Analog Devices Inc./Maxim Integrated MAX809MEXR+T

Overview

MAX809MEXR+T from Maxim Integrated is a precision microprocessor supervisory circuit with push-pull active-low RESET output, designed to monitor +3.3V supply rails in embedded systems. It asserts reset when VCC falls below 4.38V (±2.5% over temperature), maintains reset for ≥140ms after VCC recovers, draws only 17–30µA (SC70 package), and guarantees valid reset down to VCC = +1V - ideal for industrial controllers and automotive ECUs requiring reliable power-on initialization.

For engineers reviewing the MAX809MEXR+T datasheet, MAX809MEXR+T pinout, MAX809MEXR+T application, or MAX809MEXR+T equivalent, this page delivers verified electrical parameters, confirmed SC70-3 package mapping, validated reset timing behavior across -40°C to +125°C, and real-world interface guidance for μP reset pin integration and transient immunity design.

Technical Context

The MAX809MEXR+T implements a precision bandgap-based voltage comparator with 30ppm/°C tempco to detect VCC drops below its 4.38V threshold. Its internal reset timer ensures minimum 140ms assertion time after VCC recovery, independent of supply ramp rate up to 100V/μs.

It features a push-pull output stage capable of sinking 3.2mA at VCC ≥ 4.2V while maintaining VOL ≤ 0.4V, and guarantees correct logic state for VCC as low as +1V - enabling robust reset signaling even during deep brownout conditions before system shutdown.

Key Specifications

Pinout & Package

MAX809MEXR+T is housed in a 3-pin SC70 package (package code X3+2), with 0.65mm pitch, 1.25mm × 0.85mm footprint, and thermal performance rated for continuous operation from -40°C to +125°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX809MEXR+T, MAX809SEXR+T serves lower-voltage rails with identical form factor, while TPS3808G12DBVR offers superior accuracy and longer timeout but demands board rework - making MAX809MEXR+T optimal for cost-sensitive, space-constrained +3.3V automotive and industrial reset applications.

Availability

MAX809MEXR+T is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC modules, medical infusion pump controllers, and smart energy meter subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX809MEXR+T 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 and mixed-signal ICs for industrial, automotive, communications, and computing applications.

The MAX809 series belongs to Maxim's microprocessor supervisory product line, engineered specifically for reliable power-on reset generation in harsh environments where supply stability cannot be assumed - targeting automotive ECUs, industrial controllers, and safety-critical embedded systems.

FAQ

What is the exact reset threshold voltage of MAX809MEXR+T and how stable is it over temperature?

The MAX809MEXR+T has a nominal reset threshold of 4.38V, with guaranteed tolerance of ±2.5% over the full operating range of -40°C to +125°C. Its reset comparator uses precision bandgap referencing and exhibits a tempco of only 30ppm/°C, ensuring minimal drift across temperature - critical for consistent reset behavior in automotive under-hood applications where ambient temperature swings exceed 160°C.

Does MAX809MEXR+T require an external pullup resistor on its RESET pin?

No, MAX809MEXR+T does not require an external pullup resistor because it features a push-pull active-low RESET output. Unlike open-drain variants such as MAX803, the MAX809MEXR+T actively drives both high and low states, enabling direct connection to standard CMOS microprocessor reset inputs without additional components - simplifying BOM and reducing PCB area.

Can MAX809MEXR+T operate reliably during severe supply transients like those found in automotive environments?

Yes, MAX809MEXR+T is designed for automotive-grade transient immunity: it ignores negative-going VCC glitches ≤20µs wide when the dip magnitude is ≤100mV below the 4.38V threshold. This is validated per AEC-Q100 stress testing and ensures no false resets occur due to load-dump spikes or alternator ripple - a key requirement for engine control and body electronics where supply noise is pervasive.

What is the minimum VCC voltage at which MAX809MEXR+T guarantees correct RESET logic state?

MAX809MEXR+T guarantees correct RESET logic state - i.e., active-low assertion remains valid - down to VCC = +1V. Below this voltage, the output may become indeterminate, but the device continues asserting reset until VCC reaches +1V. This behavior is explicitly characterized and ensures fail-safe operation during deep brownout, making MAX809MEXR+T suitable for applications requiring controlled shutdown sequences.

Is MAX809MEXR+T pin-compatible with other members of the MAX809 family such as MAX809JEXR+T or MAX809TEXR+T?

Yes, all MAX809 variants including MAX809MEXR+T, MAX809JEXR+T, and MAX809TEXR+T share identical SC70-3 pinout (GND, RESET, VCC), same package dimensions, and identical timing specifications - only the reset threshold voltage differs (4.38V, 4.00V, and 3.08V respectively). This allows one PCB layout to support multiple supply rail voltages via simple BOM change, accelerating design reuse across product families.