MAX1669 Datasheet, PDF (12/20 Pages) Maxim Integrated Products – Fan Controller and Remote Temperature Sensor with SMBus Serial Interface

Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
Table 4. Configuration Byte Bit Assignments
BIT
7
(MSB)
6
NAME
MASK0
STBY
5
POL
4
MASK1
3
MASK2
2
FAN ON
1
0
RFU
POR STATE
0
0
0
0
0
0
1
0
FUNCTION
Masks T_HIGH, T_LOW, and diode fault ALERT interrupts when high. If all three MASK_
bits are set high, ALERT interrupts are totally masked.
Standby mode control bit. If high, the device immediately stops converting, forces FAN
low, and enters standby mode. If low, the device continuously autoconverts at a 2Hz rate.
OVERT pin polarity control:
0 = active low (low when T_CRIT is crossed)
1 = active high
Masks I/O1 ALERT interrupts when high. Set MASK1 = 1 and connect a 10k to 100k
pull-up resistor on I/O1 to configure I/O1 as an output.
Masks I/O2 ALERT interrupts when high. Set MASK2 = 1 and connect a 10k to 100k
pull-up resistor on I/O2 to configure I/O2 as an output.
Enables FAN duty factor override when high.
Must be “1”
Reserved for future use
Table 5. PWM Frequency Data Byte Bit Assignments (Write Command = 1Ah)
BIT
7 (MSB)
6
5
4
3–0
NAME
F3
F2
F1
F0
RFU
POR STATE
FUNCTION
Frequency control bit. F3–F0 are decoded as follows:
F3–F0
Frequency (SYNC = GND) Synchronized Frequency (SYNC Clocked)
0000b
20Hz
0001b
30Hz
0010b
40Hz
0011b
50Hz
0100b
60Hz
0101b
70Hz
0110b
80Hz
0
0111b
90Hz
1000b
100Hz
1001b
110Hz
1010b
120Hz
1011b
130Hz
1100b
140Hz
1101b
150Hz
1110b
160Hz
1111b
DAC Mode
f_SYNC/13100
f_SYNC/8730
f_SYNC/6550
f_SYNC/5240
f_SYNC/4370
f_SYNC/3740
f_SYNC/3270
f_SYNC/2910
f_SYNC/2620
f_SYNC/2380
f_SYNC/2180
f_SYNC/2020
f_SYNC/1870
f_SYNC/1750
f_SYNC/1640
0
Frequency control bit
0
Frequency control bit
0
Frequency control bit
0
Reserved for future use
set to 1111b. The FAN duty factor can be selected from
0% to 100% in increments of 6.67%.
FAN Output in DAC Mode
If the PWM frequency register is set to code 1111b, the
DAC is multiplexed to the FAN output and the FAN duty
factor register (Table 6) now controls the DAC output
voltage rather than the duty factor. In DAC mode, the
output swing is 0 to 0.94 · V_CC (out of 4 bits of resolu-
tion). To ensure a smooth transition, make sure that the
FAN duty factor code is 0000b prior to setting the PWM
frequency code for DAC mode (1111b). External cir-
cuitry must accept an initial FAN DAC voltage of 0.
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