19-2034; Rev 2; 3/02 ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms Features ♦ Dual Channel: Measures Remote and Local Temperature 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 MAX6657/MAX6658/ MAX6659 can function autonomously with a programmable conversion rate, which allows the control of supply current and temperature update rate to match system needs. For conversion rates of 4Hz or less, the temperature is represented in extended mode as 10 bits + sign with a resolution of 0.125°C. When the conversion rate is faster than 4Hz, output data is 7 bits + sign with a resolution of 1°C. The MAX6657/ MAX6658/MAX6659 also include an SMBus timeout feature to enhance system reliability. ♦ Programmable Conversion Rate (0.0625Hz to 16Hz) Remote accuracy is ±1°C between +60°C and +100°C with no calibration needed. The MAX6657 measures temperatures from 0°C to +125°C and the MAX6658/ MAX6659 from -55°C to +125°C. The MAX6659 has the added benefit of being able to select one of three addresses through an address pin, and a second overtemperature alarm pin for greater system reliability. ♦ 11-Bit, 0.125°C Resolution ♦ High Accuracy ±1°C (max) from +60°C to +100°C (Remote) ♦ No Calibration Required ♦ Programmable Under/Overtemperature Alarms ♦ SMBus/I2C™-Compatible Interface ♦ Two Alarm Outputs: ALERT and OVERT1 (MAX6657 and MAX6658) ♦ Three Alarm Outputs: ALERT, OVERT1, and OVERT2 (MAX6659) Ordering Information TEMP. RANGE PART MAX6657MSA -55°C to +125°C 8 SO 0°C to +125°C MAX6658MSA -55°C to +125°C 8 SO -55°C to +125°C MAX6659MEE -55°C to +125°C 16 QSOP -55°C to +125°C Pin Configurations Applications Desktop Computers Notebook Computers Servers Workstations TOP VIEW VCC 1 16 N.C. N.C. 2 15 STBY DXP 3 14 SMBCLK DXN 4 Typical Operating Circuit appears at the end of the data sheet. SMBus is a trademark of Intel Corp. PINMEASURED PACKAGE TEMP. RANGE MAX6659 13 N.C. 12 SMBDATA ADD 5 OVERT1 6 11 N.C. GND 7 10 OVERT2 GND 8 9 ALERT VCC 1 8 SMBCLK DXP 2 DXN 3 7 SMBDATA MAX6657 MAX6658 OVERT1 4 6 ALERT 5 GND SO QSOP I2C is a trademark of Philips Corp. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX6657/MAX6658/MAX6659 General Description The MAX6657/MAX6658/MAX6659 are precise, twochannel 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 NPN type 2N3904 or 2N3906 PNP type. The remote junction can also be a common-collector PNP, such as a substrate PNP of a microprocessor. MAX6657/MAX6658/MAX6659 ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms 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, OVERT1, OVERT2 ..............................................................-0.3V to +6V SMBDATA, ALERT, OVERT1, OVERT2 Current ..........................................................-1mA to +50mA DXN Current ......................................................................±1mA Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 5.9mW/°C above +70°C) .................471mW 16-Pin QSOP (derate 8.3mW/°C above +70°C) ..........664mW Junction Temperature .....................................................+150°C Storage Temperature Range ............................-65°C to +150°C Lead Temperature (soldering, 10s) ................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (Circuit of Typical Operating Circuit, VCC = +3.0V to +5.5V, TA = 0°C to +125°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN Temperature Resolution, Legacy Mode 1 Temperature Resolution, Extended Mode 0.125 Remote Temperature Error (MAX6657) Local Temperature Error (MAX6657) Remote Temperature Error (MAX6658/MAX6659) Local Temperature Error (MAX6658/MAX6659) Supply Voltage Range Undervoltage Lockout Threshold Power-On Reset (POR) Threshold 2 Bits 11 Bits °C TRJ = 0°C to +100°C, VCC = +3.3V (Note 1) -3.0 +3.0 TRJ = 0°C to +125°C, VCC = +3.3V (Note 1) -5.0 +5.0 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 TA = 0°C to +125°C, VCC = +3.3V -5.0 +5.0 TRJ = +60°C to +100°C, VCC = +3.3V (Note 1) -1.0 1.0 TRJ = 0°C to +100°C, VCC = +3.3V (Note 1) -3.0 3.0 TRJ = -55°C to +125°C, VCC = +3.3V (Note 1) -5.0 +5.0 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 TA = -55°C to +125°C, VCC = +3.3V (Note 2) -5.0 Falling edge of VCC disables ADC 2.60 1.5 SMBus static Operating Current During conversion °C °C 2.80 0.6 m°C/V V 2.95 2.0 V mV 2.5 90 Standby Supply Current °C 5.5 90 VCC, falling edge °C +5.0 0.2 3.0 POR Threshold Hysteresis Average Operating Current 8 +1.0 Undervoltage Lockout Hysteresis UNITS °C -1.0 VCC UVLO MAX TRJ = +60°C to +100°C, VCC = +3.3V (Note 1) 3.0V ≤ VCC ≤ 5.5V Line Regulation TYP V mV 3 10 µA 0.5 1.0 mA 0.25 conversions/s 40 70 2 conversions/s 150 250 _______________________________________________________________________________________ µA ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms (Circuit of Typical Operating Circuit, VCC = +3.0V to +5.5V, TA = 0°C to +125°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) PARAMETER Conversion Time SYMBOL tCONV CONDITIONS From stop bit to conversion completed (Note 4) MIN TYP MAX UNITS 95 125 156 ms Conversion Timing Error DXP and DXN Leakage Current Remote-Diode Source Current In standby mode IRJ ±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 0.8 V SMBus-COMPATIBLE INTERFACE (SMBCLK, SMBDATA, STBY) Logic Input Low Voltage Logic Input High Voltage Input Leakage Current VIL VIH ILEAK Output Low Sink Current IOL Input Capacitance CIN VCC = +3.0V 2.2 VCC = +5.5V 2.4 V VIN = GND or VCC VOL = 0.6V ±1 6 µA mA 5 pF SMBus-COMPATIBLE TIMING (Note 4) Serial Clock Frequency fSCL Bus Free Time Between STOP and START Condition tBUF (Note 5) START Condition Setup Time Repeat START Condition Setup Time 100 kHz 4.7 µs 4.7 µs tSU:STA 90% to 90% 50 ns START Condition Hold Time tHD:STA 10% of SMBDATA to 90% of SMBCLK 4 µs STOP Condition Setup Time tSU:STO 90% of SMBCLK to 90% of SMBDATA 4 µs Clock Low Period tLOW 10% to 10% 4.7 µs Clock High Period tHIGH 90% to 90% 4 µs (Note 6) 0 µs Data Setup Time tHD:DAT Receive SCL/SDA Rise Time tR 1 Receive SCL/SDA Fall Time tF 300 ns 50 ns 45 ms Pulse Width of Spike Suppressed SMBus Timeout Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: tSP 0 SMBDATA low period for interface reset 25 37 µs TA = +25°C to +85°C. If both the local and the remote junction are below TA = -20°C, then VCC > 3.15V. For conversion rates of 4Hz or slower, the conversion time doubles. Timing specifications guaranteed by design. The serial interface resets when SMBCLK is low for more than tTIMEOUT. A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK's falling edge. _______________________________________________________________________________________ 3 MAX6657/MAX6658/MAX6659 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = +3.3V, TA = +25°C, unless otherwise noted.) 3.5 3.0 MAX6657 toc03 2 TEMPERATURE ERROR (°C) OPERATING SUPPLY CURRENT (µA) 8Hz AND 16Hz ARE 1°C RESOLUTION 4.0 3 MAX6657 toc02 600 MAX6657 toc01 4.5 STANDBY SUPPLY CURRENT (µA) MAX6659 REMOTE TEMPERATURE ERROR vs. REMOTE-DIODE TEMPERATURE OPERATING SUPPLY CURRENT vs. CONVERSION RATE STANDBY SUPPLY CURRENT vs. SUPPLY VOLTAGE 400 200 1 0 -1 -2 FAIRCHILD 2N3906 0 4.0 4.5 5.0 0.063 0.125 0.25 0.5 5.5 1 2 4 8 16 SUPPLY VOLTAGE (V) CONVERSION RATE (Hz) LOCAL TEMPERATURE ERROR vs. DIE TEMPERATURE TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY TEMPERATURE ERROR (°C) 2 1 0 -1 -1 VIN = SQUARE WAVE APPLIED TO VCC WITH NO 0.1µF VCC CAPACITOR -3 -55 -30 -5 20 45 70 95 10k 120 100k 1M 10M -2 VIN = 10mVP-P SQUARE WAVE APPLIED TO DXP-DXN -2 -3 0.01k 1k 100k MAX6657 toc08 -1 -2 -3 -4 -5 -3 10k 100k 1M FREQUENCY (Hz) 4 100M 0 MAX6657 toc07 -1 10M 100M 95 120 VIN = AC-COUPLED TO DXN VIN = 100mVp-p TEMPERATURE ERROR vs. DXP-DXN CAPACITANCE TEMPERATURE ERROR (°C) TEMPERATURE ERROR (°C) 0 70 -1 FREQUENCY (Hz) TEMPERATURE ERROR vs. DIFFERENTIAL-MODE NOISE FREQUENCY 1 45 0 FREQUENCY (Hz) TEMPERATURE (°C) 20 1 -2 -3 -5 TEMPERATURE ERROR vs. COMMON-MODE NOISE FREQUENCY 0 -2 -30 TEMPERATURE (°C) 1 MAX6657 toc04 3 -55 MAX6657 toc06 3.5 MAX6657 toc05 3.0 -3 TEMPERATURE ERROR (°C) 2.5 TEMPERATURE ERROR (°C) MAX6657/MAX6658/MAX6659 ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms 0 10 20 30 40 50 60 70 80 90 100 DXP-DXN CAPACITANCE (nF) _______________________________________________________________________________________ 10M 1G ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms PIN NAME FUNCTION MAX6657 MAX6658 MAX6659 1 1 VCC Supply Voltage Input, +3V to +5.5V. Bypass to GND with a 0.1µF capacitor. A 200Ω series resistor is recommended but not required for additional noise filtering. See Typical Operating Circuit. 2 3 DXP 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. 3 4 DXN Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally biased to one diode drop above ground. 4 6 OVERT1 Overtemperature Active-Low Output, Open-Drain. Output is logic low only when temperature is above the software programmed threshold. 5 7, 8 GND Ground SMBus Alert (Interrupt) Active-Low Output, Open-Drain. Asserts when temperature exceeds user-set limits (high or low temperature). Stays asserted until acknowledged by either reading the Status register or by successfully responding to an Alert Response address. See ALERT Interrupts. 6 9 ALERT 7 12 SMBDATA 8 14 SMBCLK — 5 ADD — 10 OVERT2 — 15 STBY Hardware Standby Input. Temperature and comparison threshold data are retained in standby mode. If STBY is low, the IC is put into standby mode. — 2, 11, 13, 16 N.C. Not internally connected. Do not make connections to these pins. SMBus Serial-Data Input/Output, Open-Drain SMBus Serial-Clock Input SMBus Address-Select Pin. The MAX6659 is set to one of three available addresses (connect to VCC, GND, or leave open). See Slave Addresses section. Overtemperature Active-Low Output, Open-Drain. Output is logic low only when temperature is above the software programmed threshold. _______________________________________________________________________________________ 5 MAX6657/MAX6658/MAX6659 Pin Description ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms MAX6657/MAX6658/MAX6659 Functional Diagram VCC MAX6657 MAX6658 MAX6659 2 DXP MUX REMOTE DXN (STBY) CONTROL LOGIC ADC LOCAL DIODE FAULT ALERT Q S R REGISTER BANK COMMAND BYTE REMOTE TEMPERATURE LOCAL TEMPERATURE ALERT THRESHOLD OVERT1 S Q R ALERT RESPONSE ADDRESS (OVERT2) S OVERT1 THRESHOLD R (OVERT2 THRESHOLD) Q MAX6659 ONLY Detailed Description The MAX6657/MAX6658/MAX6659 are temperature sensors designed to work in conjunction with a microprocessor or other intelligence in thermostatic, process-control, or monitoring applications. Communication with the MAX6657/MAX6658/MAX6659 occurs through the SMBus serial interface and dedicated alert pins. Two independent overtemperature alarms (OVERT1 and OVERT2) are asserted if their software programmed temperature thresholds are exceeded. OVERT1 and OVERT2 can be connected to fans, a system shutdown, or other thermal management circuitry. The MAX6657/MAX6658/MAX6659 convert temperatures to digital data either at a programmed rate or a single conversion. Conversions have a 0.125°C resolution (extended resolution) or 1°C resolution (legacy resolution). Extended resolution represents temperature as 6 8 SMBus READ 8 WRITE SMBDATA SMBCLK 7 (ADD) ADDRESS DECODER ( ) ARE FOR MAX6659 ONLY 10 bits + sign bit and is available for autonomous conversions that are 4Hz and slower and single-shot conversions. Legacy resolution represents temperature as 7 bits + sign bit and allows for faster autonomous conversion rates of 8Hz and 16Hz. ADC and Multiplexer 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 _______________________________________________________________________________________ ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms MANUFACTURER Central Semiconductor (USA) Fairchild Semiconductor (USA) On Semiconductor (USA) Rohm Semiconductor (USA) Samsung (Korea) Siemens (Germany) Zetex (England) MODEL NUMBER CMPT3904 2N3904, 2N3906 2N3904, 2N3906 SST3904 KST3904-TF SMBT3904 FMMT3904CT-ND Note: Transistors must be diode connected (base shorted to collector). 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. Resistance in series with the remote diode causes about +1/2°C error per ohm. A/D Conversion Sequence 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. Remote-Diode Selection The MAX6657/MAX6658/MAX6659 can directly measure the die temperature of CPUs and other ICs that have on-board temperature-sensing diodes (see Typical Operating Circuit) or they can measure the temperature of a discrete diode-connected transistor. The type of remote diode used is set by bit 5 of the Configuration Byte. If bit 5 is set to zero, the remote sensor is a diode-connected transistor, and if bit 5 is set to 1, the remote sensor is a substrate or common collector PNP 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. 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. Thermal Mass and Self-Heating 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 MAX6657/ MAX6658/MAX6659, 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 V CC = +5.0V, a 16Hz conversion rate and ALERT sinking 1mA, the typical power dissipation is: VCC x 450µA + 0.4V x 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: ∆T = 2.65mW x +170°C/W = +0.45°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 mea- _______________________________________________________________________________________ 7 MAX6657/MAX6658/MAX6659 Table 1. Remote-Sensor Transistor MAX6657/MAX6658/MAX6659 ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms surements. 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. GND 10MILS 10MILS DXP MINIMUM 10MILS DXN 10MILS GND Figure 1. Recommended DXP-DXN PC Traces PC Board Layout Follow these guidelines to reduce the measurement error of the temperature sensors: 1) Place the MAX6657/MAX6658/MAX6659 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 20MΩ leakage 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). 4) Route through as few vias and crossunders as possible to minimize copper/solder thermocouple effects. 8 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. 7) Add a 200Ω resistor in series with V CC for best noise filtering (see Typical Operating Circuit). Twisted-Pair and Shielded Cables 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. For example, Belden #8451 works well for distances up to 100ft in a noisy environment. 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 1Ω of series resistance, the error is approximately +1/2°C. Low-Power Standby Mode Standby mode reduces the supply current to less than 10µA by disabling the ADC. Enter hardware standby (MAX6659 only) by forcing the STBY pin low, or enter software standby by setting the RUN/STOP bit to 1 in the Configuration Byte register. Hardware and software standbys are very similar—all data is retained in memory, and the SMB interface is alive and listening for SMBus commands. The only difference is that in software standby mode, the one-shot command initiates a conversion. With hardware standby, the one-shot command is ignored. Activity on the SMBus causes the device to draw extra supply current. Driving the STBY pin low overrides any software conversion command. If a hardware or software standby command is received while a conversion is in progress, the conversion cycle is interrupted, and the tempera- _______________________________________________________________________________________ ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms SMBus Digital Interface From a software perspective, each of the MAX6657/ MAX6658/MAX6659 appears as a series of 8-bit registers that contain temperature data, alarm threshold values, and control bits. A standard SMBus-compatible 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 MAX6657/MAX6658/MAX6659 employ 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. When the conversion rate is greater than 4Hz, temperature data can be read from the Read Internal Temperature (00h) and Read External Temperature (01h) registers. Write Byte Format S ADDRESS WR ACK COMMAND 7 bits ACK DATA 8 bits Slave Address: equivalent to chip-select line of a 3-wire interface ACK P 8 bits Command Byte: selects which register you are writing to 1 Data Byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sampling rate) Read Byte Format ADDRESS WR ACK 7 bits COMMAND ACK RD ACK 7 bits Command Byte: selects which register you are reading from Send Byte Format DATA /// P 8 bits Slave Address: repeated due to change in dataflow direction Data Byte: reads from the register set by the command byte Receive Byte Format WR 7 bits ACK COMMAND ACK P 8 bits Command Byte: sends command with no data, usually used for one-shot command S = Start condition P = Stop condition ADDRESS 8 bits Slave Address: equivalent to chip-select line ADDRESS S Shaded = Slave transmission /// = Not acknowledged S ADDRESS 7 bits RD ACK DATA /// P 8 bits Data Byte: reads data from the register commanded by the last Read Byte or Write Byte transmission; also used for SMBus Alert Response return address Figure 2. SMBus Protocols ______________________________________________________________________________________ 9 MAX6657/MAX6658/MAX6659 The temperature data format is 7 bits + sign in two'scomplement form for each channel, with the LSB representing 1°C (Table 2). The MSB is transmitted first. When the conversion rate is 4Hz or less, the first 8 bits of temperature data can be read from the Read Internal Temperature (00h) and Read External Temperature (01h) registers, the same as for faster conversion rates. An additional 3 bits can be read from the Read External Extended Temperature (10h) and Read Internal Extended Temperature (11h) registers, which extends the data to 10 bits + sign and the resolution to +0.125°C per LSB (Table 3). When a conversion is complete, the Main register and the Extended register are updated almost simultaneously. Ensure that no conversions are completed between reading the Main and Extended registers so that when data that is read, both registers contain the result of the same conversion. To ensure valid extended data, read extended resolution temperature data using one of the following approaches: 1) Put the MAX6657/MAX6658/MAX6659 into standby mode by setting bit 6 of the Configuration register to ture registers are not updated. The previous data is not changed and remains available. MAX6657/MAX6658/MAX6659 ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms A tLOW B tHIGH C D E F G H I J K L M SMBCLK SMBDATA tHD:STA tSU:STA tSU:DAT A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE E = SLAVE PULLS SMBDATA LINE LOW tHD:DAT tSU:STO tBUF J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION 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 Figure 3. SMBus Write Timing Diagram A tLOW B tHIGH C D E F G H I J K L M SMBCLK SMBDATA tSU:STA tHD:STA A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE E = SLAVE PULLS SMBDATA LINE LOW tSU:DAT tHD:DAT F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO MASTER H = LSB OF DATA CLOCKED INTO MASTER I = MASTER PULLS DATA LINE LOW tSU:STO tBUF J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION Figure 4. SMBus Read Timing Diagram 1. Initiate a one-shot conversion using Command Byte 0Fh. When this conversion is complete, read the contents of the Temperature Data registers. 2) If the MAX6657/MAX6658/MAX6659 are in run mode, read the Status register. If a conversion is in progress, the BUSY bit is set to 1. Wait for the conversion to complete as indicated by the BUSY bit being set to 0, then read the Temperature Data registers. Note that the power-on reset sets the conversion rate to 16Hz, so no extended data is valid without reducing the conversion rate to 4Hz or less. 10 Diode Fault Alarm There is a continuity fault detector at DXP that detects an open circuit 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. Additionally, if the fault is an open circuit, bit 2 (OPEN) of the status byte 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 until the end of the first conversion. ______________________________________________________________________________________ ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms DIGITAL OUTPUT TEMP (°C) MAX6657 MAX6658 MAX6659 Table 3. Extended Resolution Register FRACTIONAL TEMPERATURE CONTENTS OF EXTENDED REGISTER 0.000 000X XXXX 001X XXXX 130.00 0 111 1111 0 111 1111 0.125 127.00 0 111 1111 0 111 1111 0.250 010X XXXX 126.00 0 111 1111 0 111 1111 0.375 011X XXXX 0 001 1001 0.500 100X XXXX 25 0 001 1001 0.00 0 000 0000 0 000 0000 0.625 101X XXXX -1 1 000 0000 1 111 1111 0.750 110X XXXX 0.875 111X XXXX -25 1 000 0000 1 110 0111 -55 1 000 0000 1 100 1001 Diode Fault (Short or Open) 1 000 0000 1 000 0000 Note: Extended resolution applies only for conversion rates of 4Hz and slower. Alert Response Address Alarm Threshold Registers Four registers store ALERT threshold values—one hightemperature (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 output is asserted. The POR state of both ALERT THIGH registers is 0100 0110 or +70°C and the POR state of TLOW registers is 1100 1001 or -55°C. Four additional registers store remote and local alarm threshold data corresponding to the OVERT1 and OVERT2 (MAX6659 only) 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 OVERT output is asserted. The POR state of the OVERT threshold is 0101 0101 or +85°C. Alert Interrupts An ALERT interrupt occurs when the internal or external temperature reading exceeds a high or low temperature 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 even if the fault condition still exists, but is reasserted at the end of the next conversion. The interrupt does not halt automatic conversions. The interrupt output pin is open-drain so that multiple devices can share a common interrupt line. The interrupt rate never exceeds the conversion rate. 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 8). 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 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 completion of the Alert Response protocol clears the interrupt latch, provided the condition that caused the alert no longer exists. If the condition still exists, the device reasserts the ALERT interrupt at the end of the next conversion. OVERT Overtemperature Alarm/Warning Outputs OVERT1 and OVERT2 (MAX6659 only) are asserted when the temperature rises to a value programmed in the appropriate threshold register. They are deasserted when the temperature drops below this threshold minus the hysteresis. An OVERT output can be used to activate a cooling fan, send a warning, or trigger a system shutdown to prevent component damage. The HYST byte sets the amount of hysteresis for both OVERT outputs. The data format for the HYST byte is the same for the other temperature registers (Table 2). ______________________________________________________________________________________ 11 MAX6657/MAX6658/MAX6659 Table 2. Data Format (Two's Complement) MAX6657/MAX6658/MAX6659 ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms Table 4. Command Byte Register Assignments REGISTER ADDRESS POR STATE RLTS 00h 0000 0000 Read Internal Temperature FUNCTION RRTE 01h 0000 0000 Read External Temperature RSL 02h 1000 0000 Read Status Register RCL 03h 0010 0000 Read Configuration Byte RCRA 04h 0000 1000 Read Conversion Rate Byte RLHN 05h 0100 0110 Read Internal High Limit RLLI 06h 1100 1001 Read Internal Low Limit RRHI 07h 0100 0110 Read External High Limit RRLS 08h 1100 1001 Read External Low Limit WCA 09h 0010 0000 Write Configuration Byte WCRW 0Ah 0000 1000 Write Conversion Rate Byte WLHO 0Bh 0100 0110 Write Internal High Limit Write Internal Low Limit WLLM 0Ch 1100 1001 WRHA 0Dh 0100 0110 Write External High Limit WRLN 0Eh 1100 1001 Write External Low Limit OSHT 0Fh N/A REET 10h 0000 0000 Read External Extended Temperature RIET 11h 0000 0000 Read Internal Extended Temperature One Shot RWO2E 16h 0101 0101 Read/Write External OVERT2 Limit (MAX6659 only) RW02I 17h 0101 0101 Read/Write Internal OVERT2 Limit (MAX6659 only) RWOE 19h 0101 0101 Read/Write External OVERT1 Limit RWOI 20h 0101 0101 Read/Write Internal OVERT1 Limit HYST 21h 0000 1010 Overtemperature Hysteresis — FEh 4Dh Read Manufacture ID For example, OVERT1 has a threshold set to +50°C and is connected to a fan. OVERT2 has a threshold of +75°C and is connected to a system shutdown. If the system reaches +50°C, the fan turns on, trying to cool the system. If the system continues to heat up to the critical temperature of +75°C, OVERT2 causes the system to shut down. Command Byte Functions The 8-bit Command Byte register (Table 4) is the master index that points to the various other registers within the MAX6657/MAX6658/MAX6659. 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. One-Shot The one-shot command immediately forces a new conversion cycle to begin. If the one-shot command is received when the MAX6657/MAX6658/MAX6659 are in 12 software standby mode (RUN/STOP bit = 1), 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 = 0) 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 5) 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. Bit 5 selects the type of external junction (set to 1 for a substrate PNP on an IC or set to 0 for a discrete diode-connected transistor) for optimized measurements. Bits 0 to 4 are reserved and return a zero when read. ______________________________________________________________________________________ ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms Table 5. Configuration-Byte Bit Assignments BIT NAME POR STATE 7 (MSB) MASK1 0 Masks ALERT interrupts if a 1. 6 RUN/STOP 0 Standby mode control bit; if a 1, standby mode is initiated. 1 Set to 1 when the remote sensor is a substrate or common collector PNP. Set to 0 when the remote sensor is a diode-connected discrete transistor. 5 SPNP 4 to 0 RFU 0 FUNCTION Reserved ALERT output follows the status flag bit. Both are cleared when successfully read, but if the condition still exists, they reassert at the end of the next conversion. The bits indicating OVERT1 (bits 0 and 1) are cleared only when the condition no longer exists. Reading the status byte does not clear the OVERT1 outputs or fault bits. One way to eliminate the fault condition is for the measured temperature to drop below the temperature threshold minus the hysteresis value. Another way to eliminate the fault condition is by writing new values for the OVERT1 threshold or hysteresis so that a fault condition is no longer present. Note that the status byte does not provide status of OVERT2. The MAX6657/MAX6658/MAX6659 incorporate collision avoidance so that completely asynchronous operation is allowed between SMBus operations and temperature conversions. When autoconverting, if the THIGH and TLOW limits are close together, it’s possible for both high-temp and lowtemp 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. Conversion Rate Byte The Conversion Rate register (Table 7) programs the time interval between conversions in free-running autonomous mode (RUN/STOP = 0). This variable rate Table 6. Status Register Bit Assignments BIT NAME POR STATE 7 (MSB) BUSY 1 A/D is busy converting when high. FUNCTION 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. 1 EOT1 0 A high indicates the external junction temperature exceeds the external OVERT1 threshold. 0 IOT1 0 A high indicates the internal junction temperature exceeds the internal OVERT1 threshold. ______________________________________________________________________________________ 13 MAX6657/MAX6658/MAX6659 Status Byte Functions The status byte (Table 6) 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. Bits 2 through 6 of the Status register are cleared by any successful read of the Status register, unless the fault persists. The MAX6657/MAX6658/MAX6659 ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms Table 8. Slave Address Decoding for MAX6659 Table 7. Conversion-Rate Control Byte DATA CONVERSION RATE (Hz) ADD CONNECTION ADDRESS 00h 0.0625 GND 1001100 01h 0.125 VCC 1001110 02h 0.25 Floating 1001101 03h 0.5 04h 1 05h 2 06h 4 07h 8 08h 16 09h 16 0Ah-FFh Reserved Note: Extended resolution applies only for conversion rates of 4Hz or slower. control can be used to reduce the supply current in portable-equipment applications. The conversion rate byte’s POR state is 08h (16Hz). The MAX6657/ MAX6658/MAX6659 use 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, 156ms maximum) after initiating a conversion, whether conversion is initiated through the RUN/STOP bit, hardware STBY pin, one-shot command, or initial power-up. Slave Addresses The MAX6657/MAX6658 have a fixed address of 1001100. The MAX6659 can be programmed to have one of three different addresses, allowing up to three devices to reside on the same bus without address conflicts. Table 8 lists address information. The address pin state is checked at POR only, and the address data stays latched to reduce quiescent supply current due to the bias current needed for high-Z state detection. The MAX6657/MAX6658/MAX6659 also respond to the SMBus Alert Response slave address (see Alert Response Address section). POR and UVLO The MAX6657/MAX6658/MAX6659 have a volatile memory. To prevent unreliable power-supply conditions 14 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 V CC 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). Power-Up Defaults Power-up defaults include: • ADC begins autoconverting at a 16Hz rate (legacy resolution). • THIGH and TLOW registers are set to default limits, respectively. • Interrupt latch is cleared. • Address-select pin is sampled (MAX6659 only). • Command register is set to 00h to facilitate quick internal Receive Byte queries. • Hysteresis is set to 10°C. • Transistor type is set to a substrate or common collector PNP. Table 9. Read Format for Alert Response Address (000 1100) BIT NAME 7 (MSB) ADD7 6 ADD6 5 ADD5 4 ADD4 3 ADD3 2 ADD2 1 ADD1 0 (LSB) 1 FUNCTION Provide the current MAX6659 slave address that was latched at POR (Table 8) Logic 1 ______________________________________________________________________________________ ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms 3.3V 0.1µF 200Ω 10kΩ EACH DXP VCC (STBY) SMBDATA DXN DATA CLOCK SMBCLK 2200pF MAX6657 MAX6658 MAX6659 µP INTERRUPTED TO µP ALERT TO FAN DRIVER OVERT1 (OVERT2) (ADD) TO SYSTEM SHUTDOWN GND () ARE MAX6659 ONLY Chip Information TRANSISTOR COUNT: 16,989 PROCESS: BiCMOS ______________________________________________________________________________________ 15 MAX6657/MAX6658/MAX6659 Typical Operating Circuit ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms SOICN.EPS MAX6657/MAX6658/MAX6659 Package Information 16 ______________________________________________________________________________________ ±1°C, SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms QSOP.EPS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 17 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX6657/MAX6658/MAX6659 Package Information (continued)