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NXP Semiconductors PCA21125T/Q900/1,1
- Part No.:
- PCA21125T/Q900/1,1
- Manufacturer:
- NXP Semiconductors
- Category:
- Real Time Clocks
- Package:
- 14-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
PCA21125T/Q900/1,1.pdf
- Description:
- IC RTC CLK/CALENDAR SPI 14TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:297
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Product details
Overview
The PCA21125T/Q900/1,1 from NXP Semiconductors is a SPI-bus Real-Time Clock and calendar IC with AEC-Q100 automotive qualification, 1.3 V to 5.5 V supply range, 0.8 µA typical supply current at 25 °C, and operation up to 125 °C - used for accurate timekeeping in engine control units and battery management systems.
For engineers reviewing the PCA21125T/Q900/1,1 datasheet, PCA21125T/Q900/1,1 pinout, PCA21125T/Q900/1,1 application, or PCA21125T/Q900/1,1 equivalent, key selection considerations include its 14-pin TSSOP package, open-drain INT/CLKOUT outputs, BCD-encoded time registers, integrated oscillator capacitor, and support for second/minute interrupts and programmable alarm/timer functions.
Technical Context
The PCA21125T/Q900/1,1 implements a 32.768 kHz crystal-based RTC with auto-incrementing 16×8-bit register map, where time/date registers (02h–08h) are BCD-encoded and frozen during read/write to prevent carry corruption. Its SPI interface operates up to 6.0 Mbit/s with separate SDO/SDI lines and CE-controlled activation.
It integrates a programmable countdown timer with four selectable source clocks (4.096 kHz to 1/60 Hz), enabling delays from 244 µs to 4 h 15 min, plus two fixed-function pre-defined timers for 1-second and 1-minute interrupts - all managed via Control_1 (00h), Control_2 (01h), Timer_control (0Eh), and Countdown_timer (0Fh) registers.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Interface | SPI-bus: 4-line, CE-controlled, 6.0 Mbit/s max - enables deterministic host synchronization without I²C arbitration overhead |
| Supply Voltage | 1.3 V to 5.5 V - supports direct connection to wide-range automotive rails including 1.8 V, 3.3 V, and 5 V domains |
| Quiescent Current | 0.8 µA typical at 25 °C - ensures minimal battery drain in always-on vehicle modules |
| Operating Temp | −40 °C to +125 °C - qualified for under-hood and transmission control applications per AEC-Q100 Grade 0 |
| Time Encoding | BCD format for seconds through years - simplifies firmware parsing without binary-to-BCD conversion logic |
| Alarm Capability | Four independent alarm registers (minute/hour/day/weekday) with per-field enable bits - allows precise event scheduling down to weekday-specific wake-ups |
| Timer Range | 244 µs to 4 h 15 min via 8-bit countdown register and 4 selectable clock sources - supports both microsecond-critical and long-duration sleep intervals |
Pinout & Package
TSSOP14 package (SOT402-1), 4.4 mm body width, 0.65 mm pitch - compatible with standard automated PCB assembly and high-density automotive layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OSCI (1) | Oscillator input | Connects to 32.768 kHz crystal terminal; internal load capacitance eliminates external caps |
| OSCO (2) | Oscillator output | Drives crystal; forms Pierce oscillator with OSCI - no external buffer required |
| n.c. (3,4) | No connect | Must be left floating or tied to VDD per design rules; not usable as signal or power path |
| INT (5) | Interrupt output | Open-drain, active-low - requires external pull-up; asserts on alarm/timer/second/minute events |
| CE (6) | Chip enable | Active-HIGH with 200 kΩ internal pull-down - enables SPI transaction gating and low-power standby |
| VSS (7) | Ground | Primary reference for all analog/digital circuitry; must be low-impedance connection to system GND plane |
| SDO (8) | Serial data out | Push-pull output - drives MISO line without external pull-up; valid only when CE = HIGH |
| SDI (9) | Serial data in | Input-only; floats when CE = LOW - prevents bus contention during idle periods |
| SCL (10) | Serial clock | Input-only; floats when CE = LOW - synchronizes SPI reads/writes at up to 6.0 Mbit/s |
| n.c. (11,12) | No connect | Same handling as pins 3 and 4 - no routing or termination permitted |
| CLKOUT (13) | Clock output | Open-drain, programmable (32.768 kHz to 1 Hz); defaults to 32.768 kHz at power-on |
| VDD (14) | Supply voltage | Accepts 1.3–5.5 V; powers RTC core, SPI interface, and oscillator - decoupling cap required |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q100 Grade 0 qualification | Validated for automotive environments up to +125 °C ambient - eliminates need for additional thermal derating analysis |
| Integrated oscillator capacitor | Removes requirement for external 12.5 pF load capacitors - reduces BOM count and layout area by two components |
| BCD-encoded time registers | Enables direct decimal display or ASCII conversion in firmware without arithmetic overflow risk or binary decode routines |
| Freeze-on-access register locking | Halts RTC counters during full 7-register (seconds–years) read/write - guarantees atomic time capture without software double-read workarounds |
| Programmable CLKOUT with 7 frequencies | Provides system clock, MCU wake-up timing, or calibration reference directly from RTC - avoids need for separate oscillator or divider IC |
Applications
| Automotive Engine Control | Metering Data Logging |
|---|---|
Use Scenario: Time-stamping of fault codes and sensor readings in ECU flash memory during cold cranking or transient load conditions. IC Role / Device Role / Timing Role: Primary RTC source providing synchronized timestamps across CAN, LIN, and analog subsystems with ±2 ppm accuracy over temperature. Use Value: Enables ISO 26262-compliant diagnostic traceability with sub-second resolution and battery-backed retention during ignition-off periods. | Use Scenario: Recording energy consumption intervals in smart electricity meters operating unattended for >10 years. IC Role / Device Role / Timing Role: Low-power calendar engine maintaining date/time during mains failure using supercapacitor backup. Use Value: Achieves <1 µA real-time operation - extends backup runtime beyond 30 days while meeting IEC 62053-21 metering certification. |
| Industrial Telematics Gateway | Medical Infusion Pump |
Use Scenario: Timestamping GPS position reports and cellular handshakes in fleet management gateways deployed in extreme climates. IC Role / Device Role / Timing Role: High-temperature RTC co-located with LTE modem and GNSS receiver - shares same 32.768 kHz crystal for jitter reduction. Use Value: Maintains <±3 ppm drift from −40 °C to +125 °C - ensures accurate event sequencing even inside sun-heated vehicle cabins. | Use Scenario: Auditable dose delivery logging with tamper-proof time stamps in battery-powered infusion pumps. IC Role / Device Role / Timing Role: Secure time base for FDA 21 CFR Part 11 compliance - provides cryptographically verifiable timestamps for therapy records. Use Value: Integrates POR reset and alarm interrupt to detect clock tampering or battery removal - satisfies IEC 62304 Class C safety requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar RTC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS3231M+ | I²C interface only; ±2 ppm TCXO; higher 1.5 µA typical current; no SPI or CLKOUT | Better accuracy but no automotive qualification; limited to 85 °C max operating temp | Choose DS3231M+ only if ultra-high stability is prioritized over automotive temp range and SPI compatibility |
| RV-3032-C3 | SPI/I²C dual-interface; 1.1 µA typical current; no integrated oscillator cap; −40 °C to +85 °C rating | Lacks AEC-Q100 qualification and 125 °C operation; requires external 12.5 pF caps | Select RV-3032-C3 when dual-protocol flexibility is needed but automotive under-hood use is not required |
Compared with DS3231M+ and RV-3032-C3, the PCA21125T/Q900/1,1 uniquely combines SPI interface, AEC-Q100 Grade 0 qualification, integrated oscillator capacitor, and 125 °C operation - making it the only drop-in solution for automotive-grade RTC designs requiring minimal external components and extended temperature resilience.
Availability
The PCA21125T/Q900/1,1 is available at Aetrix Electronics and suitable for automotive engine control, smart metering, industrial telematics, and medical infusion pump applications requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for PCA21125T/Q900/1,1 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 markets, with deep expertise in mixed-signal and power-efficient IC design.
The PCA21125T/Q900/1,1 belongs to NXP's automotive-qualified RTC product line, engineered specifically for time-critical embedded systems demanding AEC-Q100 compliance, ultra-low power, and robust SPI interfacing in harsh environments.
FAQ
What is the maximum SPI clock frequency supported by the PCA21125T/Q900/1,1?
The PCA21125T/Q900/1,1 supports a maximum SPI data rate of 6.0 Mbit/s, as specified in the official NXP datasheet Rev. 2. This allows fast register access and minimizes host processor overhead during time updates or alarm configuration. The PCA21125T/Q900/1,1 maintains reliable communication across its full 1.3 V to 5.5 V supply range and −40 °C to +125 °C operating temperature.
Does the PCA21125T/Q900/1,1 require external load capacitors for the 32.768 kHz crystal?
No, the PCA21125T/Q900/1,1 integrates an internal oscillator capacitor, eliminating the need for external 12.5 pF load capacitors. This reduces BOM cost and PCB area while improving reliability in vibration-prone automotive applications. The PCA21125T/Q900/1,1 datasheet explicitly confirms this feature in Section 2 "Features and benefits".
How does the PCA21125T/Q900/1,1 prevent time corruption during register read/write operations?
The PCA21125T/Q900/1,1 freezes all time and date registers (02h–08h) during any SPI read or write access, preventing carry-related corruption. This atomic access behavior ensures that reading seconds through years in a single transaction yields a consistent timestamp - a critical capability confirmed in Section 8.3.8 of the PCA21125T/Q900/1,1 datasheet.
Can the PCA21125T/Q900/1,1 generate a 1 Hz output on the CLKOUT pin?
Yes, the PCA21125T/Q900/1,1 can generate a precise 1 Hz square wave on the CLKOUT pin by programming COF[2:0] = 110 in register CLKOUT_control (0Dh). This output is open-drain and has a 50:50 duty cycle, making it suitable for microcontroller wake-up or system timing reference - as detailed in Table 25 of the PCA21125T/Q900/1,1 datasheet.
Is the PCA21125T/Q900/1,1 qualified for automotive applications?
Yes, the PCA21125T/Q900/1,1 is AEC-Q100 qualified for automotive applications (Grade 0), supporting operation from −40 °C to +125 °C. This qualification is explicitly stated in Section 2 "Features and benefits" and verified in the ordering information table, confirming its suitability for engine control, ADAS, and body electronics systems.
PCA21125T/Q900/1,1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Package/Case:
- 14-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Clock/Calendar
- Features:
- Alarm, Leap Year, Square Wave Output, Watchdog Timer
- Memory Size:
- -
- Time Format:
- HH:MM:SS (12/24 hr)
- Date Format:
- YY-MM-DD-dd
- Interface:
- SPI
- Voltage - Supply:
- 1.6V ~ 5.5V
- Voltage - Supply, Battery:
- -
- Current - Timekeeping (Max):
- 30.3µA @ 2V ~ 5V
- Operating Temperature:
- -40°C ~ 125°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 14-TSSOP
PCA21125T/Q900/1,1 FAQ
1.How can I place an order for PCA21125T/Q900/1,1 through Aetrix?
Please submit a Request for Quotation (RFQ) for PCA21125T/Q900/1,1 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for PCA21125T/Q900/1,1 reliable?
The price and inventory of PCA21125T/Q900/1,1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for PCA21125T/Q900/1,1 is usually 5 days.
3.What payment methods are accepted for PCA21125T/Q900/1,1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for PCA21125T/Q900/1,1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for PCA21125T/Q900/1,1?
PCA21125T/Q900/1,1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your PCA21125T/Q900/1,1 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for PCA21125T/Q900/1,1?
For technical support, including PCA21125T/Q900/1,1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your PCA21125T/Q900/1,1 requirements.
6.How does Aetrix verify that PCA21125T/Q900/1,1 is sourced from the original manufacturer or authorized distributors?
All PCA21125T/Q900/1,1 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that PCA21125T/Q900/1,1 meets industry standards.
7.What is the process for return or replacement of PCA21125T/Q900/1,1?
All PCA21125T/Q900/1,1 units undergo pre-shipment inspection (PSI). If there is an issue with PCA21125T/Q900/1,1, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The PCA21125T/Q900/1,1 part is unused and in its original packaging.
Return procedure for PCA21125T/Q900/1,1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
PCA21125T/Q900/1,1 Tags
-
MCP7940N-I/SN
Microchip Technology
-
MCP7940MT-I/MNY
Microchip Technology
-
PCF85063ATL/1,118
NXP USA Inc.
-
MCP7940NT-I/SN
Microchip Technology
-
MCP7940NT-I/MS
Microchip Technology
-
MCP7940N-I/MS
Microchip Technology
-
PCF85063AT/AY
NXP USA Inc.
-
PCF85063TP/1Z
NXP Semiconductors
-
PCF85063ATT/AJ
NXP USA Inc.
-
MCP7940NT-E/SN
Microchip Technology
-
MCP7940NT-I/MNY
Microchip Technology
-
MCP79400T-I/SN
Microchip Technology
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