Real-Time-Clocks: Never lose track of time!

New Real-Time-clocks break the 150nA Time keeping barrier and allow for long backup times. Our featured suppliers IDT, NXP and ST Microelectronics offer a vast selection of Real Time Clocks with ultra low backup power and several additional functions.

Adding a super capacitor or battery from Panasonic allows users to reach the maximum time keeping period.

Applications

• Smart  meters
• Industrial measurement applications
• Building Automation
• Gaming machines
• Alarm systems
• Token for access control, secure applications

RTC Backup using Capacitors

Capacitors are staring to replace batteries for RTC backup, as batteries discharge and age over time and the exchange of the battery is often not an option. So called Gold Caps can store enough power to brigde power outage over many days while offering the advantage of virtually indefinite number of recharge cycles. New technologies like Thin-Film-Batteries offer a solution in between capacitors and primary batteries. But due to their high price and the necessary charging circuit, these solutions are mostly used in Energy Harvesting for autonomous sensor applications.

A simple circuit can be used to make sure the Backup Capacitor is charged to its maximum while adjusting the RTC supply voltage to the necessary level. For estimation of the the hold time for the RTC, one has to take the capacitor leakage current into account. This often exceeds the RTC time keeping current, especially for the above mentioned new generation RTCs with time keeping currents as low as 110nAmps!

For certain mobile applications running at 3.3V Operating Voltage, Panasonic has introduced the new EN-Series of Coin Type Gold Capacitors with leakage current of typically below 200nA and very small SMD packages.

The hold time can be calculated using the formula: T=C*(Vmax - Vmin)/IL 

Wheras C is the capacitance in Farads, Vmax is the Operating Voltage, Vmin the minimum Voltage at which time keeping still works and I (L) is the RTC time keeping current plus the capacitor leakage current in nanoamps.

Product Highlights

M41T62 – our smallest RTC in a LLC8 ceramic package measuring only 1.5 mm x 3.2 mm with embedded 32kHz crystal!
Sample request

M41ST87W – our all in one RTC for secure applications featuring a unique serial number, tamper detection and automatic RAM clear!
Sample request

PCF2123 – our RTC with lowest time keeping current and widest operating voltage. This one runs with only typically 110nAmps!
Sample request

PCF2129A – our most exact RTC with embedded crystal and temperature compensation, reaching  3ppm accuracy over the whole operating temperature range!
Sample request

Product Table RTC

Device	Supplier	Interface	int RAM	Typ. Time Keeping Current nA	Time V Max	Time V Min	Package	Features
PCF2123	NXP	SPI 8MHz	---	110	5,5	1,1	HVQFN16, TSSOP14	Progr Alarm with IRQ, Watchdog Funct.
PCF8523	NXP	I²C 1MHz	---	150	5,5	1	SO8, HVSON8, TSSOP14	Dual IRQ Out, Progr Alarm, BAT backup with switchover
PCF2127A	NXP	SPI 6,5MHz I²C 400kHz	512 Bytes	650	4,2	1,2	SO20	Integrated temperature compensated crystal Oszillator with int. Capacitors (± 3ppm accuracy from -15° to +60°C)
PCF2129A	NXP	SPI 6,5MHz I²C 400kHz	---	650	4,2	1,2	SO20	Integrated temperature compensated crystal Oszillator with int. Capacitors (± 3ppm accuracy from -15° to +60°C)
IDT1337G	IDT	I²C 400kHz		425	5,5	1,8	SO8, TSSOP8, VFQFN16	Two programmable Alarms, Square Wave output
IDT1338-18	IDT	I²C 400kHz	56 Bytes	800	5,5	1,8	SO8, SO16, TSSOP8	Integr. Crystal for SO16 Version, Bat backup with switchover, Progr. Square Wave Output
IDT1339	IDT	I²C 400kHz	56 Bytes	400	5,5	1,8	SO8, SO16, TSSOP8	Trickle Charge Capability, 2 progr. Alarms, Integr. Crystal for SO16 Version, Progr Square Wave Out
M41T62	ST	I²C 400kHz	---	350	4,4	1	LCC8, VFQFPN16	Progr Alarm, Square Wave Output, Watchdog Timer, Osc. Fail Detect
M41ST85W	ST	I²C 400kHz	44 Bytes	400	3,5	2,5	SO28	Progr Alarm, Square Wave Output, Batt Switchover, Watchdog Timer, POR, LVD, Power Fail Comparator, Reset Inputs
M41ST87W	ST	I²C 400kHz	128 Bytes	500	3,6	2,7	SO28, SSOP20	Progr Alarm, Square Wave Output, Batt Switchover, Watchdog Timer, POR, LVD, Power Fail Comparator, Reset Inputs, Osc. Fail Detect
M41T93	ST	SPI 10MHz	12 Bytes	365	5,5	2,4	SO18, VFQFPN16	Progr Alarm, Square Wave Output, Batt Switchover, Watchdog Timer, POR, LVD
M41T94	ST	SPI	44 Bytes	400	5,5	2,5	SO16, SO28	Progr Alarm, Square Wave Output, Batt Switchover, Watchdog Timer, POR, LVD, Reset Inputs, Battery Low Detect
M41T66	ST	I²C 400kHz	---	350	4,4	1,3	VFQFPN16	Progr Alarm, Square Wave Output, Watchdog Timer, Osc. Fail Detect
M41T11	ST	I²C	56 Bytes	800	5,5	2	SO8, SO28	Battery Switchover
M41T0	ST	I²C 400kHz	---	900	5,5	2	SO8	Osc. Fail Detect
M41T00AUD	ST	I²C 400kHz	---	400	3,6	1,7	DFN16	Osc. Fail Detect, Battery Switchover, Tone Generator with Output Amplifier

 

Product Table Gold Caps

Device (Datasheet)	Vendor	Type	Cap (F)	Max Op. V.	Leakage nA
EECS5R5H155	Panasonic	SG-Series	1,5	5,5	500
EECS5R5H105	Panasonic	SG-Series	1	5,5	500
EECS5R5H474	Panasonic	SG-Series	0,47	5,5	500
EECF5R5U155	Panasonic	NF- Series	1,5	5,5	500
EECF5R5U105	Panasonic	NF- Series	1	5,5	500
EECF5R5U474	Panasonic	NF- Series	0,47	5,5	500
EECF5R5U224	Panasonic	NF- Series	0,22	5,5	500
EECF5R5U104	Panasonic	NF- Series	0,1	5,5	500
EECS0HD334	Panasonic	SD-Series	0,33	5,5	300
EECS0HD224	Panasonic	SD-Series	0,22	5,5	300
EECS0HD104	Panasonic	SD-Series	0,1	5,5	300
EECS0HD473	Panasonic	SD-Series	0,047	5,5	300
EECS0HD223	Panasonic	SD-Series	0,022	5,5	300
EECEN0F224	Panasonic	EN-Series	0,22	3,3	200