R2051

The R2051 is a CMOS real-time clock IC connected to the CPU by two signal lines, SCL and SDA, and configured to perform serial transmission of time and calendar data to the CPU.

There are some features as  of R2051. First is minimum timekeeping supply voltage which is 0.75 V typ (max 1.00 V); VDD pin. The second is low power consumption which is 0.4A TYP (1.0A MAX) at VDD=3 V. Then is built-in backup switchover circuit (can be used for a primary battery, a secondary battery, or an electric double layer capacitor). Next is time counters (counting hours, minutes and seconds) and calendar counters (counting years, months, days and weeks) (in BCD format). The fifth is interrupt circuit configured to generate interrupt signals (with interrupt ranging from 0.5 seconds to 1 month) to the CPU and provided with an interrupt flag and an interrupt halt. The sixth is built-in voltage detector with delay. The seventh is with power-on flag to prove that the power supply starts from 0 V. The eighth is supply voltage monitoring circuit with two supply voltage monitoring threshold voltage. The ninth is high precision oscillation adjustment circuit. The last one is built-in oscillation stabilization capacitors (CG and CD).

What comes next is the absolute maximum ratings of R2051. The VCC (supply voltage 1) is from -0.3 to +6.5 V at VCC pin. The VDD (supply voltage 2) is from -0.3 to +6.5 V at VDD pin. The VCC (supply voltage 3) is from -0.3 to +6.5 V at VSB pin. The VI (input voltage 1) is from -0.3 to +6.5 V at SCL, SDA pin. The VI (input voltage 2) is from -0.3 to VDD+0.3 V at CIN pin.  The VO (output voltage 1) is from -0.3 to +6.5 V at /INTR, /VDCC pin. The VO (output voltage 2) is from -0.3 to VCC+0.3 V at CLKOUT pin. The maximum IOUT (output current) is 10 mA at VDD pin. The PD (power dissipation) is 300 mW at Topt=25. The Topt (operating temperature) is from -40 to +85. The Tstg (storage temperature) is from -55 to +125.