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LM75A
Digital temperature sensor and thermal watchdog
Rev. 04 -- 10 July 2007 Product data sheet
1. General description
The LM75A is a temperature-to-digital converter using an on-chip band gap temperature sensor and Sigma-delta A-to-D conversion technique. The device is also a thermal detector providing an overtemperature detection output. The LM75A contains a number of data registers: Configuration register (Conf) to store the device settings such as device operation mode, OS operation mode, OS polarity and OS fault queue as described in Section 7 "Functional description"; temperature register (Temp) to store the digital temp reading, and set-point registers (Tos and Thyst) to store programmable overtemperature shutdown and hysteresis limits, that can be communicated by a controller via the 2-wire serial I2C-bus interface. The device also includes an open-drain output (OS) which becomes active when the temperature exceeds the programmed limits. There are three selectable logic address pins so that eight devices can be connected on the same bus without address conflict. The LM75A can be configured for different operation conditions. It can be set in normal mode to periodically monitor the ambient temperature, or in shutdown mode to minimize power consumption. The OS output operates in either of two selectable modes: OS comparator mode or OS interrupt mode. Its active state can be selected as either HIGH or LOW. The fault queue that defines the number of consecutive faults in order to activate the OS output is programmable as well as the set-point limits. The temperature register always stores an 11-bit 2's complement data giving a temperature resolution of 0.125 C. This high temperature resolution is particularly useful in applications of measuring precisely the thermal drift or runaway. The device is powered-up in normal operation mode with the OS in comparator mode, temperature threshold of 80 C and hysteresis of 75 C, so that it can be used as a stand-alone thermostat with those pre-defined temperature set points.
2. Features
I Pin-for-pin replacement for industry standard LM75 and offers improved temperature resolution of 0.125 C and specification of a single part over power supply range from 2.8 V to 5.5 V I Small 8-pin package types: SO8 and TSSOP8 I I2C-bus interface with up to 8 devices on the same bus I Power supply range from 2.8 V to 5.5 V I Temperatures range from -55 C to +125 C I 11-bit ADC that offers a temperature resolution of 0.125 C
NXP Semiconductors
LM75A
Digital temperature sensor and thermal watchdog
I Temperature accuracy of: N 2 C from -25 C to +100 C N 3 C from -55 C to +125 C I Programmable temperature threshold and hysteresis set points I Supply current of 3.5 A in shutdown mode for power conservation I Stand-alone operation as thermostat at power-up I ESD protection exceeds 2000 V HBM per JESD22-A114, 200 V MM per JESD22-A115 and 1000 V CDM per JESD22-C101 I Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
3. Applications
I I I I System thermal management Personal computers Electronics equipment Industrial controllers
4. Ordering information
Table 1. Ordering information Package Name LM75AD LM75ADP SO8 TSSOP8 Description plastic small outline package; 8 leads; body width 3.9 mm plastic thin shrink small outline package; 8 leads; body width 3 mm Version SOT96-1 SOT505-1 Type number
4.1 Ordering options
Table 2. LM75AD LM75ADP Ordering options Topside mark LM75A L75A Temperature range Tamb = -55 C to +125 C Tamb = -55 C to +125 C Type number
LM75A_4
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Product data sheet
Rev. 04 -- 10 July 2007
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LM75A
Digital temperature sensor and thermal watchdog
5. Block diagram
VCC
LM75A
BIAS REFERENCE POINTER REGISTER COUNTER 11-BIT SIGMA-DELTA A-to-D CONVERTER CONFIGURATION REGISTER TEMPERATURE REGISTER TOS REGISTER THYST REGISTER OS
BAND GAP TEMP SENSOR
TIMER COMPARATOR/ INTERRUPT
OSCILLATOR
POWER-ON RESET
LOGIC CONTROL AND INTERFACE
002aad029
A2
A1
A0
SCL SDA
GND
Fig 1. Block diagram
6. Pinning information
6.1 Pinning
SDA SCL OS GND
1 2
8 7
VCC A0 A1 A2
SDA SCL OS GND
1 2 3 4
002aad028
8 7
VCC A0 A1 A2
LM75AD
3 4
002aad027
6 5
LM75ADP
6 5
Fig 2. Pin configuration for SO8
Fig 3. Pin configuration for TSSOP8
6.2 Pin description
Table 3. Symbol SDA SCL OS GND A2 Pin description Pin 1 2 3 4 5 Description Digital I/O. I2C-bus serial bidirectional data line; open-drain. Digital input. I2C-bus serial clock input. Overtemp Shutdown output; open-drain. Ground. To be connected to the system ground. Digital input. User-defined address bit 2.
LM75A_4
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
Pin description ...continued Pin 6 7 8 Description Digital input. User-defined address bit 1. Digital input. User-defined address bit 0. Power supply.
Table 3. Symbol A1 A0 VCC
7. Functional description
7.1 General operation
The LM75A uses the on-chip band gap sensor to measure the device temperature with the resolution of 0.125 C and stores the 11-bit 2's complement digital data, resulted from 11-bit A-to-D conversion, into the device Temp register. This Temp register can be read at any time by a controller on the I2C-bus. Reading temperature data does not affect the conversion in progress during the read operation. The device can be set to operate in either mode: normal or shutdown. In normal operation mode, the temp-to-digital conversion is executed every 100 ms and the Temp register is updated at the end of each conversion. In shutdown mode, the device becomes idle, data conversion is disabled and the Temp register holds the latest result; however, the device I2C-bus interface is still active and register write/read operation can be performed. The device operation mode is controllable by programming bit B0 of the configuration register. The temperature conversion is initiated when the device is powered-up or put back into normal mode from shutdown. In addition, at the end of each conversion in normal mode, the temperature data (or Temp) in the Temp register is automatically compared with the overtemperature shutdown threshold data (or Tos) stored in the Tos register, and the hysteresis data (or Thyst) stored in the Thyst register, in order to set the state of the device OS output accordingly. The device Tos and Thyst registers are write/read capable, and both operate with 9-bit 2's complement digital data. To match with this 9-bit operation, the Temp register uses only the 9 MSB bits of its 11-bit data for the comparison. The way that the OS output responds to the comparison operation depends upon the OS operation mode selected by configuration bit B1, and the user-defined fault queue defined by configuration bits B3 and B4. In OS comparator mode, the OS output behaves like a thermostat. It becomes active when the Temp exceeds the Tos, and is reset when the Temp drops below the Thyst. Reading the device registers or putting the device into shutdown does not change the state of the OS output. The OS output in this case can be used to control cooling fans or thermal switches. In OS interrupt mode, the OS output is used for thermal interruption. When the device is powered-up, the OS output is first activated only when the Temp exceeds the Tos; then it remains active indefinitely until being reset by a read of any register. Once the OS output has been activated by crossing Tos and then reset, it can be activated again only when the Temp drops below the Thyst; then again, it remains active indefinitely until being reset by a read of any register. The OS interrupt operation would be continued in this sequence: Tos trip, Reset, Thyst trip, Reset, Tos trip, Reset, Thyst trip, Reset, etc.
LM75A_4
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
In both cases, comparator mode and interrupt mode, the OS output is activated only if a number of consecutive faults, defined by the device fault queue, has been met. The fault queue is programmable and stored in the two bits, B3 and B4, of the Configuration register. Also, the OS output active state is selectable as HIGH or LOW by setting accordingly the configuration register bit B2. At power-up, the device is put into normal operation mode, the Tos is set to 80 C, the Thyst is set to 75 C, the OS active state is selected LOW and the fault queue is equal to 1. The temp reading data is not available until the first conversion is completed in about 100 ms. The OS response to the temperature is illustrated in Figure 4.
Tos
Thyst
reading temperature limits OS reset OS active OS output in comparator mode
OS reset OS active
(1)
(1)
(1)
OS output in interrupt mode
002aad032
(1) OS is reset by either reading register. It is assumed that the fault queue is met at each Tos and Thyst crossing point.
Fig 4. OS response to temperature
7.2 I2C-bus serial interface
The LM75A can be connected to a compatible 2-wire serial interface I2C-bus as a slave device under the control of a controller or master device, using two device terminals, SCL and SDA. The controller must provide the SCL clock signal and write/read data to/from the device through the SDA terminal. Notice that if the I2C-bus common pull-up resistors have not been installed as required for I2C-bus, then an external pull-up resistor, about 10 k, is needed for each of these two terminals. The bus communication protocols are described in Section 7.10.
7.3 Slave address
The LM75A slave address on the I2C-bus is partially defined by the logic applied to the device address pins A2, A1 and A0. Each of them is typically connected either to GND for logic 0, or to VCC for logic 1. These pins represent the three LSB bits of the device 7-bit address. The other four MSB bits of the address data are preset to `1001' by hard wiring inside the LM75A. Table 4 shows the device's complete address and indicates that up to
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
8 devices can be connected to the same bus without address conflict. Because the input pins, SCL, SDA and A2 to A0, are not internally biased, it is important that they should not be left floating in any application.
Table 4. Address table 1 = HIGH; 0 = LOW. MSB 1 0 0 1 A2 A1 LSB A0
7.4 Register list
The LM75A contains four data registers beside the pointer register as listed in Table 5. The pointer value, read/write capability and default content at power-up of the registers are also shown in Table 5.
Table 5. Register table R/W R/W read only R/W POR state 00h n/a 5000h Description Configuration register: contains a single 8-bit data byte; to set the device operating condition; default = 0. Temperature register: contains two 8-bit data bytes; to store the measured Temp data. Overtemperature shutdown threshold register: contains two 8-bit data bytes; to store the overtemperature shutdown Tos limit; default = 80 C. Hysteresis register: contains two 8-bit data bytes; to store the hysteresis Thyst limit; default = 75 C.
Register Pointer name value Conf Temp Tos 01h 00h 03h
Thyst
02h
R/W
4B00h
7.4.1 Pointer register
The Pointer register contains an 8-bit data byte, of which the two LSB bits represent the pointer value of the other four registers, and the other 6 MSB bits are equal to 0, as shown in Table 6 and Table 7. The Pointer register is not accessible to the user, but is used to select the data register for write/read operation by including the pointer data byte in the bus command.
Table 6. B7 0 Table 7. B1 0 0 1 1 Pointer register B6 0 B5 0 B4 0 B3 0 B2 0 B[1:0] pointer value
Pointer value B0 0 1 0 1 Selected register Temperature register (Temp) Configuration register (Conf) Hysteresis register (Thyst) Overtemperature shutdown register (Tos)
Because the Pointer value is latched into the Pointer register when the bus command (which includes the pointer byte) is executed, a read from the LM75A may or may not include the pointer byte in the statement. To read again a register that has been recently read and the pointer has been preset, the pointer byte does not have to be included. To
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
read a register that is different from the one that has been recently read, the pointer byte must be included. However, a write to the LM75A must always include the pointer byte in the statement. The bus communication protocols are described in Section 7.10. At power-up, the Pointer value is equal to 0 and the Temp register is selected; users can then read the Temp data without specifying the pointer byte.
7.4.2 Configuration register
The Configuration register (Conf) is a write/read register and contains an 8-bit non-complement data byte that is used to configure the device for different operation conditions. Table 8 shows the bit assignments of this register.
Table 8. Conf register Legend: * = default value. Bit B[7:5] B[4:3] Symbol reserved Access Value Description R/W 000* reserved for manufacturer's use; should be kept as zeroes for normal operation OS fault queue programming 00* 01 10 11 B2 OS_POL R/W 0* 1 B1 OS_COMP_INT R/W 0* 1 B0 SHUTDOWN R/W 0* 1 queue value = 1 queue value = 2 queue value = 4 queue value = 6 OS polarity selection OS active LOW OS active HIGH OS operation mode selection OS comparator OS interrupt device operation mode selection normal shutdown
OS_F_QUE[1:0] R/W
7.4.3 Temperature register
The Temperature register (Temp) holds the digital result of temperature measurement or monitor at the end of each analog-to-digital conversion. This register is read-only and contains two 8-bit data bytes consisting of one Most Significant Byte (MSByte) and one Least Significant Byte (LSByte). However, only 11 bits of those two bytes are used to store the Temp data in 2's complement format with the resolution of 0.125 C. Table 9 shows the bit arrangement of the Temp data in the data bytes.
Table 9. MSByte 7 D10 6 D9 5 D8 4 D7 3 D6 2 D5 1 D4 0 D3 Temp register LSByte 7 D2 6 D1 5 D0 4 X 3 X 2 X 1 X 0 X
LM75A_4
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Product data sheet
Rev. 04 -- 10 July 2007
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NXP Semiconductors
LM75A
Digital temperature sensor and thermal watchdog
When reading register Temp, all 16 bits of the two data bytes (MSByte and LSByte) are provided to the bus and must be all collected by the controller to complete the bus operation. However, only the 11 most significant bits should be used, and the 5 least significant bits of the LSByte are zero and should be ignored. One of the ways to calculate the Temp value in C from the 11-bit Temp data is: 1. If the Temp data MSByte bit D10 = 0, then the temperature is positive and Temp value (C) = +(Temp data) x 0.125 C. 2. If the Temp data MSByte bit D10 = 1, then the temperature is negative and Temp value (C) = -(2's complement of Temp data) x 0.125 C. Examples of the Temp data and value are shown in Table 10.
Table 10. Temp register value Hexadecimal value 3F8 3F7 3F1 3E8 0C8 001 000 7FF 738 649 648 Decimal value 1016 1015 1009 1000 200 1 0 -1 -200 -439 -440 Value +127.000 C +126.875 C +126.125 C +125.000 C +25.000 C +0.125 C 0.000 C -0.125 C -25.000 C -54.875 C -55.000 C
11-bit binary (2's complement) 011 1111 1000 011 1111 0111 011 1111 0001 011 1110 1000 000 1100 1000 000 0000 0001 000 0000 0000 111 1111 1111 111 0011 1000 110 0100 1001 110 0100 1000
Obviously, for 9-bit Temp data application in replacing the industry standard LM75, just use only 9 MSB bits of the two bytes and disregard 7 LSB of the LSByte. The 9-bit Temp data with 0.5 C resolution of the LM75A is defined exactly in the same way as for the standard LM75 and it is here similar to the Tos and Thyst registers.
7.4.4 Overtemperature shutdown threshold (Tos) and hysteresis (Thyst) registers
These two registers, are write/read registers, and also called set-point registers. They are used to store the user-defined temperature limits, called overtemperature shutdown threshold (Tos) and hysteresis temperature (Thyst), for the device watchdog operation. At the end of each conversion the Temp data will be compared with the data stored in these two registers in order to set the state of the device OS output; see Section 7.1. Each of the set-point registers contains two 8-bit data bytes consisting of one MSByte and one LSByte the same as register Temp. However, only 9 bits of the two bytes are used to store the set-point data in 2's complement format with the resolution of 0.5 C. Table 11 and Table 12 show the bit arrangement of the Tos data and Thyst data in the data bytes. Notice that because only 9-bit data are used in the set-point registers, the device uses only the 9 MSB of the Temp data for data comparison.
LM75A_4
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
Tos register LSByte 5 D6 4 D5 3 D4 2 D3 1 D2 0 D1 7 D0 6 X 5 X 4 X 3 X 2 X 1 X 0 X
Table 11. MSByte 7 D8 6 D7
Table 12. MSByte 7 D8 6 D7
Thyst register LSByte 5 D6 4 D5 3 D4 2 D3 1 D2 0 D1 7 D0 6 X 5 X 4 X 3 X 2 X 1 X 0 X
When a set-point register is read, all 16 bits are provided to the bus and must be collected by the controller to complete the bus operation. However, only the 9 most significant bits should be used and the 7 LSB of the LSByte are equal to zero and should be ignored. Table 13 shows examples of the limit data and value.
Table 13. Tos and Thyst limit data and value Hexadecimal value 0FA 032 001 000 1FF 1CE 192 Decimal value 250 50 1 0 -1 -50 -110 Value +125.0 C +25.0 C +0.5 C 0.0 C -0.5 C -25.0 C -55.0 C
11-bit binary (2's complement) 0 1111 1010 0 0011 0010 0 0000 0001 0 0000 0000 1 1111 1111 1 1100 1110 1 1001 0010
7.5 OS output and polarity
The OS output is an open-drain output and its state represents results of the device watchdog operation as described in Section 7.1. In order to observe this output state, an external pull-up resistor is needed. The resistor should be as large as possible, up to 200 k, to minimize the Temp reading error due to internal heating by the high OS sinking current. The OS output active state can be selected as HIGH or LOW by programming bit B2 (OS_POL) of register Conf: setting bit OS_POL to logic 1 selects OS active HIGH and setting bit B2 to logic 0 sets OS active LOW. At power-up, bit OS_POL is equal to logic 0 and the OS active state is LOW.
7.6 OS comparator and interrupt modes
As described in Section 7.1, the device OS output responds to the result of the comparison between register Temp data and the programmed limits, in registers Tos and Thyst, in different ways depending on the selected OS mode: OS comparator or OS interrupt. The OS mode is selected by programming bit B1 (OS_COMP_INT) of register Conf: setting bit OS_COMP_INT to logic 1 selects the OS interrupt mode, and setting to logic 0 selects the OS comparator mode. At power-up, bit OS_COMP_INT is equal to logic 0 and the OS comparator is selected.
LM75A_4
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LM75A
Digital temperature sensor and thermal watchdog
The main difference between the two modes is that in OS comparator mode, the OS output becomes active when Temp has exceeded Tos and reset when Temp has dropped below Thyst, reading a register or putting the device into shutdown mode does not change the state of the OS output; while in OS interrupt mode, once it has been activated either by exceeding Tos or dropping below Thyst, the OS output will remain active indefinitely until reading a register, then the OS output is reset. Temperature limits Tos and Thyst must be selected so that Tos > Thyst. Otherwise, the OS output state will be undefined.
7.7 OS fault queue
Fault queue is defined as the number of faults that must occur consecutively to activate the OS output. It is provided to avoid false tripping due to noise. Because faults are determined at the end of data conversions, fault queue is also defined as the number of consecutive conversions returning a temperature trip. The value of fault queue is selectable by programming the two bits B4 and B3 (OS_F_QUE[1:0]) in register Conf. Notice that the programmed data and the fault queue value are not the same. Table 14 shows the one-to-one relationship between them. At power-up, fault queue data = 0 and fault queue value = 1.
Table 14. Fault queue table Fault queue value OS_F_QUE[0] 0 1 0 1 Decimal 1 2 4 6
Fault queue data OS_F_QUE[1] 0 0 1 1
7.8 Shutdown mode
The device operation mode is selected by programming bit B0 (SHUTDOWN) of register Conf. Setting bit SHUTDOWN to logic 1 will put the device into shutdown mode. Resetting bit SHUTDOWN to logic 0 will return the device to normal mode. In shutdown mode, the device draws a small current of approximately 3.5 A and the power dissipation is minimized; the temperature conversion stops, but the I2C-bus interface remains active and register write/read operation can be performed. The OS output remains unchanged.
7.9 Power-up default and power-on reset
The LM75A always powers-up in its default state with:
* * * * * *
LM75A_4
Normal operation mode OS comparator mode Tos = 80 C Thyst = 75 C OS output active state is LOW Pointer value is logic 0
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
When the power supply voltage is dropped below the device power-on reset level of approximately 1.9 V (POR) and then rises up again, the device will be reset to its default condition as listed above.
7.10 Protocols for writing and reading the registers
The communication between the host and the LM75A must strictly follow the rules as defined by the I2C-bus management. The protocols for LM75A register read/write operations are illustrated in Figure 5 to Figure 10 together with the following definitions: 1. Before a communication, the I2C-bus must be free or not busy. It means that the SCL and SDA lines must both be released by all devices on the bus, and they become HIGH by the bus pull-up resistors. 2. The host must provide SCL clock pulses necessary for the communication. Data is transferred in a sequence of 9 SCL clock pulses for every 8-bit data byte followed by 1-bit status of the acknowledgement. 3. During data transfer, except the START and STOP signals, the SDA signal must be stable while the SCL signal is HIGH. It means that the SDA signal can be changed only during the LOW duration of the SCL line. 4. S: START signal, initiated by the host to start a communication, the SDA goes from HIGH to LOW while the SCL is HIGH. 5. RS: RE-START signal, same as the START signal, to start a read command that follows a write command. 6. P: STOP signal, generated by the host to stop a communication, the SDA goes from LOW to HIGH while the SCL is HIGH. The bus becomes free thereafter. 7. W: write bit, when the write/read bit = LOW in a write command. 8. R: read bit, when the write/read bit = HIGH in a read command. 9. A: device acknowledge bit, returned by the LM75A. It is LOW if the device works properly and HIGH if not. The host must release the SDA line during this period in order to give the device the control on the SDA line. 10. A': master acknowledge bit, not returned by the device, but set by the master or host in reading 2-byte data. During this clock period, the host must set the SDA line to LOW in order to notify the device that the first byte has been read for the device to provide the second byte onto the bus. 11. NA: Not Acknowledge bit. During this clock period, both the device and host release the SDA line at the end of a data transfer, the host is then enabled to generate the STOP signal. 12. In a write protocol, data is sent from the host to the device and the host controls the SDA line, except during the clock period when the device sends the device acknowledgement signal to the bus. 13. In a read protocol, data is sent to the bus by the device and the host must release the SDA line during the time that the device is providing data onto the bus and controlling the SDA line, except during the clock period when the master sends the master acknowledgement signal to the bus.
LM75A_4
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LM75A
Digital temperature sensor and thermal watchdog
1 SCL SDA S 1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
0
0
1
A2 A1 A0 W
A
0
0
0
0
0
0
0
1
A
0
0
0
D4 D3 D2 D1 D0 A
P
device address START write device acknowledge
pointer byte device acknowledge
configuration data byte device acknowledge STOP
001aad624
Fig 5. Write configuration register (1-byte data)
1 SCL SDA S 1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9 (next)
0
0
1
A2
A1
A0 W
A
0
0
0
0
0
0
0
1
A
RS (next)
device address START write device acknowledge 1 SCL (cont.) SDA (cont.) 1 0 0 1 A2 A1 A0 R A 2 3 4 5 6 7 8 9 1 2
pointer byte device acknowledge RE-START
3
4
5
6
7
8
9
D7 D6 D5 D4 D3 D2 D1 D0 NA data byte from device
P
device address read device acknowledge
master not acknowledged
STOP
001aad625
Fig 6. Read configuration register including pointer byte (1-byte data)
1 SCL SDA S 1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
0
0
1
A2
A1
A0 R
A
D7 D6 D5 D4 D3 D2 D1 D0 NA data byte from device
P
device address START read device acknowledge
master not acknowledged
STOP
001aad626
Fig 7. Read configuration register with preset pointer (1-byte data)
LM75A_4
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
1 SCL SDA S 1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9 (next)
0
0
1
A2
A1
A0
W
A
0
0
0
0
0
0
P1
P0
A
(next)
device address START write device acknowledge 1 SCL (cont.) SDA (cont.) D7 D6 D5 D4 D3 D2 D1 D0 A MSByte data device acknowledge 2 3 4 5 6 7 8 9 1 2
pointer byte device acknowledge
3
4
5
6
7
8
9
D7 D6 D5 D4 D3 D2 D1 D0 LSByte data device acknowledge
A
P
STOP
002aad036
Fig 8. Write Tos or Thyst register (2-byte data)
1 SCL SDA S 1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
0 (next)
0
0
1
A2 A1 A0 W A
0
0
0
0
0
0
P1 P0 A RS (next)
device address START write device acknowledge 5678
pointer byte device acknowledge 9 1 2 3 4 5 6 7 8 9 1 RE-START
1 SCL (cont) SDA (cont) 1
2
3
4
2
3
4
5
6
7
8
9
0
0
1
A2 A1 A0 R
A
D7 D6 D5 D4 D3 D2 D1 D0 A' MSByte from device
D7 D6 D5 D4 D3 D2 D1 D0 NA LSByte from device master not acknowledged
P
device address read device acknowledge
master acknowledge
STOP
002aad037
Fig 9. Read Temp, Tos or Thyst register including pointer byte (2-byte data)
1 SCL SDA S 1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
0
0
1
A2 A1 A0 R
A
D7 D6 D5 D4 D3 D2 D1 D0 A' D7 D6 D5 D4 D3 D2 D1 D0 NA MSByte from device LSByte from device master not acknowledged
P
device address START read device acknowledge
master acknowledge
STOP
002aad038
Fig 10. Read Temp, Tos or Thyst register with preset pointer (2-byte data)
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LM75A
Digital temperature sensor and thermal watchdog
8. Application design-in information
power supply
0.1 F
BUS 10 k PULL-UP RESISTORS I2C-BUS
10 k
VCC SCL SDA 8 2 1
10 k
A2 DIGITAL LOGIC A1 A0
LM75A
5 6 7 4 GND
3
OS
DETECTOR OR INTERRUPT LINE
002aad030
Fig 11. Typical application
9. Limiting values
Table 15. Limiting values In accordance with the Absolute Maximum Rating System (IEC 60134). Symbol VCC Parameter supply voltage voltage at input pins current at input pins IO(sink) VO Vesd Tstg Tj output sink current output voltage electrostatic discharge voltage storage temperature junction temperature on pin OS on pin OS human body model machine model Conditions Min -0.3 -0.3 -5.0 -0.3 -65 Max +6.0 +6.0 +5.0 10.0 +6.0 2000 200 +150 150 Unit V V mA mA V V V C C
10. Recommended operating conditions
Table 16. Symbol VCC Tamb Recommended operating characteristics Parameter supply voltage ambient temperature Conditions Min 2.8 -55 Typ Max 5.5 +125 Unit V C
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Product data sheet
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11. Static characteristics
Table 17. Static characteristics VCC = 2.8 V to 5.5 V; Tamb = -55 C to +125 C; unless otherwise specified. Symbol TACC Tres TCONV(T) IDD Parameter temperature accuracy temperature resolution temperature conversion time supply current Conditions Tamb = -25 C to +100 C Tamb = -55 C to +125 C 11-bit digital temp data normal mode normal mode: I2C-bus inactive normal mode: I2C-bus active shutdown mode VIH VIL VIHYS IIH IIL VOL ILO OSQ Tos Thyst Ci
[1] [2]
Min -2 -3 0.7 x VCC -0.3 -1.0 -1.0 1 -
Typ[1] 0.125 100 100 3.5 300 150 80 75 20
Max +2 +3 1.0 VCC + 0.3 0.3 x VCC +1.0 +1.0 0.4 0.8 10 6 -
Unit C C C ms A mA A V V mV mv A A V V A Conv[2] C C pF
HIGH-level input voltage LOW-level input voltage input voltage hysteresis HIGH-level input current LOW-level input current LOW-level output voltage output leakage current OS fault queue overtemperature shutdown threshold hysteresis temperature input capacitance
digital pins (SCL, SDA, A2 to A0) digital pins SCL and SDA pins A2, A1, A0 pins digital pins; VI = VCC digital pins; VI = 0 V SDA and OS pins; IOL = 3 mA IOL = 4 mA SDA and OS pins; VOH = VCC programmable default value default value digital pins
Typical values are at VCC = 3.3 V and Tamb = 25 C. "Conv" = device A-to-D conversion.
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Product data sheet
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Digital temperature sensor and thermal watchdog
12. Dynamic characteristics
Table 18. I2C-bus interface dynamic characteristics[1] VCC = 2.8 V to 5.5 V; Tamb = -55 C to +125 C; unless otherwise specified. Symbol TCLK tHIGH tLOW tHD;STA tSU;DAT tHD;DAT tSU;STO tf Parameter SCL clock period HIGH period of the SCL clock LOW period of the SCL clock hold time (repeated) START condition data set-up time data hold time set-up time for STOP condition fall time SDA and OS outputs; CL = 400 pF; IOL = 3 mA
[2]
Conditions see Figure 12
Min 2.5 0.6 1.3 100 100 0 100 -
Typ 250
Max -
Unit s s s ns ns ns ns ns
[1] [2]
These specifications are guaranteed by design and not tested in production. The data hold time minimum value is 10 ns for the SCL clock period of 10 s or higher.
TCLK tHIGH SCL tHD;STA tSU;DAT tHD;DAT tSU;STO tLOW
SDA
002aad031
Fig 12. Timing diagram
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Product data sheet
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13. Package outline
SO8: plastic small outline package; 8 leads; body width 3.9 mm SOT96-1
D
E
A X
c y HE vMA
Z 8 5
Q A2 A1 pin 1 index Lp 1 e bp 4 wM L detail X (A 3) A
0
2.5 scale
5 mm
DIMENSIONS (inch dimensions are derived from the original mm dimensions) UNIT mm inches Notes 1. Plastic or metal protrusions of 0.15 mm (0.006 inch) maximum per side are not included. 2. Plastic or metal protrusions of 0.25 mm (0.01 inch) maximum per side are not included. OUTLINE VERSION SOT96-1 REFERENCES IEC 076E03 JEDEC MS-012 JEITA EUROPEAN PROJECTION A max. 1.75 0.069 A1 0.25 0.10 A2 1.45 1.25 A3 0.25 0.01 bp 0.49 0.36 c 0.25 0.19 D (1) 5.0 4.8 0.20 0.19 E (2) 4.0 3.8 0.16 0.15 e 1.27 0.05 HE 6.2 5.8 L 1.05 Lp 1.0 0.4 Q 0.7 0.6 v 0.25 0.01 w 0.25 0.01 y 0.1 0.004 Z (1) 0.7 0.3 0.028 0.012
0.010 0.057 0.004 0.049
0.019 0.0100 0.014 0.0075
0.244 0.039 0.028 0.041 0.228 0.016 0.024
8o o 0
ISSUE DATE 99-12-27 03-02-18
Fig 13. Package outline SOT96-1 (SO8)
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Product data sheet
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LM75A
Digital temperature sensor and thermal watchdog
TSSOP8: plastic thin shrink small outline package; 8 leads; body width 3 mm
SOT505-1
D
E
A
X
c y HE vMA
Z
8
5
A2 pin 1 index
A1
(A3)
A
Lp L
1
e bp
4
detail X wM
0
2.5 scale
5 mm
DIMENSIONS (mm are the original dimensions) UNIT mm A max. 1.1 A1 0.15 0.05 A2 0.95 0.80 A3 0.25 bp 0.45 0.25 c 0.28 0.15 D(1) 3.1 2.9 E(2) 3.1 2.9 e 0.65 HE 5.1 4.7 L 0.94 Lp 0.7 0.4 v 0.1 w 0.1 y 0.1 Z(1) 0.70 0.35 6 0
Notes 1. Plastic or metal protrusions of 0.15 mm maximum per side are not included. 2. Plastic or metal protrusions of 0.25 mm maximum per side are not included. OUTLINE VERSION SOT505-1 REFERENCES IEC JEDEC JEITA EUROPEAN PROJECTION ISSUE DATE 99-04-09 03-02-18
Fig 14. Package outline SOT505-1 (TSSOP8)
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Digital temperature sensor and thermal watchdog
14. Soldering
This text provides a very brief insight into a complex technology. A more in-depth account of soldering ICs can be found in Application Note AN10365 "Surface mount reflow soldering description".
14.1 Introduction to soldering
Soldering is one of the most common methods through which packages are attached to Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both the mechanical and the electrical connection. There is no single soldering method that is ideal for all IC packages. Wave soldering is often preferred when through-hole and Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high densities that come with increased miniaturization.
14.2 Wave and reflow soldering
Wave soldering is a joining technology in which the joints are made by solder coming from a standing wave of liquid solder. The wave soldering process is suitable for the following:
* Through-hole components * Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless packages which have solder lands underneath the body, cannot be wave soldered. Also, leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered, due to an increased probability of bridging. The reflow soldering process involves applying solder paste to a board, followed by component placement and exposure to a temperature profile. Leaded packages, packages with solder balls, and leadless packages are all reflow solderable. Key characteristics in both wave and reflow soldering are:
* * * * * *
Board specifications, including the board finish, solder masks and vias Package footprints, including solder thieves and orientation The moisture sensitivity level of the packages Package placement Inspection and repair Lead-free soldering versus PbSn soldering
14.3 Wave soldering
Key characteristics in wave soldering are:
* Process issues, such as application of adhesive and flux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are exposed to the wave
* Solder bath specifications, including temperature and impurities
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Product data sheet
Rev. 04 -- 10 July 2007
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LM75A
Digital temperature sensor and thermal watchdog
14.4 Reflow soldering
Key characteristics in reflow soldering are:
* Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see Figure 15) than a PbSn process, thus reducing the process window
* Solder paste printing issues including smearing, release, and adjusting the process
window for a mix of large and small components on one board
* Reflow temperature profile; this profile includes preheat, reflow (in which the board is
heated to the peak temperature) and cooling down. It is imperative that the peak temperature is high enough for the solder to make reliable solder joints (a solder paste characteristic). In addition, the peak temperature must be low enough that the packages and/or boards are not damaged. The peak temperature of the package depends on package thickness and volume and is classified in accordance with Table 19 and 20
Table 19. SnPb eutectic process (from J-STD-020C) Package reflow temperature (C) Volume (mm3) < 350 < 2.5 2.5 Table 20. 235 220 Lead-free process (from J-STD-020C) Package reflow temperature (C) Volume (mm3) < 350 < 1.6 1.6 to 2.5 > 2.5 260 260 250 350 to 2000 260 250 245 > 2000 260 245 245 350 220 220
Package thickness (mm)
Package thickness (mm)
Moisture sensitivity precautions, as indicated on the packing, must be respected at all times. Studies have shown that small packages reach higher temperatures during reflow soldering, see Figure 15.
LM75A_4
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Product data sheet
Rev. 04 -- 10 July 2007
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NXP Semiconductors
LM75A
Digital temperature sensor and thermal watchdog
temperature
maximum peak temperature = MSL limit, damage level
minimum peak temperature = minimum soldering temperature
peak temperature
time
001aac844
MSL: Moisture Sensitivity Level
Fig 15. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365 "Surface mount reflow soldering description".
15. Abbreviations
Table 21. Acronym A-to-D CDM ESD HBM I2C-bus I/O LSB LSByte MM MSB MSByte POR Abbreviations Description Analog-to-Digital Charged Device Model ElectroStatic Discharge Human Body Model Inter-Integrated Circuit bus Input/Output Lease Significant Bit Least Significant Byte Machine Model Most Significant Bit Most Significant Byte Power-On Reset
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Product data sheet
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Digital temperature sensor and thermal watchdog
16. Revision history
Table 22. LM75A_4 Modifications: Revision history Release date 20070710 Data sheet status Product data sheet Change notice Supersedes LM75A_3 Document ID
* * * * *
The format of this data sheet has been redesigned to comply with the new identity guidelines of NXP Semiconductors. Legal texts have been adapted to the new company name where appropriate. added (new) Section 4.1 "Ordering options" added separate pin configuration drawings for SO8 and TSSOP8 (Figure 2 and Figure 3) Table 15 "Limiting values": - table title changed from "Absolute maximum ratings" to Table 15 "Limiting values" - symbol and parameter descriptions modified to new presentation standards
*
Table 18 "I2C-bus interface dynamic characteristics[1]": - parameter descriptions modified to new presentation standards - added Table note 2 and its reference at tHD;DAT
LM75A_3 LM75A_2 (9397 750 14174) LM75A_1 (9397 750 08571)
20060627 20041005 20010716
Product data sheet Product data sheet Product data
ECN 853-2266 26719 dated 16 July 2001
LM75A_2 LM75A_1 -
LM75A_4
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Product data sheet
Rev. 04 -- 10 July 2007
22 of 24
NXP Semiconductors
LM75A
Digital temperature sensor and thermal watchdog
17. Legal information
17.1 Data sheet status
Document status[1][2] Objective [short] data sheet Preliminary [short] data sheet Product [short] data sheet
[1] [2] [3]
Product status[3] Development Qualification Production
Definition This document contains data from the objective specification for product development. This document contains data from the preliminary specification. This document contains the product specification.
Please consult the most recently issued document before initiating or completing a design. The term `short data sheet' is explained in section "Definitions". The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status information is available on the Internet at URL http://www.nxp.com.
17.2 Definitions
Draft -- The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. Short data sheet -- A short data sheet is an extract from a full data sheet with the same product type number(s) and title. A short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. For detailed and full information see the relevant full data sheet, which is available on request via the local NXP Semiconductors sales office. In case of any inconsistency or conflict with the short data sheet, the full data sheet shall prevail.
result in personal injury, death or severe property or environmental damage. NXP Semiconductors accepts no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer's own risk. Applications -- Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Limiting values -- Stress above one or more limiting values (as defined in the Absolute Maximum Ratings System of IEC 60134) may cause permanent damage to the device. Limiting values are stress ratings only and operation of the device at these or any other conditions above those given in the Characteristics sections of this document is not implied. Exposure to limiting values for extended periods may affect device reliability. Terms and conditions of sale -- NXP Semiconductors products are sold subject to the general terms and conditions of commercial sale, as published at http://www.nxp.com/profile/terms, including those pertaining to warranty, intellectual property rights infringement and limitation of liability, unless explicitly otherwise agreed to in writing by NXP Semiconductors. In case of any inconsistency or conflict between information in this document and such terms and conditions, the latter will prevail. No offer to sell or license -- Nothing in this document may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights.
17.3 Disclaimers
General -- Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes -- NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. Suitability for use -- NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of a NXP Semiconductors product can reasonably be expected to
17.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. I2C-bus -- logo is a trademark of NXP B.V.
18. Contact information
For additional information, please visit: http://www.nxp.com For sales office addresses, send an email to: salesaddresses@nxp.com
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(c) NXP B.V. 2007. All rights reserved.
Product data sheet
Rev. 04 -- 10 July 2007
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Digital temperature sensor and thermal watchdog
19. Contents
1 2 3 4 4.1 5 6 6.1 6.2 7 7.1 7.2 7.3 7.4 7.4.1 7.4.2 7.4.3 7.4.4 7.5 7.6 7.7 7.8 7.9 7.10 8 9 10 11 12 13 14 14.1 14.2 14.3 14.4 15 16 17 17.1 17.2 17.3 17.4 18 General description . . . . . . . . . . . . . . . . . . . . . . 1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ordering information . . . . . . . . . . . . . . . . . . . . . 2 Ordering options . . . . . . . . . . . . . . . . . . . . . . . . 2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pinning information . . . . . . . . . . . . . . . . . . . . . . 3 Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 3 Functional description . . . . . . . . . . . . . . . . . . . 4 General operation . . . . . . . . . . . . . . . . . . . . . . . 4 I2C-bus serial interface . . . . . . . . . . . . . . . . . . . 5 Slave address . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Register list . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Pointer register . . . . . . . . . . . . . . . . . . . . . . . . . 6 Configuration register . . . . . . . . . . . . . . . . . . . . 7 Temperature register. . . . . . . . . . . . . . . . . . . . . 7 Overtemperature shutdown threshold (Tos) and hysteresis (Thyst) registers . . . . . . . . . . . . 8 OS output and polarity . . . . . . . . . . . . . . . . . . . 9 OS comparator and interrupt modes . . . . . . . . 9 OS fault queue . . . . . . . . . . . . . . . . . . . . . . . . 10 Shutdown mode . . . . . . . . . . . . . . . . . . . . . . . 10 Power-up default and power-on reset . . . . . . . 10 Protocols for writing and reading the registers 11 Application design-in information . . . . . . . . . 14 Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . 14 Recommended operating conditions. . . . . . . 14 Static characteristics. . . . . . . . . . . . . . . . . . . . 15 Dynamic characteristics . . . . . . . . . . . . . . . . . 16 Package outline . . . . . . . . . . . . . . . . . . . . . . . . 17 Soldering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Introduction to soldering . . . . . . . . . . . . . . . . . 19 Wave and reflow soldering . . . . . . . . . . . . . . . 19 Wave soldering . . . . . . . . . . . . . . . . . . . . . . . . 19 Reflow soldering . . . . . . . . . . . . . . . . . . . . . . . 20 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Revision history . . . . . . . . . . . . . . . . . . . . . . . . 22 Legal information. . . . . . . . . . . . . . . . . . . . . . . 23 Data sheet status . . . . . . . . . . . . . . . . . . . . . . 23 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Contact information. . . . . . . . . . . . . . . . . . . . . 23 19 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Please be aware that important notices concerning this document and the product(s) described herein, have been included in section `Legal information'.
(c) NXP B.V. 2007.
All rights reserved.
For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com Date of release: 10 July 2007 Document identifier: LM75A_4

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