PCA8525 - Automotive TCXO-Style RTC IC 125C | NXP Semiconductors
MPN: PCA8525 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.95 | $1.95 |
| 10 | $1.76 | $17.60 |
| 100 | $1.48 | $148.00 |
| 500 | $1.25 | $625.00 |
| 1,000 | $1.05 | $1,050.00 |
PCA8525 Overview
A Real Time Clock (RTC) is a timing integrated circuit that keeps track of seconds, minutes, hours, days, months, and years using an external 32.768 kHz watch crystal. Within the power-management and timing hierarchy, an RTC sits below the system microcontroller and above the raw crystal oscillator stage, providing calendar and timekeeping registers that survive main-power loss via a backup supply. Standard RTC ICs rely on an uncompensated crystal, whose frequency drifts with temperature.
The PCA8525 is the first and only crystal-based RTC IC to feature a default temperature compensation engine. It compensates a typical crystal model selectable between -0.035 ppm/degC2 and -0.04 ppm/degC2, and combined with its aging offset feature it can achieve up to 5x better timekeeping accuracy than a standard RTC IC with an uncompensated crystal.
Technically, the PCA8525 is a CMOS device optimized for nano-power consumption, with all addresses and data transferred serially over the I2C bus. The integrated temperature compensation engine measures the die temperature and applies digital frequency correction to the 32.768 kHz crystal, delivering module-class accuracy in a single IC without an external TCXO module.
Typical applications include automotive body control modules, gateway and telematics units, industrial data loggers, and smart meters - anywhere accurate time stamps are required across a wide automotive temperature range.
Design consideration: the temperature compensation engine assumes a typical tuning-fork crystal model; verify the selected crystal's parabolic coefficient matches the selectable -0.035 or -0.04 ppm/degC2 setting, and apply the aging offset register to trim long-term drift.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for PCA8525 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:
PCF8525TKX
β Drop-Inπ Reference alternative (not in catalog)
PCA8525TK/Q900X
β Drop-Inπ Reference alternative (not in catalog)
PCF8525TK
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
PCA8525 Specifications
| Product Type | Real Time Clock (RTC) and calendar IC |
| Interface | I2C serial bus |
| Temperature Compensation | Integrated default temperature compensation engine |
| Crystal Model Selection | -0.035 ppm/degC2 or -0.04 ppm/degC2 selectable |
| Timekeeping Accuracy Improvement | Up to 5x better than uncompensated RTC |
| Power Consumption Class | Nano-power optimized |
| Aging Offset Feature | Yes |
| External Crystal Required | Yes (32.768 kHz) |
| Operating Temperature | Up to +125 degC (automotive rating) |
| Package | HVSON10 |
| Mounting Type | Surface Mount |
| Process Technology | CMOS |
| Automotive Qualification | Yes (automotive variants PCA8525TK/Q900X) |
| RoHS Status | Compliant |
PCA8525 hvson10 Pin Configuration Guide
Pin configuration for PCA8525 (hvson10 package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for PCA8525.
Refer to the datasheet for full pin configuration.
Typical Applications
PCA8525 is suitable for 6 applications: Automotive Body Control Modules, Telematics and Gateway Units, Smart Meters, Industrial Data Loggers, Medical Monitoring Devices, Security and Surveillance Systems.
Automotive Body Control Modules
The PCA8525 fits body control modules (BCMs) because it combines an automotive temperature rating up to 125 degC with up to 5x better timekeeping accuracy than an uncompensated-crystal RTC. BCMs must timestamp theft alarms, lighting events, and diagnostics across the full -40 to +125 degC ambient range, where a standard RTC can drift minutes per year. Placed on the I2C bus of the BCM MCU with its external 32.768 kHz crystal, the PCA8525's compensation engine digitally corrects crystal parabolic drift using the selectable -0.035 or -0.04 ppm/degC2 model, while nano-power operation lets a backup cell hold time through key-off periods for the vehicle's entire life.
Recommended
Telematics and Gateway Units
Telematics control units and vehicle gateways need legally defensible event timestamps for eCall, fleet tracking, and secure logging. The PCA8525 supplies this with its integrated temperature compensation engine, which keeps the 32.768 kHz crystal within tightly controlled frequency error across cabin-to-engine-bay temperatures, and the aging offset register trims long-term drift. Connected via I2C to the telematics MCU, it continues timekeeping on backup power during main-rail dropout, a common event during cranking or battery service. Compared with an uncompensated RTC, the up-to-5x accuracy improvement reduces clock resynchronization traffic over the cellular link, saving bandwidth and ensuring log integrity between GNSS fixes.
Recommended
Smart Meters
Electricity, gas, and water meters require accurate time-of-use billing records over a 15-20 year service life in outdoor enclosures. The PCA8525 addresses both constraints: nano-power consumption extends the backup battery that holds time during mains outages, and the temperature compensation engine plus aging offset feature maintain timestamp accuracy across seasons without periodic service visits. The selectable crystal compensation model (-0.035 or -0.04 ppm/degC2) lets the meter designer match the actual crystal grade, achieving up to 5x better accuracy than an uncompensated RTC. Its I2C interface attaches directly to the metering SoC, and the HVSON10 package suits compact, conformally coated meter PCBs.
Recommended
Industrial Data Loggers
Industrial data loggers monitoring cold chains, process lines, or equipment health must correlate every sample with a trustworthy timestamp, often on battery power for years. The PCA8525's nano-power class draw makes a small lithium coin cell viable for the full deployment, while temperature compensation prevents the drift that would otherwise corrupt event ordering after months of unattended operation. Sampling die temperature internally, its compensation engine corrects the crystal in real time across factory-floor temperature swings, using the aging offset register for production calibration. On the I2C bus of the logger MCU, it adds negligible layout burden, and the HVSON10 footprint fits dense recorder boards.
Recommended
Medical Monitoring Devices
Portable and benchtop medical monitors require accurate, auditable event timestamps for patient records and regulatory traceability. The PCA8525 provides this with its temperature-compensated timekeeping: the integrated engine corrects crystal parabolic error in real time, delivering up to 5x better accuracy than a standard uncompensated RTC, so logs remain trustworthy between calibration cycles. Nano-power consumption preserves clock memory through battery swaps on portable units, and the I2C interface integrates cleanly with the monitor's host controller. For devices used near the patient in controlled ambient temperatures, the extended 125 degC rating provides generous margin beyond any realistic clinical environment.
Recommended
Security and Surveillance Systems
Video recorders, access controllers, and alarm panels must timestamp events accurately for forensic and insurance value, and they often operate in unheated outdoor enclosures. The PCA8525's compensation engine keeps its calendar within tight error across those swings, whereas an uncompensated crystal RTC can drift minutes per year and invalidate evidence chains. During power interruptions, nano-power operation lets a supercapacitor or small cell maintain time for days. On the system I2C bus it is trivial to integrate with NVR or panel MCUs, and the aging offset register supports periodic factory trimming. The HVSON10 package withstands the vibration profiles typical of vehicular and pole-mounted security installations.
Recommended
Recommended Products Summary
Engineering reference data for PCA8525 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCF8525TKX | PCA8525TK/Q900X | PCF8525TK |
|---|---|---|---|---|
| Package | HVSON10 | HVSON10 - same | HVSON10 - same | HVSON10 - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Interface | I2C | I2C | I2C | I2C |
| Temperature Compensation | Yes (-0.035 / -0.04 ppm/degC2 selectable) | Yes (-0.035 / -0.04 ppm/degC2 selectable) | Yes (-0.035 / -0.04 ppm/degC2 selectable) | Yes (-0.035 / -0.04 ppm/degC2 selectable) |
| Automotive Qualification | Yes | No (standard grade) | Yes (/Q900 flow) | No (standard grade) |
| Accuracy vs Uncompensated RTC | Up to 5x better | Up to 5x better | Up to 5x better | Up to 5x better |
| Aging Offset Feature | Yes | Yes | Yes | Yes |
Key Differentiators
- Integrated temperature compensation engine (vs PCF8525TKX)
- Extended temperature rating to 125 degC (vs PCF8525TKX)
- Automotive /Q900 qualified flow available (vs PCF8525TK)
Design Notes
Match the crystal to the compensation model. The PCA8525's engine compensates a typical crystal parabolic coefficient selectable between -0.035 ppm/degC2 and -0.04 ppm/degC2. If the chosen 32.768 kHz crystal has a different parabolic coefficient, residual error remains after compensation and the advertised 5x accuracy improvement is not achieved. Source a crystal whose datasheet curvature matches the configured setting, and verify load capacitance against the RTC's internal load per the NXP datasheet.
Plan the backup power path around the nano-power profile. The PCA8525 is optimized for nano-power operation so a lithium coin cell or supercapacitor can hold time for the product lifetime. Keep series resistance in the backup path low, avoid leaky keep-alive diode networks that dominate the nanoamp budget, and use a low-leakage Schottky or dedicated backup switch. Confirm the exact supply current figures in the datasheet electrical characteristics for your supply voltage and temperature before sizing the backup element.
Layout for crystal stability and I2C integrity. Place the 32.768 kHz crystal within a few millimeters of the PCA8525 OSCI/OSCO pins, keep the crystal traces short and guarded by ground, and avoid routing switching or I2C lines directly beneath the crystal to prevent coupling-induced frequency modulation. Use 1.8k to 4.7k pull-ups on SDA/SCL appropriate for the bus capacitance, and follow the HVSON10 land pattern with thermal vias per the datasheet package outline for reliable reflow assembly.
Compliance Information
Marketed by NXP and distributors as an automotive RTC IC; /Q900 suffix on PCA8525TK/Q900X indicates NXP automotive qualification flow. Exact RoHS/REACH certificates should be pulled from the NXP product page.
