LM95231_06 NSC [National Semiconductor], LM95231_06 Datasheet - Page 9

• Manufacturer Part Number: LM95231_06
• Description: Precision Dual Remote Diode Temperature Sensor with SMBus Interface and TruTherm Technology
• Manufacturer: NSC [National Semiconductor]

1.0 Functional Description
the remote diodes to sense temperatures above 127˚C.
Local temperature resolution is not programmable and is
always 9-bits plus sign and has a 0.25˚C LSb.
The LM95231 remote diode temperature accuracy will be
trimmed for the thermal diode of a Pentium 4 processor on
90nm process or a 2N3904 transistor and the accuracy will
be guaranteed only when using either of these diodes when
selected appropriately. TruTherm mode should be enabled
when measuring a Pentium 4 processor on 90nm process
and disabled when measuring a 2N3904 transistor. Enabling
TruTherm mode with a 2N3904 transistor connected may
produce unexpected temperature readings.
Diode fault detection circuitry in the LM95231 can detect the
presence of a remote diode: whether D+ is shorted to V
D- or ground, or whether D+ is floating.
The LM95231 register set has an 8-bit data structure and
includes:
1. Most-Significant-Byte (MSB) Local Temperature Regis-
2. Least-Significant-Byte (LSB) Local Temperature Regis-
3. MSB Remote Temperature 1 Register
4. LSB Remote Temperature 1 Register
5. MSB Remote Temperature 2 Register
6. LSB Remote Temperature 2 Register
7. Status Register: busy, diode fault
8. Configuration Register: resolution control, conversion
9. Remote Diode Filter Setting
10. Remote Diode Model Select
11. Remote Diode TruTherm Mode Control
12. 1-shot Register
13. Manufacturer ID
14. Revision ID
1.1 CONVERSION SEQUENCE
In the power up default state the LM95231 takes maximum a
77.5 ms to convert the Local Temperature, Remote Tem-
perature 1 and 2, and to update all of its registers. Only
during the conversion process is the busy bit (D7) in the
Status register (02h) high. These conversions are addressed
in a round robin sequence. The conversion rate may be
modified by the Conversion Rate bits found in the Configu-
ration Register (03h). When the conversion rate is modified a
delay is inserted between conversions, the actual maximum
conversion time remains at 87.7 ms. Different conversion
rates will cause the LM95231 to draw different amounts of
supply current as shown in Figure 1.
ter
ter
rate control, standby control
(Continued)
DD
,
9
1.2 POWER-ON-DEFAULT STATES
LM95231 always powers up to these known default states.
The LM95231 remains in these states until after the first
conversion.
1. Command Register set to 00h
2. Local Temperature set to 0˚C until the end of the first
3. Remote Diode Temperature set to 0˚C until the end of
4. Remote Diode digital filters are on.
5. Remote Diode 1 model is set to Pentium 4 processor on
6. Status Register depends on state of thermal diode in-
7. Configuration register set to 00h; continuous conversion,
1.3 SMBus INTERFACE
The LM95231 operates as a slave on the SMBus, so the
SMBCLK line is an input and the SMBDAT line is bidirec-
tional. The LM95231 never drives the SMBCLK line and it
does not support clock stretching. According to SMBus
specifications, the LM95231 has a 7-bit slave address. All
bits A6 through A0 are internally programmed and can not be
changed by software or hardware. The SMBus slave ad-
dress is dependent on the LM95231 part number ordered:
Part Number
LM95231BIMM,
LM95231CIMM
LM95231BIMM-1,
LM95231CIMM-1
LM95231BIMM-2,
LM95231CIMM-2
FIGURE 1. Conversion Rate Effect on Power Supply
conversion
the first conversion
90nm process with TruTherm mode enabled. Remote
Diode 2 model is set to 2N3904 with TruTherm mode
disabled.
puts
typical time = 85.8 ms when TruTherm Mode is enabled
for Remote 1 only
A6 A5 A4 A3 A2 A1 A0
0
0
0
Current
1
0
1
0
1
0
1
1
1
0
0
0
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