Real Time Clocks

What is a Real Time Clock?

A Real Time Clock (RTC) is a computer clock which is usually in the form of an integrated circuit. They have been designed to keep track of time, in real time - hence the product name. A Real Time Clock is usually an integral part of the computer motherboard. More often than not, an RTC will also include a calendar and an alarm

How do Real Time Clocks work?

The memory on the clocks system stores system descriptions and set up values such as "Current Time Value". The information that is held in the RTC is read with a microprocessor, commonly over a serial interface which facilitates the performance of the software functions that are time dependant.

Designed to run on ultra-low power consumption, RTCs often run on a lithium battery source but can also run on normal power. This power source allows them to continue running and generating real time when a system is down. The newer models of RTC use super-capacitors as a source of power that can be recharged and soldered to the board. Some Real Time Clocks feature synchronisation to an external signal, such as a compensated power line frequency. It allows the device to provide an accurate result without having an on-board temperature compensation scheme.

RTC Time Values

  • Year
  • Month
  • Date
  • Hours
  • Minutes
  • Seconds

...
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Description Price Functions Date Format Time Format User RAM Bus Type Mounting Type Package Type Pin Count Dimensions Length Width Height Maximum Operating Supply Voltage Maximum Operating Temperature
RS stock no. 124-2362
Mfr. Part No.PCF8563T/5,518
BrandNXP
R 12.467
Each (On a Reel of 2500)
units
Calendar, Clock YY:MM:DD:dd HH:MM:SS - Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.45mm 5mm 4mm 1.45mm 5.5 V +85 °C
RS stock no. 865-2208
Mfr. Part No.PCF8563T/5,518
BrandNXP
R 12.95
Each (In a Pack of 10)
units
Calendar, Clock YY:MM:DD:dd HH:MM:SS - Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.45mm 5mm 4mm 1.45mm 5.5 V +85 °C
RS stock no. 146-0203
Mfr. Part No.MCP7940M-I/P
BrandMicrochip
R 9.891
Each (In a Tube of 60)
units
Alarm, Calendar DW:DM:M:Y HH:MM:SS 64B Serial-I2C Through Hole PDIP 8 10.16 x 7.11 x 4.95mm 10.16mm 7.11mm 4.95mm 5.5 V +85 °C
RS stock no. 774-7403
Mfr. Part No.MCP7940M-I/P
BrandMicrochip
R 17.878
Each (In a Bag of 10)
units
Alarm, Calendar DW:DM:M:Y HH:MM:SS 64B Serial-I2C Through Hole PDIP 8 10.16 x 7.11 x 4.95mm 10.16mm 7.11mm 4.95mm 5.5 V +85 °C
RS stock no. 919-6337
Mfr. Part No.M48T18-100PC1
R 310.092
Each (In a Tube of 12)
units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 8192B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS stock no. 714-7298
Mfr. Part No.M48T18-100PC1
R 336.83
Each
units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 8192B Parallel Through Hole PCDIP 28 39.88 x 18.34 x 8.89mm 39.88mm 18.34mm 8.89mm 5.5 V +70 °C
RS stock no. 889-5121
Mfr. Part No.MCP79410-I/SN
BrandMicrochip
R 14.09
Each (In a Tube of 100)
units
Battery Backup, Calendar, Clock, NV Timekeeping SRAM DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS stock no. 817-3658
Mfr. Part No.MCP79410T-I/SN
BrandMicrochip
R 13.461
Each (On a Reel of 3300)
units
Alarm, Battery Backup, Calendar, Clock DW:D:M:Y HH:MM:SS 64B Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 5.5 V +85 °C
RS stock no. 726-3949
Mfr. Part No.MCP79410-I/SN
BrandMicrochip
R 23.782
Each (In a Pack of 5)
units
Battery Backup, Calendar, NV SRAM DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS stock no. 761-9711
Mfr. Part No.DS1339U-33+T&R
R 63.90
Each
units
Battery Backup, Calendar YY:MM:DD HH:MM:SS - Serial-I2C Surface Mount μSOP 8 3.1 x 3.1 x 0.95mm 3.1mm 3.1mm 0.95mm 5.5 V +85 °C
RS stock no. 923-7472
Mfr. Part No.DS1339U-33+T&R
R 31.486
Each (On a Reel of 3000)
units
Battery Backup, Calendar YY:MM:DD HH:MM:SS - Serial-I2C Surface Mount μSOP 8 3.1 x 3.1 x 0.95mm 3.1mm 3.1mm 0.95mm 5.5 V +85 °C
RS stock no. 103-1580
Mfr. Part No.M41T56M6F
R 24.116
Each (On a Reel of 2500)
units
Calendar, Chip Deselect, Switch Over DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS stock no. 761-7627
Mfr. Part No.MCP7940M-I/SN
BrandMicrochip
R 10.106
Each (In a Pack of 5)
units
Calendar, NV SRAM DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS stock no. 912-6943
Mfr. Part No.MCP7940M-I/SN
BrandMicrochip
R 9.225
Each (In a Tube of 100)
units
Calendar, NV SRAM DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS stock no. 714-7288
Mfr. Part No.M41T56M6F
R 66.815
Each (In a Pack of 2)
units
Calendar, Chip Deselect, Switch Over DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.25mm 4.9mm 3.9mm 1.25mm 5.5 V +85 °C
RS stock no. 518-299
Mfr. Part No.ISL12026IBZ
BrandIntersil
R 53.25
Each
units
Alarm, Battery Backup, Calendar, Switch Over DW:DM:M:Y HH:MM:SS 512B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 169-8293
Mfr. Part No.ISL12026IBZ
BrandIntersil
R 65.498
Each (In a Tube of 98)
units
Alarm, Battery Backup, Calendar, Switch Over DW:DM:M:Y HH:MM:SS 512B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 146-0213
Mfr. Part No.MCP79412-I/SN
BrandMicrochip
R 14.829
Each (In a Tube of 100)
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 5.5 V +85 °C
RS stock no. 798-5260
Mfr. Part No.MCP79412-I/SN
BrandMicrochip
R 16.182
Each (In a Pack of 5)
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 5.5 V +85 °C
RS stock no. 798-5267
Mfr. Part No.MCP79411-I/SN
BrandMicrochip
R 16.15
Each (In a Pack of 10)
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS 64B Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 5.5 V +85 °C