Analog Devices Inc./Maxim Integrated MAX704TCPA+

Overview

MAX704TCPA+ from Maxim Integrated is a 3.3V microprocessor supervisory circuit with active-low RESET output, 3.075V reset threshold, 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover. It monitors VCC for power-up/brownout conditions, asserts RESET to prevent erroneous code execution, and switches CMOS RAM supply from VCC to VBATT during power failure-used in embedded controllers and portable equipment requiring reliable power sequencing.

For engineers reviewing the MAX704TCPA+ datasheet, MAX704TCPA+ pinout, MAX704TCPA+ application, or MAX704TCPA+ equivalent, key selection criteria include guaranteed RESET assertion down to VCC = 1V, ±4% reset threshold accuracy, 40µA VCC supply current, battery-leakage current <1µA, and compatibility with lithium backup cells exceeding VCC voltage.

Technical Context

The MAX704TCPA+ integrates a precision reset comparator with 10mV hysteresis, a non-disableable 1.6s watchdog timer cleared by WDI edges, and a dual-path power switch: VCC-to-VOUT via 3Ω PMOS and VBATT-to-VOUT via 140Ω NMOS. Its reset generator ensures monotonic assertion during VCC ramp-down and guarantees 200ms minimum pulse width after VCC recovery or MR release.

It features independent power-fail detection (PFI/PFO) referenced to 1.237V ±20mV, manual reset input (MR) with 70µA internal pull-up, and operates across 0°C to +70°C. The device supports battery-backed RAM retention without external diodes, as VBATT may exceed VCC up to 6.0V while maintaining safe switchover at VSW = 2.40V.

Key Specifications

Pinout & Package

MAX704TCPA+ is housed in an 8-pin plastic DIP (PDIP) package with 0.300" wide body, RoHS-compliant lead finish indicated by the '+' suffix.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX704TCPA+, MAX704SCPA+ offers relaxed reset voltage for less stringent supply designs, while MAX802TCPA+ delivers enhanced threshold accuracy and configurable hysteresis-both share identical pinout, package, and core functionality but differ in tolerance and application-grade specification.

Availability

MAX704TCPA+ is available at Aetrix Electronics and suitable for battery-powered computers and controllers, intelligent instruments, and critical µP power monitoring requiring stable component supply across industrial temperature ranges and long-term design-in support.

Supply support for MAX704TCPA+ 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, computing, and communications markets.

The MAX704 series belongs to Maxim's microprocessor supervisory product line, designed specifically for reliable power monitoring and reset generation in 3.0V/3.3V embedded systems with battery backup requirements.

FAQ

What is the guaranteed minimum VCC voltage at which MAX704TCPA+ asserts RESET?

The MAX704TCPA+ guarantees RESET assertion for VCC down to 1V, regardless of VBATT status. This ensures fail-safe reset behavior during deep brownout conditions where main supply collapses below typical logic thresholds. The device continues asserting RESET as long as VCC remains below its 3.075V threshold or until it reaches 1V, making MAX704TCPA+ suitable for systems requiring robust low-voltage fault handling.

Does MAX704TCPA+ support lithium backup batteries with voltage higher than VCC?

Yes, MAX704TCPA+ explicitly supports VBATT voltages exceeding VCC-up to 6.0V-enabling direct connection of standard 3.6V lithium coin cells without diode drops or regulators. Its internal battery switchover circuit activates when VCC falls below 2.40V (VSW), connecting VBATT to VOUT through a 140Ω switch. This architecture preserves RAM data integrity while maximizing battery utilization in MAX704TCPA+ designs.

How does the watchdog timer in MAX704TCPA+ respond to WDI signal transitions?

The MAX704TCPA+ watchdog timer is edge-triggered: any rising or falling edge on WDI clears the 1.6s timeout counter. If WDI remains static (high or low) for longer than 1.6s, RESET is asserted. The timer remains cleared while RESET is active and resumes counting only after RESET deasserts. This behavior prevents firmware lockup without requiring precise timing windows, and is a fixed feature-cannot be disabled in MAX704TCPA+.

Can MAX704TCPA+ monitor a secondary power rail like +5V or -12V?

Yes, MAX704TCPA+ can monitor auxiliary rails via the PFI input using an external resistor divider. For example, a +5V rail can be scaled to 1.237V using R1/R2 to match the internal PFI threshold. The PFO output then signals undervoltage condition independently of the main reset function. This capability allows MAX704TCPA+ to serve dual roles: primary VCC supervision and secondary rail monitoring in compact space-constrained designs.

What is the maximum allowable negative-going VCC transient duration that will not trigger RESET in MAX704TCPA+?

At 100mV overdrive (i.e., VCC dropping 100mV below the 3.075V reset threshold), MAX704TCPA+ tolerates negative transients up to 40µs without issuing a reset pulse. This immunity is achieved through internal filtering and comparator hysteresis. Adding a 100nF bypass capacitor near the VCC pin further enhances noise rejection, making MAX704TCPA+ robust against switching regulator glitches and EMI-induced supply disturbances.