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ADT7470 Arkusz danych(PDF) 7 Page - Analog Devices |
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ADT7470 Arkusz danych(HTML) 7 Page - Analog Devices |
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7 / 40 page  Data Sheet ADT7470 Rev. E | Page 7 of 40 FUNCTIONAL DESCRIPTION GENERAL DESCRIPTION The ADT7470 is a multichannel, pulse-width modulation (PWM) fan controller and monitor for any system requiring monitoring and cooling. The device communicates with the system via a serial system management bus. The device has a single address line for address selection (Pin 11), a serial data line for reading and writing addresses and data (Pin 16), and an input line for the serial clock (Pin 1). All control and programming functions of the ADT7470 are performed over the serial bus, which supports both SMBus and fast I2C speci- fications. In addition, an SMBALERT interrupt output is provided to indicate out-of-limit conditions. When the ADT7470 monitoring sequence is started, it cycles through each fan tach input to measure fan speed. Measured values from these inputs are stored in value registers. These can be read out over the serial bus, or they can be automatically compared with programmed limits stored in the limit registers. The results of out-of-limit comparisons are stored in the status registers, which can be read over the serial bus to flag out-of- limit conditions. If fan speeds drop below preset levels or a fan stalls, an interrupt is generated. Likewise, the ADT7470 can flag fan over speed conditions by using limits set in the fan tach maximum registers. ADT7470 Monitoring Cycle The monitoring cycle begins when a 1 is written to the start bit (Bit 0) of Configuration Register 1 (Register 0x40). Each fan tach input is monitored in turn, and, as each measurement is completed, the result is automatically stored in the appropri- ate value register. Multiple temperature channels can also be monitored by clocking in temperatures using the TMP_IN pin. The temperature measurement function is addressed in hardware and requires no software intervention. The monitoring cycle continues unless disabled by writing a 0 to Bit 7 of Configuration Register 1. The rate of temperature measurement updates depends on the nominal conversion rate of the TMP05/TMP06 temperature sensor (approximately 120 ms) and on the number of TMP05s daisy-chained together. The total monitoring cycle time is the temperature conversion time multiplied by the number of temperature channels being monitored. Fan tach measurements are taken in parallel and are not syn- chronized with the temperature measurements in any way CONFIGURATION REGISTER 1 (ADDRESS 0X40) This register contains the STRT bit, Bit 0, which begins the monitoring cycle on the ADT7470. The SMBus timeout can be disabled , fast tach enabled, and the registers locked, by writing to this register. Control of high or low frequency fan drive, and the config- uration for Pin 13, can be accessed via this register. See Table 31 for more details. CONFIGURATION REGISTER 2 (ADDRESS 0X74) Writing a 1 to Bit 0 in this register puts the ADT7470 in shutdown mode, which puts the part into a low current consumption mode. The PWM frequency for each fan is controlled via this register. Fan speed measurement can be disabled for each fan by writing to this register. See Table 44 for more details. ID REGISTERS The ADT7470 has three read-only registers for identifying the part and silicon revision. The device ID register is located at address 0x3D, and is set to 0x70. The company ID register, located at address 0x3E, is set to 0x41. The revision number register is at address 0x3F, and contains the revision number of the ADT7470 silicon. |
Podobny numer części - ADT7470_13 |
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Podobny opis - ADT7470_13 |
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