DS75LV MAXIM | Alldatasheet
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Technical content
DESCRIPTION
This low-voltage (1.7V to 3.7V) digital thermometer and thermostat provides 9-, 10-, 11-, or 12-bit digital temperature readings over a -55°C to +125°C range with /g1772°C accuracy over a -25°C to +100°C range. At power-up, the DS75LV defaults to 9-bit resolution for software compatibility with the LM75. Communication with the DS75LV is achieved through a simple 2-wire serial interface. Three address pins allow up to eight DS75LV devices to operate on the same 2-wire bus, which greatly simplifies distributed temperature- sensing applications. The DS75LV thermostat has a dedicated open-drain output (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 (T OS and THYST). A block diagram of the DS75LV is shown in Figure 1 and detailed pin descriptions are given in Table 2.
APPLICATIONS
Any Thermally Sensitive System PIN CONFIGURATION
FEATURES
/g167/g32Operating Range from 1.7V to 3.7V /g167/g32Temperature Measurements Require No External Components /g167/g32Measures Temperatures from -55°C to +125°C (-67°F to +257°F) /g167/g32/g1772°C Accuracy Over a -25°C to +100°C Range /g167/g32Thermometer Resolution is User- Configurable from 9 (Default) to 12 Bits (0.5°C to 0.0625°C Resolution) /g167/g329-Bit Conversion Time is 25ms (Max) /g167/g32Thermostatic Settings are User-Definable /g167/g32Data Read/Write Occurs Through a 2-Wire Serial Interface (SDA and SCL Pins) /g167/g32Data Lines Filtered Internally for Noise Immunity (50ns Deglitch) /g167/g32Bus Timeout Feature Prevents Lockup Problems on 2-Wire Interface /g167/g32Multidrop Capability Simplifies Distributed Temperature-Sensing Applications /g167/g32Pin/Software Compatible with the LM75 /g167/g32Available in 8-Pin /g109SOP (/g109MAX) and SO Packages
ORDERING INFORMATION
PART TEMP RANGE PIN-PACKAGE DS75LVS+ -55°C to +125°C DS75LV (150-mil) 8-SO DS75LVS+T&R -55°C to +125°C DS75LV (150-mil) 8-SO,
2500 Piece
DS75LVU+ -55°C to +125°C DS75LV 8-µSOP (µMAX) DS75LVU+T&R -55°C to +125°C DS75LV 8-µSOP (µMAX), 3000 Piece Tape- and-Reel Ordering Information continued at the end of the data sheet. DS75LV Digital Thermometer and Thermostat www.maxim-ic.com DS75LVU— /g109SOP//g109MAX SCL VDD A2 GND O.S. SDA DS75L DS75LVS—SO (150 mils) SCL VDD A2 GND O.S. SDA DS75L
DS75LV: Digital Thermometer and Thermostat 2 of 13 ABSOLUTE MAXIMUM RATINGS* Voltage on VDD, Relative to Ground -0.3V to +4.0V Voltage on Any Other Pin, Relative to Ground -0.3V to +6.0V Operating Temperature Range -55 /g176C to +125/g176C Storage Temperature Range -55 /g176C to +125/g176C Soldering Temperature 260 /g176C for 10 seconds These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. The Dallas Semiconductor DS75LV is built to the highest quality standards and manufactured for long-term reliability. All Dallas Semiconductor devices are made using the same quality materials and manufacturing methods. However, the DS75LV is not exposed to environmental stresses, such as burn-in, that some industrial applications require. For specific reliability information on this product, please contact the factory in Dallas at (972) 371-4448. DC ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL CONDITIONS MIN MAX UNITS Supply Voltage V DD (Note 10) 1.7 3.7 V -25 to +100 /g177 2.0 Thermometer Error (Note 2) TERR -55 to +125 /g177 3.0 /g176C Input Logic High V IH (Note 1) 0.7 × V DD 5.5 V Input Logic Low V IL (Note 1) -0.5 0.3 × V DD V VOL1 3mA sink current 0 0.4 SDA Output Logic Low Voltage (Note 1) VOL2 6mA sink current 0 0.6 V O.S. Saturation Voltage V OL 4mA sink current (Notes 1, 2) 0.8 V Input current each I/O pin 0.4 < V I/O< 0.9 VDD -10 +10 /g109A I/O Capacitance C I/O 10 pF Standby Current I DD1 (Notes 3, 4) 2 /g109A Active Temp Conversions 1000 Active Current (Notes 3, 4) IDD Communication only 100 /g109A AC ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL CONDITION 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 f SCL 400 KHz Bus Free Time Between a STOP and START Condition tBUF (Note 5) 1.3 /g109s START and Repeated START Hold Time from tHD:STA (Notes 5, 6) 600 ns
Note 1: All voltages are referenced to ground. Note 3: IDD specified with O.S. pin open. Note 4: IDD specified with VDD at 3.0V and SDA, SCL = 3.0V, 0/g176C to 70/g176C. Note 5: See Timing Diagram in Figure 2. All timing is referenced to 0.9 x VDD and 0.1 x VDD. Note 6: After this period, the first clock pulse is generated. Note 7: For example, if CB = 300pF, then tR[min] = tF[min] = 50ns. Note 8: The DS75LV provides an internal hold time of at least 75ns on the SDA signal to bridge the undefined region of SCL's falling edge. Table 1. Detailed Pin Description 1 SDA Data Input/Output. For 2-wire serial communication port. Open-drain. 2 SCL Clock Input. 2-wire serial communication port. 3 O.S. Thermostat Output. Open-drain.
4 GND Ground
5 A 2 Address Input
6 A 1 Address Input
7 A 0 Address Input
8 V DD Supply Voltage. +1.7V to +3.7V supply pin.
calibrated and requires no external components to measure temperature. sheet. Note that the conversion time doubles for each additional bit of resolution. resolution, the 11 MSbs (bits 15 through 5) of the temperature register will contain data, and bit 4 will read out as 0. output data and the corresponding temperatures. Figure 3. Temperature, TOS, and THYST Register Format Table 2. 12-Bit Resolution Temperature/Data Relationship result stored in the temperature register after which the DS75LV will go into a low-power standby state. The O.S.
DS75LV: Digital Thermometer and Thermostat 6 of 13 OPERATION/g190THERMOSTAT The DS75LV thermostat has two operating modes, comparator mode and interrupt mode, which activate and deactivate the open-drain thermostat output (O.S.) based on user-programmable trip-points (T OS and T HYST). The DS75LV powers up with the thermostat in comparator mode, active-low O.S. polarity, over-temperature trip-point OS) register set to 80C, and the hystoresis trip-point (T HYST) register set to 75C. If these power-up settings are compatible with the application, the DS75LV can be used as a standalone thermostat (i.e., no 2–wire communication required). If interrupt mode operation, active-high O.S. polarity or different T OS and THYST values are desired, they must be programmed after power-up, so standalone operation is not possible. In both operating modes, the user can program the thermostat fault tolerance, which sets how many consecutive temperature readings (1, 2, 4, or 6) must fall outside of the thermostat limits before the thermostat output is triggered. The fault tolerance is set by the F1 and F0 bits in the configuration register. At power-up the fault tolerance is set to 1. The data format of the T OS and THYST registers is identical to that of the temperature register (see Figure 3), i.e., a two-byte two’s complement representation of the trip-point temperature in degrees centigrade with bits 3 through 0 hardwired to 0. After every temperature conversion, the measurement is compared to the values stored in the T OS 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 T OS and T HYST 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 T OS and THYST will be used by the thermostat comparator. The active state of the O.S. output can be changed via the POL bit in the configuration register. The power-up default is active low. If the user does not wish to use the thermostat capabilities of the DS75LV, the O.S. output should be left floating. 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 hystoresis. The O.S. output becomes active when the measured temperature exceeds the T OS 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 temperature falls below the value stored in T HYST. Putting the device into shutdown mode does not clear O.S. in comparator mode. Thermostat comparator mode operation with FT = 2 is illustrated in Figure 4. 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 DS75LV into shutdown mode or by reading from any register (temperature, configuration, T OS, or T HYST ) on the device. Once O.S. has been deactivated, it will only be reactivated when the measured temperature falls below the T HYST 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 T OS and THYST events (i.e, T OS, clear, T HYST, clear, T OS, clear, T HYST, clear, etc.). Thermostat interrupt mode operation with FT = 2 is illustrated in Figure 4.
Figure 4. O.S. OUTPUT Operation Example entire register is volatile, and thus powers–up in its default state. Figure 5. Configuration Register
0 R1 R0 F1 F0 POL TM SD
Table 3. Configuration Register Bit Descriptions The master can write to this bit, but it will always read out as a 0. Sets the thermostat fault tolerance (see Table 6). Sets the thermostat fault tolerance (see Table 6). POL = 0 — O.S. is active low. POL = 1 — O.S. is active high. SD = 0 — Active conversion and thermostat operation. Table 4. Resolution Configuration Table 5. Fault Tolerance Configuration
reading from or writing to the DS75LV, the user must “point” the DS75LV to the register that is to be accessed. refreshed each time a write is performed, even if the same register is being written to twice in a row. immediately without resetting the pointer. Table 6. Pointer Definition SDA I/O pin. All communication is MSb first. generates the SCL signal and START and STOP conditions. Slave: All devices on the bus other than the master. The DS75LV always functions as a slave. (if the SCL output is open-drain). Transmitter: A device (master or slave) that is sending data on the bus. Receiver: A device (master or slave) that is receiving data from the bus. will perform another operation. STOP is issued, the master releases the bus to its idle state. receiving data. The master indicates a NACK by leaving the SDA line high during the ACK clock cycle.
2 A 1 A 0, where A 2, A 1 and A 0 are user-selectable via the
corresponding input pins. The three address pins allow up to eight DS75LVs to be multi-dropped on the same bus.
DS75LV: Digital Thermometer and Thermostat 11 of 13 Software POR —The soft power on reset (POR) command is 54h. The master sends a START followed by an address byte containing the DS75LV bus address. The R/W bit must be a 0. The DS75LV will respond with an ACK. If the next byte is a 0x54, the DS75LV will reset as if power had been cycled. No ACK will be send by the IC after the POR command is received. Reading from the DS75LV —When reading from the DS75LV, if the pointer was already pointed to the desired register during a previous transaction, the read can be per formed immediately without changing the pointer setting. In this case the master sends a START followed by an address byte containing the DS75LV bus address. The R/W bit must be a 1, which tells the DS75LV that a read is being performed. After the DS75LV sends an ACK in response to the address byte, the DS75LV will begin transmitting the requested data on the next clock cycle. When reading from the configuration register, the DS75LV will transmit one byte of data, after which the master must respond with a NACK followed by a STOP (see Figure 9e). For two-byte reads (i.e., from the Temperature, T OS or THYST register), the DS75LV will transmit two bytes of data, and the master must respond to the first data byte with an ACK and to the second byte with a NACK followed by a STOP (see Figure 9a). If only the most significant byte of data is needed, the master can issue a NACK followed by a STOP after reading the first data byte in which case the transaction will be the same as for a read from the configuration register. If the pointer is not already pointing to the desired register, the pointer must first be updated as shown in Figure 9d, which shows a pointer update followed by a single-byte read. The value of the R/W bit in the initial address byte is a 0 (“write”) since the master is going to write a pointer byte to the DS75LV. After the DS75LV responds to the address byte with an ACK, the master sends a pointer byte that corresponds to the desired register. The master must then perform a repeated start followed by a standard one or two byte read sequence (with R/W =1) as described in the previous paragraph. Bus Timeout—The DS75LV has a bus timeout feature that prevents communication errors from leaving the IC in a state where SDA is held low disrupting other devices on the bus. If the DS75LV holds the SDA line low for a period of t TIMEOUT, its bus interface will automatically reset and release the SDA line. Bus communication frequency must be fast enough to prevent a reset during normal operation. The bus timeout feature only applies to when the DS75LV is holding SDA low. Other devices can hold SDA low for an undefined period without causing the interface to reset.
Figure 9. 2-Wire Interface Timing
DS75LV: Digital Thermometer and Thermostat 13 of 13 DS75LVS+ -55°C to +125°C DS75L* DS75LV (150-mil) 8-SO DS75LVS+T&R -55°C to +125°C DS75L* DS75LV (150-mil) 8-SO, 2500 Piece Tape-and-Reel DS75LVU+ -55°C to +125°C DS75L DS75LV 8-µSOP (µMAX) DS75LVU+T& R -55°C to +125°C DS75L DS75LV 8-µSOP (µMAX), 3000 Piece Tape-and-Reel DS75LVS -55°C to +125°C DS75L DS75LV (150-mil) 8-SO DS75LVS/T&R -55°C to +125°C DS75L DS75LV (150-mil) 8-SO, 2500 Piece Tape-and-Reel DS75LVU -55°C to +125°C DS75L DS75LV 8-µSOP (µMAX) DS75LVU/T&R -55°C to +125°C DS75L DS75LV 8-µSOP (µMAX), 3000 Piece Tape-and-Reel * A “+” symbol is also marked on the package near the pin 1 indicator. **The DS75LV has a maximum operating voltage of 3.7V. Contact Dallas Semiconductor for information on the availability of a 3.7V to 5.5V version of the DS75LV.
PACKAGE INFORMATION
(For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo.)