Low-Current I²C RTCs for High-ESR Crystals

 

Part Number	Replacement	Explanation

Description

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The DS1341/DS1342 low-current real-time clocks (RTCs) are timekeeping devices that provide an extremely low standby current, which permits longer life from a power supply. The DS1341/DS1342 support high-ESR crystals, which broaden the pool of usable crystals for the devices. The DS1341 uses a 6pF crystal, while the DS1342 uses a 12.5pF crystal. These devices are accessed through an I²C serial interface. Other features include two time-of-day alarms, two interrupt outputs, a programmable square-wave output, and a serial bus timeout mechanism.

The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either 24hr or 12hr format with an AM/PM indicator.

The DS1341/DS1342 also include an input for synchronization. When a reference clock (e.g., 60Hz power line or GPS 1PPS) is present at the CLKIN pin and the enable external clock input bit (ECLK) is set to 1, the DS1341/DS1342 RTCs are frequency-locked to the external clock and the clock accuracy is determined by the external source. In case of external clock failure, the clock is switched to the crystal oscillator.

The devices are available in lead(Pb)-free/RoHS-compliant, 8-pin µSOP or TDFN packages. The devices support a -40°C to +85°C extended temperature range.

DS1341, DS1342: Typical Operating Circuit Enlarge+

Key Features

• Low Timekeeping Current of 250nA (typ)
• Compatible with Crystal ESR Up to 100kΩ
• Use Crystals with C_L = 6pF (DS1341) or C_L= 12.5pF (DS1342)
• +1.8V to +5.5V Operating Voltage Range
• Maintain Time Down to +1.15V (typ)
• Fast (400kHz) I²C Interface
• Bus Timeout for Lockup-Free Operation
• RTC Counts Seconds, Minutes, Hours, Day, Date, Month, and Year with Leap Year Compensation Valid Through 2099
• External Clock Source for Synchronization Clock Reference (e.g., 32kHz, 50Hz/60Hz Power Line, GPS 1PPS)
• Two Time-of-Day Alarm with Two Interrupt Outputs
• Programmable Square-Wave Output
• Industrial Temperature Range (-40°C to +85°C)
• Small, 8-Pin µSOP or TDFN Packages

Applications/Uses

• Medical
• Point of Sale (POS)
• Portable Audio
• Portable Instruments
• Telematics