芯美电子 EUT1081A ±1°C, Remote and Local Temperature Sensor with SMBus Series Interface DESCRIPTION FEATURES The EUT1081A is precise, two channel digital temperature sensors. Each accurately measures the temperature of its own die and one remote PN junction, and reports the temperature in digital form on a 2-wire serial interface. The remote junction can be a diode-connected transistor like the low-cost 2N3904 NPN type or 2N3906 PNP type. The remote junction can also be a common-collector PNP, such as a substrate PNP of a microprocessor. z Dual Channel: Measures Remote and Local Temperature z 11-Bit, 0.125°C Resolution z High Accuracy: ±1°C from +60°C to +100°C,Remote ±3°C from +60°C to +100°C,Local The 2-wire serial interface accepts standard System Management Bus (SMBus) commands such as Write Byte, Read Byte, Send Byte, and Receive Byte to read the temperature data and program the alarm thresholds and conversion rate. The EUT1081A can function autonomously with a programmable conversion rate, which allows the control of supply current and temperature update rate to match system needs. For Extended resolution, the data format is 10 bits plus sign, with each bit corresponding to 0.125°C. The EUT1081A also includes an SMBus timeout feature to enhance system reliability. z Programmable Under/Overtemperature Alarms z No Calibration Required z SMBus/2-Wire Series Interface z Two Alarm Outputs: ALERT and THERM z +3V to +5.5V Supply Range z MSOP-8,SOP-8 Package Available z RoHS Compliant and 100% Lead (Pb)-Free APPLICATIONS The EUT1081A and EUT1081A-1 have the same functions but different SMBus slave addresses. This allows for one of each to be on the bus at the same time. z Notebook Computers z Workstations Remote accuracy is ±1°C between +60°C and +100°C with no calibration needed. The EUT1081A measures temperatures from -40°C to +125°C. Typical Application Circuit DS1081A Ver1.1 Jan. 2008 1 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Pin Configurations Package Type Package Type Pin Configurations MSOP-8 Pin Configurations SOP-8 Pin Description MSOP-8 SOP-8 NAME 1 1 VCC Supply Voltage Input, +3V to +5.5V. Bypass to GND with a 0.1µF capacitor. Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel. Do not leave DXP floating; connect DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and DXN for noise filtering. 2 2 DXP 3 3 DXN 4 4 5 5 THERM GND 6 6 7 7 ALERT SMBDATA 8 8 SMBCLK DS1081A Ver1.1 Jan. 2008 DESCRIPTION Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally biased to one diode drop above ground. Overtemperature Active-Low Output, Open-Drain. Ground SMBus Alert (Interrupt) Active-Low Output, Open-Drain. SMBus Serial-Data Input/Output, Open-Drain SMBus Serial-Clock Input 2 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Ordering Information Order Number Package Type Marking Operating Temperature range EUT1081AMIR1 MSOP-8 xxxxx T1081A -55 °C to 125°C EUT1081ADIR1 SOP-8 xxxxx T1081A -55 °C to 125°C EUT1081A □ □ □ □ Lead Free Code 1: Lead Free 0: Lead Packing R: Tape& Reel Operating temperature range I: Industry Standard Package Type M: MSOP D: SOP Block Diagram DS1081A Ver1.1 Jan. 2008 3 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Absolute Maximum Ratings All Voltages Referenced to GND Vcc----------------------------------------------------------------------- -0.3V to +6V DXP------------------------------------------------------------------------------------------------------ -0.3V to VCC + 0.3V DXN------------------------------------------------------------------------------------------------------------ -0.3V to +0.8V SMBCLK, SMBDATA, ALERT , THERM ------------------------------------------------------------- -0.3V to +6V SMBDATA, ALERT , THERM Current -------------------------------------------------------------- -1mA to +50mA DXN Current ------------------------------------------------------------------------------------------------------------ ±1mA Thermal Resistance θJA (SOP-8) -------------------------------------------------------------------------------------------------------- 160°C/W θJA (MSOP8) --------------------------------------------------------------------------------------------------------- 160°C/W Junction Temperature------------------------------------------------------------------------------------------------- +150°C Storage Temperature Range------------------------------------------------------------------------------- -65°C to +150°C Lead Temperature (soldering, 10s) ----------------------------------------------------------------------------------+260°C Electrical Characteristics (Circuit of Typical Operating Circuit, VCC = +3.0V to +5.5V, TA = 0°C to +85°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) Symbol Parameter Conditions EUT1081A Min. Temperature Resolution, Legacy Mode 1 Temperature Resolution, Extended Mode 0.125 Remote Temperature Error Local Temperature Error VCC Supply Voltage Range UVLO Undervoltage Lockout Threshold Bits °C Bits TRJ = +60°C to +100°C, VCC = +3.3V TRJ = 0°C to +120°C, VCC = +3.3V -1.0 -3.0 +1.0 +3.0 TA = +60°C to +100°C, VCC = +3.3V -2.0 +2.0 TA = 0°C to +100°C, VCC = +3.3V -3.0 +3.0 3.0 5.5 V 2.95 V 2.60 2.80 90 VCC, falling edge 1.5 POR Threshold Hysteresis 2.0 SMBus static Operating Current During conversion Conversion Time From stop bit to conversion completed 95 °C °C mV 2.5 V 3 10 mV µA 0.5 1.0 mA 125 156 ms 90 Standby Supply Current Jan. 2008 Units °C 11 Falling edge of VCC disables ADC Power-On Reset (POR) Threshold DS1081A Ver1.1 Max. 8 Undervoltage Lockout Hysteresis tCONV Typ. 4 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Electrical Characteristics (Continued) (Circuit of Typical Operating Circuit, VCC = +3.0V to +5.5V, TA = 0°C to +85°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) Symbol Parameter Conditions EUT1081A Min. Typ. Conversion Timing Error DXP and DXN Leakage Current IRJ In standby mode Remote-Diode Source Current Max. Units ±25 % 100 nA High level 80 100 120 Low level 8 10 12 VOL = 0.4V 1 VOL = 0.6V 6 µA ALERT , OVERT Output Low Sink Current Output High Leakage Current mA VOH = 5.5V 1 µA 0.3VCC V SMBus-COMPATIBLE INTERFACE (SMBCLK, SMBDATA) VIL Logic Input Low Voltage VIH Logic Input High Voltage ILEAK 0.7VCC Input Leakage Current VIN = GND or VCC IOL Output Low Sin Current VOL = 0.6V CIN Input Capacitance V ±1 6 µA mA 5 pF SMBus-COMPATIBLE TIMING fSCL tBUF tSU:STA Serial Clock Frequency Bus Free Time Between STOP and START Condition START Condition Setup Time Repeat START Condition Setup Time 100 kHz 4.7 µs 4.7 µs 90% to 90% 50 ns tHD:STA START Condition Hold Time 10% of SMBDATA to 90% of SMBCLK 4 µs tSU:STO STOP Condition Setup Time 90% of SMBCLK to 90% of SMBDATA 4 µs DS1081A Ver1.1 Jan. 2008 5 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Electrical Characteristics (Continued) (Circuit of Typical Operating Circuit, VCC = +3.0V to +5.5V, TA = 0°C to +85°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) Symbol tLOW tHIGH tHD:DAT Parameter Clock Low Period Clock High Period Data Setup Time Conditions 10% to 10% 90% to 90% EUT1081A Min. Typ. Max. 4.7 4 0 Units µs µs µs tR Receive SCL/SDA Rise Time 1 µs tF Receive SCL/SDA Fall Time 300 ns tSP Pulse Width of Spike Suppressed 50 ns 45 ms SMBus Timeout DS1081A Ver1.1 Jan. 2008 0 SMBDATA low period for interface reset 25 37 6 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Typical Operating Characteristics (VCC=+3.3V, TA = +25°C, unless otherwise noted.) Remote Temperature Error VS Remote-diode Temperature Standby Supply Current VS Supply Voltage Temperature Error(℃) Standby Supply Current(μA) 3.5 3 2.5 2 1.5 1 0.5 0 3 3.5 4 4.5 5 Supply Voltage(V) 5.5 Temperature Error(℃) Temperature Error(℃) 3 2 1 0 -1 -2 20 45 70 2 1 0 -1 -2 -3 -55 -30 -5 20 45 70 95 120 Temperature(℃) Local Temperature Error VS DIE Temperature -3 -55 -30 -5 3 Temperature Error VS Power-Supply Noise Frequency 1 0 -1 -2 -3 10K 95 120 100K 1M 10M Frequency(Hz) Temperature(℃) Temperature Error VS Differential-Mode Noise Frequency 1 Temperature Error(℃) Temperature Error(℃) Temperature Error VS Common-Mode Noise Frequency 0 -1 -2 -3 0.01K 1K 100K 10M 1G Frequency(Hz) DS1081A Ver1.1 Jan. 2008 1 0.5 0 -0.5 -1 -1.5 -2 -2.5 -3 10K 100K 1M 10M Frequency(Hz) 100M 7 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Detailed Description Remote-Diode Selection The EUT1081A is temperature sensor designed to work in conjunction with a microprocessor or other intelligence in thermostatic, process-control, or monitoring applications. Communication with the EUT1081A occurs through the SMBus serial interface and dedicated alert pins. The overtemperature alarms ( ALERT ) is asserted if its software programmed temperature thresholds are exceeded. THERM can be connected to fans, a system shutdown, or other thermal management circuitry. The EUT1081A can directly measure the die temperature of CPUs and other ICs that have on-board temperaturesensing diodes (see Typical Application Circuit) or they can measure the temperature of a discrete diode-connected transistor. For best accuracy, the discrete transistor should be a small-signal device with its collector and base connected together. Accuracy has been experimentally verified for all the devices listed in Table 1. Table 1. Remote-Sensor Transistor ADC and Multiplexer Manufacturer Model Number Fairchild Semiconductor (USA) 2N3904, 2N3906 On Semiconductor (USA) 2N3904, 2N3906 Samsung (Korea) KST3904-TF Siemens (Germany) SMBT3904 Note: Transistors must be diode connected (base shorted to collector) The averaging ADC integrates over a 60ms period (each channel, typically, in the 7-bit + sign legacy mode). Using an averaging ADC attains excellent noise rejection. The multiplexer automatically steers bias currents through the remote and local diodes. The ADC and associated circuitry measure each diode’s forward voltage and compute the temperature based on this voltage. If the remote channel is not used, connect DXP to DXN. Do not leave DXP and DXN unconnected. When a conversion is initiated, both channels are converted whether they are used or not. The DXN input is biased at one VBE above ground by an internal diode to set up the ADC inputs for a differential measurement. Excess resistance in series with the remote diode causes about +1/2°C error per ohm. A/D Conversion Sequence The transistor must be a small-signal type with a relatively high forward voltage; otherwise, the A/D input voltage range can be violated. The forward voltage at the highest expected temperature must be greater than 0.25V at 10µA, and at the lowest expected temperature, forward voltage must be less than 0.95V at 100µA. Large power transistors must not be used. Also, ensure that the base resistance is less than 100Ω. Tight specifications for forward current gain (50<β<150, for example) indicate that the manufacturer has good process controls and that the devices have consistent VBE characteristics. A conversion sequence consists of a local temperature measurement and a remote temperature measurement. Each time a conversion begins, whether initiated automatically in the free-running autoconvert mode (RUN/STOP = 0) or by writing a “one-shot” command, both channels are converted, and the results of both measurements are available after the end of conversion. A BUSY status bit in the Status register shows that the device is actually performing a new conversion. The results of the previous conversion sequence are still available when the ADC is busy. DS1081A Ver1.1 Jan. 2008 8 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Thermal Mass and Self-Heating PC Board Layout When sensing local temperature, these devices are intended to measure the temperature of the PC board to which they are soldered. The leads provide a good thermal path between the PC board traces and the die. Thermal conductivity between the die and the ambient air is poor by comparison, making air temperature measurements impractical. Because the thermal mass of the PC board is far greater than that of the EUT1081A, the devices follow temperature changes on the PC board with little or no perceivable delay. When measuring the temperature of a CPU or other IC with an on-chip sense junction, thermal mass has virtually no effect; the measured temperature of the junction tracks the actual temperature within a conversion cycle. When measuring temperature with discrete remote sensors, smaller packages (i.e., a SOT23) yield the best thermal response times. Take care to account for thermal gradients between the heat source and the sensor, and ensure that stray air currents across the sensor package do not interfere with measurement accuracy. Self-heating does not significantly affect measurement accuracy. Remote-sensor self-heating due to the diode current source is negligible. For the local diode, the worst-case error occurs when autoconverting at the fastest rate and simultaneously sinking maximum current at the ALERT output. For example, with VCC = +5.0V, a 16Hz Follow these guidelines to reduce the measurement error of the temperature sensors: 1) Place the EUT1081A as close as is practical to the remote diode. In noisy environments, such as a computer motherboard, this distance can be 4in to 8in (typ). This length can be increased if the worst noise sources are avoided. Noise sources include CRTs, clock generators, memory buses, and ISA/PCI buses. 2) Do not route the DXP-DXN lines next to the deflection coils of a CRT. Also, do not route the traces across fast digital signals, which can easily introduce +30°C error, even with good filtering. 3) Route the DXP and DXN traces in parallel and in close proximity to each other, away from any higher voltage traces, such as +12VDC. Leakage currents from PC board contamination must be dealt with carefully since a 20MΩleakage path from DXP to ground causes about +1°C error. If high-voltage traces are unavoidable, connect guard traces to GND on either side of the DXP-DXN traces (Figure 1). conversion rate and ALERT sinking 1mA, the typical power dissipation is: VCC × 450µA + 0.4V × 1mA = 2.65mW θJ-A for the 8-pin SO package is about +170°C/W, so assuming no copper PC board heat sinking, the resulting temperature rise is: Figure 1. Recommended DXP-DXN PC Traces 4) Route through as few vias and crossunders as possible to minimize copper/solder thermocouple effects. 5) When introducing a thermocouple, make sure that both the DXP and the DXN paths have matching thermocouples. A copper-solder thermocouple exhibits 3µV/°C, and it takes about 200µV of voltage error at DXP-DXN to cause a +1°C measurement error. Adding a few thermocouples causes a negligible error. 6) Use wide traces. Narrow traces are more inductive and tend to pick up radiated noise. The 10mil widths and spacings that are recommended in Figure 1 are not absolutely necessary, as they offer only a minor improvement in leakage and noise over narrow traces. Use wider traces when practical. ∆T = 2.65mW × 170 o C / W = +0.45 o C Even under these engineered circumstances, it is difficult to introduce significant self-heating errors. ADC Noise Filtering The integrating ADC used has good noise rejection for low-frequency signals such as 60Hz/120Hz power-supply hum. In noisy environments, high-frequency noise reduction is needed for high-accuracy remote measurements. The noise can be reduced with careful PC board layout and proper external noise filtering. High-frequency EMI is best filtered at DXP and DXN with an external 2200pF capacitor. Larger capacitor values can be used for added filtering, but do not exceed 3300pF because it can introduce errors due to the rise time of the switched current source. DS1081A Ver1.1 Jan. 2008 7) Add a 200Ω resistor in series with VCC for best noise filtering (see Typical Application Circuit). 9 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Twisted-Pair and Shielded Cables Table 3. Extended Temperature Data Format Use a twisted-pair cable to connect the remote sensor for remote-sensor distances longer than 8in or in very noisy environments. Twisted-pair cable lengths can be between 6ft and 12ft before noise introduces excessive errors. For longer distances, the best solution is a shielded twisted pair like that used for audio microphones. At the device, connect the twisted pair to DXP and DXN and the shield to GND. Leave the shield unconnected at the remote sensor. For very long cable runs, the cable’s parasitic capacitance often provides noise filtering, so the 2200Pf capacitor can often be removed or reduced in value. Cable resistance also affects remote-sensor accuracy. For every 1Ωof series resistance, the error is approximately +1/2°C. Fractional Temperature 0.000℃ 0.125℃ 0.250℃ 0.375℃ 0.500℃ 0.625℃ 0.750℃ 0.875℃ Diode Fault Alarm SMBus Digital Interface There is a fault detector at DXP that detects whether the remote diode has an open-circuit condition. At the beginning of each conversion, the diode fault is checked, and the status byte is updated. This fault detector is a simple voltage detector. If DXP rises above VCC-1V (typical) due to the diode current source, a fault is detected and the device alarms through pulling ALERT low while the remote temperature reading doesn’t update in this condition. Note that the diode fault isn’t checked until a conversion is initiated, so immediately after power-on reset the status byte indicates no fault is present, even if the diode path is broken. If the remote channel is shorted (DXP to DXN or DXP to GND), the ADC reads 1000 0000 (-128℃) so as not to trip either the THIGH or TLOW alarms at their POR settings. From a software perspective, the EUT1081A appears as a series of 8-bit registers that contain temperature data, alarm threshold values, and control bits. A standard SMBuscompatible 2-wire serial interface is used to read Temperature Data and Write Control bits and alarm threshold data. The device responds to the same SMBus slave address for access to all functions. The EUT1081A employs four standard SMBus protocols: Write Byte, Read Byte, Send Byte, and Receive Byte (Figures 2, 3, and 4). The shorter Receive Byte protocol allows quicker transfers, provided that the correct data register was previously selected by a Read Byte instruction. Use caution with the shorter protocols in multimaster systems, since a second master could overwrite the command byte without informing the first master. The temperature data format is shown in Table2 and Table3. For Extended resolution, the data format is 10 bit plus sign with each bit corresponding to +0.125℃. So the EUT1081A can measure from 0℃ to 127.875℃ (data format 0111 1111 111) 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 interrupt is asserted. Table 2. Data Format Temp (℃) 130.00 127.00 126.00 25 0.00 -1 -25 -55 Diode Fault (Short or Open) DS1081A Ver1.1 Jan. 2008 Extended Register 000x xxxx 001x xxxx 010x xxxx 011x xxxx 100x xxxx 101x xxxx 110x xxxx 111x xxxx The POR state of both ALERT THIGH registers is 0101 0101 or +85C and the POR state of TLOW registers is 0000 0000 or 0°C. Digital output 0 111 1111 0 111 1111 0 111 1111 0 001 1001 0 000 0000 1 111 1111 1 110 0111 1 100 1001 Four additional registers store remote and local alarm threshold data corresponding to the THERM outputs. The values stored in these registers are high-temperature thresholds. If any one of the measured temperatures equals or exceeds the corresponding alarm threshold value, an THERM output is asserted. The POR state of the THERM threshold is 0101 0101 or +85°C. 1 000 0000 10 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Figure 2. SMBus Protocols Figure 3. SMBus Write Timing Diagram Figure 4. SMBus Read Timing Diagram DS1081A Ver1.1 Jan. 2008 11 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A ALERT Interrupts THERM Overtemperature Alarm/Warning Outputs The ALERT interrupt output signal is latched and can only be cleared by reading the Alert Response address. Interrupts are generated in response to THIGH and TLOW comparisons and when the remote diode is disconnected (for fault detection). The interrupt does not halt automatic conversions; new temperature data continues to be available over the SMBus interface after ALERT is asserted. The interrupt output pin is open-drain so that devices can share a common interrupt line. The interrupt rate can never exceed the conversion rate. The interface responds to the SMBus Alert Response address, an interrupt pointer return-address feature (see Alert Response Address section). Prior to taking corrective action, always check to ensure that an interrupt is valid, always check to ensure that an interrupt is valid by reading the current temperature. THERM is asserted when the temperature rises to a value programmed in the appropriate threshold register. It is deasserted when the temperature drops below this threshold minus the hysteresis. An THERM output can be used to activate a cooling fan, send a warning, or trigger a system shutdown to prevent component damage. The THERMHYST byte sets the amount of hysteresis for THERM output. The data format for the THERMHYST byte is the same for the other temperature registers (Table 2). Command Byte Functions The 8-bit Command Byte register (Table 5) is the master index that points to the various other registers within the EUT1081A. This register’s POR state is 0000 0000, so a Receive Byte transmission (a protocol that lacks the command byte) occurring immediately after POR returns the current local temperature data. 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 (0001100). Then, any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus (Table 4). The Alert Response can activate several different slave devices simultaneously, similar to the SMBus 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 acknowledge and continues to hold the ALERT line low until cleared. (The conditions for clearing an alert vary, depending on the type of slave device.) Successful reading of the Alert Response address clears the interrupt latch. Table 4. Read Format for Alert Response Address (000 1100) BIT NAME 7 (MSB) 6 5 4 3 2 1 0(LSB) ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 1 DS1081A Ver1.1 Jan. 2008 One-Shot The one-shot command immediately forces a new conversion cycle to begin. If the one-shot command is received when the EUT1081A is in software standby mode ( RUN /STOP bit = High), a new conversion is begun, after which the device returns to standby mode. If a conversion is in progress when a one-shot command is received, the command is ignored. If a one-shot command is received in autoconvert mode （ RUN /STOP bit=Low ） between conversions, a new conversion begins, the conversion rate timer is reset, and the next automatic conversion takes place after a full delay elapses. Configuration Byte Functions The Configuration Byte register (Table 6) is a Read-Write register with several functions. Bit 7 is used to mask (disable) interrupts. Bit 6 puts the device into software standby mode (STOP) or autonomous (RUN) mode. Bits 0 to 5 are reserved and return a zero when read. FUNCTION Provide the current Logic 1 12 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Status Byte Functions Conversion Rate Byte The status byte (Table 7) indicates which (if any) temperature thresholds have been exceeded. This byte also indicates whether the ADC is converting and if there is an open-circuit fault detected with the external sense junction. After POR, the normal state of the MSB is 1 and all the other flag bits are 0, assuming no alert or overtemperature conditions are present. The status byte is cleared by any successful read of the Status register, unless the fault persists. The ALERT interrupt latch is not automatically cleared when the status flag bit is cleared. When reading the status byte, you must check for internal bus collisions caused by asynchronous ADC timing, or else disable the ADC prior to reading the status byte (via the RUN /STOP bit in the configuration byte). In one-shot mode, read the status byte only after the conversion is complete, which is approximately 125ms max after the one-shot conversion is commanded. To check for internal bus collisions, read the status byte. If the least significant seven bits are ones, discard the data and read the status byte again. The status bits LHIGH, LLOW , RHIGH , and RLOW are refreshed on the SMBus clock edge immediately following the stop condition, so there is no danger of losing temperature-related status data as a result of an internal bus collision. The OPEN status bit (diode continuity fault ) is only refreshed at the beginning of a conversion, so OPEN data is lost. The ALERT interrupt latch is independent of the status byte register, so no false alerts are generated by an internal bus collision. When autoconverting, if the THIGH and TLOW limits are close together, it’s possible for both high-temp and low-temp status bits to be set, depending on the amount of time between status read operations. In these circumstances, it is best not to rely on the status bits to indicate reversals in long-term temperature changes. Instead, use a current temperature reading to establish the trend direction. Table 6. Configuration-Byte Bit The Conversion Rate register (Table 8) programs the time interval between conversions in free-running autonomous mode ( RUN /STOP = 0). This variable rate control can be used to reduce the supply current in portable-equipment applications. The conversion rate byte’s POR state is 08h (16Hz). The EUT1081A uses only the 4 least-significant bits (LSBs) of this register. The 4 most-significant bits (MSBs) are “don’t care” and should be set to zero when possible. The conversion rate tolerance is ±25% at any rate setting. Valid A/D conversion results for both channels are available one total conversion time (125ms nominal) after initiating a conversion, whether conversion is initiated through the RUN /STOP bit, one-shot command, or initial power-up. BIT NAME POR STATE 7 (MSB) MASK 1 0 6 RUN / STOP 0 5 to 0 RFU 0 DS1081A Ver1.1 Jan. 2008 Table 8. Conversion-Rate Data 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 0Ah-FFh Conversion Rate (hz) 0.0625 0.125 0.25 0.5 1 2 4 8 16 16 Reserved Slave Addresses The EUT1081A appears to the SMBus as one device having a common address for both ADC channels. The EUT1081A and EUT1081A-1 have the following SMBus slave address: FUNCTION Masks ALERT interrupts if a 1. Standby mode control bit; if a 1, standby mode is initiated. Reserved A6 A5 A4 A3 A2 A1 A0 EUT1081A 1 0 0 1 1 0 0 EUT1081A-1 1 0 0 1 1 0 1 The EUT1081A also responds to the SMBus Alert Response section). 13 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Table 5. Command-Byte Bit Assignments REGISTER RLTS RRTE RSL RCL RCRA RLHN RLLI RRHI RRLS WCA WCRW WLHO WLLM WRHA WRLN OSHT RTEXT RTOFS RTOFSEXT RLEXT RHEXT RTTHERM LTTHERM THERMHYST ALERTFQ MFGIO DEVID COMMAND 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 0Ah 0Bh 0Ch 0Dh 0Eh 0Fh 10h 11h 12h 13h 14h 19h 20h 21h 22h FEh FFh POR STATE 0000 0000* 0000 0000* N/A 0000 0000 0000 1000 0101 0101 (85) 0000 0000 01010101 (85) 0000 0000 N/A N/A N/A N/A N/A N/A N/A 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0101 0101 (85) 0101 0101 (85) 0000 1010 (10) 0000 0001 0000 0000 0000 0000 FUNCTION Read local temperature. It returns latest temperature Read remote temperature. It returns latest temperature Read status byte (flags, busy signal) Read configuration byte Read conversion rate byte Read local THIGH limit Read local TLOW limit Read remote THIGH limit Read remote TLOW limit Write configuration byte Write conversion rate byte Write local THIGH limit Write local TLOW limit Write remote THIGH limit Write remote TLOW limit One-shot command (use send-byte format) Remote temperature extended byte Remote temperature offset high byte Remote temperature offset extended byte Remote THIGH limit extended byte Remote TLOW limit extended byte Remote temperature THERM limit Local temperature THERM limit THERM hysteresis ALERT fault queue code Manufacturer ID Device ID *If the device is in standby mode at POR, both temperature registers read 0℃. Table 7. Status Register Bit Assignments BIT NAME POR STATE 7 (MSB) BUSY 1 A/D is busy converting when high. 6 LHIGH 0 Internal high-temperature alarm has tripped when high; cleared by POR or readout of the Status register if the fault condition no longer exists. 5 LLOW 0 Internal low-temperature alarm has tripped when high; cleared by POR or readout of the Status register if the fault condition no longer exists. 4 RHIGH 0 External high-temperature alarm has tripped when high; cleared by POR or readout of the Status register if the fault condition no longer exists. 3 RLOW 0 External low-temperature alarm has tripped when high; cleared by POR or readout of the Status register if the fault condition no longer exists. 2 OPEN 0 A high indicates an external diode open; cleared by POR or readout of the Status register if the fault condition no longer exists. FUNCTION 1 RTHRM A high indicates a remote temperature THERM alarm has activated. 0(LSB) LTHRM A high indicates a local temperature THERM alarm has activated. DS1081A Ver1.1 Jan. 2008 14 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Serial Bus Interface POR and UVLO Control of the EUT1081A is carried out via the serial bus. The EUT1081A is connected to this bus as a slave device, under the control of a master device. There is a programmable SMBus timeout. When this is enabled, the SMBus times out after typically 25ms of no activity. However, this feature is not enabled by default. To enable it, set Bit 7 of the consecutive alert register (Address=22h). The EUT1081A has a volatile memory. To prevent unreliable power-supply conditions from corrupting the data in memory and causing erratic behavior, a POR voltage detector monitors VCC and clears the memory if VCC falls below 1.7V (typ, see Electrical Characteristics). When power is first applied and VCC rises above 2.0V (typ), the logic blocks begin operating, although reads and writes at VCC levels below 3.0V are not recommended. A second VCC comparator and the ADC undervoltage lockout (UVLO) comparator prevent the ADC from converting until there is sufficient headroom (VCC = +2.8V typ). Consecutive ALERT Register This value written to this register determines how many out-of limit measurements must occur before an ALERT is generated. The default value is that one out-of-limit measurement generates an ALERT .The maximum value that can be chosen is four. The purpose of this register is to allow the user to perform some filtering of the output. This is particularly useful at the faster two conversion rates where no averaging takes place. Low Power Standby Mode The EUT1081A can be put into a low power standby mode by setting Bit 6 of the configuration register. When Bit 6 is Low, the EUT1081A 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 10µA if there is no SMBus activity, or 100µA 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 EUT1081A is still in standby. Offset Register Series resistance on the DXP and DXN lines in processor packages and clock noise can introduce offset errors into the remote temperature measurement. To achieve the specified accuracy on this channel, these offsets must be removed. The offset value is stored as an 11-bit, twos complement value in Register 11h (high byte) and Register 12h (low byte, left justified). The value of the offset is negative if the MSB of Register 11h is 1 and positive if the MSB of Register 11h is 0. The value is added to the measured value of the remote temperature. The offset register powers up with a default value of 0℃ and has no effect if nothing is written to them. Table 9. Sample Offset Register Codes Offset 11h 12h -4℃ -1℃ -0.125℃ 0℃ +0.125℃ +1℃ +4℃ 1111 1100 1111 1111 1111 1111 0000 0000 0000 0000 0000 0001 0000 0100 0000 0000 0000 0000 1110 0000 0000 0000 0010 0000 0000 0000 0000 0000 DS1081A Ver1.1 Jan. 2008 15 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A Package Information MSOP-8 SYMBOLS Jan. 2008 INCHES MIN. MAX. MIN. MAX. A - 1.10 - 0.043 A1 0.00 0.15 0.000 0.006 D 3.00 0.118 E1 3.00 0.118 E 4.70 5.10 0.185 0.201 L 0.40 0.80 0.016 0.031 b 0.22 0.38 0.008 0.015 e DS1081A Ver1.1 MILLIMETERS 0.65 0.026 16 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUT1081A SOP-8 SYMBOLS MILLIMETERS MIN. MAX. MIN. A 1.35 1.75 0.053 0.069 A1 0.10 0.25 0.004 0.010 D E 4.90 5.80 E1 Jan. 2008 MAX. 0.193 6.20 0.228 3.90 0.244 0.153 L 0.40 1.27 0.016 0.050 b 0.31 0.51 0.012 0.020 e DS1081A Ver1.1 INCHES 1.27 0.050 17 联系电话：１５９９９６４４５７９ ８３１５１７１５