PCF8525 - ±30ppm Temperature-Compensated RTC | NXP
MPN: PCF8525 ✓ Active| Qty | Unit Price | Extended |
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| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
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| 500 | $0 | $0.00 |
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PCF8525 Overview
A real-time clock IC is a dedicated timekeeping device that maintains seconds, minutes, hours, day, weekday, month, and year counters while the host system sleeps or is powered down. Within the system hierarchy, an RTC sits below the power management IC and alongside supervisory circuits, feeding timestamp data to a microcontroller over a serial bus such as I2C. External RTCs like the PCF8525 offload timekeeping from the main SoC, cutting system power demands significantly - NXP states its RTC/calendar family can cut power demands by as much as 60 percent.
The defining feature of the PCF8525 is that it is the first and only external-crystal RTC IC to feature a default temperature compensation engine. It compensates for a typical crystal model, selectable between -0.035 ppm/degC2 and -0.04 ppm/degC2 parabolic coefficients, and adds an aging offset register for long-term drift correction. According to NXP, this yields up to 5x better timekeeping accuracy than a standard uncompensated RTC plus crystal.
Architecturally, the device uses a CMOS timekeeping core clocked from an external 32.768 kHz crystal, with the compensation engine digitally correcting frequency versus temperature. The HVSON10 version includes full temperature compensation (±30 ppm class accuracy), while the WLCSP variant omits compensation in exchange for an ultra-compact footprint.
Typical applications include battery-powered IoT sensor nodes, smart meters, data loggers, and industrial controllers requiring accurate timestamping with minimal standby current.
Design consideration: select a 32.768 kHz crystal whose parabolic coefficient matches the selectable compensation model, and verify the I2C bus pull-up values for the target data rate.
This page synthesizes verified distributor listings, drop-in alternative analysis, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for PCF8525 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with PCF8525 (same form factor and footprint) — differing in Aging Offset, Interface, Product Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PCF8525HN
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
PCF8525TKX
✅ Drop-In📋 Reference alternative (not in catalog)
PCA8525HN
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
PCF8525 Maximum Ratings & Electrical Characteristics
| Product Type | Real-Time Clock (RTC) IC with I2C interface |
| Timekeeping Accuracy (HVSON10) | up to ±30 ppm (temperature compensated) |
| Crystal Compensation Model | selectable -0.035 ppm/degC2 or -0.04 ppm/degC2 |
| Interface | I2C serial bus |
| Crystal | external 32.768 kHz crystal required |
| Aging Offset | supported (offset register) |
| Accuracy Improvement vs Uncompensated RTC | up to 5x |
| Package (PCF8525TKX) | HVSON10 |
| Package Variant | WLCSP (ultra-compact, compensation omitted) |
| Mounting Type | Surface Mount |
PCF8525 wlcsp (ultra-compact, compensation omitted) Pin Configuration Guide
Pin configuration for PCF8525 (wlcsp (ultra-compact, compensation omitted) 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 PCF8525.
Refer to the datasheet for full pin configuration.
Typical Applications
PCF8525 is suitable for 6 applications: Battery-Powered IoT Sensor Nodes, Smart Meters and Utility Metering, Industrial Data Loggers, Wearables and Compact Portable Devices, Automotive and Embedded Controller Timestamping, Security and Surveillance Timestamping.
Battery-Powered IoT Sensor Nodes
The PCF8525 fits battery-powered IoT nodes because its nano-powered timekeeping keeps calendar and alarm functions alive for years while the main MCU sleeps, and NXP states its RTC/calendar family cuts power demands by as much as 60 percent. In a typical node the RTC is wired to the microcontroller over I2C with a 32.768 kHz crystal, waking the system on alarm for scheduled sensor reads or transmissions. The ±30 ppm compensated accuracy of the HVSON10 version prevents timestamp drift that would otherwise corrupt long-interval log data - an uncompensated crystal can drift tens of seconds per month, which the PCF8525's compensation engine largely eliminates.
Recommended
Smart Meters and Utility Metering
Utility meters require legally defensible timestamps for consumption profiles and tariff switching, making the PCF8525's ±30 ppm compensated accuracy directly relevant. Placed on the meter's always-on auxiliary rail with an external 32.768 kHz crystal, the HVSON10 part maintains seconds-to-year counters and alarms for load-profile recording even through brownouts, communicating over I2C with the metering MCU. Because the compensation engine corrects the crystal's -0.035 or -0.04 ppm/degC2 parabolic drift, timestamp error stays within a few seconds per year across outdoor temperature swings - a task an uncompensated RTC cannot meet without periodic network time resynchronization.
Recommended
Industrial Data Loggers
Industrial data loggers timestamp process variables, vibration events, and alarm transitions; the PCF8525's aging offset register plus temperature compensation keep log timestamps aligned with plant time over multi-year deployments. The IC operates as the I2C timekeeping slave on the logger's standby domain, its alarm output waking the MCU for periodic sampling. Compared with an uncompensated RTC, the up-to-5x accuracy improvement means calibration intervals lengthen and drift-correction firmware complexity drops. The HVSON10 package also survives industrial temperature environments better than bare consumer parts, supporting robust logger designs on crowded PCBs.
Recommended
Wearables and Compact Portable Devices
For wearables and ultra-compact portable products, the PCF8525 WLCSP variant provides an ultra-compact footprint while still delivering reliable I2C timekeeping with an external crystal - the trade-off being that compensation is omitted in this variant to minimize area. Designers pairing the WLCSP part with a high-quality crystal can still achieve tens-of-ppm accuracy adequate for notifications and activity logging. The nano-power timekeeping current preserves small-cell battery life across charge cycles. Where display-of-time accuracy is user-visible and critical, the HVSON10 compensated variant remains the recommended choice at a modest footprint increase.
Recommended
Automotive and Embedded Controller Timestamping
Embedded controllers in factory and vehicle subsystems need event ordering for diagnostics, and the PCF8525 provides a compensated time base independent of network time availability. Wired between the always-on battery rail and the host MCU's I2C bus, it records ignition-off durations and fault timestamps with ±30 ppm accuracy over automotive temperature excursions thanks to the compensation engine. The alarm and timer functions support wake scheduling for periodic self-tests. Its small HVSON10 footprint integrates into existing controller boards without layout redesign, and the aging offset register trims long-term drift between service intervals.
Recommended
Security and Surveillance Timestamping
Security recorders and access-control panels must timestamp every event in a court-defensible sequence, so the PCF8525's compensated ±30 ppm accuracy matters when network time (NTP) is unavailable during outages. The RTC runs from the panel's backup battery, holding calendar and alarm state while host electronics are unpowered, and its I2C interface delivers timestamp data on request. Compared with an uncompensated RTC that can drift tens of seconds monthly, the PCF8525 keeps event ordering consistent across seasonal temperature swings, reducing disputes over recorded event sequences and simplifying audit reconciliation in surveillance systems.
Recommended
Recommended Products Summary
Engineering reference data for PCF8525 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCF8525HN | PCF8525TKX | PCA8525HN |
|---|---|---|---|---|
| Package | HVSON10 (compensated) / WLCSP (compact) | HVSON10 - same | HVSON10 - same | HVSON10 - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Temperature Compensation | Yes (default engine) | Yes | Yes | Yes |
| Interface | I2C | I2C | I2C | I2C |
| External Crystal | 32.768 kHz required | 32.768 kHz required | 32.768 kHz required | 32.768 kHz required |
Key Differentiators
- First external-crystal RTC with a default temperature compensation engine (vs PCF8523)
- Two-footprint portfolio trade-off (vs PCF8525TKX (WLCSP variant))
- Aging offset correction (vs PCF8523)
Design Notes
Match the crystal to the compensation model. The PCF8525 assumes a typical crystal parabolic coefficient selectable between -0.035 ppm/degC2 and -0.04 ppm/degC2; using a crystal with a different coefficient means the compensation engine applies the wrong correction curve and the ±30 ppm accuracy claim no longer holds. Check the crystal datasheet's frequency-temperature characteristic, then set the model bit and use the aging offset register to trim residual long-term drift after initial field measurement.
Keep the 32.768 kHz crystal traces short and guard them with a ground ring to minimize stray capacitance and coupled noise, since loading capacitance error translates directly into ppm-level timekeeping error that even the compensation engine cannot fully remove. Place the input decoupling capacitor close to VDD and route SDA/SCL away from the crystal traces. For the WLCSP variant, follow the manufacturer's via-in-pad escape routing guidance to keep the loop area small.
The PCF8525 is a nano-powered part, but system battery life depends on the whole standby domain: I2C pull-up resistors leak continuously, so size them as high as the bus speed and capacitance allow (typical 10k-100k for a slow RTC bus). Hold the RTC on the always-on rail and power-gate the host MCU instead. Verify the standby current budget by measuring the complete rail, not just the RTC, before committing to a battery capacity. Estimate the battery life from measured values rather than datasheet typicals alone.
Compliance Information
Verified web data did not include explicit RoHS/REACH or material declarations; confirm on the NXP product page and its environmental datasheet before release.
