Datasheet
q
kT
=
t
V
F
I
=
I
x
K
t
V
BE
V
©
§
¹
·
S
x
e
«
«
¬
ª
»
»
¼
º
-1
LM95234
SNIS136D –AUGUST 2006–REVISED MARCH 2013
www.ti.com
Bit(s) Bit Name Read/ Description
Write
7 0 RO Read only bit will always report "0".
6 0 RO Read only bit will always report "0".
5 0 RO Read only bit will always report "0".
4 16 R/W bit weight 16°C
3 8 R/W bit weight 8°C
2 4 R/W bit weight 4°C
1 2 R/W bit weight 2°C
0 1 R/W bit weight 1°C
IDENTIFICATION REGISTERS
Register Name Command Read/ D7 D6 D5 D4 D3 D2 D1 D0 POR
Byte Write Default
(Hex) (Hex)
Manufacturer ID 0xFE RO 0 0 0 0 0 0 0 1 0x01
Revision ID 0xFF RO 0 1 1 1 1 0 0 1 0x79
Applications Hints
The LM95234 can be applied easily in the same way as other integrated-circuit temperature sensors, and its
remote diode sensing capability allows it to be used in new ways as well. It can be soldered to a printed circuit
board, and because the path of best thermal conductivity is between the die and the pins, its temperature will
effectively be that of the printed circuit board lands and traces soldered to the LM95234's pins. This presumes
that the ambient air temperature is almost the same as the surface temperature of the printed circuit board; if the
air temperature is much higher or lower than the surface temperature, the actual temperature of the LM95234 die
will be at an intermediate temperature between the surface and air temperatures. Again, the primary thermal
conduction path is through the leads, so the circuit board temperature will contribute to the die temperature much
more strongly than will the air temperature.
To measure temperature external to the LM95234's die, incorporates remote diode sensing technology. This
diode can be located on the die of a target IC, allowing measurement of the IC's temperature, independent of the
LM95234's temperature. A discrete diode can also be used to sense the temperature of external objects or
ambient air. Remember that a discrete diode's temperature will be affected, and often dominated, by the
temperature of its leads. Most silicon diodes do not lend themselves well to this application. It is recommended
that an MMBT3904 transistor base emitter junction be used with the collector tied to the base.
The LM95234’s TruTherm BJT beta compensation technology allows accurate sensing of integrated thermal
diodes, such as those found on most processors. With TruTherm technology turned off, the LM95234 can
measure a diode-connected transistor such as the MMBT3904 or the thermal diode found in an AMD processor.
The LM95234 has been optimized to measure the remote thermal diode integrated in a typical Intel processor on
65 nm or 90 nm process or an MMBT3904 transistor. Using the Remote Diode Model Select register any of the
four remote inputs can be optimized for a typical Intel processor on 65 nm or 90 nm process or an MMBT3904.
DIODE NON-IDEALITY
Diode Non-Ideality Factor Effect on Accuracy
When a transistor is connected as a diode, the following relationship holds for variables V
BE
, T and I
F
:
where
•
• q = 1.6×10
−19
Coulombs (the electron charge),
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