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Diodes Incorporated PT7C4339WEX
- Part No.:
- PT7C4339WEX
- Manufacturer:
- Diodes Incorporated
- Category:
- Real Time Clocks
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
PT7C4339WEX.pdf
- Description:
- IC RTC CLK/CALENDAR I2C 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:12,460
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Product details
Overview
PT7C4339WEX from Pericom (now part of Diodes Incorporated) is a low-power, I²C-compatible real-time clock/calendar IC with integrated timekeeping logic, two programmable time-of-day alarms, and a selectable square-wave output (1 Hz / 4.096 kHz / 8.192 kHz / 32.768 kHz). It supports BCD-coded time/date (seconds to years), automatic leap-year compensation through 2100, and operates from -40°C to +85°C. Used in embedded systems requiring accurate time stamping and alarm-triggered wake-up.
For engineers reviewing the PT7C4339WEX datasheet, PT7C4339WEX pinout, PT7C4339WEX application, or PT7C4339WEX equivalent, this device delivers verified RTC functionality with power-fail detection, oscillator stop flag monitoring, backup supply switching (VBACKUP 1.3–3.7 V), and high-speed I²C interface (400 kHz) - all in an MSOP-8 package.
Technical Context
The PT7C4339WEX implements a fully autonomous BCD-based time counter chain (seconds, minutes, hours, day, date, month, year) with automatic end-of-month and leap-year correction up to 2100. Its oscillator circuit accepts an external 32.768 kHz crystal across X1/X2 pins and includes an Oscillator Stop Flag (OSF) for runtime integrity validation.
It features dual independent alarm comparators with maskable fields (seconds to day/date), a programmable SQW/INT open-drain output supporting four frequencies, and a power-fail detect circuit that switches to VBACKUP (1.3–3.7 V) when VCC drops below 1.60–1.88 V. The I²C interface operates at up to 400 kHz with level-tolerant SCL/SDA inputs (up to 5.5 V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Time Format | 24-hour or 12-hour with AM/PM indicator; BCD-coded registers ensure direct microcontroller register mapping without binary conversion. |
| I²C Speed | Up to 400 kHz high-speed mode; enables fast time/calendar reads/writes without blocking main system bus for extended periods. |
| Alarm Capability | Two independent alarms with configurable match granularity (second, minute, hour, day/date); supports one-shot or repeating triggers via register masks. |
| Square-Wave Output | Selectable frequencies: 1 Hz, 4.096 kHz, 8.192 kHz, or 32.768 kHz; used for system tick generation, watchdog timing, or clock distribution. |
| Power-Fail Threshold | Voltage trip point: 1.60–1.88 V (typ. 1.72 V); ensures seamless switchover to backup supply before RTC data corruption occurs. |
| Backup Supply Range | VBACKUP = 1.3 V to 3.7 V; compatible with lithium coin cells (e.g., CR2032) or supercapacitors; enables >10-year backup operation at 3 V. |
| Operating Temp | -40°C to +85°C ambient; validated for industrial and automotive infotainment control modules where thermal stability is critical. |
Pinout & Package
PT7C4339WEX is housed in an MSOP-8L (3.0 × 3.0 mm, 0.65 mm pitch) surface-mount package with exposed pad for thermal performance. Pin assignments are electrically identical to SOIC-8 but with reduced footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| X1 | Oscillator Input | Connects to one terminal of external 32.768 kHz crystal; requires no external load capacitors due to internal trimming (CL = 6 pF). |
| X2 | Oscillator Output | Connects to other crystal terminal; floats if using external 32.768 kHz clock source instead of crystal. |
| SCL | I²C Clock Input | Level-tolerant up to 5.5 V; synchronizes all serial transfers; pull-up required externally. |
| SDA | I²C Data I/O | Open-drain bidirectional line; requires external pull-up; supports multi-master arbitration and clock stretching. |
| VBACKUP | Backup Power Supply | Accepts 1.3–3.7 V backup source; powers RTC core during main supply loss; must be grounded if unused. |
| SQW/INT | Programmable Output | Open-drain interrupt/square-wave output; configured via RS2/RS1 bits; pull-up required; active-low by default. |
| VCC | Main Power Supply | 3.0–5.5 V operation; enables full register access; triggers automatic switchover to VBACKUP below VPF threshold. |
| GND | Ground Reference | Primary return path for all analog/digital circuits; must be low-impedance and decoupled near VCC pin. |
Key Features
| Feature | Design Value |
|---|---|
| Leap-Year Compensation | Automatically adjusts calendar through year 2100 using BCD-coded year register; eliminates firmware overhead for date rollover logic. |
| Oscillator Stop Flag (OSF) | Dedicated status bit (bit 7 of register 0Fh) latches oscillator failure events; allows host MCU to validate time integrity on boot or after brownout. |
| Trickle-Charge Control | Configurable current-limiting resistor (200 Ω / 2 kΩ / 4 kΩ) enables safe charging of backup supercapacitors from VCC. |
| Power-Fail Switchover | Hardware-controlled transition from VCC to VBACKUP within microseconds; preserves time, date, alarms, and register state without software intervention. |
| Alarm Flexibility | Each alarm supports independent enable/disable, flag-clearing, and maskable fields - enabling precise scheduling (e.g., daily wake-up at 6:00 AM). |
Applications
| Smart Energy Metering | Industrial PLC HMI |
|---|---|
|
Use Scenario: Time-stamping energy consumption data every 15 minutes for utility billing and demand-response reporting. IC Role / Device Role / Timing Role: Primary RTC providing synchronized, tamper-resistant timestamps with battery-backed continuity during grid outages. Use Value: Ensures regulatory-compliant logging accuracy (±10 ppm typical with external crystal) and maintains calendar integrity across multi-year deployments. |
Use Scenario: Scheduling periodic diagnostics, firmware updates, and event logging in programmable logic controller human-machine interfaces. IC Role / Device Role / Timing Role: Standalone calendar/timekeeper managing local event queues and triggering maintenance alerts based on elapsed runtime or calendar dates. Use Value: Offloads time management from main CPU; enables deterministic alarm-driven actions without OS dependency or timer resource contention. |
| Medical Infusion Pump | Network Router Logging |
|
Use Scenario: Recording therapy start/end times, dosage intervals, and error timestamps under strict FDA audit requirements. IC Role / Device Role / Timing Role: Certified time source maintaining traceable, battery-backed timestamps even during AC power loss or battery swap. Use Value: Meets IEC 62304 traceability mandates with hardware-level power-fail detection and OSF flag for timestamp validity verification. |
Use Scenario: Timestamping security events, configuration changes, and system reboots in enterprise-grade networking equipment. IC Role / Device Role / Timing Role: System-level RTC ensuring log entries retain chronological fidelity across firmware upgrades and unexpected power cycles. Use Value: Prevents log sequence gaps or misordering; supports NTP synchronization fallback when network time is unavailable. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar real-time clock applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS3231M | Integrated TCXO (±2 ppm accuracy); higher cost; no external crystal needed; same I²C interface and pinout. | Better long-term stability in temperature-varying environments; suited for precision instrumentation where ±10 ppm is insufficient. | Choose DS3231M when absolute time accuracy > ±2 ppm is required and board space permits slightly larger DFN package. |
| MCP79412 | Internal LDO, EEPROM-backed SRAM, and trickle-charge circuitry; uses SPI interface; different register map and alarm structure. | Offers nonvolatile memory for configuration retention; better suited for deeply embedded systems needing persistent settings across resets. | Choose MCP79412 when combining RTC with configuration storage and SPI-only host interface is acceptable. |
Compared with DS3231M and MCP79412, PT7C4339WEX provides optimal balance of cost, proven reliability, and minimal external components (only crystal + two load caps) while delivering industrial-grade timing accuracy and dual-alarm flexibility in compact MSOP-8.
Availability
PT7C4339WEX is available at Aetrix Electronics and suitable for smart metering, industrial HMI, medical infusion pumps, and network router logging requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.
Supply support for PT7C4339WEX 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
Pericom Semiconductor - acquired by Diodes Incorporated in 2016 - specialized in high-performance timing, interface, and signal-integrity solutions for communications and computing markets.
The PT7C4339 series belongs to Pericom's low-power RTC product line, designed specifically for industrial and medical applications demanding robust backup operation, deterministic alarm response, and minimal external component count.
FAQ
What is the function of the OSF (Oscillator Stop Flag) bit?
The OSF bit (bit 7 of Status Register 0Fh) indicates whether the 32.768 kHz oscillator has stopped or was previously stopped. It is set on power-up, brownout, crystal disconnection, or manual oscillator disable (/EOSC=1). Host firmware must clear it after verifying oscillator health to confirm time validity - a critical step before trusting calendar data in safety-critical systems.
Can PT7C4339WEX operate without an external crystal?
No - PT7C4339WEX requires an external 32.768 kHz tuning-fork crystal connected between X1 and X2 pins. Unlike the PT7C4339C variant, it does not integrate the crystal. Using an external clock source is possible only if X2 is left floating and a clean 32.768 kHz square wave is applied to X1, but crystal operation is the validated and recommended configuration per datasheet.
How does the power-fail detection and switchover work?
PT7C4339WEX continuously monitors VCC against an internal voltage reference (VPF = 1.60–1.88 V). When VCC falls below VPF, the device automatically disconnects from VCC and switches to VBACKUP within microseconds. During switchover, timekeeping, alarms, and register contents remain uninterrupted - no host intervention or register reinitialization is needed.
Is the SQW/INT pin capable of generating both interrupts and square waves simultaneously?
No - SQW/INT is a single open-drain output serving dual functions selected via the INTCN bit. When INTCN = 1, it acts as an interrupt output triggered by Alarm 1 or Alarm 2 matches. When INTCN = 0, it outputs the programmed square-wave frequency (1 Hz / 4.096 kHz / etc.). The function is mutually exclusive and controlled entirely by register configuration.
PT7C4339WEX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Diodes Incorporated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Clock/Calendar
- Features:
- Alarm, Leap Year, Square Wave Output
- Memory Size:
- -
- Time Format:
- HH:MM:SS (12/24 hr)
- Date Format:
- YY-MM-DD
- Interface:
- I2C, 2-Wire Serial
- Voltage - Supply:
- 3V ~ 5.5V
- Voltage - Supply, Battery:
- 1.3V ~ 3.7V
- Current - Timekeeping (Max):
- 250µA @ 3V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 8-SOIC
PT7C4339WEX FAQ
1.How can I place an order for PT7C4339WEX through Aetrix?
Please submit a Request for Quotation (RFQ) for PT7C4339WEX 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 PT7C4339WEX reliable?
The price and inventory of PT7C4339WEX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for PT7C4339WEX is usually 5 days.
3.What payment methods are accepted for PT7C4339WEX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for PT7C4339WEX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for PT7C4339WEX?
PT7C4339WEX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your PT7C4339WEX 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 PT7C4339WEX?
For technical support, including PT7C4339WEX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your PT7C4339WEX requirements.
6.How does Aetrix verify that PT7C4339WEX is sourced from the original manufacturer or authorized distributors?
All PT7C4339WEX 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 PT7C4339WEX meets industry standards.
7.What is the process for return or replacement of PT7C4339WEX?
All PT7C4339WEX units undergo pre-shipment inspection (PSI). If there is an issue with PT7C4339WEX, 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 PT7C4339WEX part is unused and in its original packaging.
Return procedure for PT7C4339WEX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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