NXP Semiconductors PCF8564AU/5BB/1,01

Overview

PCF8564AU/5BB/1,01 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, making it ideal for battery-backed timekeeping in portable instruments and electronic metering.

For engineers reviewing the PCF8564AU/5BB/1,01 datasheet, PCF8564AU/5BB/1,01 pinout, PCF8564AU/5BB/1,01 application, or PCF8564AU/5BB/1,01 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 - all critical for reliable, low-power embedded timing design.

Technical Context

The PCF8564AU/5BB/1,01 implements a fully autonomous RTC core driven by an on-chip 32.768 kHz oscillator with two integrated load capacitors, eliminating external crystal tuning components. Its 16×8-bit register map includes dedicated BCD-coded time/date counters (02h–08h), four alarm registers (09h–0Ch), CLKOUT control (0Dh), and timer control/count registers (0Eh–0Fh).

Timing integrity is maintained via hardware-level safeguards: a STOP bit halts the prescaler chain without affecting CLKOUT, a Voltage Low (VL) flag (bit 7 of seconds register) signals potential time corruption below V_LOW, and read/write access blocks the time registers during I²C transactions to prevent carry-condition errors - requiring atomic multi-byte reads/writes for accurate time updates.

Key Specifications

Pinout & Package

Bare die (wire bond) package with 9 bonding pads; substrate (rear side) connected to VSS potential and must not be externally wired.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCF8564AU/5BB/1,01, PCF8563T/5,118 offers identical functionality in a surface-mount package but requires external capacitors, while DS3231SN#T&R delivers superior accuracy via TCXO at higher cost and power - making PCF8564AU/5BB/1,01 optimal for cost-sensitive, ultra-low-power bare-die integrations.

Availability

PCF8564AU/5BB/1,01 is available at Aetrix Electronics and suitable for smart energy metering, portable medical devices, industrial control panels, and IoT edge gateways requiring stable component supply across long product lifecycles.

Supply support for PCF8564AU/5BB/1,01 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 focused on secure connectivity solutions for automotive, industrial, and IoT applications.

The PCF8564A product line was designed specifically for ultra-low-power, battery-backed real-time clock and calendar functions in space-constrained and cost-sensitive embedded systems.

FAQ

What is the primary function of the PCF8564AU/5BB/1,01?

The PCF8564AU/5BB/1,01 is a CMOS real-time clock and calendar IC that maintains accurate time-of-day and date information using an integrated 32.768 kHz oscillator. It provides BCD-coded seconds, minutes, hours, days, weekdays, months, and years; supports alarm and 8-bit countdown timer functions; and features a programmable clock output and voltage low detector. Its 250 nA typical backup current enables decade-long operation on coin cells.

How does the PCF8564AU/5BB/1,01 handle time register updates to prevent corruption?

The PCF8564AU/5BB/1,01 hardware-blocks its time registers (02h–08h) during I²C read/write operations to prevent mid-carry corruption. Engineers must perform atomic multi-byte accesses - e.g., reading all seven time registers (seconds through years) in a single I²C transaction starting at address 02h - to ensure consistency. The datasheet specifies that all accesses must complete within 1 second to avoid losing pending increments.

What are the valid I²C slave addresses for the PCF8564AU/5BB/1,01?

The PCF8564AU/5BB/1,01 uses fixed I²C slave addresses: 0xA2 (hex) for write operations and 0xA3 (hex) 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 includes an auto-incrementing word address register that advances after each byte transfer.

Does the PCF8564AU/5BB/1,01 require external load capacitors for the 32.768 kHz crystal?

No, the PCF8564AU/5BB/1,01 integrates two 12.5 pF oscillator load capacitors internally, eliminating the need for external capacitors in standard 32.768 kHz crystal configurations. This reduces bill-of-materials count and PCB area - a key advantage for bare-die implementations like PCF8564AU/5BB/1,01 where space and component count are critical constraints.

What happens to the CLKOUT pin when the CLKOE input is held LOW?

When CLKOE is held LOW, the CLKOUT pin of the PCF8564AU/5BB/1,01 is forced to logic 0 regardless of the FE bit setting or FD[1:0] frequency selection. CLKOUT only becomes active (outputting the selected square wave) when both CLKOE = HIGH and FE = 1 in register 0Dh. This dual-enable architecture prevents unintended clock injection into downstream circuits during power sequencing or reset states.