TMP400 TM P4 00 SBOS404 – DECEMBER 2007 ±1°C Remote and Local TEMPERATURE SENSOR with N-Factor and Series Resistance Correction FEATURES 1 • • • • 234 • • • • • • • • ±1°C REMOTE DIODE SENSOR ±1°C LOCAL TEMPERATURE SENSOR PROGRAMMABLE NON-IDEALITY FACTOR PROGRAMMABLE SERIES RESISTANCE CANCELLATION ALERT FUNCTION PROGRAMMABLE RESOLUTION: 9 to 12 Bits PROGRAMMABLE THRESHOLD LIMITS TWO-WIRE/SMBus™ SERIAL INTERFACE MINIMUM AND MAXIMUM TEMPERATURE MONITORS MULTIPLE INTERFACE ADDRESSES ALERT PIN CONFIGURATION DIODE FAULT DETECTION APPLICATIONS • • • • • • • • LCD/DLP®/LCOS PROJECTORS SERVERS INDUSTRIAL CONTROLLERS CENTRAL OFFICE TELECOM EQUIPMENT DESKTOP AND NOTEBOOK COMPUTERS STORAGE AREA NETWORKS (SAN) INDUSTRIAL AND MEDICAL EQUIPMENT PROCESSOR/FPGA TEMPERATURE MONITORING DESCRIPTION The TMP400 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. 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 the alarm thresholds and to read temperature data. The TMP400 is customizable with programmable: series resistance cancellation, non-ideality factor, resolution, and threshold limits. Other features are: minimum and maximum temperature monitors, wide remote temperature measurement range (up to +127.9375°C), diode fault detection, and temperature alert function. The TMP400 is available in a QSSOP-16 package. STBY 15 V+ 11 2 V+ GND 7, 8 TMP400 Interrupt Configuration ALERT Consecutive Alert Configuration Register Status Register N-Factor Correction Local Temperature Register TL Remote Temp High Limit Remote Temp Low Limit Temperature Comparators Conversion Rate Register Local Temp Low Limit Local Temperature Min/Max Register D+ 3 4 Local Temp High Limit TR Remote Temperature Register Remote Temperature Min/Max Register Manufacturer ID Register D- Device ID Register Configuration Register Resolution Register SCL SDA 14 Bus Interface 12 6 Pointer Register 10 A1 A0 1 2 3 4 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 registered trademark of Texas Instruments. SMBus is a trademark of Intel Corp. All other trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2007, Texas Instruments Incorporated TMP400 www.ti.com SBOS404 – DECEMBER 2007 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. ORDERING INFORMATION (1) (1) PRODUCT PACKAGE-LEAD PACKAGE DESIGNATOR PACKAGE MARKING TMP400 QSSOP-16 DBQ TMP400 For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI web site at www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) Power Supply, VS Input Voltage, pins 3, 4, 6, 10, and 15 only Input Voltage, pins 11, 12, and 14 only TMP400 UNIT 7 V –0.5 to VS + 0.5 V –0.5 to +7 V 10 mA Operating Temperature Range –55 to +127 °C Storage Temperature Range –60 to +130 °C +150 °C Human Body Model (HBM) 3000 V Charged Device Model (CDM) 1000 V Machine Model (MM) 200 V Input Current Junction Temperature (TJ max) ESD Rating (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. TERMINAL FUNCTIONS PIN CONFIGURATION PIN QSSOP-16 Top View NC No internal connection NC 1 16 NC 2 V+ Positive supply (2.7V to 5.5V) V+ 2 15 STBY 3 D+ Positive connection to remote temperature sensor D+ 3 14 SCL 4 D– D- 4 Negative connection to remote temperature sensor 6 A1 Address pin 13 NC TMP400 2 NAME DESCRIPTION 1, 5, 9, 13, 16 NC 5 12 SDA 7, 8 GND A1 6 11 ALERT 10 A0 GND 7 10 A0 11 ALERT GND 8 9 12 SDA Serial data line for SMBus, open-drain; requires pull-up resistor to V+ 14 SCL Serial clock line for SMBus, open-drain; requires pull-up resistor to V+ 15 STBY NC Submit Documentation Feedback Ground Address pin Alert, active low, open-drain; requires pull-up resistor to V+ Standby pin Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 ELECTRICAL CHARACTERISTICS At TA = –40°C to +125°C and VS = 2.7V to 5.5V, unless otherwise noted. TMP400 PARAMETER CONDITIONS MIN TYP MAX UNIT TEMPERATURE ERROR Local Temperature Sensor Remote Temperature Sensor (1) (2) TELOCAL TEREMOTE TA = –40°C to +125°C ±1.25 ±2.5 °C VS = 3.3V, TA = +15°C to +85°C ±0.0625 ±1 °C VS = 3.3V, TA = +15°C to +75°C, TD = –40°C to +125°C (3) ±0.0625 ±1 °C VS = 3.3V, TA = –40°C to +100°C, TD = –40°C to +125°C (3) ±1 ±3 °C TA = –40°C to +125°C, TD = –40°C to +125°C (3) ±3 ±10 °C VS = 2.7V to 5.5V ±0.2 ±0.5 °C/V 115 125 ms 12 Bits vs Supply Local/Remote TEMPERATURE MEASUREMENT Conversion Time (per channel) (4) 105 Resolution Local Temperature Sensor (programmable) 9 Remote Temperature Sensor 12 Bits Remote Sensor Source Currents 120 µA Medium High 60 µA Medium Low 12 µA 6 µA High Series Resistance 3kΩ Maximum Low Remote Transistor Ideality Factor η TMP400 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 25 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 Output Low Sink Current ALERT Forced to 0.4V 6 mA POWER SUPPLY Specified Voltage Range VS Quiescent Current IQ 5.5 V 0.0625 Conversions per Second 2.7 30 38 µA Eight Conversions per Second 420 525 µA 10 µA Serial Bus Inactive, Shutdown Mode 3 Serial Bus Active, fS = 400kHz, Shutdown Mode 90 Serial Bus Active, fS = 3.4MHz, Shutdown Mode 350 Undervoltage Lock Out Power-On Reset Threshold 2.3 POR µA µA 2.4 2.6 V 1.6 2.3 V °C TEMPERATURE RANGE Specified Range –40 +125 Storage Range –60 +130 Thermal Resistance, QSSOP (1) (2) (3) (4) 70 °C °C/W Tested with less than 5Ω effective series resistance and 100pF differential input capacitance. RC = '1'. TD is the remote temperature measured at the diode. RES1 = '1' and RES0 = '1' for 12-bit resolution. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 3 TMP400 www.ti.com SBOS404 – DECEMBER 2007 TYPICAL CHARACTERISTICS At TA = +25°C and VS = 5.0V, unless otherwise noted. REMOTE TEMPERATURE ERROR vs TEMPERATURE 3.0 VS = 3.3V TREMOTE = +25°C 2 30 Typical Units Shown h = 1.008 RC = 1 1 0 -1 -2 2.0 1.0 0 -1.0 -2.0 -3 -3.0 -50 0 -25 25 50 75 100 125 -50 25 50 75 100 125 Figure 1. Figure 2. REMOTE TEMPERATURE ERROR vs LEAKAGE RESISTANCE REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE (Diode-Connected Transistor, 2N3906 PNP) 2.0 RC = 1 Remote Temperature Error (°C) Remote Temperature Error (°C) 0 Ambient Temperature, TA (°C) 40 20 R - GND 0 R - VS -20 -40 1.5 VS = 2.7V 1.0 0.5 0 VS = 5.5V -0.5 -1.0 -1.5 -2.0 -60 0 5 10 15 20 25 0 500 1000 1500 2000 2500 Leakage Resistance (MW ) RS ( W ) Figure 3. Figure 4. REMOTE TEMPERATURE ERROR vs SERIES RESISTANCE (GND Collector-Connected Transistor, 2N3906 PNP) REMOTE TEMPERATURE ERROR vs DIFFERENTIAL CAPACITANCE 2.0 3000 3 1.5 VS = 2.7V 1.0 0.5 VS = 5.5V 0 -0.5 -1.0 -1.5 -2.0 Remote Temperature Error (°C) RC = 1 Remote Temperature Error (°C) -25 Ambient Temperature, TA (°C) 60 2 1 0 -1 -2 -3 0 4 50 Units Shown VS = 3.3V Local Temperature Error (°C) Remote Temperature Error (°C) 3 LOCAL TEMPERATURE ERROR vs TEMPERATURE 500 1000 1500 2000 2500 3000 0 0.5 1.0 1.5 2.0 RS (W) Capacitance (nF) Figure 5. Figure 6. Submit Documentation Feedback 2.5 3.0 Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 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 10 450 400 350 5 IQ (mA) Temperature Error (°C) QUIESCENT CURRENT vs CONVERSION RATE 0 300 -5 200 -10 150 -15 100 -20 50 0 0.0625 -25 0 5 10 15 VS = 2.7V 0.125 0.25 0.5 1 2 4 Frequency (MHz) Conversion Rate (conversions/sec) Figure 7. Figure 8. SHUTDOWN QUIESCENT CURRENT vs SCL CLOCK FREQUENCY SHUTDOWN QUIESCENT CURRENT vs SUPPLY VOLTAGE 500 8 450 7 400 8 6 350 5 300 250 IQ (mA) IQ (mA) VS = 5.5V 250 VS = 5.5V 200 4 3 150 2 100 1 50 VS = 3.3V 0 1k 10k 100k 1M 10M 0 2.5 SCL Clock Frequency (Hz) 3.0 3.5 4.0 4.5 5.0 5.5 VS (V) Figure 9. Figure 10. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 5 TMP400 www.ti.com SBOS404 – DECEMBER 2007 APPLICATION INFORMATION 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 TMP400. The TMP400 is a dual-channel digital temperature sensor that combines a local die temperature measurement channel and a remote junction temperature measurement channel in a QSSOP-16 package. The TMP400 is Two-Wire and SMBus interface-compatible, and is specified over a temperature range of –40°C to +125°C. The TMP400 contains multiple registers for holding configuration information, temperature measurement results, temperature comparator maximum/minimum limits, and status information. 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) can be automatically programmed to be cancelled by the TMP400 by setting the RC bit to '1' in the Resolution Register, preventing what would otherwise result in a temperature offset. User-programmed high and low temperature limits stored in the TMP400 can be used to monitor local and remote temperatures to trigger an over/under temperature alarm (ALERT). A total of up to 3kΩ of series line resistance is cancelled by the TMP400 if the RC bit is enabled, eliminating the need for additional characterization and temperature offset correction. Upon power-up, the RC bit is disabled (RC = 0). The TMP400 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 is an open-drain output that also needs a pull−up resistor. ALERT may be shared with See the two Remote Temperature Error vs Series Resistance 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. +5V 0.1mF (1) Transistor-connected configuration : Series Resistance RS RS (2) 3 15 2 STBY V+ 10kW (typ) SCL D+ 10kW (typ) 10kW (typ) 14 (3) (2) CDIFF 4 DTMP400 10 6 SDA 12 Two-Wire Bus/ SMBus Controller A0 A1 ALERT 11 GND (1) 7, 8 Diode-connected configuration : RS RS (2) (2) (3) CDIFF (1) Diode-connected configuration provides better settling time. Transistor-connected configuration provides better series resistance cancellation. (2) RS should be less than 1.5kΩ in most applications. (3) CDIFF should be less than 1000pF in most applications. Figure 11. Basic Connections 6 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 DIFFERENTIAL INPUT CAPACITANCE The TMP400 tolerates differential input capacitance of up to 1000pF if RC = 1 (if RC = 0, input capacitance can be as high as 2200pF) with minimal change in temperature error. The effect of capacitance on sensed remote temperature error is illustrated in the typical characteristic curve, Remote Temperature Error vs Differential Capacitance (Figure 6). byte stores the decimal fraction value of the temperature and allows a higher measurement resolution. 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 (Table 5). REGISTER INFORMATION TEMPERATURE MEASUREMENT DATA Temperature measurement data are taken over a default range of –55°C to +127.9375°C for both local and remote locations. Temperature data resulting from conversions within the default measurement range are represented in binary form, as shown in Table 1, Binary column. Note that any temperature above +127.9375°C results in a value of 127.9375 (7Fh/F0h). Temperatures below –65°C results in a value of –65 (BF/00h). The TMP400 is specified 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 REMOTE TEMPERATURE REGISTER DIGITAL OUTPUT (BINARY) The TMP400 contains multiple registers for holding configuration information, temperature measurement results, temperature comparator maximum/minimum, limits, and status information. These registers are described in Figure 12 and Table 2. POINTER REGISTER Figure 12 shows the internal register structure of the TMP400. 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 2 describes the pointer address of the registers available in the TMP400. The power-on reset (POR) value of the Pointer Register is 00h (0000 0000b). TEMPERATURE (°C) HIGH BYTE LOW BYTE HEX 128 0111 1111 1111 0000 7F/F0 Pointer Register 127.9375 0111 1111 1111 0000 7F/F0 Local and Remote Temperature Registers 100 0110 0100 0000 0000 64/00 80 0101 0000 0000 0000 50/00 75 0100 1011 0000 0000 4B/00 Status Register 50 0011 0010 0000 0000 32/00 Configuration Register Resolution Register Local and Remote Limit Registers SDA 25 0001 1001 0000 0000 19/00 0.25 0000 0000 0100 0000 00/40 0 0000 0000 0000 0000 00/00 –0.25 1111 1111 1100 0000 FF/C0 –25 1110 0111 0000 0000 E7/00 Identification Registers –55 1100 1001 0000 0000 C9/00 Local Temperature Min/Max –65 1011 1111 0000 0000 BF/00 Remote Temperature Min/Max 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) Conversion Rate Register I/O Control Interface SCL Consecutive Alert Register Figure 12. Internal Register Structure Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 7 TMP400 www.ti.com SBOS404 – DECEMBER 2007 Table 2. Register Map POINTER ADDRESS (HEX) READ 00 (1) (2) 8 WRITE NA (1) BIT DESCRIPTIONS POWER-ON RESET (HEX) D7 D6 D5 D4 D3 D2 D1 D0 REGISTER DESCRIPTIONS 00 LT11 LT10 LT9 LT8 LT7 LT6 LT5 LT4 Local Temperature (High Byte) RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 Remote Temperature (High Byte) 01 NA 00 02 NA 00 BUSY LHIGH LLOW RHIGH RLOW OPEN 0 0 Status Register 03 09 00 MASK1 SD 0 0 0 0 0 0 Configuration Register 04 0A 02 0 0 0 0 R3 R2 R1 R0 Conversion Rate Register 05 0B 7F LTH11 LTH10 LTH9 LTH8 LTH7 LTH6 LTH5 LTH4 Local Temperature High Limit (High Byte) 06 0C C9 LTL11 LTL10 LTL9 LTL8 LTL7 LTL6 LTL5 LTL4 Local Temperature Low Limit (High Byte) 07 0D 7F RTH11 RTH10 RTH9 RTH8 RTH7 RTH6 RTH5 RTH4 Remote Temperature High Limit (High Byte) 08 0E C9 RTL11 RTL10 RTL9 RTL8 RTL7 RTL6 RTL5 RTL4 Remote Temperature Low Limit (High Byte) NA 0F XX X (2) 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) 18 18 00 NC7 NC6 NC5 NC4 NC3 NC2 NC1 NC0 N-factor Correction 1A 1A 18 0 0 0 1 1 RC RES1 RES0 Resolution Register 22 22 01 TO_EN 0 0 0 C2 C1 C0 0 Consecutive Alert Register 30 30 7F LMT11 LMT10 LMT9 LMT8 LMT7 LMT6 LMT5 LMT4 Local Temperature Minimum (High Byte) 31 31 F0 LMT3 LMT2 LMT1 LMT0 0 0 0 0 Local Temperature Minimum (Low Byte) 32 32 80 LXT11 LXT10 LXT9 LXT8 LXT7 LXT6 LXT5 LXT4 Local Temperature Maximum (High Byte) 33 33 00 LXT3 LXT2 LXT1 LXT0 0 0 0 0 Local Temperature Maximum (Low Byte) 34 34 7F RMT11 RMT10 RMT9 RMT8 RMT7 RMT6 RMT5 RMT4 Remote Temperature Minimum (High Byte) 35 35 F0 RMT3 RMT2 RMT1 RMT0 0 0 0 0 Remote Temperature Minimum (Low Byte) 36 36 80 RXT11 RXT10 RXT9 RXT8 RXT7 RXT6 RXT5 RXT4 Remote Temperature Maximum (High Byte) 37 37 00 RXT3 RXT2 RXT1 RXT0 0 0 0 0 Remote Temperature Maximum (Low Byte) NA FC FF X (2) X X X X X X X Software Reset FE NA 55 0 1 0 1 0 1 0 1 Manufacturer ID FF NA 01 0 0 0 0 0 0 0 1 Device ID NA = not applicable; register is write- or read-only. X = indeterminate state. Writing any value to this register indicates a software reset; see the Software Reset section. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 TEMPERATURE REGISTERS The TMP400 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 analog-to-digital converter (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 read-only registers are updated by the ADC each time a temperature measurement is completed. The TMP400 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 is output first, followed by the low byte. Both bytes of this read operation are from the same ADC conversion. The power-on reset value of both temperature registers is 00h. LIMIT REGISTERS The TMP400 has eight 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. The power-on reset value of the local temperature high limit is 7Fh/00h (+127°C). 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 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 C9h/00h (–55°C). 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 7Fh/00h (+127°C). 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 C9h/00h (–55°C). STATUS REGISTER The TMP400 has a Status Register to report the state of the temperature comparators. Table 3 shows the Status Register bits. The Status Register is read-only and is read by reading from pointer address 02h. Table 3. Status Register Format STATUS REGISTER (Read = 02h, Write = NA) BIT # BIT NAME POR VALUE (1) D7 D6 D5 D4 D3 D2 D1 D0 BUSY LHIGH LLOW RHIGH RLOW OPEN — — 0 (1) 0 0 0 0 0 0 0 The BUSY bit will change to ‘1’ almost immediately (<< 100µs) following power-up, as the TMP400 begins the first temperature conversion. It is high whenever the TMP400 converts a temperature reading. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 9 TMP400 www.ti.com SBOS404 – DECEMBER 2007 The BUSY bit is ‘1’ if the ADC makes a conversion. It is ‘0’ if the ADC is not converting. The OPEN bit is ‘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 attempts to convert a remote temperature. The LHIGH bit is ‘1’ if the local high limit was exceeded since the last clearing of the Status Register. The RHIGH bit is ‘1’ if the remote high limit was exceeded since the last clearing of the Status Register. The LLOW bit is ‘1’ if the local low limit was exceeded since the last clearing of the Status Register. The RLOW bit is ‘1’ if the remote low limit was exceeded since the last clearing of the Status Register. The values of the LLOW, RLOW, and OPEN bits are latched and 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 BUSY bit is not latched and is not cleared by reading the Status Register. The BUSY bit always indicates the current state and updates 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 TMP400 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. CONFIGURATION REGISTER The Configuration Register controls shutdown mode and disables the ALERT pin. 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 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 TMP400 retains the ALERT pin status, but the ALERT pin does not go low. The shutdown (SD) bit (bit 6) enables or disables the temperature measurement circuitry. If SD = 0, the TMP400 converts continuously at the rate set in the conversion rate register. When SD is set to ‘1’, the TMP400 immediately stops converting and enters a shutdown mode. When SD is set to ‘0’ again, the TMP400 resumes continuous conversions. 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 4 summarizes the bits of the Configuration Register. Table 4. Configuration Register Bit Descriptions CONFIGURATION REGISTER (Read = 03h, Write = 09h, POR = 00h) BIT 10 NAME FUNCTION POWER-ON RESET VALUE 7 MASK 0 = ALERT Enabled 1 = ALERT Masked 0 6 SD 0 = Run 1 = Shut Down 0 5, 4, 3, 2, 1, 0 Reserved — 0 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 RESOLUTION REGISTER The RES1 and RES0 bits (resolution bits 1 and 0, respectively) 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 TMP400. The Resolution Register is set by writing to pointer address 1Ah and is read by reading from pointer address 1Ah. Table 5 shows the resolution bits for the Resolution Register. Table 5. Resolution Register: Local Channel Programmable Resolution RESOLUTION REGISTER (Read = 1Ah, Write = 1Ah, POR = 18h) 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 3 and 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 18h. Resistance correction (RC) is not automatically enabled on power-on; see the Series Resistance Cancellation section for information on RC. ONE-SHOT (OS) The TMP400 features a One-Shot Temperature Measurement Mode. When the device is in Shutdown Mode, writing a ‘1’ to the OS bit starts a single temperature conversion. The device returns to the shutdown state at the completion of the single conversion. This mode is useful to reduce power consumption in the TMP400 when continuous temperature monitoring is not required. When the configuration register is read, the OS bit always reads '0' CONVERSION RATE 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 TMP400 power dissipation to be balanced with the temperature register update rate. Table 6 shows the conversion rate options and corresponding current consumption. By default, the TMP400 converts every four seconds. N-FACTOR CORRECTION REGISTER The TMP400 allows for a different n-factor value to be used for converting remote channel measurements to temperature. The remote channel uses sequential current excitation to extract a differential VBE voltage measurement to determine the temperature of the remote transistor. Equation 1 relates this voltage and temperature. VBE2 - VBE1 = nkT ln q l2 l1 (1) The value n in Equation 1 is a characteristic of the particular transistor used for the remote channel. The default value for the TMP400 is n = 1.008. The value in the N-Factor Correction Register may be used to adjust the effective n-factor according to Equation 2 and Equation 3. 1.008 ´ 300 neff = (300 - NADJUST) (2) NADJUST = 300 - 300 ´ 1.008 neff (3) Table 6. Conversion Rate Register CONVERSION RATE REGISTER (Read = 04h, Write = 0Ah, POR = 02h) AVERAGE IQ (TYP) (µA) R7 R6 R5 R4 R3 R2 R1 R0 CONVERSION/SEC 0 0 0 0 0 0 0 0 0.0625 11 32 0 0 0 0 0 0 0 1 0.125 17 38 0 0 0 0 0 0 1 0 0.25 28 49 0 0 0 0 0 0 1 1 0.5 47 69 0 0 0 0 0 1 0 0 1 80 103 0 0 0 0 0 1 0 1 2 128 155 0 0 0 0 0 1 1 0 4 190 220 8 373 413 07h to 0Fh VS = 2.7V VS = 5.5V Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 11 TMP400 www.ti.com SBOS404 – DECEMBER 2007 The n-correction value must be stored in two’s-complement format, yielding an effective data range from –128 to +127. The n-correction value may be written to and read from pointer address 18h. The register power-on reset value is 00h; thus, the register has no effect unless written to. The n-factor range is shown in Table 7. Table 7. N-Factor Range NADJUST BINARY HEX DECIMAL N 01111111 7F 127 1.747977 00001010 0A 10 1.042759 00001000 08 8 1.035616 00000110 06 6 1.028571 00000100 04 4 1.021622 00000010 02 2 1.014765 00000001 01 1 1.011371 00000000 00 0 1.008 11111111 FF –1 1.004651 11111110 FE –2 1.001325 11111100 FC –4 0.994737 11111010 FA –6 0.988235 11111000 F8 –8 0.981818 11110110 F6 –10 0.975484 10000000 80 –128 0.706542 The Local Temperature Maximum Register may be read by reading the high byte from pointer address 32h and the low byte from pointer address 33h. The Local Temperature Maximum Register may also be read by using a two-byte read command from pointer address 32h. The Local Temperature Maximum Register is reset at power-on by executing the chip reset command, or by writing any value to any of pointer addresses 30h through 37h. The reset value for these registers is 80h/00h. The Remote Temperature Minimum Register may be read by reading the high byte from pointer address 34h and the low byte from pointer address 35h. The Remote Temperature Minimum Register may also be read by using a two-byte read command from pointer address 34h. The Remote Temperature Minimum Register is reset at power-on by executing the chip reset command, or by writing any value to any of pointer addresses 30h through 37h. The reset value for these registers is 7Fh/F0h. The Remote Temperature Maximum Register may be read by reading the high byte from pointer address 36h and the low byte from pointer address 37h. The Remote Temperature Maximum Register may also be read by using a two-byte read command from pointer address 36h. The Remote Temperature Maximum Register is reset at power-on by executing the chip reset command, or by writing any value to any of pointer addresses 30h through 37h. The reset value for these registers is 80h/00h. MINIMUM AND MAXIMUM REGISTERS The TMP400 stores the minimum and maximum temperatures measured since power-on, chip-reset, or minimum and maximum register reset for both the local and remote channels. The Local Temperature Minimum Register may be read by reading the high byte from pointer address 30h and the low byte from pointer address 31h. The Local Temperature Minimum Register may also be read by using a two-byte read command from pointer address 30h. The Local Temperature Minimum Register is reset at power-on, by executing the chip-reset command, or by writing any value to any of pointer addresses 30h through 37h. The reset value for these registers is 7Fh/F0h. 12 SOFTWARE RESET The TMP400 may be reset by writing any value to Pointer Register FCh. A reset restores the power-on reset state to all of the TMP400 registers as well as aborts any conversion in process and clears the ALERT pin. The TMP400 also supports reset via the Two-Wire general call address (00000000). The TMP400 acknowledges the general call address and responds to the second byte. If the second byte is 00000110, the TMP400 latches the status of the address pins and executes a software reset. A 500µs time delay must be observed after a general-call command. The TMP400 takes no action in response to other values in the second byte. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 CONSECUTIVE ALERT REGISTER SERIAL INTERFACE 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. The TMP400 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 TMP400 supports the transmission protocol for fast (1kHz to 400kHz) and high-speed (1kHz to 3.4MHz) modes. All data bytes are transmitted MSB first. Table 8. Consecutive Alert Register CONSECUTIVE ALERT REGISTER (READ = 22h, WRITE = 22h, POR = 01h) C2 C1 C0 NUMBER OF CONSECUTIVE OUT-OF-LIMIT MEASUREMENTS 0 0 0 1 0 0 1 2 0 1 1 3 1 1 1 4 (1) Note that 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. BUS OVERVIEW The TMP400 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 have been transferred, the master generates a STOP condition. STOP is indicated by pulling SDA from low to high, while SCL is high. SERIAL BUS ADDRESS To communicate with the TMP400, 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 TMP400 is set by the A0 and A1 pins. TMP400 addresses and corresponding A0 and A1 configurations are shown in Table 9. Table 9. Device Addresses A0 A1 ADDRESS GND GND 0011 000 GND High-Z 0011 001 GND VCC 0011 010 High-Z GND 0101 001 High-Z High-Z 0101 010 High-Z VCC 0101 011 VCC GND 1001 100 VCC High-Z 1001 101 VCC VCC 1001 110 READ/WRITE OPERATIONS Accessing a particular register on the TMP400 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 TMP400 requires a value for the Pointer Register (see Figure 14). When reading from the TMP400, 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 are 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 16 for details of this sequence. If repeated Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 13 TMP400 www.ti.com SBOS404 – DECEMBER 2007 reads from the same register are desired, it is not necessary to continually send the Pointer Register bytes, because the TMP400 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. 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. TIMING DIAGRAMS Figure 13 to Figure 16 describe various operations on the TMP400. Bus definitions are given below. Parameters for Figure 13 are defined in Table 10. 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. 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 initiates with a START condition. t(LOW) tF tR t(HDSTA) SCL t(HDSTA) t(HIGH) t(SUSTO) t(SUSTA) t(HDDAT) t(SUDAT) SDA t(BUF) P S S P Figure 13. Two-Wire Timing Diagram Table 10. Timing Diagram Definitions for Figure 13 FAST MODE PARAMETER HIGH-SPEED MODE MIN MAX MIN MAX UNIT 0.4 0.001 3.4 MHz SCL Operating Frequency f(SCL) 0.001 Bus Free Time Between STOP and START Condition t(BUF) 600 160 ns 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 (1) 0 (2) ns Data Setup Time Hold time after repeated START condition. After this period, the first clock is generated. 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 Clock/Data Rise Time tR 300 160 for SCL ≤ 100kHz tR 1000 160 (1) (2) 14 ns ns For cases with fall time of SCL less than 20ns and/or the rise time or fall time of SDA less than 20ns, the hold time should be greater than 20ns. For cases with fall time of SCL less than 10ns and/or the rise or fall time of SDA less than 10ns, the hold time should be greater than 10ns. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 1 9 9 1 SCL ¼ 1 SDA 0 0 1 1 0 0 R/W Start By Master P7 P6 P5 P4 P3 P2 P1 P0 ACK By TMP400 Frame 1 Two- Wire Slave Address Byte ¼ ACK By TMP400 (1) Frame 2 Pointer Register Byte 9 1 1 9 SCL (Continued) SDA (Continued) D6 D7 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 ACK By TMP400 ACK By TMP400 Frame 3 Data Byte 1 Stop By Master Frame 4 Data Byte 2 (1) See Table 9 for all available addresses. A0 = 1 and A1 = 0 in this example. Figure 14. Two-Wire Timing Diagram for Write Word Format 1 9 1 9 SCL SDA 1 0 0 1 1 0 R/W 0 Start By Master P7 P6 P5 P4 P3 P2 P1 P0 ACK By TMP400 Frame 1 Two-Wire Slave Address Byte ACK By TMP400 (1) 1 Frame 2 Pointer Register Byte 9 1 9 SCL (Continued) SDA (Continued) 1 0 0 1 1 0 0 R/W Start By Master D7 D6 ACK By TMP400 Frame 3 Two-Wire Slave Address Byte (1) D5 D4 D3 D2 D1 D0 From TMP400 NACK By Master (2) Frame 4 Data Byte 1 Read Register (1) See Table 9 for all available addresses. A0 = 1 and A1 = 0 in this example. (2) Master should leave SDA high to terminate a single-byte read operation. Figure 15. Two-Wire Timing Diagram for Single-Byte Read Format Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 15 TMP400 www.ti.com SBOS404 – DECEMBER 2007 1 9 1 9 SCL ¼ 1 SDA 0 0 1 1 0 R/W 0 Start By Master P7 P6 P5 P4 P3 P2 P1 P0 ACK By TMP400 ACK By TMP400 Frame 1 Two-Wire Slave Address Byte ¼ (1) Frame 2 Pointer Register Byte 1 9 1 9 SCL (Continued) ¼ SDA (Continued) 1 0 0 1 1 0 0 D7 R/W Start By Master D6 D5 D4 D3 D2 ACK By TMP400 Frame 3 Two-Wire Slave Address Byte 1 D1 D0 ¼ From TMP400 (1) ACK By Master Frame 4 Data Byte 1 Read Register 9 SCL (Continued) SDA (Continued) D7 D6 D5 D4 D3 D2 D1 D0 From TMP400 ACK By Master Stop By Master Frame 5 Data Byte 2 Read Register (1) See Table 9 for all available addresses. A0 = 1 and A1 = 0 in this example. Figure 16. Two-Wire Timing Diagram for Two-Byte Read Format ALERT 1 9 1 9 SCL SDA 0 0 0 1 Start By Master 1 0 0 1 R/W 0 0 1 1 ACK By TMP400 Frame 1 SMBus ALERT Response Address Byte 0 0 From TMP400 Status NACK By Master Frame 2 Two-Wire Slave Address Byte Stop By Master (1) (1) See Table 9 for all available addresses. A0 = 1 and A1 = 0 in this example. Figure 17. Timing Diagram for SMBus ALERT 16 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 HIGH-SPEED MODE ALERT (PIN 11) 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 TMP400 does not acknowledge this byte, but switches 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 transmits a Two-Wire slave address to initiate a data transfer operation. The bus continues to operate in Hs-mode until a STOP condition occurs on the bus. Upon receiving the STOP condition, the TMP400 switches the input and output filter back to fast-mode operation. The ALERT pin of the TMP400 is dedicated to alarm functions. This pin has an open-drain output that requires a pull-up resistor to V+. It can be wire-ORed together with other alarm pins for system monitoring of multiple sensors. The ALERT pin is intended for use as an earlier warning interrupt, and can be software disabled, or masked. The ALERT pin (pin 11) 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. TIMEOUT FUNCTION When bit 7 of the Consecutive Alert Register is set high, the TMP400 timeout function is enabled. The TMP400 resets the serial interface if either SCL or SDA are held low for 30ms (typical) between a START and STOP condition. If the TMP400 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). STBY (PIN 15) The TMP400 features a standby pin (STBY) that, when pulled low, disables the device. During normal operation STBY should be tied high (V+). When STBY is pulled low, the TMP400 is immediately disabled. If the TMP400 receives a One-Shot command when STBY is pulled low, the command is ignored and the TMP400 continues to be disabled until STBY is pulled high. ALERT High Limit Measured Temperature ALERT Low Limit Hysteresis ALERT SMBus ALERT Read Read Read Time Figure 18. SMBus Alert Timing Diagram Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 17 TMP400 www.ti.com SBOS404 – DECEMBER 2007 SMBUS ALERT FUNCTION UNDERVOLTAGE LOCKOUT The TMP400 supports the SMBus Alert function. The ALERT pin of the TMP400 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 TMP400 is active, the device acknowledges 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 is high if the temperature is greater than or equal to one of the temperature high limit settings; this bit is low if the temperature is less than one of the temperature low limit settings. See Figure 17 for details of this sequence. The TMP400 senses when the power-supply voltage has reached a minimum voltage level for the ADC converter to function. The detection circuitry consists of a voltage comparator that enables the ADC converter after the power supply (V+) exceeds 2.45V (typical). The comparator output is continuously checked during a conversion. The TMP400 does not perform a temperature conversion if the power supply is not valid. The last valid measured temperature is used for the temperature measurement result. 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 TMP400 wins the arbitration, its ALERT pin becomes inactive at the completion of the SMBus Alert command. If the TMP400 loses the arbitration, the ALERT pin remains active. GENERAL CALL RESET The TMP400 supports reset via the Two-Wire General Call address 00h (0000 0000b). The TMP400 acknowledges the General Call address and responds to the second byte. If the second byte is 06h (0000 0110b), the TMP400 executes a software reset, while latching the status of the address pins. This software reset restores the power-on reset state to all TMP400 registers, aborts any conversion in progress, and clears the ALERT pin. If the second byte is 04h (0000 0100b), the TMP400 latches the status of the address pins, but does not reset. The TMP400 takes no action in response to other values in the second byte. A 500µs time delay must be taken after a general call command. SHUTDOWN MODE (SD) The TMP400 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 typical characteristic curve Shutdown Quiescent Current vs Supply Voltage (Figure 10). 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. IDENTIFICATION REGISTERS The TMP400 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 TMP400 returns 55h for the manufacturer code and 01h for the device ID. These registers are read-only. SENSOR FAULT FILTERING The TMP400 senses 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 result reads 7FFh (0111 1111 1111b) and 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. 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 TMP400 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 increased accuracy is setup-specific. When series resistance is added, the value should not be greater than 3kΩ and resistance correction must be enabled (RC = 1). When not using the remote sensor with the TMP400, the D+ and D– inputs must be connected together to prevent meaningless fault warnings. 18 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 TMP400 www.ti.com SBOS404 – DECEMBER 2007 If filtering is needed, the suggested component values are 100pF and 50Ω on each input. Exact values are application specific. Resistance correction must be enabled to avoid offset correction. REMOTE SENSING The TMP400 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. Errors in remote temperature sensor readings are generally the consequence of the ideality factor and current excitation used by the TMP400 versus the manufacturer-specified operating current for a given transistor. Some manufacturers specify a high-level and low-level current for the temperature-sensing substrate transistors. The TMP400 uses 6µA for ILOW and 120µA for IHIGH. The TMP400 allows for different n-factor values; see the N-Factor Correction Register section. The ideality factor (n) is a measured characteristic of a remote temperature sensor diode as compared to an ideal diode. The ideality factor for the TMP400 is trimmed to be 1.008. For transistors whose ideality factor does not match the TMP400, Equation 4 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). n - 1.008 TERR = ´ [273.15 + T(°C)] 1.008 (4) Where: n = Ideality factor of remote temperature sensor T(°C) = actual temperature TERR = Error in TMP400 reading due to n ≠ 1.008 Degree delta is the same for °C and °K For n = 1.004 and T(°C) = 100°C: 1.004 - 1.008 TERR = ´ (273.15 + 100°C) 1.008 TERR = -1.48°C (5) If a discrete transistor is used as the remote temperature sensor with the TMP400, 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. 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 TMP400 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 TMP400 monitors the ambient air around the device. The thermal time constant for the TMP400 is approximately two seconds. This constant implies that if the ambient air changes quickly by 100°C, it would take the TMP400 about 10 seconds (that is, five thermal time constants) to settle to within 1°C of the final value. In most applications, the TMP400 package is in electrical (and therefore, thermal) contact with the printed circuit board (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 TMP400 is measuring. Additionally, the internal power dissipation of the TMP400 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 TMP400 dissipates 1.82mW (PDIQ = 5.5V × 420µA). If the ALERT pin is sinking 1mA, an additional power of 0.4mW is dissipated (PDOUT = 1mA × 0.4V = 0.4mW). Total power dissipation is then 2.22mW (PDIQ + PDOUT) and, with an θJA of 150°C/W, causes the junction temperature to rise approximately 0.333°C above the ambient. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 19 TMP400 www.ti.com SBOS404 – DECEMBER 2007 LAYOUT CONSIDERATIONS Remote temperature sensing on the TMP400 measures very small voltages using very low currents; therefore, noise at the IC inputs must be minimized. Most applications using the TMP400 will have high digital content, with several clocks and logic level transitions creating a noisy environment. Layout should adhere to the following guidelines: 1. Place the TMP400 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 19. If a multilayer PCB is used, bury these traces between ground or VDD planes to shield them from extrinsic noise sources. 5 mil (0.127mm) 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 TMP400, as shown in Figure 20. 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 TMP400. 5. If the connection between the remote temperature sensor and the TMP400 is less than 8 inches (203.2mm), use a twisted-wire pair connection. Beyond 8 inches, use a twisted, shielded pair with the shield grounded as close to the TMP400 as possible. Leave the remote sensor connection end of the shield wire open to avoid ground loops and 60Hz pickup. 20 GND(1) D+ (1) Ground or V+ layer on bottom and/or top, if possible. D-(1) GND (1) (1) 5mil traces with 5mil spacing. Figure 19. Example Signal Traces 0.1mF Capacitor V+ PCB Via GND 1 16 2 15 3 14 4 PCB Via 13 TMP400 5 12 6 11 7 10 8 9 Figure 20. Suggested Bypass Capacitor Placement Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s): TMP400 PACKAGE OPTION ADDENDUM www.ti.com 21-Dec-2007 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TMP400AIDBQR ACTIVE SSOP/ QSOP DBQ 16 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TMP400AIDBQT ACTIVE SSOP/ QSOP DBQ 16 250 CU NIPDAU Level-2-260C-1 YEAR Green (RoHS & no Sb/Br) 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. 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Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 19-Dec-2007 TAPE AND REEL BOX INFORMATION Device Package Pins Site Reel Diameter (mm) Reel Width (mm) A0 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant TMP400AIDBQR DBQ 16 SITE 41 330 12 6.4 5.2 2.1 8 12 Q1 TMP400AIDBQT DBQ 16 SITE 41 180 12 6.9 5.4 2.0 8 12 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 19-Dec-2007 Device Package Pins Site Length (mm) Width (mm) Height (mm) TMP400AIDBQR DBQ 16 SITE 41 346.0 346.0 29.0 TMP400AIDBQT DBQ 16 SITE 41 184.0 184.0 50.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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