DS7505_IcpdfCom

General Description The DS7505 low-voltage (1.7V to 3.7V) digital ther- mometer and thermostat provides 9-, 10-, 11-, or 12-bit digital temperature readings over a -55°C to +125°C range with ±0.5°C accuracy over a -0°C to +70°C range. A 9-bit resolution mode is software compatible with the LM75. Communication with the DS7505 is achieved through a simple 2-wire serial interface. Three address pins allow up to eight DS7505 devices to operate on the same 2-wire bus, which greatly simplifies distributed temperature-sensing applications. The DS7505 thermostat has a dedicated open-drain out- put (O.S.) and programmable fault tolerance, which allows the user to define the number of consecutive error conditions that must occur before O.S. is activated. There are two thermostatic operating modes that control thermostat operation based on user-defined trip points (TOS and THYST) that are stored in EEPROM registers. Applications Networking Equipment Cellular Base Stations Office Equipment Medical Equipment Any Thermally Sensitive System Features © Operating Range from 1.7V to 3.7V © Temperature Measurements Require No External Components © Measures Temperatures from -55°C to +125°C (-67°F to +257°F) © ±0.5°C Accuracy Over a 0°C to +70°C Range © Thermometer Resolution is User-Configurable from 9 (Default) to 12 Bits (0.5°C to 0.0625°C Resolution) © 9-Bit Conversion Time is 25ms (max) © Thermostatic Settings are User-Definable and Nonvolatile (NV) © Stand-Alone Thermostat Capability © Data Read/Write Occurs Through a 2-Wire Serial Interface (SDA and SCL Pins) © Data Lines Filtered Internally for Noise Immunity (50ns Deglitch) © Optional Bus Timeout Feature Prevents Lockup Problems on 2-Wire Interface © Multidrop Capability Simplifies Distributed Temperature-Sensing Applications © Pin/Software Compatible with the LM75 © Available in 8-Pin SO and µMAX® Packages D S 7 5 0 5 Digital Thermometer and Thermostat ________________________________________________________________ Maxim Integrated Products 1 SO TOP VIEW 2 7 A0SCL 1 8 VDDSDA A1O.S. 3 6 A2GND 4 5 DS7505 µµMAX 2 7 A0SCL 1 8 VDDSDA A1O.S. 3 6 A2GND 4 5 DS7505 Pin Configurations Ordering Information Rev 1; 3/08 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. PART TEMP RANGE PIN-PACKAGE DS7505S+ -55°C to +125°C 8 SO (150 mils) DS7505S+T&R -55°C to +125°C 8 SO (150 mils), 2500-Piece T&R DS7505U+ -55°C to +125°C 8 µMAX DS7505U+T&R -55°C to +125°C 8 µMAX, 3000-Piece T&R +Denotes a lead-free package. T&R = Tape and reel. µMAX is a registered trademark of Maxim Integrated Products, Inc. Commands are capitalized for clarity. D S 7 5 0 5 Digital Thermometer and Thermostat 2 _______________________________________________________________________________________ ABSOLUTE MAXIMUM RATINGS DC ELECTRICAL CHARACTERISTICS (1.7V ≤ VDD ≤ 3.7V, TA = -55°C to +125°C, unless otherwise noted.) Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Voltage Range on VDD Relative to Ground ..........-0.3V to +4.0V Voltage Range on Any Other Pin Relative to Ground.............................................-0.3V to +6.0V Operating Temperature Range .........................-55°C to +125°C Storage Temperature Range .............................-55°C to +125°C Soldering Temperature...........................Refer to the IPC/JEDEC J-STD-020 Specification. PARAMETER SYMBOL CONDITIONS MIN MAX UNITS Supply Voltage VDD 1.7 3.7 V Input Voltage Range (SDA, SCL, O.S., A0, A1, A2) (Note 1) -0.3 +5.5 V 0°C to +70°C ± 0.5Thermometer Error (Note 2, 3) TERR -55°C to +125°C ± 2.0 °C Input Logic-High VIH (Note 1) 0.7 × VDD V Input Logic-Low VIL (Note 1) 0.3 × VDD V SDA Output Logic-Low Voltage VOL1 6mA sink current (Note 1) 0 0.6 V O.S. Saturation Voltage VOL2 4mA sink current (Notes 1, 2) 0.8 V Input Current Each I/O pin 0.4V < VI/O < 0.9 x VDD -10 +10 µA I/O Capacitance CI/O 10 pF Standby Current IDD1 (Notes 4, 5, 6) 2 µA Active temp conversions 750 Communication only 100 Active Current (Notes 4, 5, 6) IDD E2 Copy only 500 µA AC ELECTRICAL CHARACTERISTICS (1.7V ≤ VDD ≤ 3.7V, TA = -55°C to +125°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Resolution 9 12 Bits 9-bit conversions 25 10-bit conversions 50 11-bit conversions 100 Temperature Conversion Time tCONVT 12-bit conversions 200 ms SCL Frequency fSCL 400 kHz EEPROM Copy Time tWR -40°C to +85°C 10 ms -40°C � TA � +85°C (Note 7) 10k 20k EEPROM Copy Endurance NEEWR TA = +25°C (Note 7) 40k 80k Cycles D S 7 5 0 5 Digital Thermometer and Thermostat _______________________________________________________________________________________ 3 Note 1: All voltages are referenced to ground. Note 2: Internal heating caused by O.S. loading causes the DS7505 to read approximately 0.5°C higher if O.S. is sinking the max-rated current. Note 3: Specified in 12-bit conversion mode. Quantization error must be considered when converting in lower resolutions. Note 4: IDD specified with O.S. pin open. Note 5: IDD specified with VDD at 3.0V and SDA, SCL = 3.0V, TA = -55°C to +85°C. Note 6: IDD specified with A0, A1, A2 = 0V or VDD. Note 7: VDD must be > 2.0V. Note 8: E2 Copy occurs at +25°C. Note 9: See the timing diagram (Figure 1). All timing is referenced to 0.9 x VDD and 0.1 x VDD. Note 10: After this period, the first clock pulse is generated. Note 11: The DS7505 provides an internal hold time of at least 75ns on the SDA signal to bridge the undefined region of SCL’s falling edge. Note 12: For example, if CB = 300pF, then tR(MIN) = tF(MIN) = 50ns. Note 13: This timeout applies only when the DS7505 is holding SDA low. Other devices can hold SDA low indefinitely and the DS7505 does not reset. AC ELECTRICAL CHARACTERISTICS (continued) (1.7V ≤ VDD ≤ 3.7V, TA = -55°C to +125°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS EEPROM Data Retention tEEDR -40°C to +125°C (Note 8) 10 Years Bus Free Time Between a STOP and START Condition tBUF (Note 9) 1.3 µs START and Repeated START Hold Time from Falling SCL tHD:STA (Notes 9, 10) 600 ns Low Period of SCL tLOW (Note 9) 1.3 µs High Period of SCL tHIGH (Note 9) 0.6 µs Repeated START Condition Setup Time to Rising SCL tSU:STA (Note 9) 600 ns Data-Out Hold Time from Falling SCL tHD:DAT (Notes 9, 11) 0 0.9 µs Data-In Setup Time to Rising tSU:DAT (Note 9) 100 ns Rise Time of SDA and SCL (Receive) tR (Notes 9, 12) 20 + 0.1CB 300 ns Fall Time of SDA and SCL (Receive) tF (Notes 9, 12) 20 + 0.1CB 300 ns Spike Suppression Filter Time (Deglitch Filter) tSS 0 50 ns STOP Setup Time to Rising SCL tSU:STO (Note 9) 600 ns Capacitive Load for Each Bus Line CB 400 pF Input Capacitance CI 5 pF Serial Interface Reset Time tTIMEOUT SDA time low (Note 13) 75 325 ms D S 7 5 0 5 Digital Thermometer and Thermostat 4 _______________________________________________________________________________________ Pin Description PIN NAME FUNCTION 1 SDA Data Input/Output. For 2-wire serial communication port. Open drain. 2 SCL Clock Input. For 2-wire serial communication port. 3 O.S. Thermostat Output. Open drain. 4 GND Ground 5 A2 Address Input 6 A1 Address Input 7 A0 Address Input 8 VDD Supply Voltage. +1.7V to +3.7V supply pin. SDA SCL SR P S tF tLOW tHD:STA tHD:DAT tSU:STA tSU:STO tHD:STA tSP tR tSU:DAT tR tF tBUF Figure 1. Timing Diagram OVERSAMPLING MODULATOR DIGITAL DECIMATOR PRECISION REFERENCE ADDRESS AND I/O CONTROL VDD CONFIGURATION REGISTER TEMPERATURE REGISTER SCL SDA A0 A1 A2 O.S. GND TOS AND THYST REGISTERS THERMOSTAT COMPARATOR DS7505 RF Figure 2. Block Diagram D S 7 5 0 5 Digital Thermometer and Thermostat _______________________________________________________________________________________ 5 Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 MS Byte S 26 25 24 23 22 21 20 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 LS Byte 2-1 2-2 2-3 2-4 0 0 0 0 Figure 3. Temperature, TOS, and THYST Register Format Table 1. 12-Bit Resolution Temperature/Data Relationship OperationMeasuring Temperature The DS7505 measures temperature using a bandgap temperature-sensing architecture. An on-board delta- sigma analog-to-digital converter (ADC) converts the measured temperature to a digital value that is calibrat- ed in degrees Celsius; for Fahrenheit applications a lookup table or conversion routine must be used. The DS7505 is factory-calibrated and requires no external components to measure temperature. The DS7505 can be configured to power up either automatically converting temperature or in a low-power standby state. The preferred power-up mode can be set using the SD bit in the configuration register as explained in the Configuration Register section. The resolution of the digital output data is user-configurable to 9, 10, 11, or 12 bits, corresponding to temperature increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively. The factory default resolution at power-up is 9 bits (R1 = 0, R0 = 0), however this can be pro- grammed to 10, 11, or 12 bits using the R0 and R1 bits in the configuration register as explained in the Configuration Register section. Note that the conver- sion time doubles for each additional bit of resolution. After each temperature measurement and analog-to- digital (A/D) conversion, the DS7505 stores the temper- ature as a 16-bit two’s complement number in the 2-byte temperature register (see Figure 3). The sign bit (S) indicates if the temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. The most recently converted digital measurement can be read from the temperature register at any time. Since temperature conversions are performed in the background, reading the temperature register does not affect the operation in progress. Bits 3 through 0 of the temperature register are hard- wired to 0. When the DS7505 is configured for 12-bit resolution, the 12 MSBs (bits 15 through 4) of the tem- perature register contain temperature data. For 11-bit resolution, the 11 MSBs (bits 15 through 5) of the tem- perature register contain data, and bit 4 reads out as 0. Likewise, for 10-bit resolution, the 10 MSBs (bits 15 through 6) contain data, and for 9-bit the 9 MSBs (bits 15 through 7) contain data and all unused LSBs con- tains 0s. Table 1 gives examples of 12-bit resolution dig- ital output data and the corresponding temperatures. TEMPERATURE (°C) DIGITAL OUTPUT(BINARY) DIGITAL OUTPUT (HEX) +125 0111 1101 0000 0000 7D00 +25.0625 0001 1001 0001 0000 1910 +10.125 0000 1010 0010 0000 0A20 +0.5 0000 0000 1000 0000 0080 0 0000 0000 0000 0000 0000 -0.5 1111 1111 1000 0000 FF80 -10.125 1111 0101 1110 0000 F5E0 -25.0625 1110 0110 1111 0000 E6F0 -55 1100 1001 0000 0000 C900 D S 7 5 0 5 Shutdown Mode For power-sensitive applications, the DS7505 offers a low-power shutdown mode. The SD bit in the configura- tion register controls shutdown mode. When SD is pro- grammed to 1, the conversion in progress is completed and the result stored in the temperature register, after which the DS7505 goes into a low-power standby state. The O.S. output is cleared if the thermostat is operating in interrupt mode and O.S remains unchanged in com- parator mode. The 2-wire interface remains operational in shutdown mode, and writing a 0 to the SD bit returns the DS7505 to normal operation. Upon power-up in shutdown mode, the DS7505 executes one tempera- ture measurement. The result is stored in the tempera- ture register, after which the DS7505 enters the shutdown state. OperationThermostat The DS7505 thermostat can be programmed to power up in either comparator mode or interrupt mode, which activate and deactivate the open-drain thermostat out- put (O.S.) based on user-programmable trip points (TOS and THYST). The THYST and TOS registers contain Celsius temperature values in two’s complement format and consist of EEPROM that is shadowed by SRAM. Once written to the shadow SRAM, values can be stored in EEPROM by issuance of a Copy Data com- mand from the master (see the Command Set section for more details). The device can operate using the shadow SRAM only or using the EEPROM. If the EEPROM is used, the values are NV and can be pro- grammed prior to installation of the DS7505 for stand- alone operation. The factory power-up settings for the DS7505 are with the thermostat in comparator mode, active-low O.S. polarity, overtemperature trip-point (TOS) register set to 80°C, the hysteresis trip-point (THYST) register set to +75°C, and the number of con- secutive conversion to trigger O.S. set to 1. If these power-up settings are compatible with the application, the DS7505 can be used as a stand-alone thermostat (i.e., no 2-wire communication required) with no pro- gramming required prior to installation. If interrupt mode operation, active-high O.S. polarity, different TOS and THYST values, or a different number of conversions to trigger O.S. are desired, they must be programmed into the EEPROM either after initial power-up or prior to IC installation. The programmed values then become the new power-up defaults. In both operating modes, the user can program the thermostat-fault tolerance, which sets how many con- secutive temperature readings (1, 2, 4, or 6) must fall outside the thermostat limits before the thermostat out- put is triggered. The fault tolerance is set by the F1 and F0 bits in the configuration register. The default factory power-up setting for fault tolerance is 1 (F1 = 0, F0 = 0). The data format of the TOS and THYST registers is iden- tical to that of the temperature register (see Figure 3), i.e., a 2-byte two’s complement representation of the trip-point temperature in degrees Celsius with bits 3 through 0 hardwired to 0. After every temperature con- version, the measurement is compared to the values stored in the TOS and THYST registers. The O.S. output is updated based on the result of the comparison and the operating mode of the IC. The number of TOS and THYST bits used during the thermostat comparison is equal to the conversion resolution set by the R1 and R0 bits in the configuration register. For example, if the resolution is 9 bits, only the 9 MSBs of TOS and THYST are used by the thermostat comparator. The active state of the O.S. output can be programmed by the POL bit in the configuration register. The power- up factory default is active low (POL = 0). If the user does not wish to use the thermostat capabili- ties of the DS7505, the O.S. output should be left unconnected. Note that if the thermostat is not used, the TOS and THYST registers can be used for general storage of system data. Comparator Mode When the thermostat is in comparator mode, O.S. can be programmed to operate with any amount of hystere- sis. The O.S. output becomes active when the mea- sured temperature exceeds the TOS value a consecutive number of times as defined by the F1 and F0 fault tolerance (FT) bits in the configuration register. O.S. then stays active until the first time the tempera- ture falls below the value stored in THYST. Putting the device into shutdown mode does not clear O.S. in com- parator mode. Thermostat comparator mode operation with FT = 2 is illustrated in Figure 4. Digital Thermometer and Thermostat 6 _______________________________________________________________________________________ D S 7 5 0 5 Digital Thermometer and Thermostat _______________________________________________________________________________________ 7 IN THIS EXAMPLE, THE DS7505 IS CONFIGURED TO HAVE A FAULT TOLERANCE OF 2. TOS THYST TEMPERATURE O.S. OUTPUT—COMPARATOR MODE O.S. OUTPUT—INTERRUPT MODE INACTIVE INACTIVE ACTIVE ACTIVE CONVERSIONS ASSUMES A READ HAS OCCURED Figure 4. O.S. Output Operation Example Interrupt Mode In interrupt mode, the O.S. output first becomes active when the measured temperature exceeds the TOS value a consecutive number of times equal to the FT value in the configuration register. Once activated, O.S. can only be cleared by either putting the DS7505 into shutdown mode or by reading from any register (tem- perature, configuration, TOS, or THYST) on the device. Once O.S. has been deactivated, it is only reactivated when the measured temperature falls below the THYST value a consecutive number of times equal to the FT value. Again, O.S can only be cleared by putting the device into shutdown mode or reading any register. Thus, this interrupt/clear process is cyclical between TOS and THYST events (i.e, TOS, clear, THYST, clear, TOS, clear, THYST, clear, etc.). Thermostat interrupt mode operation with FT = 2 is illustrated in Figure 4. D S 7 5 0 5 Configuration Register The configuration register allows the user to program various DS7505 options such as conversion resolution, thermostat fault tolerance, thermostat polarity, thermo- stat operating mode, and shutdown mode. The configu- ration register is arranged as shown in Figure 5 and detailed descriptions of each bit are provided in Table 2. The user has read/write access to all bits in the con- figuration register except the MSB (NVB bit), which is a read-only bit. All bits in the register but the NVB bit are NV EEPROM backed by shadow SRAM, and thus power-up in their programmed state. Once written to the shadow SRAM, values can be stored in EEPROM by issuance of a Copy Data command from the master (see the Command Set section for more details). If the values are not copied to the EEPROM, the device pow- ers up with the factory default settings or the last values that were copied to the EEPROM. The NVB bit is SRAM and powers up in the state shown in Table 2. Digital Thermometer and Thermostat 8 _______________________________________________________________________________________ MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB NVB R1 R0 F1 F0 POL TM SD Figure 5. Configuration Register Table 2. Configuration Register Bit Descriptions BIT NAME FUNCTIONAL DESCRIPTION NVB NV Memory Status Power-up state = 0, read only NVB = 1—Write to an NV memory cell is in progress. NVB = 0—NV memory is not busy. R1 Conversion Resolution Bit 1 Factory power-up state = 0 Sets conversion resolution (see Table 3). R0 Conversion Resolution Bit 0 Factory power-up state = 0 Sets conversion resolution (see Table 3). F1 Thermostat Fault Tolerance Bit 1 Factory power-up state = 0 Sets the thermostat fault tolerance (see Table 4). F0 Thermostat Fault Tolerance Bit 0 Factory power-up state = 0 Sets the thermostat fault tolerance (see Table 4). POL Thermostat Output (O.S.) Polarity Factory power-up state = 0 POL = 0—O.S. is active low. POL = 1—O.S. is active high. TM Thermostat Operating Mode Factory power-up state = 0 TM = 0—Comparator mode. TM = 1—Interrupt mode. See the Operation—Thermostat section for a detailed description of these modes. SD Shutdown Factory power-up state = 0 SD = 0—Active conversion and thermostat operation. SD = 1—Shutdown mode. See the Shutdown Mode section for a detailed description of this mode. Register Pointer The four DS7505 registers each have a unique 2-bit pointer designation, which is defined in Table 5. When reading from or writing to the DS7505, the user must “point” the DS7505 to the register that is to be accessed. When reading from the DS7505, once the pointer is set, it remains pointed at the same register until it is changed. For example, if the user desires to perform consecutive reads from the temperature regis-