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ISL12021IVZ 数据表(PDF) 6 Page - Intersil Corporation |
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ISL12021IVZ 数据表(HTML) 6 Page - Intersil Corporation |
6 / 24 page 6 FN6451.0 March 30, 2007 General Description The ISL12021 device is a low power real time clock (RTC) with embedded temperature sensors. It contains crystal frequency compensation circuitry over the operating temperature range, clock/calendar, power fail and low battery monitors, brown out indicator with separate (LVRSET) reset pin, 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 ISL12021 could be programmed for automatic Daylight Saving Time (DST) adjustment by entering local DST information. The ISL12021’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 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 Cap with automatic switchover from VDD to VBAT. The ISL12021 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 VBATM registers. The ISL12021 offers a “Brown Out” alarm once the VDD falls below a pre-selected trip level. This allows system CPU to save vital information to memory before complete power loss. There are six VDD levels that could be selected for initiation of brown out 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 21 for recommended crystal). The ISL12021 allows the user to input via I2C serial bus the temperature variation profiles of crystals not listed in the “Application Section” on page 21. This oscillator compensation network can also be used to calibrate the initial crystal timing accuracy 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. This pin can be connected to a battery, a Super Capacitor or tied to ground if not used. See the Battery Monitor parameter in the DC Operating Characteristics-RTC on page 3. IRQ (Interrupt Output) This pin provides an interrupt signal output. This signal notifies a host processor that an alarm has occurred and requests action. It is an open drain active low output. Once triggered, the output will stay low until the Alarm status register bit is reset or, if the autoreset function is used, a read is performed to the status register. FOUT (Frequency Output) This pin outputs a clock signal which is related to the crystal frequency. The frequency output is user selectable and enabled via the I2C bus. It is an open drain output. Serial Clock (SCL) The SCL input is used to clock all serial data into and out of the device. The input buffer on this pin is always active (not gated). It is disabled when the backup power supply on the VBAT pin is activated to minimize power consumption. FIGURE 1. STANDARD OUTPUT LOAD FOR TESTING THE DEVICE WITH VDD = 5.0V SDA, IRQ and FOUT 1533 Ω 100pF 5.0V FOR VOL= 0.4V AND IOL = 3mA EQUIVALENT AC OUTPUT LOAD CIRCUIT FOR VDD = 5V FIGURE 2. RECOMMENDED CRYSTAL CONNECTION X1 X2 ISL12021 |
类似零件编号 - ISL12021IVZ |
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类似说明 - ISL12021IVZ |
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