HT1381A

HT1380A/HT1381A is a real-time clock IC that provides seconds, minutes, hours, day of week, date, month, and year information. It features automatic adjustment for the number of days in each month and leap years. Designed for low-power applications, it operates in two modes: 12-hour mode with AM/PM indicator and 24-hour mode. Multiple registers store relevant information in 8-bit data format. A 32768Hz crystal provides accurate timekeeping. To minimize pin count, serial I/O is used for communication with a microprocessor, requiring only three signal lines: 1. RST; 2. SCLK; 3. I/O. Data can be transferred one byte at a time or as a burst of 8 bytes. The internal architecture primarily consists of a data transfer register array for storing clock/calendar data, command control logic, oscillator circuit, and read timer clock. Clock information is contained in the following eight read/write registers. Data in the clock registers is stored in BCD format. Both modes support data transfer between the microprocessor and HT1380A/HT1381A: single-byte mode and multi-byte mode. Two additional bits are also included: the Clock Halt bit (CH) and the Write Protect bit (WP). These bits control oscillator operation and data write access to the register array. Both bits must be set before reading from or writing to the register array.

Applications

• Microcomputer serial clock
• Clock and calendar
• Real-time clock (RTC) / perpetual calendar function

Key features

• Operating voltage: 2.0V~5.5V
• Maximum input serial clock: 500kHz@VDD=2V, 2MHz@VDD=5V
• Operating current: <0.5μA@2V, <0.7μA@3V, <1.0μA@5V
• TTL compatible
• Two data transfer modes: single-byte or pulse mode