Analog Devices Inc./Maxim Integrated DS17285E-5

Overview

DS17285E-5 from Maxim Integrated is a battery-backed real-time clock/calendar IC with 114 bytes of NV SRAM, 2kB extended NV SRAM, multiplexed 8-bit address/data bus interface, and integrated power-on control via PWR and KS pins. It supports 12/24-hour timekeeping with leap-year compensation through 2099, operates at +3.0V or +5.0V, and delivers ±1 minute/month accuracy when paired with a 32.768kHz crystal - ideal for utility metering and industrial embedded systems requiring long-term timekeeping under intermittent power.

For engineers reviewing the DS17285E-5 datasheet, DS17285E-5 pinout, DS17285E-5 application, or DS17285E-5 equivalent, key selection considerations include its dual-supply operation (3V/5V), software-controllable PWR output for system wake-up, 64-bit silicon serial number, maskable interrupt architecture, and compatibility with legacy DS12887-based designs while adding enhanced power management and extended memory.

Technical Context

The DS17285E-5 implements a temperature-compensated power-fail detection circuit that switches autonomously between VCC, VBAT, and VBAUX supplies based on voltage thresholds (VPF = 4.25–4.5V at 5V mode; 2.5–2.7V at 3V mode) and maintains RTC operation and RAM retention during primary power loss. Its oscillator supports external 32.768kHz crystals with selectable 6pF or 12.5pF load capacitance, and startup is controlled by DV2/DV1/DV0 bits in Register A.

Timekeeping is double-buffered to prevent read corruption during updates; the UIP flag indicates update-in-progress status, and the SET bit in Register B enables safe register initialization. Alarm functionality supports both exact-time triggers and "don't care" masking (C0h–FFh) across seconds/minutes/hours registers, enabling flexible wake-up intervals from once per second to once per day.

Key Specifications

Pinout & Package

DS17285E-5 is housed in a 24-pin PDIP package with 0.300" width, RoHS-compliant lead finish, and industrial temperature range (-40°C to +85°C). Pin functions are validated per Maxim Integrated datasheet Rev 2 (May 2016).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock applications.

Compared with DS1307ZN+ and PCF8583P, the DS17285E-5 uniquely combines parallel bus compatibility, dual-voltage support, hardware-assisted system power control, and scalable NV SRAM - making it the only option among the three capable of replacing DS12887 in legacy PC-compatible or industrial control designs with enhanced reliability.

Availability

DS17285E-5 is available at Aetrix Electronics and suitable for smart utility meters, industrial control panels, and network infrastructure devices requiring stable component supply, long-term lifecycle support, and guaranteed performance across -40°C to +85°C ambient conditions.

Supply support for DS17285E-5 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 precision analog, mixed-signal, and power management ICs for industrial, communications, and computing applications.

The DS17285E-5 belongs to Maxim's legacy real-time clock product line, designed specifically to replace the DS12887 in embedded systems requiring enhanced power control, extended memory, and backward-compatible parallel interfacing.

FAQ

What voltage ranges does the DS17285E-5 support?

The DS17285E-5 supports two operating voltage ranges: +2.7V to +3.7V for 3V systems and +4.5V to +5.5V for 5V systems. Its power-fail detection threshold (VPF) scales accordingly - 2.5V–2.7V in 3V mode and 4.25V–4.5V in 5V mode - ensuring robust switchover to VBAT or VBAUX during brownout conditions. This dual-voltage capability makes DS17285E-5 suitable for mixed-supply industrial platforms.

How does the DS17285E-5 handle leap year and month-end date adjustments?

The DS17285E-5 automatically adjusts the date at month-end for all months with fewer than 31 days, including full leap-year compensation through the year 2099. This behavior is implemented in hardware and requires no software intervention. The calendar logic correctly handles February 29 in leap years and transitions from January 31 to February 1, March 31 to April 1, etc., regardless of whether the device is configured in 12-hour or 24-hour mode.

Can the DS17285E-5 generate a 1Hz square-wave output?

Yes, the DS17285E-5 can generate a precise 1Hz square-wave output on the SQW pin by programming bits RS3–RS0 in Register A to 0011b (binary). The SQW output is derived from the internal 32.768kHz oscillator and supports 13 selectable frequencies ranging from 1Hz to 32.768kHz. When E32k = 1, SQW outputs 32kHz regardless of other settings; otherwise, frequency is determined solely by Register A.

What is the purpose of the RCLR pin on the DS17285E-5?

The RCLR (Active-Low RAM Clear) pin on the DS17285E-5 provides hardware-initiated clearing of the 114-byte general-purpose NV SRAM - setting all bits to logic 1. It does not affect RTC registers, extended SRAM, or control registers. RCLR is intended for manual reset via switch or button (not driven by logic buffers) and remains functional even when VCC is absent, as long as VBAT or VBAUX is present. This enables field-serviceable memory reset without firmware access.

Does the DS17285E-5 require external load capacitors for the crystal?

No, the DS17285E-5 does not require external load capacitors for the 32.768kHz crystal. Its internal oscillator circuit supports selectable load capacitance of either 6pF or 12.5pF via a dedicated crystal select bit, eliminating the need for external CL1/CL2 components. This simplifies PCB layout, improves manufacturing yield, and enhances consistency across crystal vendors - a key advantage over earlier RTCs like the DS1307.