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
3. Remote Diode Temperature set to 0°C until the end of the first conversion.
4. Status Register set to 00h.
5. Configuration register set to 00h; ALERT enabled, Remote T_CRIT alarm enabled and Local T_CRIT alarm
enabled
6. 85°C Local and Remote T_CRIT temperature setpoints
7. 70°C Local and Remote HIGH temperature setpoints
8. 0°C Local and Remote LOW temperature setpoints
9. Filter and Alert Configure Register set to 00h; filter disabled, ALERT output set as an SMBus ALERT
10. Conversion Rate Register set to 8h; conversion rate set to 16 conv./sec.
SMBus INTERFACE
The LM90 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBData line is bi-
directional. The LM90 never drives the SMBCLK line and it does not support clock stretching. According to
SMBus specifications, the LM90 has a 7-bit slave address. All bits A6 through A0 are internally programmed and
can not be changed by software or hardware.
The complete slave address is:
A6 A5 A4 A3 A2 A1 A0
1 0 0 1 1 0 0
TEMPERATURE DATA FORMAT
Temperature data can only be read from the Local and Remote Temperature registers; the setpoint registers
(T_CRIT, LOW, HIGH) are read/write.
Remote temperature data is represented by an 11-bit, two's complement word with an LSB (Least Significant Bit)
equal to 0.125°C. The data format is a left justified 16-bit word available in two 8-bit registers:
Temperature Digital Output
Binary Hex
+125°C 0111 1101 0000 0000 7D00h
+25°C 0001 1001 0000 0000 1900h
+1°C 0000 0001 0000 0000 0100h
+0.125°C 0000 0000 0010 0000 0020h
0°C 0000 0000 0000 0000 0000h
−0.125°C 1111 1111 1110 0000 FFE0h
−1°C 1111 1111 0000 0000 FF00h
−25°C 1110 0111 0000 0000 E700h
−55°C 1100 1001 0000 0000 C900h
Local Temperature data is represented by an 8-bit, two's complement byte with an LSB (Least Significant Bit)
equal to 1°C:
Temperature Digital Output
Binary Hex
+125°C 0111 1101 7Dh
+25°C 0001 1001 19h
+1°C 0000 0001 01h
0°C 0000 0000 00h
−1°C 1111 1111 FFh
−25°C 1110 0111 E7h
−55°C 1100 1001 C9h
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