ISL12008 datasheet(8/19 Pages) INTERSIL

Numer części	ISL12008

Szczegółowy opis	I2C Real Time Clock with Battery Backup

Download	19 Pages

Scroll/Zoom	100%

Producent	INTERSIL [Intersil Corporation]

Strona internetowa	http://www.intersil.com/cda/home

Logo

8 / 19 page

8

FN6690.1

September 26, 2008

The I2C bus is deactivated in battery backup mode to provide

lower power. Aside from this, all RTC functions are

operational during battery backup mode. Except for SCL and

SDA, all the inputs and outputs of the ISL12008 are active

during battery backup mode unless disabled via the control

register.

Power Failure Detection

The ISL12008 provides a Real Time Clock Failure Bit (RTCF,

address 0Bh) to detect total power failure. It allows users to

determine if the device has powered up after having lost all

power to the device (both VDD and VBAT).

Low Power Mode

The normal power switching of the ISL12008 is designed to

switch into battery backup mode only if the VDD power is

lost. This will ensure that the device can accept a wide range

of backup voltages from many types of sources while reliably

switching into backup mode. Another mode, called Low

Power Mode, is available to allow direct switching from VDD

to VBAT without requiring VDD to drop below VTRIP. Since

the additional monitoring of VDD vs VTRIP is no longer

needed, that circuitry is shut down and less power is used

while operating from VDD. Power savings are typically

600nA at VDD = 5V. Low Power Mode is activated via the

LPMODE bit (address 08h, bit 5) in the control and status

registers.

Low Power Mode is useful in systems where VDD is normally

higher than VBAT at all times. The device will switch from

VDD to VBAT when VDD drops below VBAT, with about 50mV

of hysteresis to prevent any switchback of VDD after

switchover. In a system with a VDD = 5V and backup lithium

battery of VBAT = 3V, Low Power Mode can be used.

However, it is not recommended to use Low Power Mode in

a system with VDD = 3.3V ±10%, VBAT ≥ 3.0V, and when

there is a finite I-R voltage drop in the VDD line.

InterSeal™ and ReSeal™ Battery Saver

The ISL12008 has the InterSeal Battery Saver, which

prevents initial battery current drain before it is first used. For

example, battery-backed RTCs are commonly packaged on

a board with a battery connected. In order to preserve

battery life, the ISL12008 will not draw any power from the

battery source until after the device is first powered up from

the VDD source. Thereafter, the device will switchover to

battery backup mode whenever VDD power is lost.

The ISL12008 has the ReSeal function, which allows the

device to enter into the InterSeal Battery Saver mode after

manufacture testing for board functionality. To use the

ReSeal function, simply set RESEAL bit to “1” (address 0Bh)

after the testing is completed. It will enable the InterSeal

Battery Saver mode and prevents battery current drain

before it is first used.

Real Time Clock Operation

The Real Time Clock (RTC) uses an external 32.768kHz

quartz crystal to maintain an accurate internal representation

of sub-second, second, minute, hour, day of week, date,

month, and year. The RTC has leap-year correction, and

corrects for months having fewer than 31 days. The RTC

hours is in 24-hour format only. When the ISL12008 powers

up after the loss of both VDD and VBAT, the RTC will not

begin incrementing until at least one byte is written to the

RTC registers. The sub-second register will increment after

power up but it will not casue the other RTC registers to

incremnent until at least one byte is written to the RTC

registers.

Accuracy of the Real Time Clock

The accuracy of the Real Time Clock depends on the

frequency of the quartz crystal that is used as the time base

for the RTC. Since the resonant frequency of a crystal is

temperature dependent, the RTC performance will also be

dependent upon temperature. The frequency deviation of

the crystal is a function of the turnover temperature of the

crystal from the crystal’s nominal frequency. For example, a

~20ppm frequency deviation translates into an accuracy of

~1 minute per month. These parameters are available from

the crystal manufacturer. The ISL12008 provides on-chip

crystal compensation networks to adjust load capacitance to

tune oscillator frequency from -97.0695ppm to

+206.139ppm. For more detailed information. See

“Application Section” on page 16.

I2C Serial Interface

The ISL12008 has an I2C serial bus interface that provides

access to the control and status registers and the user

SRAM. The I2C serial interface is compatible with other

industry I2C serial bus protocols using a bidirectional data

signal (SDA) and a clock signal (SCL).

Oscillator Compensation

The ISL12008 provides the option of timing correction due to

temperature variation of the crystal oscillator for either

manufacturing calibration or active calibration. The total

possible compensation is typically -97.0695ppm to

+206.139ppm. Two compensation mechanisms that are

available are as follows:

1. An analog trimming (ATR) register that can be used to

adjust individual on-chip digital capacitors for oscillator

capacitance trimming. The individual digital capacitor is

selectable from a range of 4.5pF to 20.25pF (based upon

32.758kHz). This translates to a calculated

compensation of approximately -34ppm to +80ppm (see

ATR description on page 16).

2. A digital trimming register (DTR) that can be used to

adjust the timing counter by -63.0696ppm to

+126.139ppm (see DTR description on page 16).

ISL12008

Podobny numer części - ISL12008

Producent	Numer części	Arkusz danych	Szczegółowy opis
Intersil Corporation	ISL12008	768Kb / 6P	High-Accuracy RTC Modules, Feature-Rich RTCs
Intersil Corporation	ISL12008	9Mb / 44P	Providing high-performance solutions for every link in the signal chain
Renesas Technology Corp	ISL12008	791Kb / 19P	Low Power RTC with Battery ReSeal??Function
	ISL12008IB8Z	791Kb / 19P	Low Power RTC with Battery ReSeal??Function
	ISL12008IB8Z-T	791Kb / 19P	Low Power RTC with Battery ReSeal??Function

More results

Podobny opis - ISL12008

Producent	Numer części	Arkusz danych	Szczegółowy opis
Maxim Integrated Produc...	DS3231M	1Mb / 20P	5ppm, I2C Real-Time Clock Battery Backup for Continuous Timekeeping Rev 1; 5/11
Cymbet Corporation	DS-72-34	1Mb / 18P	I2C Real-Time Clock/Calendar with Integrated Backup Power
Cymbet Corporation	CBC34803	511Kb / 9P	I2C Real-Time Clock/Calendar with Integrated Backup Power
Epson Company	RX8130CE	362Kb / 2P	REAL TIME CLOCK MODULE (I2C-Bus) Build in backup battery charge control function
Microchip Technology	MCP7940N	727Kb / 58P	Battery-Backed I2C Real-Time Clock/Calendar with SRAM 09/14/21
ARTSCHIP ELECTRONICS CO...	DS1307	249Kb / 14P	I2C Real-Time Clock
STMicroelectronics	M41T83	1,001Kb / 62P	Serial I2C bus real-time clock (RTC) with battery switchover
RICOH electronics devic...	R2061K	723Kb / 56P	wire interface Real-Time Clock ICs with Battery Backup switch-over Function
STMicroelectronics	M41T00CAP	385Kb / 27P	Serial access real-time clock (RTC) with integral backup battery and crystal
Dallas Semiconductor	DS1339	279Kb / 18P	I2C Serial Real-Time Clock

More results

ISL12008 Arkusz danych(PDF) 8 Page - Intersil Corporation

ISL12008 Arkusz danych(HTML) 8 Page - Intersil Corporation

Podobny numer części - ISL12008

Podobny opis - ISL12008

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Arkusz danych Pobierz

Link URL