lm95221cimm-eng National Semiconductor Corporation, lm95221cimm-eng Datasheet - Page 8

• Manufacturer Part Number: lm95221cimm-eng
• Description: Dual Remote Diode Digital Temperature Sensor With Smbus Interface
• Manufacturer: National Semiconductor Corporation

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1.0 Functional Description
7. Status Register: busy, diode fault
8. Configuration Register: resolution control, conversion
9. 1-shot Register
10. Manufacturer ID
11. Revision ID
1.1 CONVERSION SEQUENCE
The LM95221 takes approximately 66 ms to convert the
Local Temperature, Remote Temperature 1 and 2, and to
update all of its registers. Only during the conversion pro-
cess the busy bit (D7) in the Status register (02h) is high.
These conversions are addressed in a round robin se-
quence. The conversion rate may be modified by the Con-
version Rate bits found in the Configuration Register (03h).
When the conversion rate is modified a delay is inserted
between conversions, the actual conversion time remains at
66ms (26 ms for each remote and 14 ms for local). Different
conversion rates will cause the LM95221 to draw different
amounts of supply current as shown in Figure 2.
1.2 POWER-ON-DEFAULT STATES
LM95221 always powers up to these known default states.
The LM95221 remains in these states until after the first
conversion.
1. Command Register set to 00h
2. Local Temperature set to 0˚C
3. Remote Diode Temperature set to 0˚C until the end of
4. Status Register depends on state of thermal diode in-
5. Configuration register set to 00h; continuous conversion,
1.3 SMBus INTERFACE
The LM95221 operates as a slave on the SMBus, so the
SMBCLK line is an input and the SMBDAT line is bidirec-
tional. The LM95221 never drives the SMBCLK line and it
does not support clock stretching. According to SMBus
FIGURE 2. Conversion Rate Effect on Power Supply
rate control, standby control
the first conversion
puts
time = 66ms
Current
(Continued)
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8
specifications, the LM95221 has a 7-bit slave address. All
bits A6 through A0 are internally programmed and can not be
changed by software or hardware. The LM95221 has the
following SMBus slave address:
1.4 TEMPERATURE DATA FORMAT
Temperature data can only be read from the Local and
Remote Temperature registers .
Remote temperature data is represented by an 11-bit, two’s
complement word or unsigned binary word with an LSb
(Least Significant Bit) equal to 0.125˚C. The data format is a
left justified 16-bit word available in two 8-bit registers. Un-
used bits will always report "0".
Local Temperature data is represented by a 10-bit, two’s
complement word with an LSb (Least Significant Bit) equal to
0.25˚C. The data format is a left justified 16-bit word avail-
able in two 8-bit registers. Unused bits will always report "0".
Local temperature readings greater than +127.875˚C are not
clamped to +127.875˚C, they will roll-over to negative tem-
perature readings.
LM95221
Version
Temperature
Temperature
Temperature
+255.875˚C
+0.125˚C
−0.125˚C
+0.125˚C
+0.125˚C
+125˚C
+255˚C
+201˚C
+125˚C
+125˚C
+25˚C
−25˚C
−55˚C
+25˚C
+25˚C
+1˚C
−1˚C
+1˚C
+1˚C
0˚C
0˚C
0˚C
11-bit, 2’s complement (10-bit plus sign)
A6
0
11-bit, unsigned binary
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0010 0000
0000 0000 0000 0000
1100 1001 0000 0000
1100 1001 0000 0000
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0010 0000
0000 0000 0000 0000
0001 1001 0000 0000
0000 0001 0000 0000
0000 0000 0010 0000
0000 0000 0000 0000
0111 1101 0000 0000
0111 1101 0000 0000
0111 1101 0000 0000
A5
1110 0111 0000 0000
1111 1111 0000 0000
1111 1111 0000 0000
1111 1111 1110 0000
1111 1111 1110 0000
1
Binary
Binary
Binary
A4
0
Digital Output
Digital Output
Digital Output
A3
1
A2
0
A1
FFE0h
FFE0h
7D00h
FF00h
E700h
C900h
FF00h
C900h
7D00h
7D00h
1900h
0100h
0020h
0000h
1900h
0100h
0020h
0000h
1900h
0100h
0020h
0000h
1
Hex
Hex
Hex
A0
1