Analog Devices Inc./Maxim Integrated MAX806TCSA+

Overview

MAX806TCSA+ from Maxim Integrated is a 3.3V microprocessor supervisory circuit with active-high open-drain RESET output, 3.075V reset threshold (T-suffix), 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover. It monitors VCC, asserts reset during power-up/brownout/watchdog timeout, and switches VOUT to VBATT when VCC falls below 2.40V - used in embedded controllers requiring reliable power-fail detection and RAM backup.

For engineers reviewing the MAX806TCSA+ datasheet, MAX806TCSA+ pinout, MAX806TCSA+ application, or MAX806TCSA+ equivalent, key selection criteria include reset threshold tolerance (±2%), PFI comparator accuracy (±75mV), battery leakage current (≤1µA), and compatibility with 3.0V/3.3V systems operating from -40°C to +85°C.

Technical Context

The MAX806TCSA+ integrates a precision reset comparator with 10mV hysteresis, a 1.6s watchdog timer that clears on WDI edge transitions, and a dual-path power-switching circuit: VCC-to-VOUT via a 3Ω PMOS switch and VBATT-to-VOUT via a 140Ω switch activated when VCC < 2.40V. Its PFI input accepts external voltage dividers for monitoring auxiliary supplies.

It features guaranteed RESET assertion down to VCC = 1V, supports manual reset with 70µA internal pull-up, and provides active-high open-drain RESET (inverse of MAX690/MAX802) - enabling direct interface to µPs with bidirectional reset I/O using a 4.7kΩ series resistor.

Key Specifications

Pinout & Package

MAX806TCSA+ is housed in an 8-pin SOIC package (S8+4 outline, RoHS-compliant) with gull-wing leads, 1.27mm pitch, and 5.0mm × 4.0mm body size.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX706TCSA+, the MAX806TCSA+ adds essential watchdog supervision and tighter reset tolerance; compared with MAX802TCSA+, it eliminates need for external pull-up or level-shifting, simplifying µP interface and reducing BOM count.

Availability

MAX806TCSA+ is available at Aetrix Electronics and suitable for battery-powered computers, embedded controllers, intelligent instruments, and portable medical devices requiring stable component supply with guaranteed long-term availability.

Supply support for MAX806TCSA+ 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, mixed-signal, and power management ICs for industrial, automotive, communications, and computing applications.

The MAX806TCSA+ belongs to Maxim's 3.0V/3.3V microprocessor supervisory family, engineered specifically for systems demanding reliable power-up sequencing, brownout protection, RAM backup, and watchdog supervision in space-constrained portable and embedded platforms.

FAQ

What is the reset threshold voltage for MAX806TCSA+?

The MAX806TCSA+ has a nominal reset threshold of 3.075V (VCC falling), with ±2% tolerance over temperature. This value is specified for the "T" suffix variant and ensures reset assertion before the 3.3V supply falls below system stability margins. The threshold rises slightly to 3.085V on VCC rising due to 10mV internal hysteresis - preventing oscillation during slow supply ramps. MAX806TCSA+ is optimized for 3.3V ±5% systems.

Does MAX806TCSA+ include a watchdog timer, and how does it operate?

Yes, MAX806TCSA+ includes a 1.6s watchdog timer (1.12–2.24s range). It triggers reset if the WDI pin remains static (high or low) beyond timeout. The timer clears on any rising or falling edge at WDI - making it responsive to µP activity without requiring precise pulse timing. Unlike older families, the watchdog cannot be disabled. MAX806TCSA+ uses this to detect firmware lockups independently of power-supply conditions.

How does the battery-backup switchover work on MAX806TCSA+?

MAX806TCSA+ switches VOUT from VCC to VBATT when VCC falls below 2.40V (VSW), provided VBATT > VCC. It uses a 140Ω internal switch for VBATT-to-VOUT and a 3Ω PMOS for VCC-to-VOUT. Switchover occurs early enough to maintain >2.0V at VOUT for CMOS RAM retention. When VCC recovers, reconnection to VCC is deferred until VCC exceeds the 3.075V reset threshold - ensuring stable supply before RAM reverts to main power.

What is the function of the PFI and PFO pins on MAX806TCSA+?

PFI is a dedicated input for monitoring auxiliary power rails via external resistor dividers; it compares against a 1.237V ±75mV internal reference. PFO is an active-low open-drain output that goes low when PFI < 1.237V or VCC < 2.40V. On MAX806TCSA+, PFO can be connected to MR to generate a reset event upon auxiliary supply failure - enabling cascaded fault detection without additional logic.

Is MAX806TCSA+ pin-compatible with other devices in the MAX80x family?

MAX806TCSA+ shares the same 8-pin SOIC package and pinout as MAX802TCSA+, MAX804TCSA+, and MAX805TCSA+, but differs in reset output polarity: MAX806TCSA+ provides active-high open-drain RESET, whereas MAX802TCSA+ offers active-low push-pull. This difference requires review of µP reset pin requirements and may necessitate schematic updates - it is not a drop-in replacement for MAX802TCSA+ without logic adaptation.