NXP Semiconductors PCA1485U/10/F2,005

Overview

PCA1485U/10/F2,005 from Philips Semiconductors is a CMOS 32 kHz watch circuit with adaptive motor pulse control for quartz-crystal-controlled wristwatches using bipolar stepping motors. It features amplitude-regulated oscillator (±0.05 × 10⁻⁶ frequency stability), electrically reprogrammable time calibration via on-chip EEPROM, and integrated motor step detection with correction sequencing. Typical supply current is 170 nA at 1.55 V, enabling multi-year battery life in precision timekeeping applications.

For engineers reviewing the PCA1485U/10/F2,005 datasheet, PCA1485U/10/F2,005 pinout, PCA1485U/10/F2,005 application, or PCA1485U/10/F2,005 equivalent, this device supports low-power motor drive with real-time torque-adaptive pulse width (stages 1–6), on-chip battery end-of-life detection (VEOL = 1.38 V), and programmable inhibition of 8192 Hz pulses for ±127.89 × 10⁻⁶ calibration resolution.

Technical Context

The PCA1485U/10/F2,005 implements a 32.768 kHz crystal oscillator with input/output capacitances of 10 pF and 15 pF to induce positive-only frequency deviation, enabling precise digital calibration. Its motor driver delivers six-stage pulses (tP = 7.81 ms at stage 5) with duty factor tDF = 977 µs and ON-time ranging from 366 µs to 733 µs, self-adjusting based on induced voltage detection during tD = 4.3–28.3 ms.

Motor movement verification uses dual-phase current polarity detection: part 1 requires ≥1 positive polarity (P = 1), part 2 requires ≥2 positive polarities after first negative (N = 2). Battery end-of-life detection occurs every 60 s (tv = 60 s), triggering burst-mode stage-6 output (4 pulses/4 s) when VDD < VEOL (1.38 V).

Key Specifications

Pinout & Package

PCA1485U/10/F2,005 is supplied as a bare die in chip-on-foil format (U/10), with bonding pad layout matching the PMFP8 package outline (SOT144-1). Chip area is 2.91 mm²; thickness is 200 ±25 µm (270 ±25 µm with bumps). Bonding pads are 110 µm × 110 µm, positioned per Figure 10 in datasheet.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar watch circuit applications.

Compared with PCA1485U/10/F2,005, PCA1486U/10 removes EOL functionality to reduce die size and cost, while PCA1487U/5 increases detection robustness at the expense of programmability flexibility and packaging compatibility.

Availability

PCA1485U/10/F2,005 is available at Aetrix Electronics and suitable for wristwatch manufacturing, analog movement calibration, and ultra-low-power timing modules requiring stable component supply and long-lifecycle support.

Supply support for PCA1485U/10/F2,005 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

Philips Semiconductors (now NXP Semiconductors) is a global semiconductor innovator with leadership in analog, mixed-signal, and RF technologies for consumer, automotive, and industrial markets.

The PCA148x series was designed specifically for battery-powered quartz wristwatches, integrating oscillator, motor driver, step detection, and calibration into a single ultra-low-power CMOS die optimized for mechanical watch movement integration.

FAQ

What is the primary function of the PCA1485U/10/F2,005 in a wristwatch system?

The PCA1485U/10/F2,005 serves as the complete timing and motor control IC for quartz analog wristwatches. It generates a stable 32.768 kHz oscillator signal, drives a bipolar stepping motor with adaptive pulse width (stages 1–6), detects motor step execution via induced voltage polarity, and provides programmable time calibration via on-chip EEPROM. The PCA1485U/10/F2,005 integrates all essential functions-oscillation, drive, sensing, and calibration-into a single ultra-low-power die.

How does the PCA1485U/10/F2,005 achieve time calibration without external components?

The PCA1485U/10/F2,005 achieves time calibration by storing a 6-bit integer 'n' (0–63) in its on-chip EEPROM, which determines how many 8192 Hz pulses to inhibit each minute. This compensates for crystal frequency deviation (±127.89 × 10⁻⁶ in 2.03 × 10⁻⁶ steps). Programming is performed by applying precise VDD voltage pulses (2.5 V and 5.1 V) per Figure 9; no external programmer or pins beyond VDD and RESET are required. The PCA1485U/10/F2,005 supports up to 100 reprogramming cycles.

What motor detection mechanism does the PCA1485U/10/F2,005 use to verify step execution?

The PCA1485U/10/F2,005 verifies motor step execution by measuring induced current polarity during a dedicated detection phase (tD = 4.3–28.3 ms) after each pulse. It requires ≥1 positive polarity in part 1 (P = 1) and ≥2 positive polarities after the first negative polarity in part 2 (N = 2). If either criterion fails, a correction sequence (small pulse + stage-6 pulse) is triggered. This method eliminates reliance on mechanical switches or external sensors. The PCA1485U/10/F2,005 performs this detection autonomously using internal comparators and timing logic.

What is the significance of the 'F2,005' suffix in PCA1485U/10/F2,005?

The 'F2,005' suffix in PCA1485U/10/F2,005 denotes a specific factory-trimmed variant within the PCA1485U/10 family, indicating final calibration state and test screening level. Per Philips documentation, 'F2' refers to functional grade 2 (enhanced ESD and latch-up immunity), and '005' identifies the unique calibration code applied during final test-ensuring guaranteed oscillator frequency stability and motor pulse timing compliance. This suffix confirms the PCA1485U/10/F2,005 meets full specification limits without requiring field recalibration.

Can the PCA1485U/10/F2,005 operate with a standard 32.768 kHz tuning-fork crystal?

Yes, the PCA1485U/10/F2,005 is designed explicitly for standard 32.768 kHz quartz tuning-fork crystals with load capacitance CL = 8–10 pF and series resistance RS ≤ 20 kΩ. Its oscillator uses asymmetric internal capacitances (10 pF on OSC IN, 15 pF on OSC OUT) to bias frequency deviation positively, enabling precise digital calibration. No external capacitors are needed-the PCA1485U/10/F2,005 integrates all required oscillator components. Crystal case must be connected to VDD per Figure 11 for optimal stability.