LM90CIMMX National Semiconductor, LM90CIMMX Datasheet - Page 16

• Manufacturer Part Number: LM90CIMMX
• Manufacturer: National Semiconductor

Specifications of LM90CIMMX

• Temperature Sensor Function: Temp Sensor
• Interface Type: Serial (2-Wire)
• Output Type: Digital
• Package Type: MSOP
• Operating Temperature (min): 0C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Commercial
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (max): 3.6V
• Lead Free Status / Rohs Status: Not Compliant

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2.0 LM90 REGISTERS
For RTOHB: Remote Temperature Offset High Byte. Power up default is LHIGH = RHIGH = 0˚C. 1LSB = 1˚C. Two’s complement
format.
For RTOLB: Remote Temperature Offset High Byte. Power up default is 0˚C. 1LSB = 0.125˚C. Two’s complement format.
The offset value written to these registers will automatically be added to or subtracted from the remote temperature measurement
that will be reported in the Remote Temperature registers.
2.9 LOCAL and REMOTE T_CRIT REGISTERS (RCS and LCS)
D7–D0: T_CRIT setpoint temperature data. Power up default is T_CRIT = 85˚C. 1 LSB = 1˚C, two’s complement format.
2.10 T_CRIT HYSTERESIS REGISTER (TH)
D7–D0: T_CRIT Hysteresis temperature. Power up default is TH = 10˚C. 1 LSB = 1˚C, maximum value = 31.
2.11 FILTER and ALERT CONFIGURE REGISTER
D7-D3: is not defined defaults to ’0’.
D2-D1: input filter setting as defined the table below:
Level 2 sets maximum filtering.
D0: when set to ’1’ comparator mode is enabled.
2.12 MANUFACTURERS ID REGISTER
(Read Address FEh) Default value 01h.
2.13 DIE REVISION CODE REGISTER
(Read Address FFh) Default value 21h. This register will increment by 1 every time there is a revision to the die by National
Semiconductor.
4.0 Application Hints
The LM90 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 LM90’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
(Read and Write Address BFh):
Value
BIT
(Read/Write Address 12h):
(Read/Write Address 20h, 19h):
(Read and Write Address 21h):
Value
Value
Value
BIT
BIT
BIT
D7
0
SIGN
(Continued)
0.5
D7
D7
D7
D6
0
D2
0.25
0
0
1
1
D6
D6
D6
64
D5
0
0.125
D5
D5
D5
32
D4
0
D1
16
0
1
0
1
D4
D4
D4
16
16
0
surface temperature, the actual temperature of the of the
LM90 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 LM90’s die, use a
remote diode. This diode can be located on the die of a
target IC, allowing measurement of the IC’s temperature,
independent of the LM90’s temperature. The LM90 has been
optimized to measure the remote diode of a Pentium III
processor as shown in Figure 11 . A discrete diode can also
D3
0
D3
D3
D3
0
8
8
Filter Level
No Filter
Level 1
Level 1
Level 2
Filter Level
D2
D2
D2
D2
0
4
4
D1
D1
D1
D1
0
2
2
Configure
ALERT
D0
D0
D0
D0
0
1
1