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ISL12022IBZ Datasheet(PDF) 8 Page - Intersil Corporation |
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ISL12022IBZ Datasheet(HTML) 8 Page - Intersil Corporation |
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8 / 28 page  8 FN6659.2 June 23, 2009 General Description The ISL12022 device is a low power real time clock (RTCs) with embedded temperature sensors. It contains crystal frequency compensation circuitry over the operating temperature range, clock/calendar, power fail and low battery monitors, brownout indicator, 1 periodic or polled alarm, intelligent battery-backup switching and 128 Bytes of battery-backed user SRAM. The oscillator uses an external, low cost 32.768kHz crystal. The real time clock tracks time with separate registers for hours, minutes and seconds. The device has calendar registers for date, month, year and day of the week. The calendar is accurate through 2099, with automatic leap year correction. In addition, the ISL12022 can be programmed for automatic Daylight Savings Time (DST) adjustment by entering local DST information. The ISL12022’s alarm can be set to any clock/calendar value for a match, for example, every minute, every Tuesday or at 5:23 AM on March 21. The alarm status is available by checking the Status Register, or the device can be configured to provide a hardware interrupt via the IRQ/FOUT pin. There is a repeat mode for the alarm allowing a periodic interrupt every minute, every hour, every day, etc. The device also offers a backup power input pin. This VBAT pin allows the device to be backed up by battery or super capacitor with automatic switchover from VDD to VBAT. The ISL12022 device is specified for VDD = 2.7V to 5.5V and the clock/calendar portion of the device remains fully operational in battery-backup mode down to 1.8V (Standby Mode). The VBAT level is monitored and reported against preselected levels. The first report is registered when the VBAT level falls below 85% of nominal level, the second level is set for 75%. Battery levels are stored in PWR_VBAT registers. The ISL12022 offers a “Brownout” alarm once the VDD falls below a pre-selected trip level. This allows system Micro to save vital information to memory before complete power loss. There are six VDD levels that could be selected for initiation of the Brownout alarm. Pin Descriptions X1, X2 The X1 and X2 pins are the input and output, respectively, of an inverting amplifier. An external 32.768kHz quartz crystal is used with the device to supply a timebase for the real time clock. Internal compensation circuitry with internal temperature sensor provides frequency corrections for selected popular crystals to ±5ppm over the operating temperature range from -40°C to +85°C. (See “Application Section” on page 25 for recommended crystal). The ISL12022 allows the user to input via I2C serial bus the temperature variation profile of an individual crystal. The oscillator compensation network can also be used to calibrate the initial crystal timing accuracy to less than 1ppm error at room temperature. The device can also be driven directly from a 32.768kHz source at pin X1. VBAT This input provides a backup supply voltage to the device. VBAT supplies power to the device in the event that the VDD supply fails. Device power will automatically switch to the VBAT input when VDD drops below the switchover trip level (VTRIP). This pin can be connected to a battery, a super capacitor or tied to ground if not used. IRQ/FOUT (Interrupt Output/Frequency Output) This dual function pin can be used as an interrupt or frequency output pin. The IRQ/FOUT mode is selected via the frequency out control bits of the control/status register. It is an open drain output. FIGURE 8. IDD WITH TSE = 1 vs TEMPERATURE FIGURE 9. IBAT with TSE = 1, BTSE = 1 vs TEMPERATURE Typical Performance Curves Temperature is +25°C unless otherwise specified. (Continued) 40 50 60 70 80 90 100 110 -40 -20 0 20 406080 TEMPERATURE (°C) VBAT = 2.7V VDD = 3.3V VDD = 5.5V 20 30 40 50 60 70 80 90 100 110 -40 -20 0 20 406080 TEMPERATURE (°C) VBAT = 1.8V VBAT = 3.0V VBAT = 5.5V FIGURE 10. RECOMMENDED CRYSTAL CONNECTION X1 X2 ISL12022 |
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