User guide

MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
12 ______________________________________________________________________________________
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 useRFU0
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.
MASK14
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.
MASK23
Enables FAN duty factor override when high.FAN ON2
OVERT pin polarity control:
0 = active low (low when T
CRIT
is crossed)
1 = active high
POL5
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.
STBY6
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)
FUNCTIONNAME
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 bitF04 0
Reserved for future useRFU3–0 0
Frequency control bitF15 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
F37 (MSB)
F26
NAMEBIT