim's microprocessor supervisory product line, engineered specifically for reliable power-up/down sequencing, brownout protection, and battery-backed memory retention in 3.0V/3.3V embedded systems.

FAQ

What is the exact reset threshold voltage for MAX804SCSA and how tightly is it specified?

The MAX804SCSA has a nominal reset threshold of 2.925V, with a guaranteed tolerance of ±2% over temperature and supply voltage. This means the actual threshold falls between 2.867V and 2.983V under all operating conditions (–40°C to +85°C, VCC = 2.72V to 5.5V). The specification is tighter than earlier MAX690/704 families (±4%), enabling precise alignment with 3.3V ±10% system rails without margin overdesign. This value is confirmed in the Electrical Characteristics table on page 3 of the official datasheet.

Does MAX804SCSA support battery-backup operation when VBATT exceeds VCC, and what is the maximum allowed VBATT voltage?

Yes, MAX804SCSA explicitly supports VBATT exceeding VCC-enabling direct connection of standard 3.6V lithium coin cells without clamping diodes or regulators. The absolute maximum rating for VBATT is +6.0V (with respect to GND), and the battery switchover circuit activates when VCC falls below VSW = 2.40V (typical) while VBATT remains above VCC. This architecture preserves CMOS RAM data during main supply loss while maintaining full compatibility with common backup sources.

How does the watchdog timer in MAX804SCSA operate, and can it be disabled?

The MAX804SCSA watchdog timer has a fixed 1.6s timeout (1.12–2.24s over temperature) and cannot be disabled. It resets only upon detection of a rising or falling edge on the WDI pin; holding WDI high or low continuously triggers a reset every ~1.8s. Unlike older MAX690-family devices, there is no hardware disable option-the timer is always active once VCC is applied. This ensures fail-safe behavior in safety-critical applications where watchdog omission could lead to undetected firmware lockups.

What is the function of the PFI and PFO pins on MAX804SCSA, and what accuracy does the power-fail comparator offer?

The PFI (Power-Fail Input) pin accepts an external voltage for monitoring auxiliary supplies, comparing it against a 1.237V internal reference. When PFI falls below this threshold-or when VCC drops below VSW-the PFO (Power-Fail Output) pin goes low (open-drain). The comparator offers ±75mV accuracy over temperature, with 10mV typical hysteresis to reject noise. This allows reliable detection of supply droops (e.g., 5V rail falling to 4.85V) without external components, and PFO can be wired to MR on compatible supervisors to generate cascaded resets.

Is MAX804SCSA pin-compatible with other members of the MAX80x family, and what are the key package details?

Yes, MAX804SCSA is fully pin-compatible with MAX802/804/805/806 variants in the same SO-8 package (S8+4 outline, 3.9mm × 4.9mm, 1.27mm pitch). All share identical pin functions: VOUT, VCC, GND, PFI, PFO, WDI, RESET, VBATT. The "S" suffix denotes the 2.925V reset threshold, "C" indicates commercial temperature grade (0°C to +70°C), and "SA" specifies SOIC packaging. RoHS compliance is indicated by the "+" symbol in ordering codes, though MAX804SCSA itself is lead-free per standard manufacturing.