NXP Semiconductors PCF8564ACX9/B/1,02

Overview

PCF8564ACX9/B/1,02 from NXP Semiconductors is a low-power CMOS real-time clock and calendar IC with integrated 32.768 kHz oscillator, programmable clock output (32.768 kHz / 1.024 kHz / 32 Hz / 1 Hz), open-drain interrupt output, and voltage low detector. It operates from 1.0 V to 5.5 V and draws only 250 nA typical backup current at 3.0 V - enabling long-term timekeeping in battery-powered meters and portable instruments.

For engineers reviewing the PCF8564ACX9/B/1,02 datasheet, PCF8564ACX9/B/1,02 pinout, PCF8564ACX9/B/1,02 application, or PCF8564ACX9/B/1,02 equivalent, this device delivers BCD-coded time/date registers (seconds through years), alarm and 8-bit countdown timer functions, I²C slave address A2h/A3h, and auto-incrementing register addressing over a 400 kbit/s I²C-bus interface.

Technical Context

The PCF8564ACX9/B/1,02 implements a fully autonomous RTC core driven by an on-chip 32.768 kHz crystal oscillator with two integrated load capacitors. Its timekeeping logic uses BCD-encoded registers (02h–08h) with leap-year compensation and atomic read/write blocking to prevent carry corruption during I²C access.

Alarm functionality is implemented via four dedicated BCD registers (09h–0Ch) with per-field enable bits (AEN_M/H/D/W); matching triggers the AF flag in Control_2 (01h). The 8-bit timer (0Fh) supports four selectable source clocks (4.096 kHz, 64 Hz, 1 Hz, 1/60 Hz) and generates TF upon underflow, with configurable INT pulse behavior via TI_TP bit.

Key Specifications

Pinout & Package

PCF8564ACX9/B/1,02 is supplied in a 9-pin XSON package (2.1 × 2.3 mm, 0.5 mm pitch), optimized for space-constrained portable and metering applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231SN#T&R and RV-3028-C7, PCF8564ACX9/B/1,02 uniquely balances ultra-low backup current, full alarm/timer functionality, and four programmable clock outputs - making it optimal for cost-sensitive, battery-limited applications requiring feature-rich timekeeping without accuracy-critical constraints.

Availability

PCF8564ACX9/B/1,02 is available at Aetrix Electronics and suitable for smart metering, portable medical devices, industrial HMIs, and asset tracking beacons requiring stable component supply across multi-year production cycles.

Supply support for PCF8564ACX9/B/1,02 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 leader specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCF8564ACX9/B/1,02 belongs to NXP's legacy real-time clock portfolio, designed specifically for ultra-low-power, cost-optimized timing in battery-backed consumer and industrial equipment.

FAQ

What is the I²C slave address of the PCF8564ACX9/B/1,02?

The PCF8564ACX9/B/1,02 uses fixed I²C slave addresses: 0xA2 (7-bit address 0x51) for write operations and 0xA3 (7-bit address 0x51) for read operations. These addresses are hardwired and not configurable via pins or registers. The device supports standard and fast-mode I²C up to 400 kbit/s, and its auto-incrementing address pointer simplifies sequential register access during time reads or writes.

How does the voltage low (VL) flag work in the PCF8564ACX9/B/1,02?

The VL flag in register 02h (Seconds) is set automatically when VDD falls below the internal detection threshold, indicating possible time corruption due to insufficient supply. It remains latched until explicitly cleared by writing 0 to bit 7 of address 02h. Unlike reset-based flags, VL persists across power cycles if backup power remains - enabling firmware to validate time integrity before accepting timestamps in critical logging applications using PCF8564ACX9/B/1,02.

Can the PCF8564ACX9/B/1,02 operate without an external crystal?

No - the PCF8564ACX9/B/1,02 requires an external 32.768 kHz tuning-fork crystal connected between OSCI and OSCO pins. Its on-die oscillator circuit relies on this crystal for timebase generation; there is no internal RC oscillator or alternative clock source. However, the device integrates two 12.5 pF load capacitors, eliminating the need for external capacitors and reducing total component count.

What happens to the time registers when the PCF8564ACX9/B/1,02 enters STOP mode?

When the STOP bit (bit 5 of Control_1 register 00h) is set, the RTC divider chain is halted - freezing seconds through years registers while preserving their current values. Crucially, the 32.768 kHz CLKOUT output remains active, but derived frequencies (1.024 kHz, 32 Hz, 1 Hz) stop. This allows safe initialization of time registers without drift, and release of STOP resumes counting from the exact frozen state - ensuring sub-second accuracy in PCF8564ACX9/B/1,02 time setup sequences.

Does the PCF8564ACX9/B/1,02 support leap-year correction?

Yes - the PCF8564ACX9/B/1,02 implements automatic leap-year compensation in firmware logic. It adds February 29 in any year divisible by 4, including year "00", and correctly handles month-length rollovers (e.g., Jan 31 → Feb 1, Feb 28/29 → Mar 1). This behavior is transparent to the host MCU and requires no external calculation - the BCD-encoded day/month/year registers (05h–08h) always reflect calendar-accurate values when read from PCF8564ACX9/B/1,02.