NXP Semiconductors PCF8583T/5,518

Overview

PCF8583T/5,518 from NXP Semiconductors is a serial I²C-bus real-time clock and calendar IC with 240 × 8-bit low-voltage RAM, built-in 32.768 kHz oscillator circuit, and programmable alarm/timer functions. It supports 24-hour or 12-hour time format, four-year calendar, and operates from 1.0 V to 6.0 V supply voltage. It is used in embedded systems requiring accurate timekeeping with minimal power consumption, such as industrial control panels and utility meters.

For engineers reviewing the PCF8583T/5,518 datasheet, PCF8583T/5,518 pinout, PCF8583T/5,518 application, or PCF8583T/5,518 equivalent, this page delivers verified functional specifications, validated SO8 package mapping, confirmed I²C slave addressing (A0h/A2h write, A1h/A3h read), exact RAM allocation (first 8 bytes for clock/calendar, next 8 for alarm or free RAM), and real-world interrupt behavior (open-drain INT, active LOW, 1 Hz toggle default).

Technical Context

The PCF8583T/5,518 implements a dedicated clock/calendar core with BCD-encoded counters for hundredths of seconds through years/months/weekdays, all backed by an auto-incrementing 256-word address register. Its oscillator supports 32.768 kHz crystal, 50 Hz AC line, or external event pulses on OSCI, with divider-derived 100 Hz timing for counters.

Alarm functionality is fully configurable via memory-mapped registers: dated, daily, weekday, or timer-based alarms trigger the open-drain INT output when enabled and matched. The control/status register (00h) governs mode selection (clock/event/timer), format (12/24 hour), mask/halt flags, and interrupt enable states - all accessible over standard I²C protocol with no additional control lines required.

Key Specifications

Pinout & Package

PCF8583T/5,518 uses the SO8 (plastic small outline, 8-lead, 7.5 mm body width) package per SOT176-1. Pin 1 is OSCI; pin 8 is VDD. All pins match the SO8 variant defined in NXP's official datasheet Rev. 06.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1307+T&R, PCF8583T/5,518 offers superior flexibility with event counting, 50 Hz input, and larger RAM; versus PCF8563T/5,518, it trades higher power and older architecture for proven field reliability and simpler register-level compatibility in legacy systems.

Availability

PCF8583T/5,518 is available at Aetrix Electronics and suitable for industrial control panels, smart energy meters, point-of-sale terminals, and building automation controllers requiring stable component supply across long production lifecycles.

Supply support for PCF8583T/5,518 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCF8583T/5,518 belongs to NXP's legacy real-time clock product line, designed specifically for cost-sensitive, low-power embedded systems requiring robust calendar/timekeeping with minimal external components and I²C simplicity.

FAQ

What is the I²C slave address configuration for PCF8583T/5,518?

The PCF8583T/5,518 supports two I²C slave addresses determined by the A0 pin state: when A0 = VSS, the write address is 0xA0 and read address is 0xA1; when A0 = VDD, the write address is 0xA2 and read address is 0xA3. These are fixed 7-bit addresses with R/W bit appended, compliant with standard I²C protocol as documented in NXP's PCF8583 datasheet Rev. 06.

Does PCF8583T/5,518 support battery backup operation?

Yes, PCF8583T/5,518 supports battery backup operation with data retention down to 1.0 V supply voltage and current draw as low as 2 μA at 1.0 V and −25 °C to +70 °C. This enables reliable timekeeping during main power loss when paired with a coin-cell or supercapacitor on VDD, preserving both clock/calendar state and 240-byte RAM contents.

Can PCF8583T/5,518 operate without an external crystal?

Yes, PCF8583T/5,518 can operate without a crystal by using the 50 Hz AC line input on the OSCI pin or external event pulses - the oscillator circuit disables automatically in these modes. In 50 Hz mode, the internal divider derives timing directly from the input signal, eliminating need for quartz, trimmer capacitor, or load capacitance matching.

How does the alarm function work in PCF8583T/5,518?

The PCF8583T/5,518 alarm function compares BCD-encoded values in alarm registers (08h–0Fh) against corresponding clock/calendar registers (01h–07h). When matched, the alarm flag (bit 1 of control register 00h) sets and - if enabled - drives the open-drain INT pin LOW. Alarm types include dated, daily, weekday, and timer-based, each selected via bits in the alarm control register (08h).

What is the maximum count capacity of the event counter in PCF8583T/5,518?

The event counter in PCF8583T/5,518 stores up to six hexadecimal digits across registers 01h–03h, enabling a maximum count of 1,000,000 events. Each digit is stored in BCD format, and the counter increments on rising edges applied to the OSCI pin while in event-counter mode (control register bits 4–5 = 10b), with resolution selectable via alarm control register bits 0–2.