Datasheet

MAX6653/MAX6663/MAX6664
Temperature Monitors and
PWM Fan Controllers
_______________________________________________________________________________________ 9
Temperature Comparison
and Interrupt System
At the end of each conversion cycle, the converted
temperature data are compared to various set-point
thresholds to control the INT, THERM, SDL, and SDR
outputs. All temperature threshold limits are stored in
the threshold limit registers (Table 6) and can be
changed through the SMBus digital interface.
THERM is an active-low thermal-overload output indicat-
ing that the THERM overtemperature set point is exceed-
ed. With the THERM threshold set to an appropriate value,
the THERM output can be used to control clock throttling.
When this pin is pulled low by an external signal, a status
bit (bit 7, status register 2) is set, and the fan speed is
unconditionally forced to full-on speed. The only way to
reset the status bit is to read status register 2. Connect a
10kΩ pullup resistor between THERM and V
CC
.
Table 4. Temperature Data Low Byte Format Structure: LLLXXRRR*
Table 5. Temperature Conversion Rate Setting (Fan Filter Register (23h)—POR = 111)
FRACTIONAL TEMPERATURE (°C) DIGITAL OUTPUT (LOCAL) DIGITAL OUTPUT (REMOTE)
0.000 000X XXXX XXX XX 000
0.125 001X XXXX XXX XX 001
0.25 010X XXXX XXX XX 010
0.375 011X XXXX XXX XX 011
0.5 100X XXXX XXX XX 100
0.625 101X XXXX XXX XX 101
0.75 110X XXXX XXX XX 110
0.875 111X XXXX XXX XX 111
BIT 4 BIT 3 BIT2 CONVERSION RATE (Hz) CONVERSION TIME (s)
0 0 0 0.0625 16
0 0 1 0.125 8
0 1 0 0.25 4
0 1 1 0.5 2
100 1 1
101 2 0.5
1 1 0 4 0.25
1 1 1 4 0.25
*Where: LLL = local fractional temperature bits, XX = don’t care, RRR = remote fractional temperature bits.
NAME ADDRESS R/W MAX6653 POR VALUE
MAX6663/MAX6664 POR STATE
DESCRIPTION
LTH 14h R/W Set by CRIT0 and CRIT1
0011 1100
Local temp high limit
LTL 15h R/W Set by CRIT0 and CRIT1
0000 0000
Local temp low limit
LTHER 16h R/W Set by CRIT0 and CRIT1
0100 0110
Local temp THERM limit
RTH 18h R/W Set by CRIT0 and CRIT1
0101 0000
Remote temp high limit
RTL 19h R/W Set by CRIT0 and CRIT1
0000 0000
Remote temp low limit
RTHER 1Ah R/W Set by CRIT0 and CRIT1
0110 0100
Remote temp THERM limit
LTSD 1Bh R/W Set by CRIT0 and CRIT1 N/A
Local temp shutdown limit
(MAX6653 only)
RTSD 1Ch R/W Set by CRIT0 and CRIT1 N/A
Remote temp shutdown limit
(MAX6653 only)
Table 6. Threshold Limit Registers