TMP401 SBOS371 − AUGUST 2006 +15C Programmable, Remote/Local, Digital Out TEMPERATURE SENSOR FEATURES DESCRIPTION D D D D D D The TMP401 is a remote temperature sensor monitor with a built-in local temperature sensor. The remote temperature sensor diode-connected transistors are typically low-cost, NPN- or PNP-type transistors or diodes that are an integral part of microcontrollers, microprocessors, or FPGAs. D D D ±1°C REMOTE DIODE SENSOR ±3°C LOCAL TEMPERATURE SENSOR SERIES RESISTANCE CANCELLATION THERM FLAG OUTPUT ALERT/THERM2 FLAG OUTPUT PROGRAMMABLE OVER/UNDER TEMPERATURE LIMITS PROGRAMMABLE RESOLUTION: 9- to 12-Bit DIODE FAULT DETECTION SMBus SERIAL INTERFACE Features included in the TMP401 are series resistance cancellation, wide remote temperature measurement range (up to +150°C), diode fault detection, and temperature alert functions. APPLICATIONS D D D D D D Remote accuracy is ±1°C for multiple IC manufacturers, with no calibration needed. The Two-Wire serial interface accepts SMBus write byte, read byte, send byte, and receive byte commands to program alarm thresholds and to read temperature data. LCD/DLPE/LCOS PROJECTORS SERVERS INDUSTRIAL CONTROLLERS CENTRAL OFFICE TELECOM EQUIPMENT DESKTOP AND NOTEBOOK COMPUTERS STORAGE AREA NETWORKS 4 V+ 1 V+ 6 TMP401 5 GND Interrupt Configuration THERM ALERT/THERM2 Consecutive Alert Configuration Register Remote Temp High Limit One− Shot Start Register Status Register Remote THERM Limit Remote Temp Low Limit Local Temperature Register TL THERM Hysteresis Register Local Temp High Limit Local THERM Limit Temperature Comparators Conversion Rate Register Manufacturer ID Register D+ 2 3 Local Temp Low Limit Remote Temperature Register TR Device ID Register Configuration Register D− Resolution Register SCL SDA 8 7 Bus Interface Pointer Register Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. DLP is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. Copyright 2006, Texas Instruments Incorporated ! ! www.ti.com "#$% www.ti.com SBOS371 − AUGUST 2006 ABSOLUTE MAXIMUM RATINGS(1) Power Supply, VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0V Input Voltage(2) . . . . . . . . . . . . . . . . . . . . . . . . . . −0.5V to VS + 0.5V Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10mA Operating Temperature Range . . . . . . . . . . . . . . . −55°C to +127°C Storage Temperature Range . . . . . . . . . . . . . . . . . −60°C to +130°C Junction Temperature (TJ max) . . . . . . . . . . . . . . . . . . . . . . +150°C ESD Rating: Human Body Model (HBM) . . . . . . . . . . . . . . . . . . . . . . . 4000V Charged Device Model (CDM) . . . . . . . . . . . . . . . . . . . . 1000V (1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not supported. (2) Input voltage rating applies to all TMP401 input voltages. This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PACKAGE/ORDERING INFORMATION(1) PRODUCT DESCRIPTION ADDRESS PACKAGE DESIGNATOR PACKAGE-LEAD PACKAGE MARKING TMP401 Remote Junction Temperature Sensor 1001100 MSOP-8 DGK BRB (1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website at www.ti.com. PIN CONFIGURATION PIN ASSIGNMENTS TOP VIEW MSOP-8 PIN NAME 1 V+ Positive supply (3V to 5.5V) 2 D+ Positive connection to remote temperature sensor 3 D− Negative connection to remote temperature sensor TMP401 V+ 1 8 SCL D+ 2 7 SDA 4 THERM D− 3 6 ALERT/THERM2 5 GND THERM 4 5 GND 6 2 DESCRIPTION Thermal flag, active low, open-drain; requires pull-up resistor to V+ Ground Alert (reconfigurable as second ALERT/THERM2 thermal flag), active low, open-drain; requires pull-up resistor to V+ 7 SDA Serial data line for SMBus, open-drain; requires pull-up resistor to V+ 8 SCL Serial clock line for SMBus, open-drain; requires pull-up resistor to V+ "#$% www.ti.com SBOS371 − AUGUST 2006 ELECTRICAL CHARACTERISTICS: VS = 3V to 5.5V At TA = −40°C to +125°C, and VS = 3V to 5.5V, unless otherwise noted. TMP401 PARAMETER CONDITION MIN TYP MAX UNITS ±1 TEMPERATURE ERROR Local Temperature Sensor Remote Temperature Sensor(1) TELOCAL TEREMOTE ±3 °C TA = +15°C to +75°C, TD = −40°C to +150°C, VS = 3.3V ±1 °C TA = −40°C to +100°C, TD = −40°C to +150°C, VS = 3.3V ±3 °C TA = −40°C to +125°C, TD = −40°C to +150°C, VS = 3.3V ±5 °C ±0.5 °C/V TA = −40°C to +125°C vs Supply Local/Remote VS = 3V to 5.5V ±0.2 One Shot Mode 115 TEMPERATURE MEASUREMENT Conversion Time (per channel) ms Resolution Local Temperature Sensor (programmable) 9 Remote Temperature Sensor 12 Bits 12 Bits Remote Sensor Source Currents 120 µA Medium High 60 µA Medium Low 12 µA Low 6 µA High Remote Transistor Ideality Factor Series Resistance 3kΩ Max η TMP401 Optimized Ideality Factor 1.008 SMBus INTERFACE Logic Input High Voltage (SCL, SDA) VIH Logic Input Low Voltage (SCL, SDA) VIL 2.1 V 0.8 Hysteresis 500 SMBus Output Low Sink Current 6 Logic Input Current −1 SMBus Input Capacitance (SCL, SDA) mA +1 µA 3.4 MHz 35 ms 1 µs 3 SMBus Clock Frequency SMBus Timeout V mV 30 SCL Falling Edge to SDA Valid Time pF DIGITAL OUTPUTS Output Low Voltage VOL IOUT = 6mA 0.15 0.4 V High-Level Output Leakage Current IOH VOUT = VS 0.1 1 µA ALERT/THERM2 Output Low Sink Current THERM Output Low Sink Current ALERT/THERM2 Forced to 0.4V 6 mA THERM Forced to 0.4V 6 mA POWER SUPPLY Specified Voltage Range Quiescent Current Power-On Reset Threshold VS IQ 5.5 V 0.0625 Conversions per Second 3 25 30 µA 8 Conversions per Second 350 425 µA Serial Bus Inactive, Shutdown Mode 3 10 µA Serial Bus Active, fS = 400kHz, Shutdown Mode 90 Serial Bus Active, fS = 3.4MHz, Shutdown Mode 350 POR 1.6 µA µA 2.5 V TEMPERATURE RANGE Specified Range −40 +125 °C Storage Range −60 +130 °C Thermal Resistance qJA MSOP-8 150 °C/W (1) Tested with less than 5Ω effective series resistance and 100pF differential input capacitance. 3 "#$% www.ti.com SBOS371 − AUGUST 2006 TYPICAL CHARACTERISTICS At TA = +25°C and VS = 5.0V, unless otherwise noted. REMOTE TEMPERATURE ERROR vs TEMPERATURE 3 VS = 3.3V TREMOTE = +25_C 2 28 Typical Units Shown Local Temperature Error (_ C) Remote Temperature Error (_C) 3 LOCAL TEMPERATURE ERROR vs TEMPERATURE 30 Typical Units Shown η = 1.008 1 0 −1 −2 −3 −50 −25 0 25 50 75 100 1 0 −1 −2 −3 −50 125 −25 25 50 75 100 125 Ambient Temperature, TA (_ C) Figure 1 Figure 2 REMOTE TEMPERATURE ERROR vs LEAKAGE RESISTANCE REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE (Diode Connected Transistor, 2N3906 PNP) Remote Temperature Error (_C) 16 40 20 R −GND 0 R −VS −20 −40 −60 14 12 10 VS = 3.3V 8 6 4 VS = 5.5V 2 0 −2 0 5 10 15 20 25 30 0 500 1000 1500 Leakage Resistance (MΩ) RS (Ω) Figure 3 Figure 4 REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE (GND Collector Connected Transistor, 2N3906 PNP) 2000 2500 3000 REMOTE TEMPERATURE ERROR vs DIFFERENTIAL CAPACITANCE 3 Remote Temperature Error (_C) 5 Remote Temperature Error (_C) 0 Ambient Temperature, TA (_ C) 60 Remote Temperature Error (_C) 2 4 3 VS = 3.3V 2 1 0 2 1 0 −1 −2 VS = 5.5V −1 −3 0 500 1000 1500 RS (Ω) Figure 5 4 2000 2500 3000 0 0.5 1.0 1.5 2.0 Capacitance (nF) Figure 6 2.5 3.0 "#$% www.ti.com SBOS371 − AUGUST 2006 TYPICAL CHARACTERISTICS (continued) At TA = +25°C and VS = 5.0V, unless otherwise noted. TEMPERATURE ERROR vs POWER−SUPPLY NOISE FREQUENCY 25 500 Local 100mVPP Noise Remote 100mVPP Noise Local 250mVPP Noise Remote 250mVPP Noise 20 15 10 5 450 400 350 I Q (µA) Temperature Error (_C) QUIESCENT CURRENT vs CONVERSION RATE 0 −5 300 250 200 −10 150 −15 100 −20 50 −25 0 5 10 0 0.0625 15 0.25 0.5 1 2 Conversion Rate (samples/s) Figure 7 Figure 8 SHUTDOWN QUIESCENT CURRENT vs SCL CLOCK FREQUENCY 4 8 SHUTDOWN QUIESCENT CURRENT vs SUPPLY VOLTAGE 500 8 450 7 400 6 350 5 300 250 I Q (µA) IQ (µA) 0.125 Frequency (MHz) VS = 5.5V 200 4 3 150 2 100 1 50 VS = 3.3V 0 1k 10k 100k 1M SCL CLock Frequency (Hz) Figure 9 10M 0 3.0 3.5 4.0 4.5 5.0 5.5 6.0 VS (V) Figure 10 5 "#$% www.ti.com SBOS371 − AUGUST 2006 (ALERT). Additional thermal limits can be programmed into the TMP401 and used to trigger another flag (THERM) that can be used to initiate a system response to rising temperatures. APPLICATIONS INFORMATION The TMP401 is a dual-channel digital temperature sensor that combines a local die temperature measurement channel and a remote junction temperature measurement channel in a single MSOP-8 package. The TMP401 is Two-Wire- and SMBus interface-compatible and is specified over a temperature range of −40°C to +125°C. The TMP401 contains multiple registers for holding configuration information, temperature measurement results, temperature comparator limits, and status information. The TMP401 requires only a transistor connected between D+ and D− for proper remote temperature sensing operation. The SCL and SDA interface pins require pull-up resistors as part of the communication bus, while ALERT and THERM are open-drain outputs that also need pull-up resistors. ALERT and THERM may be shared with other devices if desired for a wired-OR implementation. A 0.1µF power-supply bypass capacitor is recommended for good local bypassing. Figure 11 shows a typical configuration for the TMP401. User-programmed high and low temperature limits stored in the TMP401 can be used to monitor local and remote temperatures to trigger an over/under temperature alarm +5V 0.1µF Transistor−connected configuration(1) : 1 Series Resistance RS(2) V+ SCL RS(2) 2 CDIFF(3) 3 D+ 10kΩ (typ) 10kΩ (typ) 10kΩ (typ) 10kΩ (typ) 8 TMP401 SDA 7 D− ALERT/THERM2 THERM SMBus Controller 6 4 Fan Controller GND Diode−connected configuration(1): 5 RS(2) RS(2) CDIFF(3) NOTES: (1) Transistor−connected configuration provides better settling time. Diode−connected configuration provides better series resistance cancellation. (2) RS should be < 1.5kΩ in most applications. (3) CDIFF should be < 1000pF in most applications. Figure 11. Basic Connections 6 "#$% www.ti.com SBOS371 − AUGUST 2006 SERIES RESISTANCE CANCELLATION Series resistance in an application circuit that typically results from printed circuit board (PCB) trace resistance and remote line length (see Figure 11) is automatically cancelled by the TMP401, preventing what would otherwise result in a temperature offset. When using a 5V supply voltage, a total of up to 3kΩ of series line resistance is cancelled by the TMP401, eliminating the need for additional characterization and temperature offset correction. Series line resistance should be limited to 500Ω total when using a 3.3V supply voltage. See typical characteristics curves (Figure 4 and Figure 5) for details on the effect of series resistance and power-supply voltage on sensed remote temperature error. DIFFERENTIAL INPUT CAPACITANCE The TMP401 tolerates differential input capacitance of up to 1000pF with minimal change in temperature error. The effect of capacitance on sensed remote temperature error is shown in Figure 6, Remote Temperature Error vs Differential Capacitance. TEMPERATURE MEASUREMENT DATA Temperature measurement data is taken over a default range of 0°C to +127°C for both local and remote locations. Measurements from −55°C to +150°C can be made both locally and remotely by reconfiguring the TMP401 for the extended temperature range. To change the TMP401 configuration from the standard to the extended temperature range, switch bit 2 (RANGE) of the Configuration Register from low to high. Temperature data resulting from conversions within the default measurement range is represented in binary form, as shown in Table 1, Standard Binary column. Note that any temperature below 0°C results in a data value of zero (00h). Likewise, temperatures above +127°C result in a value of 127 (7Fh). The device can be set to measure over an extended temperature range by changing bit 2 of the Configuration Register from low to high. The change in measurement range and data format from standard binary to extended binary occurs at the next temperature conversion. For data captured in the extended temperature range configuration, an offset of 64 (40h) is added to the standard binary value, as shown in Table 1, Extended Binary column. This configuration allows measurement of temperatures below 0°C. Note that binary values corresponding to temperatures as low as −64°C, and as high as +191°C are possible; however, most temperature sensing diodes only measure with the range of −55°C to +150°C. Additionally, the TMP401 is rated only for ambient temperatures ranging from −40°C to +125°C. Parameters in the Absolute Maximum Ratings table must be observed. Table 1. Temperature Data Format (Local and Remote Temperature High Bytes) LOCAL/REMOTE TEMPERATURE REGISTER HIGH BYTE VALUE (+15C RESOLUTION) TEMP (5C) STANDARD BINARY EXTENDED BINARY BINARY HEX BINARY HEX −64 0000 0000 00 0000 0000 00 −50 0000 0000 00 0000 1110 0E −25 0000 0000 00 0010 0111 27 0 0000 0000 00 0100 0000 40 1 0000 0001 01 0100 0001 41 5 0000 0101 05 0100 0101 45 10 0000 1010 0A 0100 1010 4A 25 0001 1001 19 0101 1001 59 50 0011 0010 32 0111 0010 72 75 0100 1011 4B 1000 1011 8B 100 0110 0100 64 1010 0100 A4 125 0111 1101 7D 1011 1101 BD 127 0111 1111 7F 1011 1111 BF 150 0111 1111 7F 1101 0110 D6 175 0111 1111 7F 1110 1111 EF 191 0111 1111 7F 1111 1111 FF NOTE: Whenever changing between standard and extended temperature ranges, be aware that the temperatures stored in the temperature limit registers are NOT automatically reformatted to correspond to the new temperature range format. These temperature limit values must be reprogrammed in the appropriate binary or extended binary format. Both local and remote temperature data use two bytes for data storage. The high byte stores the temperature with 1°C resolution. The second or low byte stores the decimal fraction value of the temperature and allows a higher measurement resolution; see Table 2. The measurement resolution for the remote channel is 0.0625°C, and is not adjustable. The measurement resolution for the local channel is adjustable; it can be set for 0.5°C, 0.25°C, 0.125°C, or 0.0625°C by setting the RES1 and RES0 bits of the Resolution Register; see the Resolution Register section. 7 "#$% www.ti.com SBOS371 − AUGUST 2006 Table 2. Decimal Fraction Temperature Data Format (Local and Remote Temperature Low Bytes) REMOTE TEMPERATURE REGISTER LOW BYTE VALUE 0.06255C RESOLUTION LOCAL TEMPERATURE REGISTER LOW BYTE VALUE 0.55C RESOLUTION 0.255C RESOLUTION 0.1255C RESOLUTION HEX STANDARD AND EXTENDED BINARY HEX STANDARD AND EXTENDED BINARY TEMP (5C) STANDARD AND EXTENDED BINARY HEX STANDARD AND EXTENDED BINARY 0.0000 0000 0000 00 0000 0000 00 0000 0000 00 0.0625 0001 0000 10 0000 0000 00 0000 0000 00 0.1250 0010 0000 20 0000 0000 00 0000 0000 0.1875 0011 0000 30 0000 0000 00 0000 0000 0.2500 0100 0000 40 0000 0000 00 0.3125 0101 0000 50 0000 0000 0.3750 0110 0000 60 0000 0000 0.4375 0111 0000 70 0.5000 1000 0000 80 0.5625 1001 0000 0.6250 0.6875 0.06255C RESOLUTION HEX STANDARD AND EXTENDED BINARY HEX 0000 0000 00 0000 0000 00 0000 0000 00 0001 0000 10 00 0010 0000 20 0010 0000 20 00 0010 0000 20 0011 0000 30 0100 0000 40 0100 0000 40 0100 0000 40 00 0100 0000 40 0100 0000 40 0101 0000 50 00 0100 0000 40 0110 0000 60 0110 0000 60 0000 0000 00 0100 0000 40 0110 0000 60 0111 0000 70 1000 0000 80 1000 0000 80 1000 0000 80 1000 0000 80 90 1000 0000 80 1000 0000 80 1000 0000 80 1001 0000 90 1010 0000 A0 1000 0000 80 1000 0000 80 1010 0000 A0 1010 0000 A0 1011 0000 B0 1000 0000 80 1000 0000 80 1010 0000 A0 1011 0000 B0 0.7500 1100 0000 C0 1000 0000 80 1100 0000 C0 1100 0000 C0 1100 0000 C0 0.8125 1101 0000 D0 1000 0000 80 1100 0000 C0 1100 0000 C0 1101 0000 D0 0.8750 1110 0000 E0 1000 0000 80 1100 0000 C0 1110 0000 E0 1110 0000 E0 0.9375 1111 0000 F0 1000 0000 80 1100 0000 C0 1110 0000 E0 1111 0000 F0 REGISTER INFORMATION The TMP401 contains multiple registers for holding configuration information, temperature measurement results, temperature comparator limits, and status information. These registers are described in Figure 12 and Table 3. Pointer Register Local and Remote Temperature Registers Local and Remote Limit Registers Hysteresis Register SDA Status Register POINTER REGISTER Figure 12 shows the internal register structure of the TMP401. The 8-bit Pointer Register is used to address a given data register. The Pointer Register identifies which of the data registers should respond to a read or write command on the Two-Wire bus. This register is set with every write command. A write command must be issued to set the proper value in the Pointer Register before executing a read command. Table 3 describes the pointer address of the registers available in the TMP401. The power-on reset (POR) value of the Pointer Register is 00h (0000 0000b). 8 Configuration Register Resolution Register I/O Control Interface Conversion Rate Register One−Shot Register Consecutive Alert Register Identification Registers Figure 12. Internal Register Structure SCL "#$% www.ti.com SBOS371 − AUGUST 2006 Table 3. Register Map POINTER ADDRESS (HEX) READ WRITE POWERON RESET (HEX) 00 NA 00 LT11 LT10 LT9 LT8 LT7 LT6 LT5 LT4 Local Temperature (High Byte) 01 NA 00 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 Remote Temperature (High Byte) 02 NA XX BUSY LHIGH LLOW RHIGH RLOW OPEN RTHRM LTHRM Status Register 03 09 00 MASK1 SD AL/TH 0 0 RANGE 0 0 Configuration Register 04 0A 08 0 0 0 0 R3 R2 R1 R0 Conversion Rate Register 05 0B 55 LTH11 LTH10 LTH9 LTH8 LTH7 LTH6 LTH5 LTH4 Local Temperature High Limit (High Byte) 06 0C 00 LTL11 LTL10 LTL9 LTL8 LTL7 LTL6 LTL5 LTL4 Local Temperature Low Limit (High Byte) 07 0D 55 RTH11 RTH10 RTH9 RTH8 RTH7 RTH6 RTH5 RTH4 Remote Temperature High Limit (High Byte) 08 0E 00 RTL11 RTL10 RTL9 RTL8 RTL7 RTL6 RTL5 RTL4 Remote Temperature Low Limit (High Byte) NA 0F XX X X X X X X X X One−Shot Start 10 NA 00 RT3 RT2 RT1 RT0 0 0 0 0 Remote Temperature (Low Byte) 13 13 00 RTH3 RTH2 RTH1 RTH0 0 0 0 0 Remote Temperature High Limit (Low Byte) 14 14 00 RTL3 RTL2 RTL1 RTL0 0 0 0 0 Remote Temperature Low Limit (Low Byte) 15 NA 00 LT3 LT2 LT1 LT0 0 0 0 0 Local Temperature (Low Byte) 16 16 00 LTH3 LTH2 LTH1 LTH0 0 0 0 0 Local Temperature High Limit (Low Byte) 17 17 00 LTL3 LTL2 LTL1 LTL0 0 0 0 0 Local Temperature Low Limit (Low Byte) BIT DESCRIPTION D7 D6 D5 D4 D3 D2 D1 D0 REGISTER DESCRIPTION 19 19 55 RTHL11 RTHL10 RTHL9 RTHL8 RTHL7 RTHL6 RTHL5 RTHL4 Remote THERM Limit 1A 1A 1C 0 0 0 1 1 1 RES1 RES0 Resolution Register 20 20 55 LTHL11 LTHL10 LTHL9 LTHL8 LTHL7 LTHL6 LTHL5 LTHL4 Local THERM Limit 21 21 0A TH11 TH10 TH9 TH8 TH7 TH6 TH5 TH4 THERM Hysteresis 22 22 80 TO_EN 0 0 0 C2 C1 C0 0 Consecutive Alert Register FE NA 55 0 1 0 1 0 1 0 1 Manufacturer ID FF NA 11 0 0 0 1 0 0 0 1 Device ID NOTE: NA = Not applicable; register is write-only or read-only. X = Indeterminate state. 9 "#$% www.ti.com SBOS371 − AUGUST 2006 TEMPERATURE REGISTERS The TMP401 has four 8-bit registers that hold temperature measurement results. Both the local channel and the remote channel have a high byte register that contains the most significant bits (MSBs) of the temperature ADC result and a low byte register that contains the least significant bits (LSBs) of the temperature ADC result. The local channel high byte address is 00h; the local channel low byte address is 15h. The remote channel high byte is at address 01h; the remote channel low byte address is 10h. These registers are read-only and are updated by the ADC each time a temperature measurement is completed. The TMP401 contains circuitry to assure that a low byte register read command returns data from the same ADC conversion as the immediately preceding high byte read command. This assurance remains valid only until another register is read. For proper operation, the high byte of a temperature register should be read first. The low byte register should be read in the next read command. The low byte register may be left unread if the LSBs are not needed. Alternatively, the temperature registers may be read as a 16-bit register by using a single two-byte read command from address 00h for the local channel result or from address 01h for the remote channel result. The high byte will be output first, followed by the low byte. Both bytes of this read operation will be from the same ADC conversion. The power-on reset value of both temperature registers is 00h. LIMIT REGISTERS The TMP401 has 11 registers for setting comparator limits for both the local and remote measurement channels. These registers have read and write capability. The high and low limit registers for both channels span two registers, as do the temperature registers. The local temperature high limit is set by writing the high byte to pointer address 0Bh and writing the low byte to pointer address 16h, or by using a single two-byte write command (high byte first) to pointer address 0Bh. The local temperature high limit is obtained by reading the high byte from pointer address 05h and the low byte from pointer address 16h, or by using a two-byte read command from pointer address 05h. The power-on reset value of the local temperature high limit is 55h/00h (+85°C in standard temperature mode; +21°C in extended temperature mode). Similarly, the local temperature low limit is set by writing the high byte to pointer address 0Ch and writing the low byte to pointer address 17h, or by using a single two-byte write command to pointer address 0Ch. The local 10 temperature low limit is read by reading the high byte from pointer address 06h and the low byte from pointer address 17h, or by using a two-byte read from pointer address 06h. The power-on reset value of the local temperature low limit register is 00h/00h (0°C in standard temperature mode; −64°C in extended mode). The remote temperature high limit is set by writing the high byte to pointer address 0Dh and writing the low byte to pointer address 13h, or by using a two-byte write command to pointer address 0Dh. The remote temperature high limit is obtained by reading the high byte from pointer address 07h and the low byte from pointer address 13h, or by using a two-byte read command from pointer address 07h. The power-on reset value of the remote temperature high limit register is 55h/00h (+85°C in standard temperature mode; +21°C in extended temperature mode). The remote temperature low limit is set by writing the high byte to pointer address 0Eh and writing the low byte to pointer address 14h, or by using a two-byte write to pointer address 0Eh. The remote temperature low limit is read by reading the high byte from pointer address 08h and the low byte from pointer address 14h, or by using a two-byte read from pointer address 08h. The power-on reset value of the remote temperature low limit register is 00h/00h (0°C in standard temperature mode; −64°C in extended mode). The TMP401 also has a THERM limit register for both the local and the remote channels. These registers are eight bits and allow for THERM limits set to 1°C resolution. The local channel THERM limit is set by writing to pointer address 20h. The remote channel THERM limit is set by writing to pointer address 19h. The local channel THERM limit is obtained by reading from pointer address 20h; the remote channel THERM limit is read by reading from pointer address 19h. The power-on reset value of the THERM limit registers is 55h (+85°C in standard temperature mode; +21°C in extended temperature mode). The THERM limit comparators also have hysteresis. The hysteresis of both comparators is set by writing to pointer address 21h. The hysteresis value is obtained by reading from pointer address 21h. The value in the hysteresis register is an unsigned number (always positive). The power-on reset value of this register is 0Ah (+10°C). Whenever changing between standard and extended temperature ranges, be aware that the temperatures stored in the temperature limit registers are NOT automatically reformatted to correspond to the new temperature range format. These values must be reprogrammed in the appropriate binary or extended binary format. "#$% www.ti.com SBOS371 − AUGUST 2006 STATUS REGISTER The RHIGH bit reads as ‘1’ if the remote temperature has exceeded the remote high limit and remains greater than the remote high limit less the value in the Hysteresis Register. The TMP401 has a status register to report the state of the temperature comparators. Table 4 shows the Status Register bits. The Status Register is read-only and is read by reading from pointer address 02h. The LLOW and RLOW bits are not affected by the AL/TH bit. The LLOW bit reads as ‘1’ if the local low limit was exceeded since the last clearing of the Status Register. The RLOW bit reads as ‘1’ if the remote low limit was exceeded since the last clearing of the Status Register. The BUSY bit reads as ‘1’ if the ADC is making a conversion. It reads as ‘0’ if the ADC is not converting. The OPEN bit reads as ‘1’ if the remote transistor was detected as open since the last read of the Status Register. The OPEN status is only detected when the ADC is attempting to convert a remote temperature. The values of the LLOW, RLOW, and OPEN (as well as LHIGH and RHIGH when AL/TH is ‘0’) are latched and will read as ‘1’ until the Status Register is read or a device reset occurs. These bits are cleared by reading the Status Register, provided that the condition causing the flag to be set no longer exists. The values of BUSY, LTHRM, and RTHRM (as well as LHIGH and RHIGH when AL/TH is ‘1’) are not latched and are not cleared by reading the Status Register. They always indicate the current state, and are updated appropriately at the end of the corresponding ADC conversion. Clearing the Status Register bits does not clear the state of the ALERT pin; an SMBus alert response address command must be used to clear the ALERT pin. The RTHRM bit reads as ‘1’ if the remote temperature has exceeded the remote THERM limit and remains greater than the remote THERM limit less the value in the shared hysteresis register; see Figure 17. The LTHRM bit reads as ‘1’ if the local temperature has exceeded the local THERM limit and remains greater than the local THERM limit less the value in the shared hysteresis register; see Figure 17. The LHIGH and RHIGH bit values depend on the state of the AL/TH bit in the Configuration Register. If the AL/TH bit is ‘0’, the LHIGH bit reads as ‘1’ if the local high limit was exceeded since the last clearing of the Status Register. The RHIGH bit reads as ‘1’ if the remote high limit was exceeded since the last clearing of the Status Register. If the AL/TH bit is ‘1’, the remote high limit and the local high limit are used to implement a THERM2 function. LHIGH reads as ‘1’ if the local temperature has exceeded the local high limit and remains greater than the local high limit less the value in the Hysteresis Register. The TMP401 NORs LHIGH, LLOW, RHIGH, RLOW, and OPEN, so a status change for any of these flags from ‘0’ to ‘1’ automatically causes the ALERT pin to go low (only applies when the ALERT/THERM2 pin is configured for ALERT mode). Table 4. Status Register Format STATUS REGISTER (Read = 02h, Write = NA) BIT # BIT NAME POR VALUE D7 D6 D5 D4 D3 D2 D1 D0 BUSY LHIGH LLOW RHIGH RLOW OPEN RTHRM LTHRM 0(1) 0 0 0 0 0 0 0 (1) The BUSY bit will change to ‘1’ almost immediately (<< 100µs) following power-up, as the TMP401 begins the first temperature conversion. It will be high whenever the TMP401 is converting a temperature reading. 11 "#$% www.ti.com SBOS371 − AUGUST 2006 CONFIGURATION REGISTER The Configuration Register sets the temperature range, controls Shutdown mode, and determines how the ALERT/THERM2 pin functions. The Configuration Register is set by writing to pointer address 09h and read by reading from pointer address 03h. The MASK bit (bit 7) enables or disables the ALERT pin output if AL/TH = 0. If AL/TH = 1 then the MASK bit has no effect. If MASK is set to ‘0’, the ALERT pin goes low when one of the temperature measurement channels exceeds its high or low limits for the chosen number of consecutive conversions. If the MASK bit is set to ‘1’, the TMP401 retains the ALERT pin status, but the ALERT pin will not go low. The shutdown (SD) bit (bit 6) enables or disables the temperature measurement circuitry. If SD = 0, the TMP401 converts continuously at the rate set in the Conversion Rate Register. When SD is set to ‘1’, the TMP401 immediately stops converting and enters a shutdown mode. When SD is set to ‘0’ again, the TMP401 resumes continuous conversions. A single conversion can be started when SD = 1 by writing to the One-Shot Register. The AL/TH bit (bit 5) controls whether the ALERT pin functions in ALERT mode or THERM2 mode. If AL/TH = 0, the ALERT pin operates as an interrupt pin. In this mode, the ALERT pin goes low after the set number of consecutive out-of-limit temperature measurements occur. If AL/TH = 1, the ALERT/THERM2 pin implements a THERM function (THERM2). In this mode, THERM2 functions similar to the THERM pin except that the local high limit and remote high limit registers are used for the thresholds. THERM2 goes low when either RHIGH or LHIGH is set. The temperature range is set by configuring bit 2 of the Configuration Register. Setting this bit low configures the TMP401 for the standard measurement range (0°C to +127°C); temperature conversions will be stored in the standard binary format. Setting bit 2 high configures the TMP401 for the extended measurement range (−55°C to +150°C); temperature conversions will be stored in the extended binary format (see Table 1). The remaining bits of the Configuration Register are reserved and must always be set to ‘0’. The power-on reset value for this register is 00h. Table 5 summarizes the bits of the Configuration Register. Table 5. Configuration Register Bit Descriptions CONFIGURATION REGISTER (Read = 02h, Write = NA) 12 BIT NAME FUNCTION POWER-ON RESET VALUE 7 MASK 0 = ALERT Enabled 1 = ALERT Masked 0 6 SD 0 = Run 1 = Shut Down 0 5 AL/TH 0 = ALERT Mode 1 = THERM Mode 0 4, 3 Reserved — 0 2 Temperature Range 0 = 0°C to +127°C 1 = −55°C to +150°C 0 1, 0 Reserved — 0 "#$% www.ti.com SBOS371 − AUGUST 2006 RESOLUTION REGISTER CONVERSION RATE REGISTER The RES1 and RES0 bits (resolution bits 1 and 0) of the Resolution Register set the resolution of the local temperature measurement channel. Remote temperature measurement channel resolution is not affected. Changing the local channel resolution also affects the conversion time and rate of the TMP401. The resolution register is set by writing to pointer address 1Ah and is read by reading from pointer address 1Ah. Table 6 shows the resolution bits for the Resolution Register. The Conversion Rate Register controls the rate at which temperature conversions are performed. This register adjusts the idle time between conversions but not the conversion timing itself, thereby allowing the TMP401 power dissipation to be balanced with the temperature register update rate. Table 7 shows the conversion rate options and corresponding current consumption. ONE-SHOT CONVERSION Table 6. Resolution Register: Local Channel Programmable Resolution When the TMP401 is in shutdown mode (SD = 1 in the Configuration Register), a single conversion on both channels is started by writing any value to the One-Shot Start Register, pointer address 0Fh. This write operation starts one conversion; the TMP401 returns to shutdown mode when that conversion completes. The value of the data sent in the write command is irrelevant and is not stored by the TMP401. When the TMP401 has been set to shutdown mode, an initial 200µs is required before a one-shot command can be given. This wait time only applies to the 200µs immediately following shutdown. One-shot commands can be issued without delay thereafter. RESOLUTION REGISTER (Read = 1Ah, Write = 1Ah, POR = 1Ch) RESOLUTION CONVERSION TIME (Typical) 0 9 Bits (0.5°C) 12.5ms 1 10 Bits (0.25°C) 25ms RES1 RES0 0 0 1 0 11 Bits (0.125°C) 50ms 1 1 12 Bits (0.0625°C) 100ms Bits 2 through 4 of the Resolution Register must always be set to ‘1’. Bits 5 through 7 of the Resolution Register must always be set to ‘0’. The power-on reset value of this register is 1Ch. Table 7. Conversion Rate Register CONVERSION RATE REGISTER AVERAGE IQ (typ) (µA) R7 R6 R5 R4 R3 R2 R1 R0 CONVERSION/SEC VS = 3V VS = 5V 0 0 0 0 0 0 0 0 0.0625 8 29 0 0 0 0 0 0 0 1 0.125 11 31 0 0 0 0 0 0 1 0 0.25 15 36 0 0 0 0 0 0 1 1 0.5 24 45 0 0 0 0 0 1 0 0 1 41 63 0 0 0 0 0 1 0 1 2 69 92 0 0 0 0 0 1 1 0 4 111 136 8 320 355 07h to 0Fh 13 "#$% www.ti.com SBOS371 − AUGUST 2006 CONSECUTIVE ALERT REGISTER Local Temperature High Limit Register value, Remote Temperature High Limit Register value, Local THERM Limit Register value, or Remote THERM Limit Register value; otherwise, the respective temperature comparator will not trip on the measured temperature falling edges. Allowable hysteresis values are shown in Table 9. The default hysteresis value is 10°C, whether the device is operating in the standard or extended mode setting. The value in the Consecutive Alert Register (address 22h) determines how many consecutive out-of-limit measurements must occur on a measurement channel before the ALERT signal is activated. The value in this register does not affect bits in the Status Register. Values of one, two, three, or four consecutive conversions can be selected; one conversion is the default. This function allows additional filtering for the ALERT pin. The consecutive alert bits are shown in Table 8. Table 9. Allowable THERM Hysteresis Values THERM HYSTERESIS VALUE Table 8. Consecutive Alert Register CONSECUTIVE ALERT REGISTER C2 0 C1 0 NUMBER OF CONSECUTIVE OUT-OF-LIMIT MEASUREMENTS C0 0 1 0 0 1 2 0 1 1 3 1 1 1 4 NOTE: Bit 7 of the Consecutive Alert Register controls the enable/disable of the timeout function. See the Timeout Function section for a description of this feature. THERM HYSTERESIS REGISTER The THERM Hysteresis Register stores the hysteresis value used for the THERM pin alarm function. This register must be programmed with a value that is less than the TEMPERATURE (5C) TH[11:4] (STANDARD BINARY) (HEX) 0 0000 0000 00 1 0000 0001 01 5 0000 0101 05 10 0000 1010 0A 25 0001 1001 19 50 0011 0010 32 4B 75 0100 1011 100 0110 0100 64 125 0111 1101 7D 127 0111 1111 7F 150 1001 0110 96 175 1010 1111 AF 200 1100 1000 C8 225 1110 0001 E1 255 1111 1111 FF Table 10. THERM Hysteresis Register Format THERM HYSTERESIS REGISTER (Read = 21h, Write = 21h) BIT # BIT NAME POR VALUE 14 D7 D6 D5 D4 D3 D2 D1 D0 TH11 TH10 TH9 TH8 TH7 TH6 TH5 TH4 0 0 0 0 1 0 1 0 "#$% www.ti.com SBOS371 − AUGUST 2006 BUS OVERVIEW The TMP401 is SMBus interface-compatible. In SMBus protocol, the device that initiates the transfer is called a master, and the devices controlled by the master are slaves. The bus must be controlled by a master device that generates the serial clock (SCL), controls the bus access, and generates the START and STOP conditions. To address a specific device, a START condition is initiated. START is indicated by pulling the data line (SDA) from a high to low logic level while SCL is high. All slaves on the bus shift in the slave address byte, with the last bit indicating whether a read or write operation is intended. During the ninth clock pulse, the slave being addressed responds to the master by generating an Acknowledge and pulling SDA low. Data transfer is then initiated and sent over eight clock pulses followed by an Acknowledge bit. During data transfer SDA must remain stable while SCL is high, because any change in SDA while SCL is high is interpreted as a control signal. Once all data has been transferred, the master generates a STOP condition. STOP is indicated by pulling SDA from low to high, while SCL is high. SERIAL INTERFACE The TMP401 operates only as a slave device on either the Two-Wire bus or the SMBus. Connections to either bus are made via the open-drain I/O lines, SDA and SCL. The SDA and SCL pins feature integrated spike suppression filters and Schmitt triggers to minimize the effects of input spikes and bus noise. The TMP401 supports the transmission protocol for fast (1kHz to 400kHz) and high-speed (1kHz to 3.4MHz) modes. All data bytes are transmitted MSB first. SERIAL BUS ADDRESS To communicate with the TMP401, the master must first address slave devices via a slave address byte. The slave address byte consists of seven address bits, and a direction bit indicating the intent of executing a read or write operation. The address of the TMP401 is 4Ch (1001100b). READ/WRITE OPERATIONS Accessing a particular register on the TMP401 is accomplished by writing the appropriate value to the Pointer Register. The value for the Pointer Register is the first byte transferred after the slave address byte with the R/W bit low. Every write operation to the TMP401 requires a value for the Pointer Register (see Figure 14). When reading from the TMP401, the last value stored in the Pointer Register by a write operation is used to determine which register is read by a read operation. To change the register pointer for a read operation, a new value must be written to the pointer register. This transaction is accomplished by issuing a slave address byte with the R/W bit low, followed by the pointer register byte. No additional data is required. The master can then generate a START condition and send the slave address byte with the R/W bit high to initiate the read command. See Figure 15 for details of this sequence. If repeated reads from the same register are desired, it is not necessary to continually send the pointer register bytes, because the TMP401 retains the Pointer Register value until it is changed by the next write operation. Note that register bytes are sent MSB first, followed by the LSB. TIMING DIAGRAMS The TMP401 is Two-Wire and SMBus compatible. Figure 13 to Figure 16 describe the various operations on the TMP401. Bus definitions are given below. Parameters for Figure 13 are defined in Table 11. Bus Idle: Both SDA and SCL lines remain high. Start Data Transfer: A change in the state of the SDA line, from high to low, while the SCL line is high, defines a START condition. Each data transfer is initiated with a START condition. Stop Data Transfer: A change in the state of the SDA line from low to high while the SCL line is high defines a STOP condition. Each data transfer terminates with a repeated START or STOP condition. Data Transfer: The number of data bytes transferred between a START and a STOP condition is not limited and is determined by the master device. The receiver acknowledges the transfer of data. Acknowledge: Each receiving device, when addressed, is obliged to generate an Acknowledge bit. A device that acknowledges must pull down the SDA line during the Acknowledge clock pulse in such a way that the SDA line is stable low during the high period of the Acknowledge clock pulse. Setup and hold times must be taken into account. On a master receive, data transfer termination can be signaled by the master generating a Not-Acknowledge on the last byte that has been transmitted by the slave. 15 "#$% www.ti.com SBOS371 − AUGUST 2006 t(LOW) tF tR t(HDSTA) SCL t(HDSTA) t (HIGH) t(SUSTO) t(SUSTA) t(HDDAT) t(SUDAT) SDA t(B U F) P S S P Figure 13. Two-Wire Timing Diagram Table 11. Timing Diagram Definitions for Figure 13 MIN MAX MIN MAX SCL Operating Frequency PARAMETER f(SCL) 0.001 0.4 0.001 3.4 Bus Free Time Between STOP and START Condition t(BUF) 600 160 ns Hold time after repeated START condition. After this period, the first clock is generated. t(HDSTA) 100 100 ns Repeated START Condition Setup Time t(SUSTA) 100 100 ns STOP Condition Setup Time t(SUSTO) 100 100 ns Data Hold Time t(HDDAT) 0 0 ns Data Setup Time t(SUDAT) 100 10 ns SCL Clock LOW Period t(LOW) 1300 160 ns SCL Clock HIGH Period t(HIGH) 600 60 ns Clock/Data Fall Time tF 300 160 Clock/Data Rise Time for SCL ≤ 100kHz tR tR 300 1000 160 1 9 1 UNITS MHz ns ns 9 … SCL 1 SDA 0 0 1 1 0 0 R/W Start By Master P7 P6 P5 P4 P3 P2 P1 ACK By TMP401 ACK By TMP401 Frame 2 Pointer Register Byte Frame 1 Two−Wire Slave Address Byte 1 … P0 9 1 9 SCL (Continued) SDA (Continued) D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 ACK By TMP401 ACK By TMP401 Frame 3 Data Byte 1 Frame 4 Data Byte 2 Figure 14. Two-Wire Timing Diagram for Write Word Format 16 D0 Stop By Master "#$% www.ti.com SBOS371 − AUGUST 2006 1 9 1 9 … SCL 1 SDA 0 0 1 1 0 0 R/W Start By Master P7 P6 P5 P4 P3 P2 P1 … P0 ACK By TMP401 ACK By TMP401 Frame 1 Two−Wire Slave Address Byte Frame 2 Pointer Register Byte 1 9 1 9 … SCL (Continued) SDA (Continued) 1 0 0 0 1 0 0 D7 R/W Start By Master D6 D5 D4 D3 D2 ACK By TMP401 … D0 From TMP401 Frame 3 Two−Wire Slave Address Byte 1 D1 ACK By Master Frame 4 Data Byte 1 Read Register 9 SCL (Continued) SDA (Continued) D7 D6 D5 D4 D3 D2 D1 D0 From TMP401 ACK By Master Stop By Master Frame 5 Data Byte 2 Read Register Figure 15. Two-Wire Timing Diagram for Read Word Format ALERT 1 9 1 9 SCL SDA Start By Master 0 0 0 1 1 0 0 R/W 1 0 0 1 1 ACK By TMP401 Frame 1 SMBus ALERT Response Address Byte 0 0 From TMP401 Status NACK By Master Stop By Master Frame 2 Slave Address Byte Figure 16. Timing Diagram for SMBus ALERT 17 "#$% www.ti.com SBOS371 − AUGUST 2006 HIGH-SPEED MODE In order for the Two-Wire bus to operate at frequencies above 400kHz, the master device must issue a High-speed mode (Hs-mode) master code (00001XXX) as the first byte after a START condition to switch the bus to high-speed operation. The TMP401 will not acknowledge this byte, but will switch the input filters on SDA and SCL and the output filter on SDA to operate in Hs-mode, allowing transfers at up to 3.4MHz. After the Hs-mode master code has been issued, the master will transmit a Two-Wire slave address to initiate a data transfer operation. The bus will continue to operate in Hs-mode until a STOP condition occurs on the bus. Upon receiving the STOP condition, the TMP401 switches the input and output filter back to fast-mode operation. TIMEOUT FUNCTION When bit 7 of the Consecutive Alert Register is set high, the TMP401 timeout function is enabled. The TMP401 resets the serial interface if either SCL or SDA are held low for 30ms (typ) between a START and STOP condition. If the TMP401 is holding the bus low, it releases the bus and waits for a START condition. To avoid activating the timeout function, it is necessary to maintain a communication speed of at least 1kHz for the SCL operating frequency. The default state of the timeout function is enabled (bit 7 = high). THERM (PIN 4) AND ALERT/THERM2 (PIN 6) The TMP401 has two pins dedicated to alarm functions, the THERM and ALERT/THERM2 pins. Both pins are open-drain outputs that each require a pull-up resistor to V+. These pins can be wire-ORed together with other alarm pins for system monitoring of multiple sensors. The THERM pin provides a thermal interrupt that cannot be software disabled. The ALERT pin is intended for use as an earlier warning interrupt, and can be software disabled, or masked. The ALERT/THERM2 pin can also be configured for use as THERM2, a second THERM pin (Configuration Register: AL/TH bit = 1). The default setting configures pin 6 to function as ALERT (AL/TH = 0). The THERM pin asserts low when either the measured local or remote temperature is outside of the temperature range programmed in the corresponding Local/Remote THERM Limit Register. The THERM temperature limit range can be programmed with a wider range than that of the limit registers, which allows ALERT to provide an earlier warning than THERM. The THERM alarm resets automatically when the measured temperature returns to within the THERM temperature limit range minus the hysteresis value stored in the THERM Hysteresis Register. The allowable values of hysteresis are shown in Table 9. The default hysteresis is 10°C. When the ALERT/THERM2 pin is configured as a second thermal alarm (Configuration Register: bit 7 = 0, bit 5 = 1), it functions the same as THERM, but uses the temperatures stored in the Local/Remote Temperature High/Low Limit Registers to set its comparison range. When ALERT/THERM2 (pin 6) is configured as ALERT (Configuration Register: bit 7 = 0, bit 5 = 0), the pin asserts low when either the measured local or remote temperature violates the range limit set by the corresponding Local/Remote Temperature High/Low Limit Registers. This alert function can be configured to assert only if the range is violated a specified number of consecutive times (1, 2, 3, or 4). The consecutive violation limit is set in the Consecutive Alert Register. False alerts that occur as a result of environmental noise can be prevented by requiring consecutive faults. ALERT also asserts low if the remote temperature sensor is open-circuit. When the MASK function is enabled (Configuration Register: bit 7 = 1), ALERT is disabled (that is, masked). ALERT resets when the master reads the device address, as long as the condition that caused the alert no longer persists, and the Status Register has been reset. THERM Limit and ALERT High Limit Measured Temperature ALERT Low Limit and THERM Limit Hysteresis THERM ALERT SMBus ALERT Read Read Read Time Figure 17. SMBus Alert Timing Diagram 18 "#$% www.ti.com SBOS371 − AUGUST 2006 SMBus ALERT FUNCTION The TMP401 supports the SMBus Alert function. When pin 6 is configured as an alert output, the ALERT pin of the TMP401 may be connected as an SMBus Alert signal. When a master detects an alert condition on the ALERT line, the master sends an SMBus Alert command (00011001) on the bus. If the ALERT pin of the TMP401 is active, the devices will acknowledge the SMBus Alert command and respond by returning its slave address on the SDA line. The eighth bit (LSB) of the slave address byte indicates whether the temperature exceeding one of the temperature high limit settings or falling below one of the temperature low limit settings caused the alert condition. This bit will be high if the temperature is greater than or equal to one of the temperature high limit settings; this bit will be low if the temperature is less than one of the temperature low limit settings. See Figure 16 for details of this sequence. If multiple devices on the bus respond to the SMBus Alert command, arbitration during the slave address portion of the SMBus Alert command determines which device will clear its alert status. If the TMP401 wins the arbitration, its ALERT pin becomes inactive at the completion of the SMBus Alert command. If the TMP401 loses the arbitration, the ALERT pin remains active. SHUTDOWN MODE (SD) The TMP401 Shutdown Mode allows the user to save maximum power by shutting down all device circuitry other than the serial interface, reducing current consumption to typically less than 3µA; see Figure 10, Shutdown Quiescent Current vs Supply Voltage. Shutdown Mode is enabled when the SD bit of the Configuration Register is high; the device shuts down once the current conversion is completed. When SD is low, the device maintains a continuous conversion state. SENSOR FAULT The TMP401 will sense a fault at the D+ input resulting from incorrect diode connection or an open circuit. The detection circuitry consists of a voltage comparator that trips when the voltage at D+ exceeds (V+) − 0.6V (typical). The comparator output is continuously checked during a conversion. If a fault is detected, the last valid measured temperature is used for the temperature measurement result, the OPEN bit (Status Register, bit 2) is set high, and, if the alert function is enabled, ALERT asserts low. When not using the remote sensor with the TMP401, the D+ and D− inputs must be connected together to prevent meaningless fault warnings. GENERAL CALL RESET The TMP401 supports reset via the Two-Wire General Call address 00h (0000 0000b). The TMP401 acknowledges the General Call address and responds to the second byte. If the second byte is 06h (0000 0110b), the TMP401 executes a software reset. This software reset restores the power-on reset state to all TMP401 registers, aborts any conversion in progress, and clears the ALERT and THERM pins. The TMP401 takes no action in response to other values in the second byte. IDENTIFICATION REGISTERS The TMP401 allows for the Two-Wire bus controller to query the device for manufacturer and device IDs to allow for software identification of the device at the particular Two-Wire bus address. The manufacturer ID is obtained by reading from pointer address FEh. The device ID is obtained by reading from pointer address FFh. The TMP401 returns 55h for the manufacturer code and 11h for the device ID. These registers are read-only. FILTERING Remote junction temperature sensors are usually implemented in a noisy environment. Noise is most often created by fast digital signals, and it can corrupt measurements. The TMP401 has a built-in 65kHz filter on the inputs of D+ and D− to minimize the effects of noise. However, a bypass capacitor placed differentially across the inputs of the remote temperature sensor is recommended to make the application more robust against unwanted coupled signals. The value of the capacitor should be between 100pF and 1nF. Some applications attain better overall accuracy with additional series resistance; however, this is setup-specific. When series resistance is added, the value should not be greater than 100Ω. 19 "#$% www.ti.com SBOS371 − AUGUST 2006 REMOTE SENSING The TMP401 is designed to be used with either discrete transistors or substrate transistors built into processor chips and ASICs. Either NPN or PNP transistors can be used, as long as the base-emitter junction is used as the remote temperature sense. Either a transistor or diode connection can also be used (see Figure 11, Basic Connections). Errors in remote temperature sensor readings will be the consequence of the ideality factor and current excitation used by the TMP401 versus the manufacturer’s specified operating current for a given transistor. Some manufacturers specify a high-level and low-level current for the temperature-sensing substrate transistors. The TMP401 uses 6µA for ILOW and 120µA for IHIGH. The ideality factor (η) is a measured characteristic of a remote temperature sensor diode as compared to an ideal diode. The ideality factor for the TMP401 is trimmed to be 1.008. For transistors whose ideality factor does not match the TMP401, Equation (1) can be used to calculate the temperature error. Note that for the equation to be used correctly, actual temperature (°C) must be converted to Kelvin (°K). T ERR + ƪ ƫ ǒh * 1.008Ǔ 1.008 ƪ273.15 ) T(°C)ƫ (1) Where: η = Ideality factor of remote temperature sensor. T(°C) = actual temperature. TERR = Error in TMP401 reading due to η ≠ 1.008. Degree delta is the same for °C and °K. For η = 1.004 and T(°C) = 100°C: T ERR + ƪ(1.004*1.008) ƫ 1.008 T ERR + * 1.48°C ƪ273.15)100°Cƫ (2) If a discrete transistor is used as the remote temperature sensor with the TMP401, the best accuracy can be achieved by selecting the transistor according to the following criteria: 1. Base-emitter voltage > 0.25V at 6µA, at the highest sensed temperature. 20 2. Base-emitter voltage < 0.95V at 120µA, at the lowest sensed temperature. 3. Base resistance < 100Ω. 4. Tight control of VBE characteristics indicated by small variations in hFE (that is, 50 to 150). Based on these criteria, two recommended small-signal transistors are the 2N3904 (NPN) or 2N3906 (PNP). MEASUREMENT ACCURACY AND THERMAL CONSIDERATIONS The temperature measurement accuracy of the TMP401 depends on the remote and/or local temperature sensor being at the same temperature as the system point being monitored. Clearly, if the temperature sensor is not in good thermal contact with the part of the system being monitored, then there will be a delay in the response of the sensor to a temperature change in the system. For remote temperature sensing applications using a substrate transistor (or a small, SOT23 transistor) placed close to the device being monitored, this delay is usually not a concern. The local temperature sensor inside the TMP401 monitors the ambient air around the device. The thermal time constant for the TMP401 is approximately two seconds. This constant implies that if the ambient air changes quickly by 100°C, it would take the TMP401 about 10 seconds (that is, five thermal time constants) to settle to within 1°C of the final value. In most applications, the TMP401 package is in electrical and therefore thermal contact with the PCB, as well as subjected to forced airflow. The accuracy of the measured temperature directly depends on how accurately the PCB and forced airflow temperatures represent the temperature that the TMP401 is measuring. Additionally, the internal power dissipation of the TMP401 can cause the temperature to rise above the ambient or PCB temperature. The internal power dissipated as a result of exciting the remote temperature sensor is negligible because of the small currents used. For a 5.5V supply and maximum conversion rate of eight conversions per second, the TMP401 dissipates 1.82mW (PDIQ = 5.5V x 330µA). If both the ALERT/THERM2 and THERM pins are each sinking 1mA, an additional power of 0.8mW is dissipated (PDOUT = 1mA × 0.4V + 1mA × 0.4V = 0.8mW). Total power dissipation is then 2.62mW (PDIQ + PDOUT) and, with an qJA of 150°C/W, causes the junction temperature to rise approximately 0.393°C above the ambient. "#$% www.ti.com SBOS371 − AUGUST 2006 LAYOUT CONSIDERATIONS Remote temperature sensing on the TMP401 measures very small voltages using very small currents; therefore, noise at the IC inputs must be minimized. Most applications using the TMP401 will have high digital content, with several clocks and logic level transitions creating a noisy environment. Layout should adhere to the following guidelines: GND(1) D+(1) 1. Place the TMP401 as close to the remote junction sensor as possible. 2. Route the D+ and D− traces next to each other and shield them from adjacent signals through the use of ground guard traces, as shown in Figure 18. If a multilayer PCB is used, bury these traces between ground or VDD planes to shield them from extrinsic noise sources. 5 mil PCB traces are recommended. 3. Minimize additional thermocouple junctions caused by copper-to-solder connections. If these junctions are used, make the same number and approximate locations of copper-to-solder connections in both the D+ and D− connections to cancel any thermocouple effects. 4. Use a 0.1µF local bypass capacitor directly between the V+ and GND of the TMP401, as shown in Figure 19. Minimize filter capacitance between D+ and D− to 1000pF or less for optimum measurement performance. This capacitance includes any cable capacitance between the remote temperature sensor and TMP401. 5. If the connection between the remote temperature sensor and the TMP401 is between 8 inches and 12 feet, use a twisted-wire pair connection. Beyond this distance (up to 100ft), use a twisted, shielded pair with the shield grounded as close to the TMP401 as possible. Leave the remote sensor connection end of the shield wire open to avoid ground loops and 60Hz pickup. Ground or V+ layer on bottom and/or top, if possible. D− (1) GND(1) NOTE: (1) 5 mil traces with 5 mil spacing. Figure 18. Example Signal Traces 0.1µF Capacitor V+ PCB Via GND 1 8 2 7 3 6 4 5 PCB Via TMP401 Figure 19. Suggested Bypass Capacitor Placement 21 PACKAGE OPTION ADDENDUM www.ti.com 12-Sep-2006 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TMP401AIDGKR ACTIVE MSOP DGK 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TMP401AIDGKRG4 ACTIVE MSOP DGK 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TMP401AIDGKT ACTIVE MSOP DGK 8 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TMP401AIDGKTG4 ACTIVE MSOP DGK 8 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Lead/Ball Finish MSL Peak Temp (3) (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. 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