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, a 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 facilitate the performance of the software functions that are time dependant. They are designed to run on an ultra-low power consumption, often run on a lithium battery source or 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. 540-2726
Mfr. Part No.DS1307+
R 108.12
Each
units
Alarm, Battery Backup, Calendar, Power Fail DW:DM:M:Y HH:MM:SS 56B Serial-I2C Through Hole PDIP 8 9.91 x 7.87 x 4.45mm 9.91mm 7.87mm 4.45mm 5.5 V +70 °C
RS stock no. 165-9062
Mfr. Part No.DS1307+
R 42.213
Each (In a Tube of 50)
units
Alarm, Battery Backup, Calendar, Power Fail DW:DM:M:Y HH:MM:SS 56B Serial-I2C Through Hole PDIP 8 9.91 x 7.87 x 4.45mm 9.91mm 7.87mm 4.45mm 5.5 V +70 °C
RS stock no. 732-7582
Mfr. Part No.DS3231SN#
R 228.41
Each
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SOIC 16 10.5 x 7.6 x 2.35mm 10.5mm 7.6mm 2.35mm 5.5 V +85 °C
RS stock no. 103-9916
Mfr. Part No.DS3231SN#
R 129.892
Each (In a Tube of 46)
units
Battery Backup, Calendar DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SOIC 16 10.5 x 7.6 x 2.35mm 10.5mm 7.6mm 2.35mm 5.5 V +85 °C
RS stock no. 923-7490
Mfr. Part No.DS1307Z+T&R
R 22.703
Each (On a Reel of 2500)
units
Battery Backup, Calendar, NV RAM YY:MM:DD HH:MM:SS 56B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +70 °C
RS stock no. 169-8316
Mfr. Part No.DS1307Z+
R 58.751
Each (In a Tube of 100)
units
Alarm, Battery Backup, Calendar, Power Fail DW:DM:M:Y HH:MM:SS 56B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +70 °C
RS stock no. 540-4772
Mfr. Part No.DS1307Z+
R 48.27
Each
units
Alarm, Battery Backup, Calendar, Power Fail DW:DM:M:Y HH:MM:SS 56B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +70 °C
RS stock no. 761-9759
Mfr. Part No.DS1307Z+T&R
R 51.65
Each
units
Battery Backup, Calendar, NV RAM YY:MM:DD HH:MM:SS 56B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +70 °C
RS stock no. 865-2208
Mfr. Part No.PCF8563T/5,518
BrandNXP
R 11.082
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. 124-2362
Mfr. Part No.PCF8563T/5,518
BrandNXP
R 10.958
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. 146-0203
Mfr. Part No.MCP7940M-I/P
BrandMicrochip
R 9.238
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 12.916
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 322.086
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 337.23
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. 817-3658
Mfr. Part No.MCP79410T-I/SN
BrandMicrochip
R 12.763
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 17.402
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. 889-5121
Mfr. Part No.MCP79410-I/SN
BrandMicrochip
R 14.518
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. 170-8114
Mfr. Part No.ISL12026IBZ-T7A
BrandIntersil
R 36.616
Each (On a Reel of 250)
units
Alarm, Calendar, Clock, EEPROM DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 100-0651
Mfr. Part No.ISL12026IBZ-T7A
BrandIntersil
R 55.955
Each (In a Pack of 2)
units
Alarm, Calendar, Clock, EEPROM DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS stock no. 732-7365
Mfr. Part No.DS1339U-33+
R 57.73
Each
units
Battery Backup, Calendar DW:DM:M:Y 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