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. 923-5794
Mfr. Part No.DS1305EN+
HK$45.644
Each (In a Tube of 74)
units
Battery Backup, Calendar, NV RAM DW:DM:M:Y HH:MM:SS 96B Serial-SPI Surface Mount TSSOP 20 6.6 x 4.5 x 0.95mm 6.6mm 4.5mm 0.95mm 5.5 V +85 °C
RS Stock No. 188-9366
Mfr. Part No.M41ST85WMX6TR
HK$57.64
Each
units
Alarm, Battery Backup, Calendar, Watchdog Timer Binary, D:D:M:Y:C - 64bit - Surface Mount SOX 28 18.01 x 7.67 x 2.39mm 18.01mm 7.67mm 2.39mm 3.6 V +85 °C
RS Stock No. 189-8496
Mfr. Part No.DS1307N+
HK$36.05
Each (In a Pack of 2)
units
Clock DM:M:DW:Y SS:MM:HH 56B Serial-I2C Through Hole PDIP 8 9.91 x 7.87 x 4.45mm 9.91mm 7.87mm 4.45mm 5.5 V +85 °C
RS Stock No. 813-5781
Mfr. Part No.RV-3049-C3-TB-QA-Opt.A
HK$68.87
Each
units
Alarm, Battery Backup, Calendar, Clock D:W:M:Y HH:MM:SS 8B Serial-4 Wire, Serial-SPI Surface Mount SON 10 3.7 x 2.5 x 0.9mm 3.7mm 2.5mm 0.9mm 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. 191-3677
Mfr. Part No.DS1308U-33+
HK$36.815
Each (In a Pack of 2)
units
NV SRAM, Real Time Clock DM:M:DW: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. 189-7252
Mfr. Part No.DS3232MZ+
HK$52.18
Each (In a Tube of 100)
units
Calendar DD:M:Y SS:MM:HH 236B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 4.5 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. 191-5742
Mfr. Part No.DS1687-3+
HK$127.53
Each
units
NV SRAM, Real Time Clock - - 242B Multiplexed Surface Mount EDIP 24 1.34 x 0.72 x 0.37mm 1.34mm 0.72mm 0.37mm 5.5 V +70 °C
RS Stock No. 813-5775
Mfr. Part No.RV-3029-C3-TB-QA-Opt.B
HK$55.24
Each
units
Alarm, Battery Backup, Calendar, Clock D:W:M:Y HH:MM:SS 8B Serial-2 Wire, Serial-I2C Surface Mount SON 10 3.7 x 2.5 x 0.9mm 3.7mm 2.5mm 0.9mm 5.5 V +85 °C
RS Stock No. 177-0305
Mfr. Part No.MCP7940N-E/SN
BrandMicrochip
HK$6.091
Each (In a Tube of 100)
units
- D:M:Y, DW HH:MM:SS - Serial-I2C Surface Mount SOIC 8 4.9 x 3.9 x 1.5mm 4.9mm 3.9mm 1.5mm 5.5 V +125 °C
RS Stock No. 192-1449
Mfr. Part No.DS1685E-3+
HK$53.50
Each (In a Pack of 2)
units
Alarm, Calendar YY:MM:DD HH:MM:SS 128B Multiplexed Surface Mount TSSOP 24 7.9 x 4.5 x 0.95mm 7.9mm 4.5mm 0.95mm 5 V +70 °C
RS Stock No. 714-0855
Mfr. Part No.M41T00SM6F
HK$23.27
Each
units
- DW:DM:M:Y HH:MM:SS 8B Serial-2 Wire, Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.25mm 5mm 4mm 1.25mm 5.5 V +85 °C
RS Stock No. 189-8635
Mfr. Part No.DS1337S+
HK$26.596
Each (In a Pack of 5)
units
Calendar 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. 540-4750
Mfr. Part No.DS1302Z+
HK$33.87
Each
units
Calendar, NV RAM, Trickle Charger DW:DM:M:Y HH:MM:SS 31B Serial Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +70 °C
RS Stock No. 169-8140
Mfr. Part No.Q41457451000200
BrandEPSON
HK$20.931
Each (On a Reel of 250)
units
Alarm, Calendar, Timer - - - Serial Surface Mount SOP 14 5 x 10.1 x 3.2mm 5mm 10.1mm 3.2mm 5.5 V +85 °C
RS Stock No. 880-5349
Mfr. Part No.M41T94MQ6F
HK$31.198
Each (In a Pack of 5)
units
Alarm, Battery Backup, Interrupt, NVRAM, Real Time Clock, Watchdog Timer Binary, D:D:M:Y:C Binary, HH:MM:SS 44B Serial-SPI Surface Mount SOIC 16 10 x 4 x 1.6mm 10mm 4mm 1.6mm 5.5 V +85 °C
RS Stock No. 511-103
Mfr. Part No.PCF8563TS/4,118
BrandNXP
HK$14.424
Each (In a Pack of 5)
units
Alarm, Battery Backup, Calendar, Watchdog 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 +85 °C
RS Stock No. 190-4737
Mfr. Part No.DS1340Z-33+T&R
HK$14.116
Each (On a Reel of 2500)
units
Real Time Clock, Trickle Charger D:D:M:Y SS:MM:HH - Serial-I2C Surface Mount SO 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 196-9066
Mfr. Part No.ISL12057IUZ
HK$18.69
Each (In a Tube of 50)
units
- DW:DM:M:Y HH:MM:SS - - - MSOP 8 - - - - - -