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
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SNIS126A –MAY 2004–REVISED MARCH 2013
DIGITAL FILTER
In order to suppress erroneous remote temperature readings due to noise, the LM90 incorporates a user-
configured digital filter. The filter is accessed in the FILTER and ALERT CONFIGURE REGISTER at BFh. The
filter can be set according to the following table.
D2 D1 Filter
0 0 No Filter
0 1 Level 1
1 0 Level 1
1 1 Level 2
Level 2 sets maximum filtering.
Figure 12 depict the filter output to in response to a step input and an impulse input. Figure 13 depicts the digital
filter in use in a Pentium 4 processor system. Note that the two curves, with filter and without, have been
purposely offset so that both responses can be clearly seen. Inserting the filter does not induce an offset as
shown.
Filter Output Response to a Step Input
Figure 11. a) Step Response Figure 12. b) Impulse Response
The filter on and off curves were purposely offset to better show noise performance.
Figure 13. Digital Filter Response in a Pentium 4 processor System
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