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ISL12022MA Datasheet(PDF) 11 Page - Intersil Corporation |
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ISL12022MA Datasheet(HTML) 11 Page - Intersil Corporation |
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11 / 29 page  ISL12022MA 11 FN7575.1 July 9, 2010 Functional Description Power Control Operation The power control circuit accepts a VDD and a VBAT input. Many types of batteries can be used with Intersil RTC products. For example, 3.0V or 3.6V Lithium batteries are appropriate, and battery sizes are available that can power the ISL12022MA for up to 10 years. Another option is to use a supercapacitor for applications where VDD is interrupted for up to a month. See the “Application Section” on page 26 for more information. Normal Mode (VDD) to Battery Backup Mode (VBAT) To transition from the VDD to VBAT mode, both of the following conditions must be met: Condition 1: VDD < VBAT - VBATHYS where VBATHYS ≈ 50mV Condition 2: VDD < VTRIP where VTRIP ≈ 2.2V Battery Backup Mode (VBAT) to Normal Mode (VDD) The ISL12022MA device will switch from the VBAT to VDD mode when one of the following conditions occurs: Condition 1: VDD > VBAT + VBATHYS where VBATHYS ≈ 50mV Condition 2: VDD > VTRIP + VTRIPHYS where VTRIPHYS ≈ 30mV These power control situations are illustrated in Figures 12 and 13. The I2C bus is deactivated in battery backup mode to reduce power consumption. Aside from this, all RTC functions are operational during battery backup mode. Except for SCL and SDA, all the inputs and outputs of the ISL12022MA are active during battery backup mode unless disabled via the control register. The device Time Stamps the switchover from VDD to VBAT and VBAT to VDD, and the time is stored in tSV2B and tSB2V registers respectively. If multiple VDD power-down sequences occur before the status is read, the earliest VDD to VBAT power-down time is stored and the most recent VBAT to VDD time is stored. Temperature conversion and compensation can be enabled in battery backup mode. Bit BTSE in the BETA register controls this operation, as described in “BETA Register (BETA)” on page 19. Power Failure Detection The ISL12022MA provides a Real Time Clock Failure Bit (RTCF) 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). Brownout Detection The ISL12022MA monitors the VDD level continuously and provides warning if the VDD level drops below prescribed levels. There are six (6) levels that can be selected for the trip level. These values are 85% below popular VDD levels. The LVDD bit in the Status Register will be set to “1” when brownout is detected. Note that the I2C serial bus remains active unless the Battery VTRIP levels are reached. Battery Level Monitor The ISL12022MA has a built-in warning feature once the backup battery level drops first to 85% and then to 75% of the battery’s nominal VBAT level. When the battery voltage drops to between 85% and 75%, the LBAT85 bit is set in the status register. When the level drops below 75%, both LBAT85 and LBAT75 bits are set in the status register. The battery level monitor is not functional in battery backup mode. In order to read the monitor bits after powering up VDD, instigate a battery level measurement by setting the TSE bit to "1" (BETA register), and then read the bits. There is a Battery Time Stamp Function available. Once the VDD is low enough to enable switchover to the battery, the RTC time/date are written into the TSV2B register. This information can be read from the TSV2B registers to discover the point in time of the VDD power-down. If there are multiple power-down cycles VBAT - VBATHYS VBAT VBAT + VBATHYS BATTERY BACKUP MODE VDD VTRIP 2.2V 1.8V FIGURE 12. BATTERY SWITCHOVER WHEN VBAT < VTRIP FIGURE 13. BATTERY SWITCHOVER WHEN VBAT > VTRIP VTRIP VBAT VTRIP + VTRIPHYS BATTERY BACKUP MODE VDD VTRIP 3.0V 2.2V |
Similar Part No. - ISL12022MA_10 |
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Similar Description - ISL12022MA_10 |
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