AMC6821SDBQG4 Datasheet, PDF (14/56 Pages) Texas Instruments – Intelligent Temperature Monitor and PWM Fan Controller

AMC6821
SBAS386C – MAY 2006 – REVISED JULY 2007
www.ti.com
Table 11. Temperature Data Format
TEMPERATURE (°C)
+127
+125
+100
+75
+50
+25
+10
+1
0
–1
–25
–50
–75
–100
–125
–128
BINARY DIGITAL CODE (11 bits)
01111111000
01111101000
01100100000
01001011000
00110010000
00011001000
00001010000
00000001000
00000000000
11111111000
11100111000
11001110000
10110101000
10011100000
10000011000
10000000000
Temperature Out-of-Range Detection
The AMC6821 has the following temperature limitation detections:
1. High and Low Temperature Limit: The value of the High-Temp-Limit and Low-Temp-Limit registers specify
the remote or local temperature ranges of normal operation. When the local or remote temperatures are
equal to or above the value of the corresponding High-Temp-Limit register, the LTH or RTH bits in the status
register are set ('1'). Likewise, when the local or remote temperatures are less than or equal to the
corresponding Low-Temp-Limit register, the LTL or RTL bits in the status register are set ('1').
When the local temperature is out-of-range (LTH = 1 or LTL = 1), the local temperature out-of-range event
occurs. The LTO bit in the status register is set ('1'), and the LTO interrupt is generated via the SMBALERT
pin if it is enabled (the LTOIE bit of Configuration Register 2 is set). Similarly, when the remote temperature
is out-of range (RTH = 1 or RTL = 1), the remote temperature out-of-range event occurs. The RTO bit in the
status register is set ('1'), and the RTO interrupt is generated via the SMBALERT pin if it is enabled (that is,
the RTOIE bit of Configuration Register 2 is set).
2. Critical Limit: Critical temperature limit is the highest allowed of remote or local temperature. When the
temperature is greater than or equal to the corresponding critical temperature, the LTCT or RTCT bit of the
status register is set ('1'), the output of the OVR pin goes low, and a non-maskable interrupt is generated
through the SMBALERT pin (low).
3. Passive Cooling Temperature (PSV) Limit: This limit defines the passive cooling threshold. In the auto
remote-temperature-fan control mode, the system enters a passive cooling condition when the remote
temperature is equal to or below this limit, and the fan stops. In the maximum fast speed calculated control
mode, the fan stops and the system enters a passive cooling condition when both the remote and local
temperatures are equal to or below this limit. In passive cooling, the LPSV bit of Status Register 2 (0x03) is
set ('1'), and a PSV interrupt is generated on the SMBALERT pin if enabled (PSVIE = 1). Note that reading
the Status Register clears the LPSV bit. After reading, if the active control temperature remains equal to or
below the PSV temperature, this bit reasserts on next monitoring cycle.
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