Analog Devices Inc./Maxim Integrated MAX7705CSA

Overview

MAX7705CSA from Maxim Integrated is a microprocessor supervisory circuit that monitors +5V power supplies and asserts an active-low RESET signal during power-up, power-down, and brownout conditions. It features a precise 4.65V reset threshold, guaranteed 280ms power-on reset delay, operates down to VCC = 1V, and consumes only 65µA typical supply current. It replaces TL7705 in cost-sensitive µP systems without external components.

For engineers reviewing the MAX7705CSA datasheet, MAX7705CSA pinout, MAX7705CSA application, or MAX7705CSA equivalent, key selection criteria include guaranteed reset timeout stability over temperature, glitch immunity against sub-40µs VCC transients, low-quiescent-current operation, and compatibility with 8-pin SO footprint for drop-in replacement in legacy TL7705 designs.

Technical Context

The MAX7705CSA integrates a precision voltage comparator, internal timing oscillator, and push-pull RESET output driver. Its reset threshold is trimmed to 4.65V ±15mV and remains stable across -40°C to +85°C for the E-grade variants; the C-grade (0°C to +70°C) version used in MAX7705CSA maintains ±15mV accuracy over its rated range.

Reset assertion is triggered when VCC falls below the threshold and held for ≥280ms after VCC rises above it. The device guarantees this delay across temperature and supply voltage, eliminating need for external RC timing networks - a key differentiator from TL7705, which requires three discrete components for equivalent functionality.

Key Specifications

Pinout & Package

MAX7705CSA is housed in an 8-pin SO (Small Outline) package, 3.9mm × 4.9mm body, 1.27mm pitch, RoHS-compliant lead finish. Pin 1 is VCC; pins 2–3 and 6–7 are No Connect; pin 4 is GND; pin 5 is active-low RESET output; pin 8 is VCC (dual VCC pins for improved supply decoupling).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX706R and TL7705CP, the MAX7705CSA delivers superior value for +5V µP systems through guaranteed timing, ultra-low power, and zero-component implementation - reducing total cost, board space, and qualification risk without compromising reliability.

Availability

MAX7705CSA is available at Aetrix Electronics and suitable for industrial control panels, point-of-sale terminals, medical handhelds, and smart energy meters requiring stable component supply and long-term obsolescence management.

Supply support for MAX7705CSA 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, communications, and computing applications.

The MAX7705CSA belongs to Maxim's µP supervisory product line, engineered to replace discrete reset circuits with integrated, factory-trimmed solutions for reliable power-on sequencing and brownout protection in cost-sensitive embedded systems.

FAQ

What is the reset threshold voltage of the MAX7705CSA?

The MAX7705CSA has a precisely trimmed reset threshold of 4.65V ±15mV, guaranteed over its 0°C to +70°C operating temperature range. This value is factory-tested and ensures consistent detection of +5V supply collapse before microprocessor malfunction occurs. The MAX7705CSA uses an internal bandgap reference to maintain threshold stability across voltage and temperature variations.

Does the MAX7705CSA require external components to function?

No, the MAX7705CSA requires no external components to operate. Unlike the TL7705, it eliminates the need for a reset pull-up resistor, timing capacitor, and reference bypass capacitor. Its internal oscillator provides the guaranteed 280ms power-on reset delay, and the precision voltage comparator needs no external trimming - enabling true single-chip reset supervision.

Can the MAX7705CSA be used in 3.3V systems?

The MAX7705CSA is optimized for +5V systems with a 4.65V reset threshold and is not recommended for direct use in 3.3V applications. For 3.3V rails, Maxim offers alternatives like the MAX706R (2.63V threshold) or MAX708R (2.63V/2.93V/3.08V selectable). Using MAX7705CSA on 3.3V would result in permanent reset assertion since VCC never reaches the 4.65V threshold.

What is the minimum VCC voltage at which the MAX7705CSA guarantees valid RESET output?

The MAX7705CSA guarantees valid RESET output down to VCC = 1.0V. Below this voltage, the RESET output becomes high-impedance and no longer actively sinks current. This behavior ensures deterministic reset hold during deep brownout recovery and aligns with the operational limits of most +5V microcontrollers, which cease functioning below ~1.2V.

How does the MAX7705CSA handle short VCC transients or noise?

The MAX7705CSA provides inherent immunity to short-duration negative-going VCC transients: it will not assert RESET for glitches ≤40µs wide when the transient magnitude is ≤100mV below the 4.65V threshold. This is achieved via internal filtering and comparator hysteresis. Adding a 0.1µF ceramic capacitor close to pin 2 (VCC) further enhances immunity to high-frequency noise.