Analog Devices Inc./Maxim Integrated DS1705EPA

Overview

DS1705EPA from Maxim Integrated is a 5V ±5% microprocessor supervisory circuit that provides power-on reset, watchdog timer, non-maskable interrupt (NMI), and pushbutton reset functions in an 8-pin PDIP package. It monitors VCC for out-of-tolerance conditions, generates a 130 ms minimum active-low reset pulse on power-up/power-down, detects early power failure via the IN pin (1.25 V trip), and delivers watchdog timeout at 1.0–2.2 s. It is used in embedded industrial controllers requiring reliable boot sequencing and fault recovery.

For engineers reviewing the DS1705EPA datasheet, DS1705EPA pinout, DS1705EPA application, or DS1705EPA equivalent, key selection criteria include its 5V-5% VCC trip point (4.50–4.75 V), guaranteed 130 ms reset pulse width, NMI generation with 200 µs pulse width and 100 µV hysteresis, watchdog strobe timing compatibility, and pin compatibility with MAX705/MAX706 in DIP/SOIC/µSOP packages.

Technical Context

The DS1705EPA implements three independent monitoring functions: precision VCC sensing using an internal bandgap reference and comparator (VCCTP = 4.50–4.75 V), high-impedance IN-pin voltage monitoring (VTP = 1.20–1.30 V) for early power-fail warning, and a 1-second watchdog timer triggered by ST input transitions. All functions operate across –40°C to +85°C with no external components required.

Its reset logic asserts /RST low for ≥130 ms during power-up and power-down events; the NMI output pulses low for ≥200 µs when IN falls below VTP, with built-in 5 µs noise immunity and hysteresis. The PBRST input is internally pulled up (40 kΩ typical) and debounced to guarantee a clean 130 ms reset pulse upon button release.

Key Specifications

Pinout & Package

DS1705EPA is housed in an 8-pin plastic DIP (300-mil) package with through-hole mounting and industry-standard footprint. Pin assignments are fully compatible with MAX705/MAX706 in DIP, SOIC, and µSOP packages.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1705EPA, MAX705CPA offers pin-compatible reset/NMI but omits watchdog status output, while TPS3823-50DBVR reduces footprint and cost at the expense of supervision depth - making DS1705EPA the only choice for full-feature 5V system monitoring with NMI, watchdog, and pushbutton support in DIP format.

Availability

DS1705EPA is available at Aetrix Electronics and suitable for industrial automation, medical instrumentation, telecom infrastructure, and energy metering applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole packaging.

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 U.S.-based 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 robust microprocessor supervision in mission-critical embedded systems where power integrity, fault detection, and deterministic recovery are mandatory.

FAQ

What is the exact VCC trip point range for DS1705EPA?

The DS1705EPA has a guaranteed VCC trip point range of 4.50 V to 4.75 V, corresponding to a nominal 5V supply with ±5% tolerance. This specification is validated across the full industrial temperature range (–40°C to +85°C) and ensures reliable reset assertion before the microprocessor enters undefined operation. DS1705EPA uses an internal temperature-compensated bandgap reference to maintain accuracy over voltage and temperature variations.

Does DS1705EPA support both active-high and active-low reset outputs?

No, DS1705EPA provides only an active-low reset output (/RST). The part marking "DS1705EPA" explicitly denotes the /RST, /WDS version (as confirmed in the Ordering Information table). Unlike DS1706 variants such as DS1706LEPA which offer RST (active-high), DS1705EPA does not include an active-high reset output. Its /RST pin is open-drain and requires an external pull-up resistor for proper microprocessor interface.

How does the watchdog timer in DS1705EPA interact with the reset function?

The DS1705EPA watchdog timer operates independently of the power-monitor reset: it begins timing only after /RST becomes inactive (i.e., after power-up stabilization), and times out after 1.0–2.2 seconds if the ST input is not strobed. Upon timeout, WDS goes low for ≥130 ms but does not assert /RST - the reset output remains controlled solely by VCC, IN, or PBRST events. This separation allows DS1705EPA to signal watchdog faults without forcing immediate system reset unless explicitly wired to do so.

Can DS1705EPA monitor a 3.3V supply?

No, DS1705EPA is specified exclusively for 5V systems with a 4.50–4.75 V trip point. For 3.3V monitoring, Maxim offers DS1706 variants (e.g., DS1706TEUA for 3.3V ±5%). Attempting to use DS1705EPA on a 3.3V rail would result in permanent /RST assertion because VCC remains below the minimum trip threshold. The DS1705EPA datasheet confirms its designation as "5V-5% MONITOR" in the Ordering Information section.

Is DS1705EPA pin-compatible with MAX705/MAX706 in all packages?

Yes, DS1705EPA is pin-compatible with MAX705 and MAX706 in all three package types: 8-pin PDIP (P), 8-pin SOIC (S), and 8-pin µSOP (U). The Pin Assignment diagram and feature list explicitly state "Pin-compatible with the MAXIM MAX705/MAX706 in 8-pin DIP, 8-pin SOIC, and µ-SOP". This compatibility extends to electrical behavior, timing, and functional pin mapping - enabling drop-in replacement in existing designs using those Maxim parts.