LM75AD 데이터 시트보기 (PDF) - Philips Electronics
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LM75AD Datasheet PDF : 18 Pages
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Philips Semiconductors
Digital temperature sensor and thermal Watchdog™
Product data sheet
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
Name
R/W POR Description
B7–B5 Reserved
R/W 000 Reserved for the manufacterer use.
B4–B3 OS Fault queue
R/W 00
For OS Fault Queue programming.
Programmable queue data = 0, 1 ,2, 3 for queue value = 1, 2, 4, 6 respectively. Default = 0.
B2
OS Polarity
R/W 0
For OS Polarity selection.
1 = OS active HIGH, 0 = OS active LOW (default).
B1
OS Comp/Interrupt R/W 0
For OS operation Mode selection.
1 = OS interrupt, 0 = OS comparator (default).
B0
Shut-down
R/W 0
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
Temp LS byte
MSB
LSB MSB
LSB
B7
B6
B5
B4
B3
B2
B1
B0
B7
B6
B5
B4
B3
B2
B1
B0
Temp data (11 bits)
Not used
MSB
LSB
D10 D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
X
X
X
X
X
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
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
Temp data
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
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