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ADM1032ARMZ-1 Datasheet(PDF) 13 Page - ON Semiconductor |
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ADM1032ARMZ-1 Datasheet(HTML) 13 Page - ON Semiconductor |
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ADM1032 http://onsemi.com 13 seven bits, an LSB of 1 is added. The address of the device is now known, and it can be interrogated in the usual way. 4. If more than one device’s ALERT output is low, the one with the lowest device address has priority in accordance with normal SMBus arbitration. 5. Once the ADM1032 has responded to the alert response address, it resets its ALERT output, provided that the error condition that caused the ALERT no longer exists. If the SMBALERT line remains low, the master sends ARA again, and so on until all devices whose ALERT outputs were low have responded. Low Power Standby Mode The ADM1032 can be put into a low power standby mode by setting Bit 6 of the configuration register. When Bit 6 is low, the ADM1032 operates normally. When Bit 6 is high, the ADC is inhibited and any conversion in progress is terminated without writing the result to the corresponding value register. The SMBus is still enabled. Power consumption in the standby mode is reduced to less than 10 mA if there is no SMBus activity, or 100 mA if there are clock and data signals on the bus. When the device is in standby mode, it is still possible to initiate a one-shot conversion of both channels by writing XXh to the one-shot register (Address 0Fh), after which the device returns to standby. It is also possible to write new values to the limit register while it is in standby. If the values stored in the temperature value registers are now outside the new limits, an ALERT is generated even though the ADM1032 is still in standby. The ADM1032 Interrupt System The ADM1032 has two interrupt outputs, ALERT and THERM. These have different functions. ALERT responds to violations of software-programmed temperature limits and is maskable. THERM is intended as a fail-safe interrupt output that cannot be masked. If the temperature goes equal to or below the lower temperature limit, the ALERT pin is asserted low to indicate an out-of-limit condition. If the temperature is within the programmed low and high temperature limits, no interrupt is generated. If the temperature exceeds the high temperature limit, the ALERT pin is asserted low to indicate an overtemperature condition. A local and remote THERM limit can be programmed into the device to set the temperature limit above which the overtemperature THERM pin is asserted low. This temperature limit should be equal to or greater than the high temperature limit programmed. The behavior of the high limit and THERM limit is as follows: 1. If either temperature measured exceeds the high temperature limit, the ALERT output is asserted low. 2. If the local or remote temperature continues to increase and either one exceeds the THERM limit, the THERM output asserts low. This can be used to throttle the CPU clock or switch on a fan. A THERM hysteresis value is provided to prevent a cooling fan cycling on and off. The power-on default value is 10 °C, but this can be reprogrammed to any value after powerup. This hysteresis value applies to both the local and remote channels. Using these two limits in this way, allows the user to gain maximum performance from the system by only slowing it down should it be at a critical temperature. The THERM signal is open drain and requires a pullup to VDD. The THERM signal must always be pulled up to the same power supply as the ADM1032, unlike the SMBus signals (SDATA, SCLK, and ALERT) that can be pulled to a different power rail, usually that of the SMBus controller. Figure 17. Operation of the THERM Output 100°C 90°C 80°C 70°C 60°C 50°C 40°C TEMPERATURE THERM LOCAL THERM LIMIT LOCAL THERM LIMIT − HYSTERESIS Table 13. THERM HYSTERESIS SAMPLE VALUES THERM Hysteresis Binary Representation 0°C 0 000 0000 1°C 0 000 0001 10°C 0 000 1010 Sensor Fault Detection At the D+ input, the ADM1032 has a fault detector that detects if the external sensor diode is open circuit. This is a simple voltage comparator that trips if the voltage at D+ exceeds VDD − 1.0 V (typical). The output of this comparator is checked when a conversion is initiated and sets Bit 2 of the status register if a fault is detected. If the remote sensor voltage falls below the normal measuring range, for example, due to the diode being short-circuited, the ADC outputs −128 (1000 0000). Since the normal operating temperature range of the device only extends down to 0 °C, this output code should never be seen in normal operation, so it can be interpreted as a fault condition. Since it is outside the power-on default low temperature limit (0 °C) and any low limit that would normally be programmed, a short-circuit sensor causes an SMBus alert. |
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