Analog Devices Inc./Maxim Integrated DS1705EPA+

Overview

DS1705EPA+ from Maxim Integrated is a 5V ±5% microprocessor supervisory circuit that monitors VCC, provides pushbutton reset control, and implements a 1-second watchdog timer. It delivers active-low reset (RST), non-maskable interrupt (NMI), and watchdog status (WDS) outputs in an 8-pin PDIP package, operating across –40°C to +85°C for industrial embedded systems requiring reliable power-up/power-down sequencing and software fault recovery.

For engineers reviewing the DS1705EPA+ datasheet, DS1705EPA+ pinout, DS1705EPA+ application, or DS1705EPA+ equivalent, this page details its precise reset threshold (4.65 V typ), 130 ms minimum reset pulse width, 1 s watchdog timeout, NMI early-warning capability at 1.25 V IN trip point, and compatibility with 5V microcontroller power rails and reset architectures.

Technical Context

The DS1705EPA+ integrates three independent monitoring functions: precision VCC detection using an internal bandgap reference and comparator, debounced pushbutton reset with guaranteed 130 ms active-low pulse, and a monostable watchdog timer triggered by ST input transitions. Its dual reset signaling-RST (active-low) and WDS (active-low watchdog status)-enables layered system response to power faults and software hangs.

It supports flexible voltage sensing via the high-impedance IN pin (1.25 V trip point), allowing external resistor dividers to monitor upstream supplies up to 11.88 V at VCC = 3.3 V. The NMI output provides early warning with 200 µs pulse width and 100 µV hysteresis, while RST remains asserted for ≥130 ms after VCC recovery to ensure processor stabilization.

Key Specifications

Pinout & Package

DS1705EPA+ is housed in an 8-pin plastic DIP (300-mil) package with through-hole mounting compatibility and industry-standard footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX705CPA+, DS1705EPA+ adds watchdog status (WDS) and full ST-input watchdog functionality; compared with TPS3808G33DBVR, it supports 5V operation, offers NMI, pushbutton reset, and configurable IN sensing-making DS1705EPA+ uniquely suited for robust industrial 5V microcontroller supervision.

Availability

DS1705EPA+ is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, telecom infrastructure, and automotive electronics requiring stable component supply and long-term manufacturability.

Supply support for DS1705EPA+ 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 markets.

The DS1705EPA+ belongs to Maxim's MicroMonitor™ family-designed specifically for comprehensive microprocessor supervision in harsh, real-time embedded systems demanding deterministic reset, early-failure warning, and runtime fault detection.

FAQ

What is the exact VCC reset threshold voltage for DS1705EPA+?

The DS1705EPA+ has a nominal VCC trip point of 4.65 V, with a guaranteed range of 4.50 V to 4.75 V (±5% tolerance). This threshold is factory-trimmed and temperature-compensated, ensuring consistent reset activation across the full –40°C to +85°C operating range. The DS1705EPA+ uses this value to assert RST when VCC falls below specification, protecting the microprocessor from undervoltage operation.

Does DS1705EPA+ provide both active-high and active-low reset outputs?

No, DS1705EPA+ provides only an active-low reset output (RST). Unlike some variants in the DS1706 family (e.g., DS1706LEPA+), the DS1705EPA+ does not include an active-high RST output. Its RST pin is push-pull, capable of sinking 10 mA and sourcing 350 µA, and is asserted low for ≥130 ms during power-up or fault conditions.

How does the watchdog timer in DS1705EPA+ operate, and what is its timeout period?

The DS1705EPA+ watchdog timer starts timing after RST becomes inactive and requires a high-to-low transition on the ST pin at least once every 1.0 to 2.2 seconds. If no ST edge occurs within that window, WDS is driven low for ≥130 ms. This timeout is tested at 4.5 V for 5V operation and provides deterministic detection of firmware stalls without requiring external timing components.

Can DS1705EPA+ monitor a 3.3V supply, or is it limited to 5V systems?

DS1705EPA+ is specified for 5V ±5% monitoring and is not designed to directly monitor 3.3V supplies. Its VCC trip point is fixed at ~4.65 V. However, it can monitor higher-voltage rails (e.g., 12V) via the IN pin using an external resistor divider-enabling indirect supervision of upstream 3.3V regulators by sensing their input supply. For native 3.3V monitoring, DS1706TEUA+ or DS1706SEUA+ would be appropriate alternatives.

Is DS1705EPA+ pin-compatible with MAX705 devices, and what does that mean for design reuse?

Yes, DS1705EPA+ is pin-compatible with MAX705/MAX706 in 8-pin DIP, SOIC, and µSOP packages. This means identical PCB footprints, identical pin assignments (PBRST, VCC, GND, IN, NMI, ST, RST, WDS), and identical electrical interface-allowing drop-in replacement without layout changes. Engineers can migrate from MAX705 designs to DS1705EPA+ to gain added watchdog status (WDS) functionality while retaining full hardware compatibility.