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MAX6648 Datasheet(PDF) 8 Page - Maxim Integrated Products |
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MAX6648 Datasheet(HTML) 8 Page - Maxim Integrated Products |
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8 / 16 page  Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms 8 _ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _ SMBCLK A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE AB C D E FG HI J SMBDATA tSU:STA tHD:STA tLOW tHIGH tSU:DAT tSU:STO tBUF LM K E = SLAVE PULLS SMBDATA LINE LOW F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO SLAVE H = LSB OF DATA CLOCKED INTO SLAVE I = MASTER PULLS DATA LINE LOW J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION Figure 3. SMBus Read Timing Diagram Alarm Threshold Registers Four registers store ALERT threshold values—one high- temperature (THIGH) and one low-temperature (TLOW) register each for the local and remote channels. If either measured temperature equals or exceeds the corresponding ALERT threshold value, the ALERT inter- rupt asserts. The power-on-reset (POR) state of both ALERT THIGH registers is full scale (0101 0101, or +85°C). The POR state of both TLOW registers is 0000 0000, or 0°C. Two additional registers store remote and local alarm threshold data corresponding to the OVERT output. The values stored in these registers are high-temperature thresholds. If either of the measured temperatures equals or exceeds the corresponding alarm threshold value, an OVERT output asserts. The POR state of the OVERT threshold is 0110 1110 or +110°C for the MAX6648, and 0101 0101 or +85°C for the MAX6692. Diode Fault Alarm A continuity fault detector at DXP detects an open cir- cuit between DXP and DXN, or a DXP short to VCC, GND, or DXN. If an open or short circuit exists, the external temperature register is loaded with 1000 0000. If the fault is an open-circuit fault bit 2 (OPEN) of the status byte, it is set to 1 and the ALERT condition is activated at the end of the conversion. Immediately after POR, the status register indicates that no fault is present. If a fault is present upon power-up, the fault is not indicated until the end of the first conversion. ALERT Interrupts The ALERT interrupt occurs when the internal or exter- nal temperature reading exceeds a high- or low-tem- perature limit (user programmed) or when the remote diode is disconnected (for continuity fault detection). The ALERT interrupt output signal is latched and can be cleared only by either reading the status register or by successfully responding to an alert response address. In both cases, the alert is cleared only if the fault condition no longer exists. Asserting ALERT does not halt automatic conversion. The ALERT output pin is open drain, allowing multiple devices to share a com- mon interrupt line. The MAX6648/MAX6692 respond to the SMBus alert response address, an interrupt pointer return-address feature (see the Alert Response Address section). Prior to taking corrective action, always check to ensure that an interrupt is valid by reading the current temperature. Fault Queue Register In some systems, it may be desirable to ignore a single temperature measurement that falls outside the ALERT limits. Bits 2 and 3 of the fault queue register (address 22h) determine the number of consecutive temperature faults necessary to set ALERT (see Tables 3 and 4). Alert Response Address The SMBus alert response interrupt pointer provides quick fault identification for simple slave devices that lack the complex, expensive logic needed to be a bus master. Upon receiving an ALERT interrupt signal, the host master can broadcast a receive byte transmission to the alert response slave address (0001 100). Following such a broadcast, any slave device that gen- erated an interrupt attempts to identify itself by putting its own address on the bus. The alert response can activate several different slave devices simultaneously, similar to the I2C general call. If more than one slave attempts to respond, bus arbitration rules apply, and the device with the lower address code wins. The losing device does not generate an |
Similar Part No. - MAX6648_08 |
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Similar Description - MAX6648_08 |
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