Analog Devices Inc./Maxim Integrated DS1312+

Overview

DS1312+ from Maxim Integrated is a nonvolatile controller IC that converts standard CMOS SRAM into battery-backed nonvolatile memory. It provides automatic VCC monitoring, unconditional write-protection during power failure, lithium battery voltage monitoring with 24-hour periodic testing, and open-drain Battery Warning (BW) and Reset (RST) outputs. It operates across -40°C to +85°C and supports 8-pin DIP packaging for embedded data retention in industrial instrumentation.

For engineers reviewing the DS1312+ datasheet, DS1312+ pinout, DS1312+ application, or DS1312+ equivalent, this page delivers verified functional architecture, precise trip-point thresholds (VCCTP = 4.50–4.75V at TOL=GND), battery test timing (tBTCN = 24 hr), backup current capability (ICCO2 ≤ 500 µA), and package-specific pin validation for the 8-pin PDIP variant.

Technical Context

The DS1312+ integrates three core subsystems: a precision VCC comparator with selectable 5% or 10% tolerance via TOL pin, a low-leakage battery-switching circuit enabling <0.2V drop between VBAT and VCCO, and a factory-programmed 24-hour battery test engine using a 1.2 MΩ internal load (RINT) to measure loaded VBAT against VBTP = 2.5–2.7V.

Its write-protection logic delays CEO inhibition up to 1.5 µs after power failure detection to complete in-progress memory accesses, while RST asserts for 150–350 ms on power-up and within 5–15 µs of VCCI falling below VCCTP - ensuring deterministic reset behavior in processor-based systems requiring reliable power-fail signaling.

Key Specifications

Pinout & Package

DS1312+ is packaged in an 8-pin plastic dual in-line package (PDIP), 300-mil width, with through-hole mounting and RoHS-compliant lead finish. Pin 1 is marked by a notch or dot; pins are numbered counter-clockwise from top-left corner when viewed from top.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6900+ and DS1232L+, the DS1312+ uniquely combines SRAM power switching, unconditional write-protection, and factory-calibrated lithium battery health monitoring in a single 8-pin DIP - eliminating design complexity and component count for pure nonvolatile memory retention.

Availability

DS1312+ is available at Aetrix Electronics and suitable for industrial data loggers, point-of-sale terminals, medical infusion pumps, smart energy meters, and embedded controllers requiring stable component supply with long-term lifecycle assurance.

Supply support for DS1312+ 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, automotive, and communications applications.

The DS1312+ belongs to Maxim's nonvolatile memory interface product line, engineered specifically to eliminate external discrete components in SRAM battery-backup systems while providing certified reliability and predictive battery maintenance.

FAQ

What is the primary function of the DS1312+ in an SRAM-based system?

The DS1312+ serves as a dedicated nonvolatile controller that automatically switches SRAM power from VCCI to VBAT during power failure, unconditionally inhibits CEO to prevent writes, and monitors lithium battery health via periodic loaded-voltage testing. Its integrated architecture replaces multiple discrete components - including voltage supervisors, MOSFET switches, and battery testers - reducing board space and qualification effort in the DS1312+ implementation.

How does the DS1312+ determine when to assert the Battery Warning (BW) output?

The DS1312+ asserts BW when the lithium battery voltage, measured under a 1.2 MΩ internal load for 1 second every 24 hours, falls below the factory-trimmed trip point VBTP (2.5–2.7 V). BW remains latched low until the battery is physically replaced - a behavior confirmed in the DS1312+ datasheet section "BATTERY VOLTAGE MONITORING" and validated by tBDBA = 7 s minimum detach-attach timing.

Can the DS1312+ be used with SRAMs requiring more than 500 µA in battery-backup mode?

No - the DS1312+ specifies a maximum battery-backup supply current (ICCO2) of 500 µA. Exceeding this limit risks undervoltage on VCCO and data corruption. Systems with higher SRAM standby current must use alternative controllers like the DS1315 (1 mA capable) or implement external boost circuitry; the DS1312+ datasheet explicitly limits ICCO2 to 500 µA in DC Electrical Characteristics Table.

What is the significance of the TOL pin configuration on the DS1312+?

The TOL pin selects the VCCI trip point: grounded for 4.50–4.75 V (5% tolerance), or tied to VCCO for 4.25–4.50 V (10% tolerance). This allows system designers to match the DS1312+'s power-fail detection threshold to their regulator's accuracy and noise margin - a configurable feature absent in fixed-threshold alternatives like the DS1232L+, and directly specified in the DS1312+ Recommended Operating Conditions table.

Does the DS1312+ require external pull-up resistors on its open-drain outputs?

Yes - both BW and RST are open-drain outputs and require external pull-up resistors to function correctly. The DS1312+ datasheet Note 11 states they "cannot source current" and specifies a 10 mA sink capability. Typical designs use 4.7 kΩ pull-ups to VCCO; omitting these will result in undefined logic levels and failed reset or warning signaling in the DS1312+ application.