Datasheet

Mask Register (03h)
This register masks the ALERT, OT, THERM, and
FANFAIL outputs. A 1 prevents the corresponding fail-
ures from being asserted on these outputs. The mask
bits do not affect the status register.
Global Configuration Register (04h)
The global configuration register controls the shutdown
mode, power-on reset, SMBus timeout, and tempera-
ture channel 2 source select:
• D7: Run/Standby. Normal operation is run (0).
Setting this bit to 1 suspends conversions and puts
the MAX6639 into low-power sleep mode.
• D6: Software POR. Writing a 1 resets all registers to
their default values.
• D5: SMBus Timeout Disable. Writing a zero enables
SMBus timeout for prevention of bus lockup. When
the timeout function is enabled, the SMBus interface
is reset if SDA or SCL remains low for more than
74ms (typ).
• D4: Temperature Channel 2 Source. Selects either
local or remote 2 as the source for temperature chan-
nel 2 register data. Writing a zero to this bit selects
remote 2 for temperature channel 2.
• D3: PWM Output Frequency Range. Selects either
the 20Hz to 100Hz range or the 5kHz to 25kHz range
for the PWM outputs (see Table 9).
Extended Temperature Registers (05h and 06h)
These registers contain the extended temperature data
from channels 1 and 2. Bits D[7:5] contain the 3 LSBs
of the temperature data. The bit values are 0.5°C,
0.25°C, and 0.125°C. When bit 0 is set to 1, a diode
fault has been detected.
Channel 1 and Channel 2 ALERT, OT, and THERM
Limits (08h Through 0Dh)
These registers contain the temperatures above which
the ALERT, THERM, and OT status bits set and outputs
assert (for the temperature channels that are not
masked). The data format is the same as that of the
channel 1 and channel 2 temperature registers: the
LSB weight is +1°C and the MSB is +128°C.
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
Maxim Integrated 13
MAX6639/MAX6639F
READ/
WRITE
REGISTER
NO.
ADDRESS
POR
STATE
FUNCTION D7 D6 D5 D4 D3 D2 D1 D 0
W 26h
0011
1100
Fan 1 target
duty cycle
MSB——————LS B
R 27h
0000
0000
Fan 2 current
duty cycle
MSB——————LS B
W 27h
0011
1100
Fan 2 target
duty cycle
MSB——————LS B
R/W 28h
0100
000
Channel 1
minimum
fan-start
temperature
MSB——————LS B
R/W 29h
0100
0000
Channel 2
minimum
fan-start
temperature
MSB——————LS B
R 3Dh
0101
1000
Read device
ID
01011000
R 3Eh
0100
1101
Read
manufacturer
ID
01001101
R 3Fh
0000
0000
Read device
revision
00000000
Table 4. Register Map (continued)