Analog Devices Inc./Maxim Integrated DS1312E+

Overview

DS1312E+ from Maxim Integrated is a nonvolatile controller with integrated lithium battery monitor, designed to convert standard CMOS SRAM into battery-backed nonvolatile memory. It provides automatic VCC fail detection (4.5–4.75V range), unconditionally write-protects SRAM via CEO inhibition, switches to VBAT backup supply (<0.2V drop), and asserts open-drain BW and RST outputs. Used in industrial data loggers requiring long-term RAM retention during power loss.

For engineers reviewing the DS1312E+ datasheet, DS1312E+ pinout, DS1312E+ application, or DS1312E+ equivalent, key selection criteria include its 20-pin TSSOP package, dual tolerance-selectable power-fail detection (5%/10%), 24-hour periodic battery voltage monitoring under load, and guaranteed 1.5µs write-protection delay to complete in-progress memory accesses.

Technical Context

The DS1312E+ integrates three core functional blocks: a precision VCCI comparator with TOL-selectable trip points (4.25–4.75V), a low-leakage VCC/VBAT power switch enabling <0.2V dropout, and a factory-programmed 24-hour battery test circuit that applies a 1.2MΩ internal load to VBAT and compares resulting voltage against VBTP = 2.6V ±0.1V.

Its RST output delivers 200ms nominal power-on reset pulse and sub-15µs response to VCCI failure; BW output remains latched active until physical battery replacement occurs and tBDBA ≥7s is observed. All control logic operates with ICCO2 ≤500µA in battery-backup mode and ICC1 ≤400µA during normal operation.

Key Specifications

Pinout & Package

DS1312E+ is housed in a 20-pin Thin Shrink Small Outline Package (TSSOP) with 0.65mm pitch, JEDEC MO-187AC compliant, thermal resistance θJA = 73.8°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar nonvolatile SRAM controller applications.

Compared with DS1312E+, DS1232L+T&R offers simpler reset-only supervision but no battery-backed memory control, while MAX6900EAP+ adds timekeeping at the cost of losing integrated SRAM power switching and write-protection logic-neither provides the DS1312E+'s guaranteed 1.5µs memory access completion guarantee.

Availability

DS1312E+ is available at Aetrix Electronics and suitable for industrial data loggers, medical patient monitors, smart energy meters, and factory automation PLCs requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for DS1312E+ 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, medical, and communications applications.

The DS1312E+ belongs to Maxim's nonvolatile memory controller product line, engineered specifically to eliminate external discrete components needed to back up SRAM with lithium batteries while providing predictive battery health monitoring.

FAQ

What is the function of the TOL pin on the DS1312E+?

The TOL pin on the DS1312E+ selects the VCCI power-fail detection tolerance: connecting TOL to GND configures a 5% trip window (4.50–4.75V), while connecting it to VCCO sets a 10% window (4.25–4.50V). This allows system designers to align DS1312E+ behavior precisely with their power supply's specified regulation limits without modifying firmware or external circuitry.

How does the DS1312E+ prevent data corruption during power failure?

The DS1312E+ prevents data corruption by asserting CEO low within nanoseconds of VCCI dropping below VCCTP, thereby disabling SRAM writes. Crucially, it delays this action for up to 1.5µs if CEI is active-ensuring any ongoing memory access completes before write protection engages. This hardware-enforced timing guarantee is built into the DS1312E+ silicon and requires no software intervention.

Why does the BW output remain active after power is restored?

The BW output on the DS1312E+ remains latched low because it signals irreversible lithium battery end-of-life-not transient low-voltage conditions. It stays active until the depleted battery is physically removed and replaced with a fresh cell, and the DS1312E+ observes tBDBA ≥7s between detachment and reattachment. This prevents false resets caused by temporary voltage dips.

Can the DS1312E+ operate with a 3.3V system supply?

No-the DS1312E+ is specified only for VCCI = 4.5–5.5V operation per its Recommended Operating Conditions table. Its internal comparators, switch architecture, and CEO drive strength are optimized for 5V SRAM interfaces. Using 3.3V on VCCI violates absolute maximum ratings and will cause incorrect trip-point detection and unreliable VCCO regulation.

What is the purpose of Freshness Seal Mode in the DS1312E+?

Freshness Seal Mode in the DS1312E+ prevents battery discharge during manufacturing, shipping, and storage by inhibiting VCCO output until VCCI first exceeds VCCTP. This ensures zero standby current draw from the lithium cell prior to system commissioning-extending shelf life and guaranteeing full battery capacity is available at first power-on.