FRTC1339M I²C Real-Time Clock with Dual Alarms, Backup Switchover and Trickle Charge
NYFEA FRTC1339M is an MSOP-8 I²C real-time clock with two programmable alarms, automatic backup switching, programmable square-wave output and trickle-charge capability.
Product scope: FRTC1339M is a compact calendar RTC with a separate backup supply. A trickle-charge path must only be enabled for an energy-storage element and charging arrangement qualified for that function. It is not a battery charger with cell-safety supervision.
Use the current controlled PDF for register definitions, timing, test conditions, package dimensions and production release decisions.
Product Overview and Scope
NYFEA FRTC1339M is an MSOP-8 I²C real-time clock with two programmable alarms, automatic backup switching, programmable square-wave output and trickle-charge capability.
Selection boundary: Similar I²C functionality or pin count does not establish drop-in compatibility with another RTC. Compare address, registers, oscillator and power architecture before committing a PCB or firmware migration.
Key Features
Calendar
Seconds through year, 12/24-hour operation and leap-year compensation through 2100 as stated.
Alarms
Two programmable time-of-day alarms with maskable repeat rates.
Backup
Power-fail detection, automatic source switching and optional trickle-charge path.
Square wave
Programmable SQW/INT open-drain output.
Function Block
The functional block diagram shows how the oscillator, divider and calendar logic, control/status registers, host interface and output or interrupt functions are connected inside FRTC1339M.
Timekeeping and Calendar Operation
The calendar is encoded in BCD unless the controlled PDF states otherwise. Firmware should use a coherent multi-byte read, validate field ranges and apply the device-specific century and leap-year rules.
| Calendar | Seconds through year, 12/24-hour operation and leap-year compensation through 2100 as stated. |
|---|---|
| Alarms | Two programmable time-of-day alarms with maskable repeat rates. |
| Backup | Power-fail detection, automatic source switching and optional trickle-charge path. |
| Square wave | Programmable SQW/INT open-drain output. |
I²C Interface, Outputs and Interrupts
| Host interface | 2-wire serial interface, up to 400 kHz |
|---|---|
| Output and interrupt scope | Alarms; Backup; Square wave |
| Pull-up requirement | SDA and open-drain interrupt/output pins require external pull-up resistors sized for the selected bus voltage and capacitance. |
| Firmware responsibility | Initialize control registers, read status flags, clear interrupt sources and prevent calendar rollover errors during multi-byte access. |
Power, Backup and Time-Validity Strategy
| Primary supply | VCC 2.97 V to 5.5 V |
|---|---|
| Timekeeping / backup | VBACKUP 1.4 V to 3.7 V |
| Backup architecture | Automatic power-fail detection and switchover; programmable trickle-charge network |
| Retained user memory | No general-purpose NVRAM stated |
| Current condition | Active VCC current: 450 µA max; standby VCC current: 80 µA typ., 150 µA max under the stated bus-inactive condition |
Current values are meaningful only with the adjacent voltage, interface, output and temperature conditions. Estimate system backup life from the worst-case current, source capacity after derating, leakage paths, pull-ups and switchover behavior.
Electrical Conditions and Accuracy
| Operating supply | VCC 2.97 V to 5.5 V |
|---|---|
| Timekeeping / backup condition | VBACKUP 1.4 V to 3.7 V |
| I²C interface | 2-wire serial interface, up to 400 kHz |
| Operating temperature | -40 °C to +85 °C |
| Current condition | Active VCC current: 450 µA max; standby VCC current: 80 µA typ., 150 µA max under the stated bus-inactive condition |
| Accuracy / stability | Set by the external crystal, capacitive load, PCB parasitics and operating temperature |
| Package | MSOP-8, 0.65 mm pitch |
PDF audit note: The feature page states -40 °C to +125 °C, but the recommended operating conditions and DC/AC test ranges state -40 °C to +85 °C. This page uses the supported -40 °C to +85 °C range.
Typical Application Circuit
The circuit is a product-level connection reference, not a complete end-product schematic. The host, power sequencing, energy source, EMC protection and production test strategy remain system responsibilities.
- Verify the rechargeable cell or supercapacitor, current limiting, diode selection and safety requirements before enabling trickle charge.
- Reserve the specified crystal matching network when system time-accuracy targets require final-assembly adjustment.
- Use a coherent multi-byte time-read procedure and clear interrupt flags according to the register definition.
Package Information
Available package: MSOP-8. Mechanical dimensions and terminal numbering are package-specific and must not be inferred from the product appearance image.
Application Guidance and Design Limitations
The controlled product specification explicitly lists handhelds, consumer electronics, office equipment, medical equipment and telecommunications. These categories describe possible uses; they do not establish end-product certification or finished-system performance.
Handheld GPS and POS TerminalsUse automatic power-fail detection and backup switchover to retain calendar time. Verify the selected backup element, leakage, source impedance, switchover thresholds and service life.
Consumer and Network AppliancesThe PDF lists set-top boxes, digital recording equipment and network appliances. Confirm external-crystal accuracy, alarm behavior, firmware initialization and retained-time validity after supply transitions.
Office EquipmentThe PDF lists fax machines, printers and copiers. Keep the crystal loop short and quiet, provide correct I²C pull-ups and verify immunity to switching and electromechanical noise.
Medical EquipmentThe PDF lists glucometers and medicine dispensers. This listing does not establish safety or regulatory compliance; risk management, timestamp-failure analysis and product qualification remain required.
TelecommunicationsThe PDF lists routers, switches and servers. Use the RTC for local event time and schedules; network synchronization and traceable time require a separate system-level architecture.Application boundary: Use the controlled PDF for electrical limits and validate clock accuracy, initialization, time validity, backup life, I²C operation, interrupts, EMC, safety, assembly and environmental behavior in the complete product.
FRTC1339M Engineering FAQs
What is the FRTC1339M?
FRTC1339M is a NYFEA I²C real-time clock device. FRTC1339M is a compact calendar RTC with a separate backup supply. A trickle-charge path must only be enabled for an energy-storage element and charging arrangement qualified for that function. It is not a battery charger with cell-safety supervision.
What supply range does FRTC1339M use?
The controlled PDF specifies VCC 2.97 V to 5.5 V. The timekeeping or backup condition is listed separately as VBACKUP 1.4 V to 3.7 V.
Does FRTC1339M include a crystal?
External 32.768 kHz crystal; CL 6 pF and ESR up to 70 kΩ in the crystal table.
What is the FRTC1339M operating temperature range?
The supported operating range used on this page is -40 °C to +85 °C.
Can FRTC1339M replace another RTC without redesign?
Do not infer a drop-in replacement from a similar function, interface or package. Verify pinout, I²C address, register map, power-fail behavior, oscillator network, interrupt handling, package dimensions and firmware in the final system.
How should time validity be checked after power-up?
Initialize the device as required, inspect the available oscillator-stop or voltage-status flags, perform a coherent calendar read and reject timestamps until the system has established a valid time source.
This page summarizes the FRTC1339M product specification for product evaluation and engineering reference. It does not replace the complete controlled specification. Confirm the current revision, register definitions, pin configuration, interface timing, absolute maximum ratings, oscillator and backup requirements, package dimensions, PCB layout, assembly process and qualification requirements before production release.
Download FRTC1339M Product SpecificationContact NYFEA for Product Support