AMC6821 Datasheet, PDF (29/54 Pages) Burr-Brown (TI) – Analog Monitor and Control Circuit

AMC6821
www.ti.com
SBAS386C – MAY 2006 – REVISED JULY 2007
When the actual duty cycle is different from the desired value, the duty cycle is adjusted automatically. When the
RAMPE bit of the DCY-RAMP Register is cleared ('0'), the duty cycle changes to the desired value immediately
after being calculated. When the RAMPE bit is '1', the duty cycle changes to the new value gradually.
The DCY-RAMP Register specifies how quickly the duty cycle changes. The duty cycle can be checked every
0.0625 second to every eight seconds, depending on the bits [RATE2:RATE0] bits. It changes 1/255(0.392%) to
4/255 (1.57%) each time, depending on the bits [STEP1:STEP0] bits. When the difference between the actual
value and the target value is equal to or less than the adjustment threshold (as defined by the bits
[THRE1:THRE0] bits), the adjustment finishes. See the DCY-RAMP Register for details. When the TACH
monitoring is enabled (TACH-EN bit, bit 2 of 0x02, is set to '1') and the TACH-MODE bit (bit 1 of 0x02) is cleared
('0'), the duty cycle is forced to 0% when the calculated value is less than 7%. If the TACH monitoring is disabled
(TACH-EN = 0) or the TACH-MODE bit is set ('1'), the duty cycle is always set to the calculated value even if the
value is less than 7%.
Read Local
Temperature
Read Remote
Temperature
(Update DCY with the rate defined by the
bits [RATE2:RATE0] of the DCY ramp register.
Temperature ³
Local-High-Temp-Limit
Yes
LTH = 1,
LTO = 1
Temperature ³
Remote-High-Temp-Limit
Yes
RTH = 1,
RTO = 1
No
No
Temperature ³
No
Local-Critical-Temp
Temperature ³
No
Remote-Critical-Temp
Yes
LTC = 1,
OVR is Low
Yes
RTC = 1,
OVR is Low
LTL = 1, ^Yes
LTO = 1
Temperature £
Local-Low-Temp-Limit
No
Temperature £
Remote-Low-Temp-Limit
No
Yes
RTL = 1,
RTO = 1
No
Update DCY?
The temperature updating rate may be faster than the DCY updating rate. _Yes
Remote Fan Temperature Control Mode
(Remote Fan Temperature Control)
Yes
Calculate New DCY for the Remote
Fan Temperature Control
No
(Maximum fast speed calculated control)
Calculate DCY for the remote fan temperature control
and local fan temperature control, respectively.
Use the larger one as the new DCY.
Update DCY
Figure 29. Temperature Monitoring Flow Chart
Copyright © 2006–2007, Texas Instruments Incorporated
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