Timer ICs / ASSPs

Real-Time Clock with Switch Input Detection Function (2-wire Interface, Remote Control Signal Header Detection Enabled) S-78390A Series


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The S-78390A Series is a CMOS real-time clock IC which operates with low current consumption and a wide voltage range. This IC counts time in year, month, day, days of the week, hour, minute, and second. It also includes an auto calculation function for leap-year and its calendar is up to 2099. An alarm interrupt function is included in units of years, months, days, days of the week, hours, and minutes. Due to its operation with low voltage and low current consumption, this IC is suitable for equipment which works with battery. Just in the clock operation in which users do not use the communicational function, this IC operates with a power supply of 1.1 V. A 8-channel switch input detection circuit is also included. One of these channels can be optionally changed as a remote control signal header detection circuit. When either switch input or a remote control signal header is detected, this IC outputs a signal for notification to the CPU or other devices. Since this IC is able to detect a trigger input, it can greatly suppress power consumption during the host device’s sleep mode.


Low current consumption
0.35 µA Typ. (VDD = 3.0 V, Ta = 25°C, BKUP=”L”)
Wide operating voltage range
1.3 to 5.5 V
Time keeping operation voltage
1.1 V
2-wire (I2C-bus) CPU interface
Built-in input detection circuit
Built-in remote control pre-decode circuit (by option)
Report signal output function by trigger input detection
Built-in user free register
Built-in clock adjustment function
Built-in alarm interrupter
Built-in constant-voltage circuit
Built-in flag generator at power down and power on
Auto calendar up to the year 2099, automatic leap year calculation function
Built-in 32 kHz crystal oscillator circuit (Cd built in, Cg external)
Lead-free product


  • Digital video cameras
  • Digital still cameras
  • DVD recorders
  • Thin-screen televisions
  • Car Navigation system
  • IC recorder