Renesas 1337GCSRI

Overview

1337GCSRI from Renesas Electronics is a serial real-time clock (RTC) IC with integrated 32.768 kHz crystal, delivering ultra-low-power timekeeping in BCD format across seconds to years with leap-year compensation through 2100, 56-byte battery-backed NV SRAM, and fast-mode I²C interface - deployed in telecom routers, medical glucometers, and utility meters requiring continuous timestamping during main power loss.

For engineers reviewing the 1337GCSRI datasheet, 1337GCSRI pinout, 1337GCSRI application, or 1337GCSRI equivalent, key selection criteria include VBAT current draw under oscillator-on conditions (≤1.4 µA), I²C fast-mode support (400 kHz), automatic power-fail detection and switchover latency (≤2 ms recovery), and guaranteed operation across −40°C to +85°C industrial temperature range.

Technical Context

The 1337GCSRI implements a fully autonomous RTC core with hardware-based leap-year logic, calendar register auto-adjustment for variable month lengths, and dual-buffered read architecture that transfers live time/date to shadow registers on I²C START/STOP to prevent rollover corruption during multi-byte reads. Its oscillator block integrates a factory-tuned 32.768 kHz quartz crystal with 12.5 pF load capacitance and adds ±10 ppm frequency error at 3.3 V / 25°C.

Power management uses a precision voltage comparator to monitor VCC against programmable power-fail threshold (VPF = 1.62 V typical for 1337GCSRI variant), enabling seamless switchover to VBAT (1.3–3.7 V) without register access interruption; the device maintains timekeeping and RAM retention while drawing only 120–300 nA in data-retention mode with oscillator disabled.

Key Specifications

Pinout & Package

1337GCSRI is packaged in a 16-pin SOIC surface-mount package with integrated crystal. All NC pins (4–13) must be grounded per design requirements.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231SN#T&R and PCF8563T/2,118, the 1337GCSRI uniquely balances integrated-crystal convenience, 2100 leap-year support, and sub-300 nA retention current - making it optimal for industrial meters and medical devices needing decade-long unattended operation without accuracy trade-offs.

Availability

1337GCSRI is available at Aetrix Electronics and suitable for telecom infrastructure, smart utility meters, medical monitoring equipment, and industrial printers requiring stable component supply with guaranteed long-term availability and full traceability.

Supply support for 1337GCSRI 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 specializing in microcontrollers, analog, power, and timing solutions for automotive, industrial, and IoT applications.

The 1337GCSRI belongs to Renesas' high-reliability RTC product line, engineered specifically for mission-critical timekeeping in battery-backed infrastructure where accuracy, longevity, and integration reduce system-level design risk.

FAQ

What is the crystal specification integrated into the 1337GCSRI package?

The 1337GCSRI integrates a factory-calibrated 32.768 kHz quartz tuning-fork crystal with 12.5 pF load capacitance and contributes a maximum frequency error of ±10 ppm at VCC = 3.3 V and TA = +25°C. This eliminates external crystal selection, layout, and tuning effort. The crystal is sealed within the 16-pin SOIC package and is not user-replaceable. No external load capacitors are required.

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

Yes, the 1337GCSRI supports both formats. Bit 6 of the hours register (address 02H) selects the mode: logic high enables 12-hour format with AM/PM indication (bit 5), while logic low enables 24-hour format. When switching modes, the hours register must be re-initialized to avoid invalid time states. The device retains format selection across power cycles in its non-volatile control register.

How does the 1337GCSRI handle power failure and switchover to backup supply?

The 1337GCSRI uses an internal voltage comparator to monitor VCC against a fixed power-fail threshold (VPF ≈ 1.62 V). When VCC drops below VPF, the device automatically switches to VBAT within microseconds, maintaining continuous timekeeping and RAM retention. Full I²C accessibility resumes after tREC (≤2 ms) once VCC rises above VPF. The OSF bit flags any oscillator stop event during switchover.

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

The OSF bit (bit 5 of register 07H) is a latched status flag indicating oscillator failure. It sets to logic 1 upon detection of oscillator stop due to power loss, CH bit activation, insufficient VBAT/VCC, or crystal disturbance. It remains asserted until explicitly cleared to 0 by firmware. This allows reliable validation of time/date integrity after power-up - if OSF = 1, the clock data may be invalid and requires reset.

Can the 1337GCSRI operate without an external pull-up resistor on the SDA and SCL lines?

No. The 1337GCSRI's SDA and SCL pins are open-drain outputs and require external pull-up resistors to function correctly on the I²C bus. The datasheet specifies 2 kΩ typical for both lines. Omitting pull-ups will prevent signal high states, resulting in I²C communication failure. Pull-up voltage must match the master's logic level (e.g., 3.3 V or 5 V) and remain within VIH/VIL specifications.