PCF8583T/5 - I2C RTC Calendar with 256x8 RAM | NXP
MPN: PCF8583T/5 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
PCF8583T/5 Overview
A real-time clock (RTC) is a timekeeping IC that maintains seconds, minutes, hours, date, month, year, and weekday information using a low-frequency crystal oscillator. RTCs form part of the broader timing IC family alongside clock buffers and supervisors, and are foundational power-management companions in any battery-backed embedded system that must keep time when main power is absent.
Key features include the 256 x 8-bit low-power static CMOS RAM, automatic word address incrementing after each read or written data byte, an A0 address pin allowing two devices on one I2C bus, programmable alarm and timer functions, and an interrupt output (INT) that can assert on alarm or timer events.
Architecturally, the PCF8583 divides the 32.768 kHz oscillator output down to 1 Hz for the time-counting chain and stores all counters and control registers within the on-chip RAM map, giving software a flat, I2C-addressable register file. CMOS design keeps supply current in the microampere class, enabling years of operation from a lithium coin cell.
Typical applications include utility meters, battery-powered data loggers, set-top boxes, white goods, and industrial control panels requiring time-stamping and calendar-driven events.
A critical design consideration is the 32.768 kHz crystal layout: keep oscillator traces short and guard them from noisy digital lines, since PCB contamination or stray coupling can cause timekeeping drift or startup failure.
This page synthesizes distributor availability, drop-in alternative guidance, and practical design notes not found in the manufacturer datasheet, helping engineers source and apply the PCF8583T/5 with confidence.
Drop-in alternatives for PCF8583T/5 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PCF8583T/2
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
PCF8593T
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
PCF8583T/5 Specifications
| Function | Clock/Calendar with 240 x 8-bit free RAM |
| RAM Organization | 256 words x 8 bits (2048-bit static CMOS RAM) |
| Interface | I2C-bus, two-line bidirectional serial |
| Oscillator Frequency | 32.768 kHz crystal |
| Operating Modes | Clock mode (12/24-hour), calendar, counter modes |
| Alarm Function | Yes, programmable alarm register |
| Timer Function | Yes, programmable timer interrupt |
| Interrupt Output | INT, open-drain |
| Device Addressing | A0 pin, allows 2 devices on one I2C bus |
| Package | SO-8 (SOIC-8) |
| Mounting Type | Surface Mount |
| Technology | Static CMOS |
PCF8583T/5 Pin Configuration
| Pin 1 | OSCI β Oscillator input, 32.768 kHz crystal |
| Pin 2 | OSCO β Oscillator output, 32.768 kHz crystal |
| Pin 3 | INT β Interrupt output (open-drain), alarm/timer events |
| Pin 4 | VSS β Ground supply |
| Pin 5 | SDA β I2C-bus serial data |
| Pin 6 | SCL β I2C-bus serial clock |
| Pin 7 | A0 β Hardware address pin, selects 1 of 2 slave addresses |
| Pin 8 | VDD β Positive supply |
Typical Applications
PCF8583T/5 is suitable for 6 applications: Utility Metering, Battery-Powered Data Loggers, Set-Top Boxes and Consumer Electronics, Industrial Control Panels, White Goods and Home Appliances, Point-of-Sale and Security Terminals.
Utility Metering
Electricity, gas, and water meters need a persistent calendar to time-stamp consumption intervals and drive tariff switching. The PCF8583T/5 fits this role because its 32.768 kHz CMOS oscillator draws microampere-class current from the meter's backup lithium cell, and its 240 x 8-bit free RAM stores meter constants or rolling event logs directly in the timekeeping device, removing the need for a separate serial EEPROM in cost-sensitive designs. It sits on the meter MCU's I2C-bus with the A0 pin providing address selection, and its open-drain INT output can flag alarm events such as end-of-billing-period without polling. Because no switching circuitry exists inside the chip, it contributes no noise to sensitive analog front-end measurement paths.
Recommended
Battery-Powered Data Loggers
Portable data loggers must keep accurate wall-clock time across sleep cycles and battery swaps. The PCF8583T/5 maintains seconds-through-year counters autonomously from its 32.768 kHz crystal while the host MCU sleeps, and the I2C-bus interface (SDA/SCL on pins 5 and 6) reads the time in a single burst thanks to the auto-incrementing word address register. The 2048-bit static CMOS RAM retains 240 free bytes that survive as long as the backup cell lasts, letting the logger cache configuration or the last fault record. Programmable alarm and timer registers can wake the host at fixed intervals via the INT pin, reducing average system current and extending field deployment life between battery replacements.
Recommended
Set-Top Boxes and Consumer Electronics
Set-top boxes, DVD recorders, and connected appliances need the local calendar for scheduling recordings and displaying time after mains loss. The PCF8583T/5 provides 12/24-hour clock and full calendar modes with weekday, and holds state with a coin cell at negligible drain, so the device resumes with correct time immediately after power restoration. Its two-wire I2C-bus interface integrates directly with the main SoC or MCU, and the A0 pin allows a second PCF8583 on the same bus if the product also needs a dedicated hardware timer. The SO-8 package is low-cost, hand-solderable for repair, and widely second-sourced through the distribution channel for consumer service operations.
Recommended
Industrial Control Panels
Industrial controllers time-stamp fault events, drive shift schedules, and enforce maintenance intervals. The PCF8583T/5 supplies the calendar reference and, via its programmable timer register, periodic interrupts to the PLC or panel MCU through the open-drain INT line - useful where a crash of the main processor must not corrupt the time base. Its 240 free RAM bytes hold a fault ring buffer with date stamps, retained by the panel's backup supply. The I2C-bus needs only two board nets, easing routing on dense control PCBs, and the 2-device A0 addressing supports redundancy designs that carry two independent clocks for safety-critical time comparisons in process industries.
Recommended
White Goods and Home Appliances
Ovens, washing machines, and climate appliances display a clock and schedule delayed-start programs. The PCF8583T/5 keeps time and date through power interruptions using a small backup cell, so the appliance does not blink 00:00 after an outage - a direct user-experience benefit. The counter modes support program-duration timing independent of the main MCU timers, freeing MCU resources for motor and heater control. Because the entire device is low-power static CMOS and needs only a 32.768 kHz crystal plus two I2C lines, board cost impact is minimal, and the SO-8 package suits the wave- or reflow-soldered single-sided boards common in appliance control electronics.
Recommended
Point-of-Sale and Security Terminals
Receipt printers, payment terminals, and access-control panels require legally meaningful, tamper-resistant time stamps. The PCF8583T/5 supplies the system clock and calendar, while its 240 x 8-bit free RAM can hold a transaction sequence counter guarded by the backup cell - data that survives mains removal and battery tamper better than volatile SRAM. The alarm function generates a once-per-day or once-per-hour interrupt for key rollover or polling routines over the I2C-bus. With only a crystal, backup cell, and pull-ups on the two-wire bus, the bill of materials stays small, and the widely stocked SO-8 part simplifies long-term service of deployed terminal fleets.
Recommended
Recommended Products Summary
Engineering reference data for PCF8583T/5 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCF8583T/2 | PCF8593T |
|---|---|---|---|
| Package | SO-8 | SO-8 - same | SO-8 - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Free User RAM | 240 x 8-bit | 240 x 8-bit | None (register file only) |
| Interface | I2C-bus | I2C-bus | I2C-bus |
| Oscillator | 32.768 kHz crystal | 32.768 kHz crystal | 32.768 kHz crystal |
| Register Map Compatibility | Reference | Identical | Different - firmware changes required |
Key Differentiators
- 240 bytes of free user RAM integrated in the RTC (vs PCF8593T)
- Two-device addressing via A0 pin (vs PCF8593T)
- Proven legacy register map with huge installed base (vs DS1307 (cross-reference equivalent))
Design Notes
Route the 32.768 kHz crystal between pins 1 (OSCI) and 2 (OSCO) with traces under 10 mm and a guard ground ring. Keep the crystal loop away from I2C SDA/SCL lines and any switching regulator inductors - stray coupling here is the leading cause of PCF8583 time drift and oscillator startup failures reported in the field. Load capacitors should match the crystal manufacturer's specified CL value; verify startup on the actual PCB, not on a bench module, because parasitic capacitance shifts the oscillation margin.
The PCF8583T/5 is designed for battery backup, so structure the power tree so the backup cell feeds VDD (pin 8) through a diode-OR with the main supply. Decouple VDD with a 100 nF ceramic capacitor placed within 5 mm of pin 8 and pin 4 (VSS). Avoid letting VDD fall below the retention level specified in the NXP datasheet during brownouts - if the RAM contents matter, add a supervisor on the main rail and ensure firmware re-initializes the control register after any brownout event.
The INT output (pin 3) is open-drain: it will not work without an external pull-up resistor (typically 10 kilo-ohm to VDD). Also remember that A0 (pin 7) must not be left floating in electrically noisy environments - strap it firmly to VSS or VDD to define the I2C slave address. When clearing alarm flags, follow the datasheet read-modify-write sequence on the control register; writing the whole register blindly can inadvertently clear timer configuration bits and mute the interrupt source.
Compliance Information
Compliance status not stated in the provided verified web data; consult the NXP product page for PCF8583T for current RoHS/REACH declarations.
