Renesas 1337GNLGI8

Overview

1337GNLGI8 from Renesas Electronics is a serial real-time clock (RTC) IC with battery-backed non-volatile RAM, providing BCD-formatted timekeeping (seconds to years) with leap-year compensation through 2100, ultra-low active current (7.5 µA typical), I²C fast-mode (400 kHz) interface, and programmable square-wave output (1 Hz / 4.096 kHz / 8.192 kHz / 32.768 kHz). It serves as the primary timekeeping engine in networked embedded systems requiring long-term accuracy during main power loss.

For engineers reviewing the 1337GNLGI8 datasheet, 1337GNLGI8 pinout, 1337GNLGI8 application, or 1337GNLGI8 equivalent, key selection criteria include its industrial temperature range (–40°C to +85°C), automatic VCC-to-VBAT switchover on power fail, 56-byte battery-backed SRAM retention, and compatibility with standard 32.768 kHz crystals (12.5 pF load capacitance).

Technical Context

The 1337GNLGI8 integrates a precision 32.768 kHz oscillator with internal load capacitance optimization for 12.5 pF crystals, supporting both crystal and external oscillator inputs via X1/X2 pins. Its power-sense circuitry compares VCC against device-specific VPF thresholds (1.40–1.71 V for 1337GNLGI8 variant) to trigger seamless backup supply activation without software intervention.

Time data is buffered using dual-register architecture: on I²C START/STOP or address wraparound, the live clock registers copy to secondary buffers, enabling atomic multibyte reads without time rollover corruption. The control register (07H) provides oscillator status monitoring (OSF flag), square-wave enable (SQWE), and rate selection (RS1/RS0) with hardware-level edge-triggered fault detection.

Key Specifications

Pinout & Package

1337GNLGI8 is packaged in an 8-pin MSOP surface-mount package (3.0 mm × 3.0 mm × 0.85 mm), optimized for space-constrained PCB layouts in networking and portable equipment. All NC pins are absent - no unused terminals require grounding.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock applications.

Compared with DS3231M and PCF8563, the 1337GNLGI8 delivers balanced trade-offs: superior accuracy vs. PCF8563 (±20 ppm vs. ±50 ppm), lower cost and smaller footprint than DS3231M, and unique diagnostic features (OSF flag, atomic read buffers) essential for mission-critical logging.

Availability

1337GNLGI8 is available at Aetrix Electronics and suitable for telecom infrastructure, medical monitoring devices, industrial gateways, smart utility meters, and office automation equipment requiring stable component supply across multi-year production cycles.

Supply support for 1337GNLGI8 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

Renesas Electronics is a global semiconductor leader delivering microcontrollers, analog, power, and timing solutions for automotive, industrial, and IoT markets, with over 40 years of mixed-signal design heritage.

The 1337GNLGI8 belongs to Renesas' IDT real-time clock family, engineered specifically for high-reliability, low-power timekeeping in networked embedded systems where data integrity and long-term battery operation are mandatory.

FAQ

What is the primary function of the 1337GNLGI8 in an embedded system?

The 1337GNLGI8 serves as a standalone real-time clock with battery-backed non-volatile RAM, maintaining accurate time-of-day and calendar data (seconds, minutes, hours, day, date, month, year) across main power interruptions. Its integrated I²C interface enables direct connection to host microcontrollers for configuration and readback, while the 56-byte RAM stores critical application data such as event logs or calibration parameters that must persist during VCC loss. The 1337GNLGI8 does not require external firmware to manage leap-year logic or month-end adjustments.

How does the 1337GNLGI8 handle power failure and backup switchover?

The 1337GNLGI8 incorporates dedicated power-sense circuitry that continuously monitors VCC against a fixed VPF threshold (1.40–1.71 V for this variant). When VCC drops below VPF, the device automatically switches to VBAT within 3 ms (t_VCCF), preserving timekeeping and RAM contents without host intervention. During switchover, the oscillator remains active, and all registers remain accessible via I²C using VBAT power. The 1337GNLGI8 resumes full VCC operation after t_REC (2 ms) once VCC rises above VPF, ensuring zero time loss during brownouts.

Can the 1337GNLGI8 operate with an external 32.768 kHz oscillator instead of a crystal?

Yes - the 1337GNLGI8 supports external oscillator input: connect the oscillator signal directly to the X1 pin and leave X2 floating. This configuration bypasses the internal crystal oscillator circuitry while retaining all timing, RAM, and I²C functionality. The device does not require load capacitors in oscillator-drive mode, simplifying layout and eliminating crystal matching concerns. All timing specifications, including ±20 ppm accuracy and 1.3–3.7 V VBAT operation, remain valid under external drive, making the 1337GNLGI8 adaptable to systems where crystal placement is mechanically constrained.

What is the purpose of the OSF (Oscillator Stop Flag) bit in the 1337GNLGI8 control register?

The OSF bit (bit 5 of register 07H) is an edge-triggered status flag that latches when the internal 32.768 kHz oscillator stops - caused by insufficient VCC/VBAT, crystal disconnection, excessive ESR, noise injection, or manual halt (CH=1). Once set, OSF remains asserted until the host MCU writes '0' to clear it; writing '1' has no effect. This allows firmware to detect and log oscillator faults independently of time-read operations. In the 1337GNLGI8, OSF provides actionable diagnostics for field-deployed units where crystal reliability impacts regulatory compliance or service uptime.

Does the 1337GNLGI8 support both 12-hour and 24-hour time formats?

Yes - the 1337GNLGI8 supports configurable time format via bit 6 of the hours register (02H). When set to '1', the device operates in 12-hour mode with AM/PM indication (bit 5 = PM flag); when cleared to '0', it uses 24-hour format (bit 5 = tens digit for hours 20–23). Format changes require re-initialization of the hours register to avoid invalid states. All other calendar functions - including automatic month-end adjustment and leap-year compensation through 2100 - operate identically in both modes. The 1337GNLGI8 retains format selection across power cycles in its non-volatile register set.