Rainbow Electronics MAX1669 User Manual
Page 12
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
12
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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.
Must be “1”
1
Reserved for future use
RFU
0
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.
MASK1
4
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.
MASK2
3
Enables FAN duty factor override when high.
FAN ON
2
OVERT pin polarity control:
0 = active low (low when T
CRIT
is crossed)
1 = active high
POL
5
BIT
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.
STBY
6
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.
MASK0
7
(MSB)
FUNCTION
NAME
1
0
0
0
0
0
0
0
POR STATE
Table 4. Configuration Byte Bit Assignments
Table 5. PWM Frequency Data Byte Bit Assignments (Write Command = 1Ah)
Frequency control bit
F0
4
0
Reserved for future use
RFU
3–0
0
Frequency control bit
F1
5
0
0
0
POR STATE
Frequency control bit. F3–F0 are decoded as follows:
F3–F0
Frequency (SYNC = GND)
Synchronized Frequency (SYNC Clocked)
0000b
20Hz
f
SYNC
/13100
0001b
30Hz
f
SYNC
/8730
0010b
40Hz
f
SYNC
/6550
0011b
50Hz
f
SYNC
/5240
0100b
60Hz
f
SYNC
/4370
0101b
70Hz
f
SYNC
/3740
0110b
80Hz
f
SYNC
/3270
0111b
90Hz
f
SYNC
/2910
1000b
100Hz
f
SYNC
/2620
1001b
110Hz
f
SYNC
/2380
1010b
120Hz
f
SYNC
/2180
1011b
130Hz
f
SYNC
/2020
1100b
140Hz
f
SYNC
/1870
1101b
150Hz
f
SYNC
/1750
1110b
160Hz
f
SYNC
/1640
1111b
DAC Mode
Frequency control bit
FUNCTION
F3
7 (MSB)
F2
6
NAME
BIT