Analog Devices Inc./Maxim Integrated MAX709SESA+

Overview

MAX709SESA+ from Maxim Integrated is a precision power-supply monitor IC with active-low reset output, designed for +3V systems with 2.93V reset threshold. It guarantees RESET assertion down to VCC = 1V, provides 140ms minimum power-on reset delay, and operates across –40°C to +85°C in an 8-pin SO package. It eliminates external components in microprocessor supervisory circuits for embedded controllers.

For engineers reviewing the MAX709SESA+ datasheet, MAX709SESA+ pinout, MAX709SESA+ application, or MAX709SESA+ equivalent, key selection criteria include reset threshold accuracy (±1.5% over temperature), immunity to short VCC transients (<40µs at 100mV overdrive), low quiescent current (35µA typ.), and guaranteed reset state integrity during brownout recovery.

Technical Context

The MAX709SESA+ integrates a precision voltage comparator with hysteresis, internal timing capacitor, and open-drain RESET driver. Its reset threshold is factory-trimmed to 2.93V ±1.5% over –40°C to +85°C, and its 140ms reset timeout is internally generated without external RC components.

It features dual-stage reset assertion: immediate low-going response on VCC drop below threshold, followed by guaranteed hold time after VCC rise. The device remains functional with VCC as low as 1.0V, and its RESET output is specified for sink capability up to 1.2mA at VCC = threshold min.

Key Specifications

Pinout & Package

MAX709SESA+ is housed in an 8-pin SO (Small Outline) package, 150mil width, with gull-wing leads and RoHS-compliant lead-free finish (+ suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX706SESA+, MAX709SESA+ reduces BOM count by omitting MR and watchdog circuitry; compared with TPS3808G12DBVR, it delivers tighter threshold accuracy, lower quiescent current, and documented immunity to short VCC transients-critical for industrial +3V applications.

Availability

MAX709SESA+ is available at Aetrix Electronics and suitable for industrial PLC controllers, medical handheld diagnostics, automotive body control modules, and smart energy meters requiring stable component supply and long-term lifecycle support.

Supply support for MAX709SESA+ 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, and communications markets.

The MAX709 family targets cost-sensitive, high-reliability microprocessor supervisory functions-delivering integrated reset generation with minimal external components for +3V, +3.3V, and +5V systems.

FAQ

What is the exact reset threshold voltage of MAX709SESA+ and how stable is it over temperature?

The MAX709SESA+ has a nominal reset threshold of 2.93V, with guaranteed tolerance of ±1.5% over the full operating temperature range of –40°C to +85°C. This stability is achieved via laser-trimmed on-chip resistors and process-compensated bandgap references. The normalized threshold variation across temperature is less than ±0.5% relative to nominal, as confirmed in the Typical Operating Characteristics plot on page 4 of the MAX709 datasheet. This ensures consistent brownout detection in MAX709SESA+ across thermal extremes without external calibration.

Does MAX709SESA+ require any external components to function as a reset supervisor?

No, MAX709SESA+ requires no external components to perform basic power-on and brownout reset supervision. A 0.1µF ceramic bypass capacitor on VCC (pin 2) is strongly recommended for noise immunity but not strictly required for functional operation. Unlike discrete solutions, MAX709SESA+ integrates the voltage reference, comparator, timing capacitor, and output driver-enabling single-chip reset generation for +3V systems without resistors, capacitors, or diodes.

Can MAX709SESA+ drive a microprocessor reset pin directly, or is additional buffering needed?

MAX709SESA+ can drive most microprocessor reset pins directly using its open-drain RESET output (pin 7) with an external pull-up resistor (typically 10kΩ to VCC). However, for µPs with bidirectional reset I/O (e.g., Motorola 68HC11), a 4.7kΩ series resistor between MAX709SESA+ RESET and the µP pin is required to prevent contention. The MAX709SESA+ RESET output sinks up to 1.2mA at VCC = threshold min, sufficient for standard CMOS inputs without additional buffering.

How does MAX709SESA+ behave when VCC falls below 1.0V?

Below 1.0V, the MAX709SESA+ RESET output transitions to a high-impedance (open-circuit) state and no longer actively sinks current. While the output remains logically low due to external pull-up, leakage paths may cause undefined voltage levels. For guaranteed RESET validity down to 0V, a 100kΩ pull-down resistor to GND is recommended per Figure 2 in the MAX709 datasheet. This ensures deterministic low state regardless of VCC, critical for fail-safe behavior in MAX709SESA+ deployments.

Is MAX709SESA+ pin-compatible with other members of the MAX709 family, such as MAX709LESA+?

Yes, all MAX709 variants-including MAX709SESA+, MAX709LESA+, and MAX709RESA+-share identical 8-pin SO package footprints and pinouts. The only differences are reset threshold voltage (2.93V for S, 4.65V for L, 2.63V for R) and minor supply current variations. No PCB redesign is needed when substituting within the MAX709 family; only the BOM and firmware reset timing assumptions require review to match the new threshold and delay characteristics of MAX709SESA+.