Analog Devices Inc./Maxim Integrated MAX709SCUA+

Overview

MAX709SCUA+ from Maxim Integrated is a precision power-supply monitor IC with active-low reset output, designed for +3V systems (2.93V nominal reset threshold), operating from 1.0V to 5.5V supply, delivering 140ms minimum power-on reset delay and guaranteed RESET state down to VCC = 1V. It eliminates external components in microprocessor supervisory circuits for embedded controllers, industrial PLCs, and battery-backed instrumentation.

For engineers reviewing the MAX709SCUA+ datasheet, MAX709SCUA+ pinout, MAX709SCUA+ application, or MAX709SCUA+ equivalent, key selection criteria include reset threshold tolerance (±2.5% over temperature), immunity to short VCC transients (<40µs at 100mV overdrive), low quiescent current (35µA typ.), and µMAX-8 package compatibility with space-constrained PCB layouts.

Technical Context

The MAX709SCUA+ integrates a precision voltage reference, comparator, and reset timer in a single die. Its reset threshold is factory-trimmed to 2.93V ±2.5% across –40°C to +85°C, with temperature coefficient <100ppm/°C. The internal timer ensures minimum 140ms reset assertion after VCC rises above threshold, independent of VCC slew rate.

RESET output is open-drain with guaranteed sink capability of 1.2mA at VCC = reset threshold min (2.85V), and logic-level compatibility with CMOS/TTL inputs. The device features no external timing components and requires only a 0.1µF bypass capacitor on VCC for transient immunity-no pull-up resistor needed unless interfacing with bidirectional µP reset pins.

Key Specifications

Pinout & Package

MAX709SCUA+ is housed in an 8-pin µMAX package (3.05mm × 3.05mm, 0.65mm pitch), pin-compatible with SO-8 and PDIP-8 footprints but optimized for high-density layouts. Pin 1 is top-left corner (notch-marked), with pin 1 function confirmed as N.C., pin 2 = VCC, pin 3 = GND, pin 7 = RESET.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power-supply monitor applications.

Compared with MAX706S and TPS3808G30, MAX709SCUA+ provides the lowest quiescent current in its class (35µA), best-in-class transient immunity (40µs @ 100mV), and drop-in µMAX-8 compatibility-making it ideal for cost-sensitive, space-constrained industrial designs where reliability under voltage disturbance is critical.

Availability

MAX709SCUA+ is available at Aetrix Electronics and suitable for industrial PLCs, medical sensor nodes, automotive body control units, and smart meter data loggers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX709SCUA+ 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 analog, mixed-signal, and power-management ICs for industrial, automotive, and communications markets.

The MAX709 family was engineered specifically for microprocessor supervisory functions in resource-constrained embedded systems-delivering precision reset generation with zero external components and minimal board footprint.

FAQ

What is the exact reset threshold voltage of MAX709SCUA+ and how tightly is it specified?

The MAX709SCUA+ has a nominal reset threshold of 2.93V, with a guaranteed tolerance of ±2.5% over the full operating temperature range (–40°C to +85°C). This specification is factory-trimmed and verified per datasheet Electrical Characteristics table, ensuring consistent brownout detection in +3V systems without external calibration. The MAX709SCUA+ achieves this accuracy using on-chip bandgap reference and laser trimming.

Does MAX709SCUA+ require an external pull-up resistor on the RESET pin?

Yes, MAX709SCUA+ features an open-drain RESET output and requires an external pull-up resistor to a valid logic-high voltage (e.g., VCC or another supply rail). A typical value is 10kΩ to 100kΩ. Without it, the RESET signal remains floating when deasserted, risking indeterminate logic levels at the microprocessor's reset input. This is explicitly stated in the Applications Information section of the MAX709SCUA+ datasheet.

Can MAX709SCUA+ operate reliably when VCC drops below 1.0V?

No-MAX709SCUA+ guarantees correct RESET output state only down to VCC = 1.0V. Below that, the internal circuitry cannot maintain sink capability, and RESET becomes high-impedance (open-circuit). For applications requiring valid reset signaling all the way to 0V, a pull-down resistor (e.g., 100kΩ to GND) on the RESET line is recommended, as documented in Figure 2 of the MAX709SCUA+ datasheet.

What is the maximum duration of a negative VCC transient that MAX709SCUA+ can ignore without asserting RESET?

At a 100mV overdrive (i.e., VCC dipping 100mV below the 2.93V threshold), MAX709SCUA+ will not assert RESET for transients ≤40µs in duration. This immunity is characterized and plotted in Figure 1 of the MAX709SCUA+ datasheet. Longer or deeper transients will trigger reset, ensuring protection against sustained brownout while ignoring brief noise spikes.

Is MAX709SCUA+ pin-compatible with other packages like SO-8 or PDIP-8?

MAX709SCUA+ uses the µMAX-8 package (3.05mm × 3.05mm), which shares the same 8-pin linear pinout (1–8) as SO-8 and PDIP-8 variants of the MAX709 family-but with different physical dimensions and pitch (0.65mm vs. 1.27mm). While electrical pin functions match, direct PCB footprint substitution is not possible without layout revision. The MAX709SCUA+ is not a drop-in replacement for SO-8 or DIP versions.