LM95214CISD National Semiconductor, LM95214CISD Datasheet - Page 34

• Manufacturer Part Number: LM95214CISD
• Description: SENSOR, TEMP, 4-DIODE, 2-WIRE I/F
• Manufacturer: National Semiconductor

Specifications of LM95214CISD

• Ic Output Type: Current
• Sensing Accuracy Range: ± 1°C
• Supply Current: 0.57mA
• Supply Voltage Range: 3V To 3.6V
• Resolution (bits): 11bit
• Sensor Case Style: LLP
• No. Of Pins: 14
• Svhc: No SVHC
• Temperature Sensing Range: -40°C To +140°C
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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TruTherm technology can be found in the LM95234 four
channel remote diode sensor that is pin and register compat-
ible with the LM95214. The LM95214 does not support this
technology.
3.1.2 Calculating Total System Accuracy
The voltage seen by the LM95214 also includes the I
age drop of the series resistance. The non-ideality factor, η,
is the only other parameter not accounted for and depends
on the diode that is used for measurement. Since ΔV
proportional to both η and T, the variations in η cannot be
distinguished from variations in temperature. Since the non-
ideality factor is not controlled by the temperature sensor, it
will directly add to the inaccuracy of the sensor. For the for
Intel processor on 65 nm process, Intel specifies a +4.06%/
−0.897% variation in η from part to part when the processor
diode is measured by a circuit that assumes diode equation,
Equation 4, as true. As an example, assume a temperature
sensor has an accuracy specification of ±1.0°C at a temper-
ature of 80°C (353 Kelvin) and the processor diode has a non-
ideality variation of +1.19%/−0.27%. The resulting system
accuracy of the processor temperature being sensed will be:
and
The next error term to be discussed is that due to the series
resistance of the thermal diode and printed circuit board
traces. The thermal diode series resistance is specified on
most processor data sheets. For the MMBT3904 transistor,
this is specified at 0Ω typical. The LM95214 accommodates
the typical series resistance of a circuit with the offset register
compensation. The error that is not accounted for is the
spread of the thermal diodes series resistance. If a circuit has
a series resistance spread that is 2.79Ω to 6.24Ω or 4.515Ω
±1.73Ω, the 4.515Ω can be cancelled out with the offset reg-
ister setting. The ±1.73Ω spread cannot be cancelled out. The
equation to calculate the temperature error due to series re-
sistance (T
T
T
ACC
ACC
ER
= + 1.0°C + (+4.06% of 353 K) = +15.3 °C
= - 1.0°C + (−0.89% of 353 K) = −4.1 °C
) for the LM95214 is simply:
FIGURE 9. Thermal Diode Current Paths
F
R
S
BE
volt-
(6)
is
34
Solving Equation 6 for R
additional error due to the spread in the series resistance of
±1.07°C. The bulk of the error caused by the 4.515 ohms will
cause a positive offset in the temperature reading of 2.79°C
wich can be cancelled out by setting the offset register to
- 2.75°C. The spread in error cannot be canceled out, as it
would require measuring each individual thermal diode de-
vice. This is quite difficult and impractical in a large volume
production environment.
Equation 6 can also be used to calculate the additional error
caused by series resistance on the printed circuit board. Since
the variation of the PCB series resistance is minimal, the bulk
of the error term is always positive and can simply be can-
celled out by subtracting it from the output readings of the
LM95214.
Processor Family
Pentium ™ III
CPUID 67h
Pentium III CPUID
68h/
PGA370Socket/
Celeron
Pentium 4, 423 pin
Pentium 4, 478 pin
Pentium 4 on 0.13
micron process, 2 -
3.06 GHz
Pentium 4 on 90 nm
process
Intel Processor on
65 nm process
Pentium M
(Centrino)
MMBT3904
AMD Athlon MP
model 6
AMD Athlon 64
1.00151 1.00220 1.00289
1.0057
0.9933
0.9933
1.0011
1.0083
30006115
1.000
1.002
1.008
Diode Equation η
min
PCB
1
equal to ±1.73Ω results in the
ideality
1.0065
1.0045
1.0045
1.0021
1.008
1.011
1.009
1.003
1.008
1.008
typ
D
, non-
1.0125
1.0125
1.0368
1.0368
1.0030
1.023
1.050
1.016
1.096
max
Series
3.64
3.33
4.52
3.06
R,Ω