Datasheet
Table Of Contents
- FEATURES
- Applications
- Key Specifications
- DESCRIPTION
- Absolute Maximum Ratings
- Operating Ratings
- Temperature-to-Digital Converter Characteristics
- Logic Electrical Characteristics
- SMBus DIGITAL SWITCHING CHARACTERISTICS
- Functional Description
- CONVERSION SEQUENCE
- THE ALERT OUTPUT
- T_CRIT_A OUTPUT and T_CRIT LIMIT
- POWER ON RESET DEFAULT STATES
- SMBus INTERFACE
- TEMPERATURE DATA FORMAT
- OPEN-DRAIN OUTPUTS
- DIODE FAULT DETECTION
- COMMUNICATING with the LM90
- SERIAL INTERFACE RESET
- DIGITAL FILTER
- Fault Queue
- One-Shot Register
- LM90 REGISTERS
- COMMAND REGISTER
- LOCAL and REMOTE TEMPERATURE REGISTERS (LT, RTHB, RTLB)
- STATUS REGISTER (SR)
- CONFIGURATION REGISTER
- CONVERSION RATE REGISTER
- LOCAL and REMOTE HIGH SETPOINT REGISTERS (LHS, RHSHB, and RHSLB)
- LOCAL and REMOTE LOW SETPOINT REGISTERS (LLS, RLSHB, and RLSLB)
- REMOTE TEMPERATURE OFFSET REGISTERS (RTOHB and RTOLB)
- LOCAL and REMOTE T_CRIT REGISTERS (RCS and LCS)
- T_CRIT HYSTERESIS REGISTER (TH)
- FILTER and ALERT CONFIGURE REGISTER
- MANUFACTURERS ID REGISTER
- DIE REVISION CODE REGISTER
- Application Hints
- Revision History
LM90
SNIS126A –MAY 2004–REVISED MARCH 2013
www.ti.com
D7–D0: T_CRIT setpoint temperature data. Power up default is T_CRIT = 85°C. 1 LSB = 1°C, two's complement
format.
T_CRIT HYSTERESIS REGISTER (TH)
Table 13. T_CRIT HYSTERESIS REGISTER (TH) (Read and Write Address 21h):
BIT D7 D6 D5 D4 D3 D2 D1 D0
Value 16 8 4 2 1
D7–D0: T_CRIT Hysteresis temperature. Power up default is TH = 10°C. 1 LSB = 1°C, maximum value = 31.
FILTER and ALERT CONFIGURE REGISTER
Table 14. FILTER and ALERT CONFIGURE REGISTER (Read and Write Address BFh):
BIT D7 D6 D5 D4 D3 D2 D1 D0
Value 0 0 0 0 0 Filter Level ALERT Configure
D7-D3: is not defined defaults to "0".
D2-D1: input filter setting as defined the table below:
D2 D1 Filter Level
0 0 No Filter
0 1 Level 1
1 0 Level 1
1 1 Level 2
Level 2 sets maximum filtering.
D0: when set to "1" comparator mode is enabled.
MANUFACTURERS ID REGISTER
(Read Address FEh) Default value 01h.
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.
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 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 15. 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.
20 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated
Product Folder Links: LM90