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LM75A Digital temperature sensor and thermal WatchdogTM
Product data sheet Supersedes data of 2001 Jul 16 2004 Oct 05
Philips Semiconductors
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
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 over-temp 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 the functional description section; temperature register (Temp) to store the digital temp reading, and set-point registers (Tos & Thyst) to store programmable overtemp 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 and 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.
FEATURES
* Pin-for-pin replacement for industry standard LM75 and offers * Small 8-pin package types: SO8 and TSSOP8 * I2C-bus interface with up to 8 devices on the same bus * Power supply range from 2.8 V to 5.5 V * Temperatures range from -55 C to +125 C * 11-bit ADC that offers a temperature resolution of 0.125 C * Temperature accuracy of:
2 C from -25 C to +100 C 3 C from -55 C to +125 C
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.
* Programmable temperature threshold and hysteresis set points * Supply current of 3.5 A in shut-down mode for power
conservation
* Stand-alone operation as thermostat at power-up. * ESD protection exceeds 2000 V HBM per JESD22-A114, * Latch-up testing is done to JESDEC Standard JESD78 which
exceeds 100 mA 200 V MM per JESD22-A115 and 1000 V CDM per JESD22-C101
APPLICATIONS
* System thermal management * Personal computers * Electronics equipment * Industrial controllers.
ORDERING INFORMATION
Tamb = -55 C to +125 C
PACKAGE TYPE NUMBER LM75AD LM75ADP Topside mark LM75A LM75A NAME 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
WATCHDOGTM is a trademark of National Semiconductor Corporation.
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
PINNING Pin configuration
SDA SCL OS GND 1 2 3 4 8 7 6 5 VCC A0 A1 A2
Pin description
PIN 1 2 3 4
SL01388
SYMBOL SDA SCL OS GND A2 A1 A0 VCC
DESCRIPTION Digital I/O. I2C serial bi-directional data line. Open Drain. Digital input. I2C serial clock input. Overtemp Shutdown output. Open Drain. Ground. To be connected to the system ground. Digital input. User-defined address bit2. Digital input. User-defined address bit1. Digital input. User-defined address bit0. Power supply.
5 Figure 1. SO8 and TSSOP8 pin configurations. 6 7 8
SIMPLIFIED BLOCK DIAGRAM
VCC
LM75A
BIAS REFERENCE POINTER REGISTER CONFIGURATION REGISTER
BAND-GAP TEMP SENSOR
11-BIT SIGMA-DELTA A-TO-D CONVERTER
COUNTER
TEMPERATURE REGISTER
TIMER
TOS REGISTER
OSC COMPARATOR / INTERRUPT THYST REGISTER OS
POWER-ON RESET
LOGIC CONTROL AND INTERFACE
A2
A1
A0
SCL
SDA
GND
SL01389
Figure 2. Simplified block diagram.
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
TYPICAL APPLICATION
VCC POWER SUPPLY
0.1 F BUS 10 k PULL-UP RESISTORS 10 k 8 VCC 2 I2C-BUS 1 SCL SDA 10 k
LM75A
5 DIGITAL LOGIC 6 7 A2 A1 A0 GND 4
OS
3
DETECTOR OR INTERRUPT LINE
SL01390
Figure 3. Typical application.
ABSOLUTE MAXIMUM RATINGS1
SYMBOL VCC to GND Voltage at input pins Current at input pins OS output sink current OS output voltage ESD Human Body Model Machine Model Tstg Tj Storage temperature range Junction temperature PARAMETER 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
NOTE: 1. This is a stress rating only. Functional operation of the device as indicated in the operational section is not applied to this absolute maximum rating. Stresses above those listed in `Absolute Maximum Ratings' may cause permanent damage to the device and exposure to any of these rating conditions for extended periods may affect device reliability.
OPERATING RATINGS
SYMBOL VCC Tamb Supply voltage Operating ambient temperature range PARAMETER MIN. 2.8 -55 MAX. 5.5 125 UNIT V C
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
DC ELECTRICAL CHARACTERISTICS
VCC = 2.8 V to 5.5 V, Tamb = -55 C to +125 C unless otherwise noted. SYMBOL TACC PARAMETER Temperature accuracy CONDITIONS Tamb = -25 C to +100 C Tamb = -55 C to +125 C TRES TCON IDD Temperature resolution Temperature conversion Supply quiescent current 11-bit digital temp data Normal mode Normal mode: I2C inactive Normal mode: I2C active Shut-down mode VIH VIL VIHYS HIGH-level input voltage LOW-level input voltage Input voltage hysteresis Digital pins (SCL, SDA, A2-A0) Digital pins SCL and SDA pins A2-A0 pins IIH IIL VOL HIGH-level input current LOW-level input current LOW-level output voltage Digital pins; VIN = VCC Digital pins; VIN = 0 V SDA and OS pins; IOL = 3 mA IOL = 4 mA ILO OSQ Tos Thyst CIN Output leakage current OS fault queue Overtemp shutdown Hysteresis Input capacitance SDA and OS pins; VOH = VCC Programmable Default value Default value Digital pins 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
NOTE: 1. Typical values are at VCC = 3.3 V and Tamb = 25 C. 2. Conv: device A-to-D conversion.
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
I2C INTERFACE AC CHARACTERISTICS 1
VCC = 2.8 V to 5.5 V, Tamb = -55 C to +125 C unless otherwise noted. SYMBOL tCLK tHIGH tLOW tHD:STA tSU:DAT tHD;DAT tSU;STO tF PARAMETER SCL clock period SCL HIGH pulse width SCL LOW pulse width Start Hold time Data set-up time Data hold time Stop set-up time Fall time (SDA and OS outputs) CL = 400 pF; IOL = 3 mA CONDITIONS See timing diagram (Figure 4) MIN. 2.5 0.6 1.3 100 100 0 100 - TYP. - - - - - - - 250 MAX. - - - - - - - - UNIT s s s ns ns ns ns ns
NOTE: 1. These specifications are guaranteed by design and not tested in production.
tCLK tHIGH SCL tHD;STA tSU;DAT tHD;DAT SDA tSU;STO tLOW
SL01391
Figure 4. Timing diagram.
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
FUNCTIONAL DESCRIPTION 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 shut-down. 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 shut-down mode, the device becomes idle, data conversion is disabled and the Temp register holds the latest result; however, the device I2C 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 shut-down. 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 over-temp shut-down 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 shut-down 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, ... Putting the device into shut-down mode also resets the OS output. 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 5.
Tos Temp Thyst
READING TEMPERATURE & LIMITS OS RESET OS ACTIVE OS OUTPUT IN COMPARATOR MODE
OS RESET OS ACTIVE
*
*
OS OUTPUT IN INTERRUPT MODE
*
TIME POWER-UP
* = OS is reset by either reading register or putting the device in shutdown.
Assumed that the fault queue is met at each Tos and Thyst crossing point.
SL01392
Figure 5. OS response to temperature. 2004 Oct 05 7
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
I2C 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 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 the data communication section.
complete address and indicates that up to 8 devices can be connected to the same bus without address conflict. Because the input pins, SCL, SDA, A2-A0, are not internally biased, it is important that they should not be left floating in any application.
Table 1. Address table
1 = HIGH, 0 = LOW MSB 1 0 0 1 A2 A1 LSB A0
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 1 shows the device's
Register list
The LM75A contains four data registers beside the pointer register as listed in Table 2. The pointer value, read/write capability and default content at power up of the registers are also shown in the Register table.
Table 2. Register table
Register name Conf Pointer value 01H R/W R/W POR state 00H 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. Over-temp Shutdown threshold Register. Contains two 8-bit data bytes. To store the over-temp shut-down Tos limit. Default = 80 C. Hysteresis Register. Contains two 8-bit data bytes. To store the hysteresis Thyst limit. Default = 75 C.
Temp Tos
00H 03H
Read only R/W
N/A 50 00H
Thyst
02H
R/W
4B 00H
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 the Pointer register table (Table 3) and the Pointer value table (Table 4). 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 3. Pointer register table
B7 0 B6 0 B5 0 B4 0 B3 0 B2 0 B1 B0 Pointer value
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, which has been recently read and the pointer has been preset, the pointer byte does not have to be included. To read a register, which is different with 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 detail in the data communication section. 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.
Table 4. Pointer value
B1 0 0 1 1 B0 0 1 0 1 Selected register Temperature register (Temp) Configuration register (Conf) Hysteresis register (Thyst) Overtemp shut-down register (Tos)
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
Configuration register
The Configuration register 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. The Configuration register table (Table 5) shows the bit assignments of this register.
Table 5. Configuration register table
Bit B7-B5 B4-B3 B2 B1 B0 Name Reserved OS Fault queue OS Polarity OS Comp/Interrupt Shut-down R/W R/W R/W R/W R/W R/W POR 000 00 0 0 0 Description Reserved for the manufacterer use. For OS Fault Queue programming. Programmable queue data = 0, 1 ,2, 3 for queue value = 1, 2, 4, 6 respectively. Default = 0. For OS Polarity selection. 1 = OS active HIGH, 0 = OS active LOW (default). For OS operation Mode selection. 1 = OS interrupt, 0 = OS comparator (default). For Device Operation Mode selection. 1 = Shut-down, 0 = Normal (default).
Temperature register (Temp)
The Temp register holds the digital result of temperature measurement or monitor at the end each A-to-D conversion. This register is read only and contains two 8-bit data bytes consisting of one most significant (MS) data byte and one least significant (LS) data byte. 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. The Temp register table (Table 6) shows the bit arrangement of the Temp data in the data bytes.
Table 6. Temp register table
Temp MS byte MSB B7 MSB D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 B6 B5 B4 B3 B2 B1 Temp data (11 bits) LSB D0 X X X X X LSB B0 MSB B7 B6 B5 B4 B3 B2 Not used B1 Temp LS byte LSB B0
Notice that when the Temp register is read, all 16 bits are provided to the bus and must be all collected by the controller to complete the bus operation. However, only the 11 significant bits should be used, and the 5 LSB bits of the LS byte 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 MSB bit D10 = 0 then the temperature is positive and Temp value (C) = + (Temp data) * 0.125 C 2. If the Temp data MSB bit D10 = 1 then the temperature is negative and Temp value (C) = - (2's complement of Temp data) * 0.125 C The Temp table (Table 7) shows examples of the Temp data and value.
Table 7. Temp table
Temp data 11-bit Binary (2's complement) 0111 1111 000 0111 1110 111 0111 1110 001 0111 1101 000 0001 1001 000 0000 0000 001 0000 0000 000 1111 1111 111 1110 0111 000 11001001 001 1100 1001 000 3-bit Hex 3F8h 3F7h 3F1h 3E8h 0C8h 001h 000h 7FFh 738h 649h 648h Decimal value 1016 1015 1009 1000 200 1 0 -1 -200 -439 -440 Temp value C +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
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 bits of the LS byte. 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 that is described next. 2004 Oct 05 9
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
Overtemp shut-down 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 overtemp shut-down threshold (Tos) and hysteresis (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 accordingly as described in the "General operation" section. Each of the set-point registers contains two 8-bit data bytes consisting of one MS data byte and one LS data byte the same as the Temp register. 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. The Tos register table (Table 8) and Thyst register table (Table 9) 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 bits of the Temp data for data comparison.
Table 8. Tos register table
Tos MS byte MSB B7 MSB D8 D7 D6 D5 D4 D3 D2 D1 B6 B5 B4 B3 B2 B1 Tos data (9 bits) LSB D0 X X X X X X X LSB B0 MSB B7 B6 B5 B4 B3 Not used B2 B1 Tos LS byte LSB B0
Table 9. Thyst register table
Thyst MS byte MSB B7 MSB D8 D7 D6 D5 D4 D3 D2 D1 B6 B5 B4 B3 B2 B1 Thyst data (9 bits) LSB D0 X X X X X X X LSB B0 MSB B7 B6 B5 B4 B3 Not used B2 B1 Thyst LS byte LSB B0
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 significant bits should be used and the 7 LSB bits of the LS byte are equal to zero and should be ignored. The Tos and Thyst table (Table 10) shows examples of the limit data and value.
Table 10. Tos and Thyst table
Limit data 11-bit Binary (2's complement) 0111 1101 0 0001 1001 0 0000 0000 1 0000 0000 0 1111 1111 1 1110 0111 0 1100 1001 0 3-bit Hex 0FAh 032h 001h 000h 1FFh 1CEh 192h Decimal value 250 50 1 0 -1 -50 -110 Limit temp value C +125.0 C +25.0 C +0.5 C 0.0 C -0.5 C -25.0 C -55.0 C
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
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 the "General operation" section. In order to observe this output state, an external pull-up resistor is needed. The resistor should be as large as possible, up 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 of the Configuration register: setting B2 to 1 selects OS active HIGH and setting B2 to 0 sets OS active LOW. At power-up, this bit is equal to 0 and the OS active state is LOW.
the configuration register. Notice that the programmed data and the fault queue value are not the same. The Fault queue table (Table 11) shows the one-to-one relationship between them. At power-up, fault queue data = 0 and fault queue value = 1.
Table 11. Fault queue table
Fault queue data B4 0 0 1 1 B3 0 1 0 1 Fault queue value Decimal 1 2 4 6
OS comparator and interrupt modes
As described in the "General operation" section, the device OS output responds to the result of the comparison between the Temp data and the programmed limits, 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 of the configuration register: setting B1 to 1 selects the OS interrupt mode, and setting B1 to 0 selects the OS comparator mode. At power up, this bit is equal to 0 and the OS comparator is selected. The main difference between the two modes is that in OS comparator mode, the OS output becomes active when the Temp has exceeded the Tos and reset when the Temp has dropped below the Thyst, reading a register or putting the device into shut-down does not change the state of the OS output; while in OS interrupt mode, once it has been activated either by exceeding the Tos or dropping below the Thyst, the OS output will remain active indefinitely until reading a register or putting the device into shut-down occurs, then the OS output is reset. The Tos & Thyst limits must be selected so that Tos temp value > Thyst temp value. Otherwise, the OS output state will be undefined.
Shutdown mode
The device operation mode is selected by programming bit B0 of the Configuration register: Setting B0 to 1 will put the device into shut-down mode. Resetting B0 to 0 for the device normal mode. In shut-down mode, the device draws a small current of about 3.5 A and the power dissipation is minimized; the temperature conversion stops, but the I2C interface remains active and register write/read operation can be performed. If the OS output is in comparator mode, then it remains unchanged. Otherwise, the OS output is reset in interrupt mode.
Power-up default and Power-on Reset
The LM75A always powers-up in its default state with: - Normal operation mode - OS comparator mode - Tos = 80 C - Thyst = 75 C - OS output active state = LOW - Pointer value = 0. When the power supply voltage is dropped below the device power-on reset level of about 1.9 V (POR) and then rises up again, the device will be reset to its default condition as listed above.
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 of
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
Data communication
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 by the Figures as follows with these definitions: 1. Before a communication, the I2C-bus must be free or not busy. It means that the SCL and SDA lines must be both 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 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 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 notice 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 to the bus the device acknowledgement signal. 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 to the bus the master acknowledgement signal.
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Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
Protocols for writing and reading the registers
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
POINTER BYTE DEVICE ACKNOWLEDGE
CONFIGURATION DATA BYTE STOP DEVICE ACKNOWLEDGE DEVICE ACKNOWLEDGE
SL01393
Figure 6. 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
0 (next)
0
0
1
A2
A1
A0
W
A
0
0
0
0
0
0
0
1
A
RS
(next)
DEVICE ADDRESS START WRITE
POINTER BYTE DEVICE ACKNOWLEDGE DEVICE ACKNOWLEDGE
RE-START
1 SCL (cont.) SDA (cont.) 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
P
DEVICE ADDRESS READ
DATA BYTE FROM DEVICE STOP DEVICE ACKNOWLEDGE MASTER NOT ACKNOWLEDGED
SL01398
Figure 7. 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
P
DEVICE ADDRESS START READ
DATA BYTE FROM DEVICE STOP DEVICE ACKNOWLEDGE MASTER NOT ACKNOWLEDGED
SL01394
Figure 8. Read configuration register with preset Pointer (1-byte data).
2004 Oct 05
13
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
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
POINTER BYTE DEVICE ACKNOWLEDGE DEVICE ACKNOWLEDGE
1 SCL (cont.) SDA (cont.) D7
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
D6
D5
D4
D3
D2
D1
D0 A
D7
D6
D5
D4
D3
D2
D1
D0
A
P
MS BYTE DATA
LS BYTE DATA STOP DEVICE ACKNOWLEDGE DEVICE ACKNOWLEDGE
SL01397
Figure 9. 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
POINTER BYTE DEVICE ACKNOWLEDGE DEVICE ACKNOWLEDGE
RE-START
1 SCL (cont.) SDA (cont.) 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
P
DEVICE ADDRESS READ
MS BYTE FROM DEVICE DEVICE ACKNOWLEDGE MASTER ACKNOWLEDGE
LS BYTE FROM DEVICE STOP MASTER NOT ACKNOWLEDGED
SL01396
Figure 10. Read Temp or 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
P
DEVICE ADDRESS START READ
MS BYTE FROM DEVICE DEVICE ACKNOWLEDGE MASTER ACKNOWLEDGE
LS BYTE FROM DEVICE STOP MASTER NOT ACKNOWLEDGED
SL01395
Figure 11. Read Temp or Tos or Thyst register with preset Pointer (2-byte data).
2004 Oct 05
14
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
SO8: plastic small outline package; 8 leads; body width 3.9 mm
SOT96-1
2004 Oct 05
15
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
TSSOP8: plastic thin shrink small outline package; 8 leads; body width 3 mm
SOT505-1
2004 Oct 05
16
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
REVISION HISTORY
Rev _2 Date 20041005 Description Product data sheet (9397 750 14174). Supersedes data of 2001 Jul 16 (9397 750 08571).
* "Features" section:
Modifications:
- 7th bullet: add "3 C from -55 C to +125 C" - add "ESD" bullet - add "Latch-up" bullet
* "Ordering information" table: `Topside mark' column * Figure 2, "Simplified block diagram" modified. * Section "Typical connection" re-named to "Typical application" (page 4); added resistor values to Figure 3.
_1 20010716 Product data (9397 750 08571). ECN 853-2266 26719 of 16 July 2001.
2004 Oct 05
17
Philips Semiconductors
Product data sheet
Digital temperature sensor and thermal WatchdogTM
LM75A
Data sheet status
Level
I
Data sheet status [1]
Objective data sheet
Product status [2] [3]
Development
Definitions
This data sheet contains data from the objective specification for product development. Philips Semiconductors reserves the right to change the specification in any manner without notice. This data sheet contains data from the preliminary specification. Supplementary data will be published at a later date. Philips Semiconductors reserves the right to change the specification without notice, in order to improve the design and supply the best possible product. This data sheet contains data from the product specification. Philips Semiconductors reserves the right to make changes at any time in order to improve the design, manufacturing and supply. Relevant changes will be communicated via a Customer Product/Process Change Notification (CPCN).
II
Preliminary data sheet
Qualification
III
Product data sheet
Production
[1] Please consult the most recently issued data sheet before initiating or completing a design. [2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at URL http://www.semiconductors.philips.com. [3] For data sheets describing multiple type numbers, the highest-level product status determines the data sheet status.
Definitions
Short-form specification -- The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see the relevant data sheet or data handbook. Limiting values definition -- Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability. Application information -- Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or modification.
Disclaimers
Life support -- These products are not designed for use in life support appliances, devices, or systems where malfunction of these products can reasonably be expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application. Right to make changes -- Philips Semiconductors reserves the right to make changes in the products--including circuits, standard cells, and/or software--described or contained herein in order to improve design and/or performance. When the product is in full production (status `Production'), relevant changes will be communicated via a Customer Product/Process Change Notification (CPCN). Philips Semiconductors assumes no responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless otherwise specified.
Contact information
For additional information please visit http://www.semiconductors.philips.com. Fax: +31 40 27 24825
(c) Koninklijke Philips Electronics N.V. 2004 All rights reserved. Published in the U.S.A. Date of release: 10-04
For sales offices addresses send e-mail to: sales.addresses@www.semiconductors.philips.com.
Document number:
9397 750 14174
Philips Semiconductors
2004 Oct 05 18

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