AMC6821 Datasheet, PDF (20/47 Pages) Burr-Brown (TI) – Analog Monitor and Control Circuit

AMC6821
SBAS386A – MAY 2006 – REVISED MAY 2006
www.ti.com
When the THERM limit is exceeded, the corresponding status flag bit (R-THERM or L-THERM of Status
Register 1 or Status Register 2) is set to '1', and the THERM interrupt through the SMBALERT pin is generated
if it is enabled (THERMOVIE of bit Configuration Register 1 is set to '1'). This interrupt forces the SMBALERT
pin low. Reading the status registers clears the flag bit (R-THERM and L-THERM). Clearing the flag bit makes
the SMBALERT pin go back to high, but does not negate the THERM pin. It remains low until the temperature
falls 5°C below the exceeded THERM limit. After this bit is cleared, the active flag bit (R-THERM for remote
temperature or L-THERM for local temperature) and the THERM interrupt are not re-armed until the temperature
falls 5°C below the exceeded THERM limit. This procedure is shown in Figure 14.
THERM Limit
5°
Temperature
THERM
INT via SMBALERT
INT via SMBALERT
Status Register Read
Figure 14. Operation of the THERM Interrupt and the THERM Pin
When working as an output, the status of the THERM pin affects the RPM fan. If the THERM-FAN-EN bit is set
('1'), the fan goes to full-speed (that is, the duty cycle is 100%) when the THERM pin goes low. However, when
THERM-FAN-EN = 0, the status of the THERM pin does not affect the fan speed.
THERM Pin As An Input
When this pin works as input, it is the input of the external hardware control signal; the THERM-IN bit of Status
Register 2 reflects the input. When the THERM pin is pulled low as an input, THERM-IN is set ('1') and the fan is
driven at full speed (that is, the duty cycle is 100%), no matter what THERM-FAN-EN is. The THERM-FAN-EN
bit has no effect when the THERM pin works as an input.
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