NXP Semiconductors PCF85263ATT1/AJ

Overview

PCF85263ATT1/AJ from NXP Semiconductors is a CMOS real-time clock (RTC) and calendar IC with battery switch-over, two independent alarms, three timestamp registers, and I²C-bus interface. It operates from 0.9 V to 5.5 V, draws only 0.28 µA at 3.0 V/25 °C, and supports stop-watch mode up to 999 999 hours - used in battery-backed systems requiring precise timekeeping during main power loss.

For engineers reviewing the PCF85263ATT1/AJ datasheet, PCF85263ATT1/AJ pinout, PCF85263ATT1/AJ application, or PCF85263ATT1/AJ equivalent, this page delivers verified technical context, TSSOP10 package mapping, I²C timing constraints, alarm register behavior, and direct alternatives for industrial time-stamping, metering, and embedded logging designs.

Technical Context

The PCF85263ATT1/AJ implements a dual-mode RTC architecture: standard calendar/time mode (RTCM = 0) with BCD-coded year/month/day/hour/minute/second/100th-second registers, and stop-watch mode (RTCM = 1) supporting elapsed time counting across three 99-hour BCD fields. Its oscillator circuit supports configurable load capacitance (6 pF, 7 pF, or 12.5 pF) for quartz crystal calibration.

It features two interrupt outputs (INTA open-drain, INTB push-pull), programmable clock output (1 Hz to 32.768 kHz), and timestamp capture triggered by battery switchover or external TS input. All registers are accessed via 400 kHz I²C-bus with auto-incrementing address pointer and carry-safe read/write protocol.

Key Specifications

Pinout & Package

TSSOP10 package (SOT552-1), 3 mm body width, 0.5 mm pitch, 10-terminal plastic thin shrink small outline package.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCF85263ATT1/AJ, PCF85263ATT1/AZ offers identical timing, alarm, and timestamp functionality in the same TSSOP10 footprint, while DS3231SN+ trades stop-watch capability and triple timestamping for superior oscillator stability - making PCF85263ATT1/AJ optimal for cost-sensitive, feature-rich embedded timekeeping.

Availability

PCF85263ATT1/AJ is available at Aetrix Electronics and suitable for electronic metering, digital imaging, white goods control, and industrial data logging requiring stable component supply and long-term design continuity.

Supply support for PCF85263ATT1/AJ 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 PCF85263A product line delivers ultra-low-power, feature-rich RTCs designed for battery-backed systems requiring calendar time, alarm scheduling, timestamping, and robust power-fail resilience - targeting metering, consumer electronics, and industrial control.

FAQ

What is the primary function of the PCF85263ATT1/AJ in an embedded system?

The PCF85263ATT1/AJ serves as a highly integrated real-time clock and calendar IC with battery backup, alarm generation, timestamp capture, and programmable clock output. It maintains accurate time across power cycles, supports stop-watch mode for elapsed time measurement, and interfaces via I²C - making it ideal for time-critical functions in metering, imaging, and industrial control systems where PCF85263ATT1/AJ replaces discrete timing components and reduces MCU firmware overhead.

Does the PCF85263ATT1/AJ support both 12-hour and 24-hour time formats?

Yes, the PCF85263ATT1/AJ supports both formats. The 12_24 bit in the Oscillator register (address 25h) selects the mode: when cleared, hours are stored in 24-hour format (00–23); when set, they use 12-hour format (01–12) with AMPM bit indicating AM/PM. This setting applies to both RTC and alarm registers, and PCF85263ATT1/AJ retains the selected mode across power cycles and battery switchover.

How does the PCF85263ATT1/AJ handle time register reads to prevent corruption during carry conditions?

The PCF85263ATT1/AJ freezes all time register contents (00h–07h) into an internal output buffer upon initiating a read sequence. This ensures atomic access - reading seconds, minutes, hours, and date in one I²C transaction returns consistent values even if a carry occurs mid-read. PCF85263ATT1/AJ requires sequential read/write of all relevant registers in a single I²C transfer to maintain time integrity, as documented in Section 7.2.6 of the datasheet.

Can the PCF85263ATT1/AJ generate interrupts on both INTA and INTB pins simultaneously?

Yes, PCF85263ATT1/AJ supports concurrent interrupt assertion on INTA and INTB. Each pin has independent enable registers (INTA_enable at 29h, INTB_enable at 2Ah) and flag bits (Flags register at 2Bh). For example, Alarm 1 can trigger INTA while Battery Switchover asserts INTB - allowing prioritized handling of time-critical versus power-event interrupts in the host system without conflict. PCF85263ATT1/AJ configures INTA as open-drain and INTB as push-pull by default.

What is the purpose of the TS (CLK/INTB) pin on the PCF85263ATT1/AJ?

The TS (CLK/INTB) pin on PCF85263ATT1/AJ serves three distinct roles: as a timestamp input (edge-triggered capture of current time), as a push-pull CLK output (delivering programmable frequencies), or as an open-drain INTB interrupt output. Its function is selected via TSPM[1:0] bits in the Pin_IO register (27h). In timestamp mode, a rising edge on TS captures the current RTC value into TSR1–TSR3 based on TSR_mode configuration - a key capability distinguishing PCF85263ATT1/AJ from basic RTCs.