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. 189-7242
Mfr. Part No.DS1685EN-3+
HK$59.483
Each (In a Tube of 62)
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 +85 °C
RS Stock No. 189-8382
Mfr. Part No.DS1747-70+
HK$477.32
Each
units
Calendar YY:MM:DD HH:MM:SS 512 x 8bit Parallel Through Hole EDIP 32 44.2 x 18.8 x 10.92mm 44.2mm 18.8mm 10.92mm 0.8 V, 5.3 V +70 °C
RS Stock No. 189-7236
Mfr. Part No.DS1390U-33+
HK$29.736
Each (In a Tube of 50)
units
Battery Backup, Calendar, NV RAM DW:DM:M:Y HH:MM:SS - Serial-SPI Surface Mount μSOP 10 3.05 x 3.05 x 0.95mm 3.05mm 3.05mm 0.95mm 5.5 V +85 °C
RS Stock No. 190-5176
Mfr. Part No.DS3234S#T&R
HK$69.98
Each
units
SRAM D:D:M:Y SS:MM:HH 256B - Surface Mount SO 20 13 x 7.6 x 2.35mm 13mm 7.6mm 2.35mm 5.5 V +70 °C
RS Stock No. 191-3286
Mfr. Part No.DS1339AU+
HK$30.686
Each (In a Tube of 50)
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. 165-2097
Mfr. Part No.MCP79511-I/MS
BrandMicrochip
HK$9.686
Each (In a Tube of 100)
units
Calendar D:W:M:Y, LY HH, HS, MM, SS 64B Serial-SPI Surface Mount MSOP 10 3 x 3 x 0.95mm 3mm 3mm 0.95mm 3.6 V +85 °C
RS Stock No. 729-3221
Mfr. Part No.RV-3049-C2-TB-008
HK$139.44
Each
units
Battery Backup, Calendar, NV RAM DW:DM:M:Y HH:MM:SS 8B Serial-SPI Surface Mount SON 10 5 x 3.2 x 1.2mm 5mm 3.2mm 1.2mm 5.5 V +125 °C
RS Stock No. 189-8698
Mfr. Part No.DS1337+
HK$28.666
Each (In a Pack of 5)
units
Clock DD:M:Y SS:MM:HH 7B 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. 189-7226
Mfr. Part No.DS1339C-33#
HK$47.755
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. 196-9062
Mfr. Part No.ISL12020MIRZ
HK$51.755
Each (In a Tube of 53)
units
- DW:DM:M:Y HH:MM:SS 128B - - DFN 20 - - - - - -
RS Stock No. 829-0355
Mfr. Part No.M41T81SM6F
HK$23.814
Each (In a Pack of 5)
units
Calendar D:D:M:Y:C HH:MM:SS:HSS 20B Serial-I2C Surface Mount SOIC 8 5 x 4 x 1.5mm 5mm 4mm 1.5mm 5.5 V +85 °C
RS Stock No. 732-7327
Mfr. Part No.DS1305EN+
HK$55.26
Each
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. 189-8385
Mfr. Part No.DS17887-5+
HK$174.02
Each
units
Alarm, Calendar YY:MM:DD HH:MM:SS 114B Multiplexed Through Hole EDIP 24 38.1 x 18.29 x 10.67mm 38.1mm 18.29mm 10.67mm 5.5 V +70 °C
RS Stock No. 171-0197
Mfr. Part No.AB1815-T3
BrandAbracon
HK$7.644
Each (On a Reel of 3000)
units
- - - - - Surface Mount 16-VFQFN - - - - - - 85 °C
RS Stock No. 166-0790
Mfr. Part No.M41T65Q6F
HK$9.168
Each (On a Reel of 3000)
units
Alarm, Battery Backup, Calendar, Watchdog Timer DW:DM:M:Y HH:MM:SS:hh 16B Serial-I2C Surface Mount QFN 16 3 x 3 x 0.88mm 3mm 3mm 0.88mm 4.4 V +85 °C
RS Stock No. 190-4738
Mfr. Part No.DS1347T+T&R
HK$14.183
Each (On a Reel of 2500)
units
Alarm, Real Time Clock, SRAM DM:M:Y:C SS:MM:HH - - Surface Mount TDFN-EP 8 3.1 x 3.1 x 0.8mm 3.1mm 3.1mm 0.8mm 5.5 V +85 °C
RS Stock No. 185-1011
Mfr. Part No.BU9873FVT-GE2
BrandROHM
HK$7.424
Each (In a Pack of 10)
units
Real Time Clock YY:MM:DD:dd HH:MM:SS - Serial-I2C Surface Mount TSSOP 8 4.4 x 3 x 1mm 4.4mm 3mm 1mm 5.5 V +85 °C
RS Stock No. 171-1639
Mfr. Part No.RV-3029-C2-TA-006
HK$77.593
Each (On a Tape of 100)
units
Battery Backup, Calendar, RAM DW:DM:M:Y HH:MM:SS 8B Serial-I2C Surface Mount SON 10 5 x 3.2 x 1.2mm 5mm 3.2mm 1.2mm 5.5 V +85 °C
RS Stock No. 667-6287
Mfr. Part No.Q418564C2000511
BrandEPSON
HK$31.50
Each
units
Alarm, Calendar, Timer DW:DM:M:Y HH:MM:SS - Serial-I2C Surface Mount VSOJ 12 - 3.6mm 2.4mm - 5.5 V +85 °C
RS Stock No. 165-9386
Mfr. Part No.DS1340C-33#
HK$47.457
Each (In a Tube of 46)
units
Trickle Charger DD:M:Y SS:MM:HH 7B Serial-I2C Surface Mount SOIC 16 18.1 x 7.6 x 2.35mm 18.1mm 7.6mm 2.35mm 5.5 V +85 °C