Renesas 1339-31DVGI8

Overview

1339-31DVGI8 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, I²C fast-mode interface (400 kHz), programmable square-wave output (1 Hz / 4.096 kHz / 8.192 kHz / 32.768 kHz), and automatic power-fail detection/switching between VCC and VBAT - deployed in telecom routers and medical glucometers requiring long-term time retention during main power loss.

For engineers reviewing the 1339-31DVGI8 datasheet, 1339-31DVGI8 pinout, 1339-31DVGI8 application, or 1339-31DVGI8 equivalent, key selection criteria include industrial temperature range (-40°C to +85°C), ultra-low VBAT current (800 nA typical with oscillator active), 56-byte NV SRAM retention, I²C slave address 0x68 (1101000b), and MSOP-8/SOIC-8 package compatibility with crystal-integrated 16-pin SOIC variants.

Technical Context

The 1339-31DVGI8 implements a precision 32.768 kHz crystal oscillator with internal load capacitance optimized for 12.5 pF crystals, integrated power-sense comparator with programmable VPF threshold (2.45–2.97 V), and dual-register buffering to prevent read corruption during clock updates. Its I²C interface supports both standard (100 kHz) and fast (400 kHz) modes with open-drain SDA/SCL requiring external pull-ups.

Internal architecture separates timekeeping logic from RAM access via dedicated register maps: RTC registers (00H–07H) store BCD-encoded time/date with CH bit control and OSF flag for oscillator health monitoring; RAM space (08H–3FH) provides 56 bytes of battery-backed storage; control register (07H) configures SQW/OUT frequency and output polarity.

Key Specifications

Pinout & Package

1339-31DVGI8 is packaged in an 8-pin MSOP (3.0 mm × 3.0 mm, 0.65 mm pitch) surface-mount package. Pin assignments match the 8-pin SOIC variant per Renesas datasheet Rev. 14-Dec-2023.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231M+ and PCF8563T, the 1339-31DVGI8 delivers optimal balance of ultra-low VBAT current (800 nA), diagnostic capability (OSF flag), flexible SQW frequencies, and industrial qualification - making it ideal for long-life, safety-aware applications where time integrity must survive extended power loss.

Availability

1339-31DVGI8 is available at Aetrix Electronics and suitable for telecom infrastructure, medical diagnostics, industrial control panels, and smart utility meters requiring stable component supply with guaranteed long-term manufacturability.

Supply support for 1339-31DVGI8 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 enterprise applications.

The 1339-31DVGI8 belongs to Renesas' legacy IDT RTC portfolio, engineered specifically for ultra-low-power, high-reliability timekeeping in battery-backed systems where data integrity and decades-long operation are critical.

FAQ

What is the I²C slave address of the 1339-31DVGI8?

The 1339-31DVGI8 uses a fixed 7-bit I²C slave address of 0x68 (1101000b), with the R/W bit determining direction. This address is hardwired and not configurable. During communication, the master sends this address followed by the R/W bit; the 1339-31DVGI8 acknowledges only when the full 8-bit byte matches. No address pins or EEPROM-based addressing exist on the 1339-31DVGI8.

Does the 1339-31DVGI8 require an external crystal?

Yes, the 1339-31DVGI8 requires an external 32.768 kHz tuning-fork crystal connected between X1 and X2 pins. It is not shipped with an integrated crystal - unlike the 16-pin SOIC variant (e.g., 1338CSRI). The internal oscillator is optimized for crystals with 12.5 pF load capacitance; ESR should be ≤110 kΩ. An external oscillator may drive X1 with X2 left floating, but crystal use is standard for lowest power.

How does the 1339-31DVGI8 handle leap-year calculation?

The 1339-31DVGI8 performs automatic leap-year compensation in hardware up to year 2100. It correctly adjusts February days (28 or 29) and end-of-month dates for all months, including century years (e.g., 2100 is not a leap year). This logic is embedded in the RTC counter block and requires no host firmware intervention - the calendar registers always reflect accurate civil time when read.

What is the function of the OSF bit in the 1339-31DVGI8 control register?

The OSF (Oscillator Stop Flag) bit (bit 5 of register 07H) is a latched status indicator that goes high when the oscillator stops due to power loss, crystal fault, or CH=1 setting. It remains set until explicitly cleared by writing 0 to that bit. Reading OSF=1 signals invalid time/date data; firmware must reinitialize the RTC after power restoration. The 1339-31DVGI8 sets OSF on first power-up, confirming initialization necessity.

Can the 1339-31DVGI8 operate solely on VBAT without VCC applied?

Yes, the 1339-31DVGI8 fully maintains timekeeping, calendar, and 56-byte RAM contents on VBAT alone when VCC is absent or below VPF (2.45–2.97 V). All functions - including SQW/OUT output and I²C communication - remain operational as long as VBAT stays within 1.3 V to 3.7 V. However, I²C writes require VBAT ≥1.3 V and proper pull-up resistors on SDA/SCL referenced to VBAT.