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. 190-5136
Mfr. Part No.DS1390U-33+T&R
HK$33.874
Each (In a Pack of 5)
units
Trickle Charger D:D:M:Y - - Serial-SPI Surface Mount μSOP 10 3.16 x 3.12 x 0.95mm 3.16mm 3.12mm 0.95mm 5.5 V +85 °C
RS Stock No. 100-0649
Mfr. Part No.ISL1208IU8Z-T7A
BrandIntersil
HK$38.975
Each (On a Tape of 2)
units
Alarm, Calendar, Clock, SRAM DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount MSOP 8 3.05 x 3.05 x 0.95mm 3.05mm 3.05mm 0.95mm 5.5 V +85 °C
RS Stock No. 889-5121
Mfr. Part No.MCP79410-I/SN
BrandMicrochip
HK$6.874
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. 189-8345
Mfr. Part No.DS1394U-33+
HK$34.104
Each (In a Pack of 5)
units
Trickle Charger DD:M:Y SS:MM:HH - Serial-SPI Surface Mount μMAX 10 3.05 x 3.05 x 0.95mm 3.05mm 3.05mm 0.95mm 5.5 V +85 °C
RS Stock No. 189-7231
Mfr. Part No.DS1371U+
HK$21.857
Each (In a Tube of 50)
units
Calendar, NV RAM Binary Binary 3B 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. 189-8655
Mfr. Part No.DS1305E+
HK$49.36
Each (In a Pack of 2)
units
Alarm, Calendar DW:DM:M:Y HH:MM:SS 96B Serial-SPI Surface Mount TSSOP 20 6.5 x 4.4 x 0.9mm 6.5mm 4.4mm 0.9mm 5.5 V +70 °C
RS Stock No. 809-1420
Mfr. Part No.M41T81M6F
HK$22.912
Each (In a Pack of 5)
units
Alarm Binary HH:MM:SS:hh 20B Serial Surface Mount SOIC 8 5 x 4 x 1.25mm 5mm 4mm 1.25mm 5.5 V +85 °C
RS Stock No. 190-5166
Mfr. Part No.DS3232SN#T&R
HK$81.67
Each
units
Alarm, SRAM DM:M:DW:Y SS:MM:HH 236B Serial-I2C Surface Mount SO 20 13 x 7.6 x 2.35mm 13mm 7.6mm 2.35mm 5.5 V +85 °C
RS Stock No. 919-6337
Mfr. Part No.M48T18-100PC1
HK$179.913
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. 103-9921
Mfr. Part No.DS3234SN#
HK$72.324
Each (In a Tube of 36)
units
Battery Backup, Calendar, SRAM DW:DM:M:Y HH:MM:SS 256B Serial-SPI Surface Mount SOIC 20 13 x 7.6 x 2.35mm 13mm 7.6mm 2.35mm 5.5 V +85 °C
RS Stock No. 191-6881
Mfr. Part No.DS1050Z-001+
HK$21.156
Each (In a Pack of 5)
units
Clock DM:M:DM:Y SS:MM:HH - - Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 761-9755
Mfr. Part No.DS1302ZN+T&R
HK$37.02
Each
units
Battery Backup, Calendar, NV RAM YY:MM:DD HH:MM:SS 31B Serial-3 Wire Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 727-5743
Mfr. Part No.PCA8565TS/1,118
BrandNXP
HK$14.10
Each (In a Pack of 2)
units
Alarm, Calendar, Interrupt, Timer DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount TSSOP 8 3.1 x 3.1 x 0.95mm 3.1mm 3.1mm 0.95mm 5.5 V +125 °C
RS Stock No. 190-4750
Mfr. Part No.DS3231SN#T&R
HK$50.222
Each (On a Reel of 1000)
units
Real Time Clock DM:M:DW:Y SS:MM:HH 236B Serial-I2C Surface Mount SO 16 10.5 x 7.6 x 2.35mm 10.5mm 7.6mm 2.35mm 5.5 V +85 °C
RS Stock No. 518-429
Mfr. Part No.ISL1208IB8Z
BrandIntersil
HK$23.856
Each (In a Pack of 5)
units
Alarm, Battery Backup, Calendar DW:DM:M:Y HH:MM:SS 2B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 624-8466
Mfr. Part No.M48T35Y-70PC1
HK$243.89
Each
units
Battery Backup, Calendar, Chip Deselect, Switch Over, Write Protection DW:DM:M:Y HH:MM:SS 32768B 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. 191-3234
Mfr. Part No.DS1337U+T&R
HK$11.804
Each (On a Reel of 3000)
units
Real Time Clock D:D:M:Y SS:MM:HH - Serial-I2C Surface Mount μSOP 8 3.1 x 0.65 x 0.95mm 3.1mm 0.65mm 0.95mm 5.5 V +85 °C
RS Stock No. 912-6738
Mfr. Part No.MCP79411-I/SN
BrandMicrochip
HK$8.718
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. 667-6252
Mfr. Part No.Q41856471000111
BrandEPSON
HK$34.42
Each
units
Alarm, Calendar, Timer DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount VSOJ 20 - 7mm 5.4mm - 5.5 V +85 °C
RS Stock No. 188-9342
Mfr. Part No.M41T80M6F
HK$19.13
Each
units
Alarm, Calendar Binary, D:D:M:Y:C - - Serial-2 Wire, Serial-I2C Surface Mount SO 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C