Analog Devices Inc./Maxim Integrated MAX704CSA

Overview

MAX704CSA from Maxim Integrated is a microprocessor supervisory circuit providing precision 4.40V supply-voltage monitoring, battery-backup switching for CMOS RAM, active-low reset with 200ms pulse width, and 1.25V power-fail comparator input - used in embedded controllers and intelligent instruments requiring reliable power-up/brownout protection.

For engineers reviewing the MAX704CSA datasheet, MAX704CSA pinout, MAX704CSA application, or MAX704CSA equivalent, key selection criteria include reset threshold accuracy (4.40V ±150mV), guaranteed RESET assertion down to VCC = 1V, battery switchover hysteresis (40mV), and SO-8 package compatibility with industrial temperature range (0°C to +70°C).

Technical Context

The MAX704CSA integrates four tightly coupled functions: a precision bandgap-based voltage monitor triggering reset at 4.40V with 40mV hysteresis; a p-channel MOSFET-based battery switchover circuit with 20mV turn-on threshold and 80Ω on-resistance in backup mode; a 1.25V reference comparator for PFI/PFO power-fail signaling; and a debounced TTL/CMOS-compatible manual reset input with internal 250µA pullup.

Its architecture ensures deterministic behavior during brownout: RESET remains asserted as long as VCC stays below 4.40V, and the internal timer restarts on each voltage dip, guaranteeing minimum 140ms (typ. 200ms) reset pulse after recovery - critical for μP initialization stability in noisy power environments.

Key Specifications

Pinout & Package

MAX704CSA is housed in an 8-pin SO (Small Outline) package compliant with JEDEC MS-012, with 1.27mm pitch and gull-wing leads - suitable for automated SMT assembly and space-constrained PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX703CSA, MAX704CSA triggers reset at a lower supply voltage - better suited for wider-tolerance +5V rails - while MAX706CSA trades battery switching for watchdog functionality, making it appropriate for systems prioritizing runtime reliability over data retention during power loss.

Availability

MAX704CSA is available at Aetrix Electronics and suitable for industrial controllers, intelligent instruments, critical μP power monitoring, and legacy computer systems requiring stable component supply and long-term lifecycle support.

Supply support for MAX704CSA 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 high-performance analog and mixed-signal semiconductor solutions for industrial, communications, and computing markets.

The MAX703/MAX704 product line delivers cost-optimized, integrated supervisory functions - specifically targeting μP-based systems needing reliable reset generation, battery-backed RAM support, and power-fail warning without external components.

FAQ

What is the exact reset threshold voltage for MAX704CSA, and how tightly is it specified?

The MAX704CSA has a nominal reset threshold of 4.40V, with a guaranteed range of 4.25V to 4.50V across the full operating temperature range (0°C to +70°C). This specification ensures consistent brownout detection in +5V systems with ±10% supply tolerance, and the 40mV hysteresis prevents chatter during slow voltage decay. The threshold is derived from an internal bandgap reference, not resistor dividers, so it remains stable over time and temperature.

Can MAX704CSA operate with a 3.3V main supply, or is it strictly for +5V systems?

The MAX704CSA is designed for +5V systems and requires VCC between +4.5V and +5.5V per its Absolute Maximum Ratings and Electrical Characteristics tables. It does not support 3.3V operation - attempting to power it from 3.3V will result in undefined reset behavior and potential failure to assert RESET correctly. For 3.3V applications, consider the MAX6326 or MAX6342 families, which feature 3.08V or adjustable thresholds.

How does the battery switchover function work in MAX704CSA, and what is the maximum allowable VBATT voltage?

In MAX704CSA, when VCC falls below the reset threshold (4.40V), the internal p-channel MOSFET disconnects VCC from VOUT and connects VBATT to VOUT if VBATT exceeds VCC by at least 20mV. The switchover includes 40mV hysteresis to prevent oscillation. Per Table 2 in the datasheet, the maximum allowed VBATT is 4.55V - exceeding this risks forward-biasing internal substrate diodes and damaging the device or causing excessive leakage.

Is the RESET output of MAX704CSA push-pull or open-drain, and what are its drive capabilities?

The RESET output of MAX704CSA is a push-pull (totem-pole) structure, not open-drain. It sources current when high (VOH ≥ VCC – 1.5V at 800µA) and sinks current when low (VOL ≤ 0.4V at 3.2mA). It remains functional down to VCC = 1V, with VOL ≤ 0.3V under specified sinking conditions. This eliminates the need for an external pullup resistor in most μP interface configurations.

Does MAX704CSA include a watchdog timer, and how does it compare to MAX706CSA in that regard?

No, MAX704CSA does not include a watchdog timer - it provides only reset generation, battery switchover, power-fail detection, and manual reset. In contrast, MAX706CSA integrates a 1.6-second watchdog timer alongside its 4.40V reset function. If your design requires runtime supervision to recover from software lockups, MAX706CSA is the appropriate alternative; MAX704CSA is optimized purely for power-supply integrity and data retention.