View FM75_984148.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
PRELIMINARY July 2001
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
General Description
The FM75 is a high-precision CMOS temperature sensor with a Delta-Sigma analog-to-digital converter and a SMBus compatible serial digital interface. The FM75 is typically accurate to 2C over the full temperature range of -40C to 125C and to 1C over the range of 0C to 100C. The FM75 provides digital temperature data with 9 to 12-bit resolution. The default resolution is 9 bits, but for applications requiring higher resolution, the user can program the FM75 to provide 10, 11, or 12 bit data. The FM75 features a thermal alarm function with a user-programmable trip temperature and turn-off temperature. This alarm can operate in two modes -- interrupt mode and comparator mode -- which allows flexibility for many types of applications. The FM75 is available in SOP-8 and MSOP-8 surface mount packages.
Features
I User Configurable to 9, 10, 11 or 12-bit Resolution I Precision Calibrated to 1C from 0C to 100C Typical I Temperature Range: -40C to 125C I Low Operating Current (less than 250A) I Low Self Heating (0.2C max in still air) I Operating Voltage Range: 2.7V to 5.5V
Applications
I Battery Management I FAX Management I Printers I Portable Medical Instruments I HVAC I Power Supply Modules I Disk Drives I Computers I Automotive
Pin Configuration
Application Diagram
2.7 to 5.5V
SDA SCL O.S. GND
1
8
VDD A0
User Programmable Address
8
2
7
A0 A1 A2
SMBus Interface
7 6 5
FM75
3 6
A1 A2
FM75
8 Pin Configuration
3
O.S.
4
5
SDA SCL
1 2
4
(c) 2001 Fairchild Semiconductor Corporation FM75 Rev. A.4
1
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Absolute Maximum Ratings (Note 1)
Parameter Supply Voltage Output Voltage Output Current Rating +7V VCC + 0.5V 10mA Storage Temperature Range Lead Soldering Temperature ESD2 Human Body Model Machine Model 2000V 250V -60C to +150C 220C
Notes: 1. Absolute maximum ratings are limits beyond which operation may cause permanent damage to the device. These are stress ratings only; functional operation at or above these limits is not implied. 2. Human Body Model: 100pF capacitor discharged through a 1.5kOhm resistor into each pin. Machine Model: 200pF capacitor discharged directly into each pin.
Electrical Characteristics3
(-40C TA +125C, VCC = 5.0V unless otherwise noted. Specifications subject to change without notice.) Parameter
Specified Temperature Range Temperature Conversion Accuracy5 Time4 TA = 0C TA = +25C TA = +100C TA = -40C (TMIN) TA = +125C (TMAX) -1 -1 -1 -3 -3
Symbol
TMIN, TMAX
Conditions
Min
-40
Typ
90
Max
+125
Units
C ms
+1 +1 +1 +3 +3
C C C C C
Notes: 3. These specifications are guaranteed only for the test conditions listed. 4. This specification only indicates how often temperature information is updated to the Temperature Register. The FM75 can be read at any time without interrupting the temperature conversion process. 5. Accuracy (expressed in C) = Difference between the FM75 output temperature and the measured temperature.
Logic Electrical Characteristics
Parameter
Min. Input Voltage Logic High Max. Input Voltage Logic Low Max. Output Voltage Logic Low Quiescent Supply Current Shutdown Current Input Leakage Current Output Sink Current Output Leakage Current Output Transition Time Input Capacitance
Symbol
VIH VIL VOL IDD IDD-SD IIN IOL ILEAK tF CIN
Conditions
Min
VDD x 0.7 -0.3
Typ
Max
VDD + 0.5 VDD x 0.3 0.36 0.36
Units
V V V V A A A A A A mA A ns pF
VDD = 5V, IOL = -3mA VDD = 3V, IOL = -1.5mA Interface inactive R/W Activity on SDA Interface inactive R/W Activity on SDA VIN = 0V or 5V, TA = 25C -40C < TA < 125C TA = 25C, VOL = 0.4V VOH = 5V, VDD = 0V CL = 400pF, IOL = -3mA All Digital Inputs 0.001 220 350 0.15 83
250 500 1 150 0.1 1.0 3 5 250 20
2
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Serial Port Timing
Parameter
SCL Clock Period SCL Clock Transition Time SCL Clock Low Period SCL Clock High Period Bus free time between a Stop and a new Start Condition Data in Set-up to SCL High Data Out Stable after SCL Low SCL Low Set-up to SDA Low (Repeated Start Condition) SCL High Hold after SDA Low (Start Condition) SDA High after SCL High (Stop Condition) Time in which a FM75 must be operational after a power-on reset
Symbol
tSCL tT:LH, tT:HL tLOW tHIGH tBUF tSU:DAT tHD:DAT tSU:STA tHD:STA tSU:STO tPOR
Conditions
Min
2.5
Typ
Max
300
Units
ms ns s
0.470 0.400 1.0 100 0 100 100 100 500 50
s s ns ns ns ns ns ms
tSCL
SCL
tHD:STA tSU:DAT
tSU:STA tSU:STO
SDA
Data In tBUF
tLOW
tHIGH
tT:LH 90% 10%
tT:HL
SCL SDA
Data Out
90% 10%
tHD:DAT
Pin Descriptions
Pin #
1 2 3 4 5, 6, 7 8
Name
SDA SCL O.S. GND A0, A1, A2 VDD
Direction
Input/Output Input Output Supply Input Supply
Description
Serial Data-Open drain to I/O-data pin for two-wire interface. Serial Clock-Clock for 2-wire serial interface. Over-Limit Signal-Open drain thermostat output that indicates if the temperature has exceeded user-programmable limits. Ground Address LSBs-User selectable address pins for the 3 LSBs of the serial interface address. Supply Voltage
3
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Basic Operation
The FM75 temperature sensing circuitry continuously produces an analog voltage that is proporational to the device temperature. At regular intervals the FM75 converts the analog voltage to a two's complement digital value, which is placed into the temperature register. The FM75 has an SMBus compatible digital serial interface which allows the user to access the data in the temperature register at any time. In addition, the serial interface gives the user easy access to all other FM75 registers to customize operation of the device. The FM75 temperature-to-digital conversion can have 9, 10, 11, or 12-bit resolution as selected by the user, providing 0.5C, 0.25C, 0.125C, and 0.0625C temperature resolution, respectively. At power-up the default conversion resolution is 9-bits. The conversion resolution is controlled by the R0 and R1 bits in the Configuration Register. Table 1 gives examples of the relationship between the output digital data and the external temperature. The 9-bit, 10-bit, 11-bit and 12-bit columns in Table 1 indicate the right-most bit in the output data stream that can contain temperature information for each conversion accuracy. Since the output digital data is in two'scomplement format, the most significant bit of the temperature is the "sign" bit. If the sign bit is a zero, the temperature is positive and if the sign bit is a one, the temperature is negative. The FM75 has a Shutdown Mode that reduces the operating current of the FM75 to 150nA. This mode is controlled by the SD bit in the configuration register.
Table 1. Relationship Between Temperature and Digital Output
Temperature Number of bits used by conversion resolution Digital Output
Sig
bit 9
bit 10
bit 11
bit 12
Always zero
12-Bit Resolution All Temperatures 11-Bit Resolution 10-Bit Resolution 9-Bit Resolution +125 C +100.0625 C +50.125 C +12.25 C 0 C -20.5 C -33.25 C -45.0625 C -55 C 0 0 0 0 0 1 1 1 1 111 110 011 000 000 110 101 101 100 1101 0100 0010 1100 0000 1011 1110 0010 1001 0 0 0 0 0 1 1 1 0 0 0 0 0 1 0 0 1 1 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0
0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
Power Up Default Conditions
The FM75 always powers up in the following default state: I Thermostat mode: Comparator Mode I O.S. polarity: active low I Fault tolerance: 1 fault (i.e., F0 = 0 and F1 = 0 in the Configuration Register) I TOS = 80C I THYST = 75C I Register pointer: 00 (Temperature Register) I Conversion resolution: 9 bits (i.e., R0 = 0 and R1 = 0 in the Configuration Register) After power up these conditions can be reprogrammed via the serial interface. Refer to the Serial Data Bus Operation section for FM75 programming instructions.
The O.S. polarity is controlled by the POL bit in the Configuration Register. The user-programmable upper trip-point temperature for the thermal alarm is stored in the TOS Register, and the userprogrammable hysteresis temperature (i.e., the lower trip point) is stored in the THYST Register. The thermal alarm has two modes of operation: Comparator Mode and Interrupt Mode. At power-up the default is Comparator Mode. The alarm mode is controlled by the CMP/INTR bit in the Configuration Register.
Fault Tolerance
In both modes the alarm "fault tolerance" setting plays a role in determining when the O.S. output will be activated. Fault tolerance refers to the number of consecutive times an error condition must be detected before the user is notified. Higher fault tolerance settings can help eliminate false alarms caused by noise in the system. The alarm fault tolerance is controlled by bits F0 and F1 in the Configuration Register. These bits can be used to set the fault tolerance to 1, 2, 4 or 6 as shown in Table 4. At power-up, these bits both default to 0 (fault tolerance = 1).
Thermal Alarm Function
The FM75 thermal alarm function provides user programmable thermostat capability and allows the FM75 to function as a stand alone thermostat without using the serial interface. The Over-Limit Signal (O.S.) output is the alarm output. This signal is an open drain output, and at power-up this pin is configured with active-low polarity.
4
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Comparator Mode
In Comparator Mode, each time a temperature-to-digital (T-to-D) temperature conversion occurs, the new digital temperature is compared to the value stored in the TOS and THYST registers. If a fault tolerance number of consecutive temperature measurements are greater than the value stored in the TOS register, the O.S. output will be activated. For example, if bits F1 and F0 are equal to "10" (fault tolerance = 4), four consecutive temperature measurements must exceed TOS to activate the O.S. output. Once the O.S output is active, it will remain active until the first time the measured temperature drops below the temperature stored in the THYST register. The operation of the alarm in Comparator Mode with fault tolerance=2 is illustrated in Figure 1.
Interrupt Mode
In Interrupt Mode the O.S. output will first become active after a fault tolerance number of consecutive temperature measurements exceed the value stored in the TOS register (similar to Comparator Mode). Once O.S. is active, it can only be cleared by a user read from any of the FM75 registers (Temperature, Configuration, TOS, or THYST) or by putting the FM75 into Shutdown Mode (i.e., by setting the shutdown bit in the Configuration Register to "1"). Once cleared, the O.S. output can only be activated the next time by a fault tolerance number of consecutive temperature measurements that are lower than the value stored in THYST. Again, once it is activated the O.S. output can only be deactivated by a user read or shutdown. Thus, in Interrupt Mode the activate/clear cycle for O.S. has the following pattern: temperature > TOS, clear, temperature < THYST, clear, temperature > TOS, clear, etc. The operation of the alarm in Interrupt Mode with fault tolerance=2 is also illustrated in Figure 1.
Temperature-to-Digital Conversion
TOS
THYST
O.S. (Comparator Mode)
O.S. (Interrupt Mode)
For this example: Fault Tolerance = 2 Output Polarity = Active Low
Read (or Shutdown
Figure 1. Thermal Alarm Operation in Comparator and Interrupt Modes
5
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Registers
The FM75 contains the following five registers: 1) Command Register 2) Temperature Register 3) Configuration Register 4) Over-Limit-Signal Temperature Register (TOS) 5) Hysteresis Temperature Register (THYST) All of these registers can be accessed by the user via the digital serial interface at any time (see Serial Interface Operation for instructions). A detailed description of these registers and their functions is provided in the following paragraphs. A diagram of the register hierarchy is shown in Figure 2
Command Register
The Command Register is a one-byte (8-bit) write-only register. The data stored in the Command Register indicates which of the other four registers (Temperature, Configuration, TOS, or THYST) the user intends to read from or write to during an upcoming operation. In other words the Command Register "points" to the selected register as shown in Figure 2 The Command Register is illustrated in Figure 3. The P1 and P0 bits of the Command Register determine which register is to be accessed as shown in Table 2. The six MSBs of the Command Register must always be zero. Writing a 1 into any of these bits will cause the current operation to be terminated. The Command Register retains pointer information between operations. Therefore, this register only needs to be updated once for consecutive read operations from the same register. All bits in the Command Register default to zero at power-up.
SDA
SCL Temperature Register
Serial Interface
Read/Write Data
2-byte Read Only Command Reg. = 00000000
Configuration Register
Command ('Pointer') Data 1-byte Read/Write Command Reg. = 00000001
THYST Register 2-byte Read/Write Command Reg. = 00000010 Command Register
1-byte Write Only
TOS Register 2-byte Read/Write Command Reg. = 00000011 1
Figure 2. FM75 Register Hierarchy
MSB
LSB
0
0
0
0
0
0 P1 P0
Table 2. Register Assignments for Command Bits P1 and P2 Register P1
0 0 1 1
P0
0 1 0 1
Figure 3. Command Register Format
Temperature Register Configuration Register THYST Register TOS Register
6
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Temperature Register
The Temperature Register is a two-byte (16-bit) read-only register. Digital temperatures from the T-to-D converter are stored in the Temperature Register in two's complement format, and the contents of this register are updated at regular intervals--i.e., each time the T-to-D conversion is finished. The user can read data from the Temperature Register at any time. When a T-to-D conversion is completed, the new data is loaded into a comparator buffer to evaluate fault conditions, and will update the Temperature Register is a read cycle is not ongoing. The FM75 is continuously evaulating fault conditions regardless of read or write activity on the bus. If a read is ongoing, the previous temperature will be read. The readable temperature will be updated upon the completion of the next T-to-D conversion that is not masked by a read cycle. The Temperature Register is illustrated in Figure 4. Depending on the resolution of the T-to-D conversion, the 9, 10, 11 or 12 MSBs of the register will contain temperature data. All unused bits following the digital temperature will be zero. The MSB position of the Temperature Register always contains the sign bit for the digital temperature and bit 14 contains the temperature MSB. All bits in the Temperature Register default to zero at power-up.
Configuration Register
The Configuration Register is a one-byte (8-bit) read/write register (see Figure 5). This register allows the user to control the FM75 Shutdown Mode as well as the following thermal alarm features: polarity, operating mode, and fault tolerance. The Configuration Register contains two bits that set the fault tolerance trip point. The fault tolerance trip point is the number of consecutive times the internal circuit reads the temperature and finds the tempterature outside the limits programmed. The programmed limited are defined by the TOS Register for the upper limit, and by the THYST Register for the lower limit. Table 4 shows the relationship between F1 and F0 and the number of consecutive errors or "trips" needed to activate the alarm. The Configuration Register also contains the two bits that set the T-to-D conversion resolution to 9, 10, 11, or 12 bits. Table 3 shows the relationship between R1 and T0 and the conversion resolution. All bits in the configuration register default to zero at power-up.
MSB
6
5
4
3
2
1
LSB
X R1 R0 F1 F0
R1 = Resolution bit 1. (See Table 3) R0 = Resolution bit 0. (See Table 3)
POL CMP/ INT
SD
MSB 14
13
12
11
10
9
F1 = Fault tolerance bit 1. (See Table 4)
8
F0 = Fault tolerance bit 0. (See Table 4) POL = O.S. output polarity. 0 = active low, 1 = active high. CMP/INT = Thermostat mode. 0 = comparator mode, 1 = interrupt mode. SD = Shutdown. 0 = normal operation, 1 = shutdown mode.
SB
TMSB
T
T
T
T
T
T
Figure 5. Configuration Register Format
7
9-bit LSB
6
10-bit LSB
5
11-bit LSB
4
12-bit LSB
3
2
1
LSB
Table 3. Conversion Resolution Settings A-to-D Conversion Resolution
9 Bits 10 Bits 11 Bits 12 Bits
0
0
0
0
R1
0 0 1 1
R0
0 1 0 1
SB = Two's complement sign bit TMSB = Temperature MSB T = Temperature data 9-bit LSB = Temperature LSB for 9-bit conversions 10-bit LSB = Temperature LSB for 10-bit conversions 11-bit LSB = Temperature LSB for 11-bit conversions 12-bit LSB = Temperature LSB for 12-bit conversions
Figure 4. Temperature Register Format
Table 4. Fault Tolerance Settings Fault Tolerance
1 2 4 6
F1
0 0 1 1
F0
0 1 0 1
7
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Over-Limit-Signal Temperature Register (TOS)
The TOS Register is a two-byte (16-bit) read/write register that stores the user-programmable upper trip-point temperature for the thermal alarm in two's-complement format. At power-up this register defaults to 80C (i.e., 0101 0000 0000 0000). The format of the TOS register is identical to that of the Temperature Register (see Figure 6). The 4 LSBs of the TOS Register are hardwired to zero, so data written to these register bits will be ignored. The MSB position of the TOS Register contains the sign bit for the digital temperature and bit 14 contains the temperature MSB. The resolution setting for the T-to-D conversion determines how many bits of the TOS Register are used by the thermal alarm. For example, for 9-bit conversions the trip-point temperature is defined by the 9 MSBs of the TOS register, and all remaining bits are "don't cares."
Hysteresis Temperature Register (THYST)
The THYST Register is a two-byte (16-bit) read/write register that stores the user programmable lower trip-point temperature for the thermal alarm in two's-complement format. At power-up this register defaults to 75C (i.e., 0100 1011 0000 0000). The THYST register is illustrated in Figure 6. The format of this register is the same as that of the Temperature Register. The 4 LSBs of the THYST register are hardwired to zero, so data written to these bits is ignored. The resolution setting for the T-to-D conversion determines how many bits of the THYST Register are used by the thermal alarm. For example, for 9-bit conversions the hysteresis temperature is defined by the 9 MSBs of the THYST Register, and all remaining bits are "don't cares."
MSB 14
13
12
11
10
9
8
SB
TMSB
T
T
T
T
T
T
7
9-bit LSB
6
10-bit LSB
5
11-bit LSB
4
12-bit LSB
3
2
1
LSB
0
0
0
0
SB = Two's complement sign bit TMSB = Hysteresis temperature MSB T = Temperature data 9-bit LSB = Hysteresis temperature LSB for 9-bit conversions 10-bit LSB = Hysteresis temperature LSB for 10-bit conversions 11-bit LSB = Hysteresis temperature LSB for 11-bit conversions 12-bit LSB = Hysteresis temperature LSB for 12-bit conversions
Figure 6. THYST Register and TOS Register Format
8
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Serial Data Bus Operation
General Operation
Writing to and reading from the FM75 registers is accomplished via the SMBus-compatible two-wire serial interface. SMBus protocol requires that one device on the bus initiates and controls all read and write operations. This device is called the "master" device. The master device also generates the SCL signal which is the clock signal for all other devices on the bus. All other devices on the bus are called "slave" devices. The FM75 is a slave device. Both the master and slave devices can send and receive data on the bus. During SMBus operations, one data bit is transmitted per clock cycle. All SMBus operations follow a repeating nine clock-cycle pattern that consists of eight bits (one byte) of transmitted data followed by an acknowledge (ACK) or not acknowledge (NACK) from the receiving device. Note that there are no unused clock cycles during any operation--therefore there must be no breaks in the stream of data and ACKs/NACKs during data transfers. Conversely having too few clock cycles can lead to incorrect operation if an inadverstne 8-bit read from a 16-bit register occurs. For most operations, SMBus protocol requires the SDA line to remain stable (unmoving) whenever SCL is high--i.e., transitions on the SDA line can only occur when SCL is low. The exceptions to this rule are when the master device issues a start or stop signal. Note that the slave device cannot issue a start or stop condition. The following are definitions for some general SMBus terms: Start Condition: This condition occurs when the SDA line transitions from high to low while SCL is high. The master device uses this condition to indicate that a data transfer is about to begin. Stop Condition: This condition occurs when the SDA line transitions from low to high while SCL is high. The master device uses this condition to signal the end of a data transfer. Acknowledge and Not Acknowledge: When data is transferred to the slave device it sends an acknowledge (ACK) after receiving every byte of data. A master device sends an acknowledge (ACK) following only the first byte read from a 2-byte register. The receiving device sends an ACK by pulling SDA low for one clock. Following the last byte, a master device sends a "not acknowledge" (NACK) followed by a stop condition. A NACK is indicated by leaving SDA high during the clock after the last byte.
Slave Address
Each slave device on the bus has a unique 7-bit address so the master can identify which device is being read from or written to. The FM75 address is as follows:
1
0
0
1
A2 A1 A0
The four MSBs of the FM75 address are hardwired to 1001. The three LSBs are user configurable by tying the A0, A1 and A2 pins to either VDD or ground. This provides eight different FM75 addresses, which allows up to eight FM75s to be connected to the same bus.
Writing To and Reading From the FM75
All read and write operations must begin with a start signal generated by the master device. After the start condition, the master device must immediately send a slave address (7 bits) followed by a read/write bit. If the slave address matches the address of the FM75, the FM75 sends an ACK after receiving the read/write bit by pulling the SDA line low for one clock. See Figure 8 - Figure 13 for timing diagrams for all FM75 operations.
Setting the Pointer
For all operations the pointer stored in the Command Register must be pointing to the register (Temperature, Configuration, TOS or THYST) that is going to be written to or read from. To change the pointer value in the Command Register, the read/write bit following the address must be 0. This indicates that the master will now write new information into the Command Register. After the FM75 sends an ACK in response to receiving the address and read/write bit, the master device must transmit an appropriate 8-bit pointer value as explained in the Registers section of this data sheet. The FM75 will send an ACK after receiving the new pointer data. The pointer set operation is illustrated in Figure 8. Anytime a pointer set is performed, it must be immediately followed by a read or write operation. Note that the 6 MSBs of the pointer value must be zero. If the 6 MSBs are not zero, the FM75 will not send an ACK and will internally terminate the operation. Also recall that the Command Register retains the current pointer value between operations. Therefore, once a register is being pointed to, subsequent read operations do not require a pointer set cycle. Write operations always require the pointer be reset.
9
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Reading
If the pointer is already pointing to the desired register, the master can read from that register by setting the read/write bit (following the slave address) to a 1. After sending an ACK, the FM75 will begin transmitting data during the following clock cycle. If the Configuration Register is being read, the FM75 will transmit one byte of data (see Figure 10). The master device should respond with a NACK followed by a stop condition. If the Temperature, TOS or THYST Register is being read, the FM75 will transmit two bytes of data (see Figure 9). The master must respond to the first byte of data with an ACK and to the second byte of data with a NACK followed by a stop condition. To read from a register other than the one currently being pointed to by the Command Register, a pointer set to the desired register must be done as described previously. Immediately following the pointer set, the master must perform a repeat start condition (see Figures 8 and 12) which indicates to the FM75 that a new operation is about to occur. It is important to note that if the repeat start condition does not occur, the FM75 will assume that a write is taking place, and the selected register will be overwritten by the upcoming data on the data bus. After the start condition, the master must again send the device address and read/write bit. This time the read/write bit must be set to 1 to indicate a read. The rest of the read cycle is the same as described in the previous paragraph for reading from a preset pointer location.
Writing
All writes must be proceeded by a pointer set as described previously, even if the pointer is already pointing to the desired register. Immediately following the pointer set, the master must begin transmitting the data to be written. If the master is writing to the Configuration Register, one byte of data must be sent (see Figure 13). If the TOS or THYST Register is being written to, the master must send two bytes of data (see Figure 11). After transmitting each byte of data, the master must release the SDA line for one clock to allow the FM75 to acknowledge receiving the byte. The write operation should be terminated by a stop signal from the master.
Inadvertent 8-Bit Read from a 16-Bit Register: A Caution
An inadvertent 8-bit read from a 16-bit register, with the D7 bit low, can cause the FM75 to pause in a state where the SDA line is pulled low by the output data and is incapable of receiving either a stop or a start condition from the master. The only way to remove the FM75 from this state is to continue clocking for 9 cycles until SDA goes high, at which time issuing a stop condition will reset the FM75. This sequence can be seen in Figure 7 below.
Nine additional clock cycles to reset the FM75 SCL SDA 1 Start from Master 0 0 1 A2 A1 A0 R/W A D7 D6 D5 D4 D3 D2 D1 D0 N Ack from FM75 No Ack from Master D7 D6 D5 D4 D3 D2 D1 D0 N No Ack Stop from Condition from Master Master
Address Byte
Most Significant Data Byte (from FM75)
Stop intended by Master, but FM75 SDA line locked low
Master must detect error condition on FM75
Figure 7. Inadvertent 8-Bit Read from 16-Bit Register Where D7 = 0 and Forces Output Low
10
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Note: This segment of this timing diagram is a generic pointer set cycle which must be followed by either an immediate read cycle or write cycle as shown in this figure and in figures 10, 11, and 12.
SCL
....
S 1 0 0 1 A2 A1 A0 R/W A 0 0 0 0 0 0 P1 P0 A Ack from aTS75
SDA
....
Address Byte
SCL ... SDA
Ack from FM75
Pointer Byte
...
S
1
0
0
1
A2
A1
A0 R/W
A
D7
D6
D5
D4
D3
D2
D1
D0
A Ack from Master
D7
D6
D5
D4
0
0
0
0
N No Ack from Master
P
Repeat Start from Master
Address Byte
Ack from FM75
Most Significant Data Byte (from FM75)
Least Significant Data Byte (from FM75)
Figure 8. Pointer set followed by immediate read from a 2-byte register (Temperature, TOS or THYST Register)
SCL
SDA
S
1
0
0
1
A2
A1
A0
R/W
A Ack from FM75
D7
D6
D5
D4
D3
D2
D1
D0
A Ack from Master
D7
D6
D5
D4
0
0
0
0
N
P
Address Byte
Most Significant Data Byte (from FM75)
Least Significant Data Byte (from FM75)
No Ack from Master
Figure 9. Two-byte read from preset pointer location (Temperature, TOS or THYST Register)
SCL
SDA
S
1
0
0
1
A2
A1
A0
R/W
A
X
D6
D5
D4
D3
D2
D1
D0
N
P
Address Byte
Ack from FM75
Data Byte (from FM75)
No Ack from Master
Figure 10. One-byte read from Configuration Register with preset pointer
11
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
SCL 0 0 0
....
S 1 0 0 1 A2 A1 A0 R/W A 0 0 0 P1 P0 A
SDA
....
Address Byte
Ack from FM75
Pointer Byte
Ack from FM75
.... ....
A D7 D6 D5 D4 D3 D2 D1 D0 A D7 D6 D5 D4 0 0 0 0 A P
Most Significant Data Byte (from Master)
Ack from FM75
Least Significant Data Byte (from Master)
Ack from FM75
Figure 11. Pointer set followed by immediate write to a 2-byte register (TOS or THYST Register)
SCL
SDA
S
1
0
0
1
A2
A1
A0
R/W
A
0
0
0
0
0
0
P1
P0
A
S
1
0
0
1
A2
A1
A0
R/W
Address Byte
Ack from FM75
Pointer Byte
Ack from Repeat Start from FM75 Master
Address Byte
.... ....
1 0 0 1 A2 A1 A0 R/W A X D6 D5 D4 D3 D2 D1 D0 N No Ack from Master P
Address Byte (repeated here for clarity, transmitted only once in the actual sequence)
Ack from FM75
Data Byte (from FM75)
Figure 12. Pointer set followed by immediate read from Configuration Register
SCL S SDA 1 0 0 1 A2 A1 A0 R/W A Ack from FM75 0 0 0 0 0 0 P1 P0 A Ack from FM75 X D6 D5 D4 D3 D2 D1 D0 A Ack from FM75 P
Address Byte
Pointer Byte
Data Byte (from Master)
Figure 13. Pointer set followed by immediate write to the Configuration Register
12
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Physical Dimensions inches (millimeters) unless otherwise noted
0.189 - 0.197 (4.800 - 5.004)
8765
0.228 - 0.244 (5.791 - 6.198)
1234
Lead #1 IDENT 0.150 - 0.157 (3.810 - 3.988) 8 Max, Typ. All leads 0.004 (0.102) All lead tips
0.010 - 0.020 x 45 (0.254 - 0.508)
0.053 - 0.069 (1.346 - 1.753)
0.004 - 0.010 (0.102 - 0.254) Seating Plane
0.0075 - 0.0098 (0.190 - 0.249) Typ. All Leads
0.016 - 0.050 (0.406 - 1.270) Typ. All Leads
0.014 (0.356) 0.050 (1.270) Typ 0.014 - 0.020 Typ. (0.356 - 0.508)
Molded Package, Small Outline, 0.15 Wide, 8-Lead (M8) FS Package Number M08A
8-Lead Molded Mini Small Outline Package (MSOP), JEDEC MO-187, 3.0mm Wide FS Package Number MA08D
13
FM75 Rev. A.4
www.fairchildsemi.com
FM75 Low Voltage 2-Wire Digital Temperature Sensor with Thermal Alarm
Ordering Information
Part Number
FM75M8 FM75M8x FM75MM8 FM75MM8x
Package
8-Lead SOP 8-Lead SOP 8-Lead MSOP 8-Lead MSOP
Temperature Range
-40C to 125C -40C to 125C -40C to 125C -40C to 125C
How Supplied
95 units in Tube 1000 units on T&R 95 units in Tube 1000 units on T&R
Life Support Policy
Fairchild's products are not authorized for use as critical components in life support devices or systems without the express written approval of the President of Fairchild Semiconductor Corporation. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
Fairchild Semiconductor Americas Customer Response Center Tel. 1-888-522-5372 Fairchild Semiconductor Europe Fax: +44 (0) 1793-856858 Deutsch Tel: +49 (0) 8141-6102-0 English Tel: +44 (0) 1793-856856 Francais Tel: +33 (0) 1-6930-3696 Italiano Tel: +39 (0) 2-249111-1
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
Fairchild Semiconductor Hong Kong 8/F, Room 808, Empire Centre 68 Mody Road, Tsimshatsui East Kowloon. Hong Kong Tel; +852-2722-8338 Fax: +852-2722-8383
Fairchild Semiconductor Japan Ltd. 4F, Natsume Bldg. 2-18-6, Yushima, Bunkyo-ku Tokyo, 113-0034 Japan Tel: 81-3-3818-8840 Fax: 81-3-3818-8841
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and Fairchild reserves the right at any time without notice to change said circuitry and specifications.
14
FM75 Rev. A.4
www.fairchildsemi.com

▲Up To Search▲

Price & Availability of FM75

	To Download FM75 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .