User guide
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Temperature error = measured - actual, T
A
= +25°C, unless otherwise noted.)
Pin Description
0
20
40
60
80
100
042 5 7 8 10 1231 6 9 11 131415
PWM DUTY FACTOR vs. CODE (D3D2D1D0)
MAX1669-09
CODE (D3D2D1D0)
DUTY FACTOR (%)
V
CC
= +3.3V OR +5V
0
0.5
1.5
1.0
2.0
3.5
3.0
2.5
4.0
4.5
5.0
042 5 7 8 10 1231691114
13
15
DAC OUTPUT vs. CODE (D3D2D1D0)
MAX1669-10
CODE (D3D2D1D0)
DAC OUTPUT (V)
I
LOAD
= +10mA TO -10mA
V
CC
= +5V
NAME FUNCTION
1
I/O1
General-Purpose Open-Drain Logic Input/Output 1. I/O1 is intended for driving LEDs, driving power-plane
switching MOSFETs, or detecting fan presence or chassis intrusion.
2 I/O2
General-Purpose Open-Drain Logic Input/Output 2. I/O2 is intended for driving LEDs, driving power-plane
switching MOSFETs, or detecting fan presence or chassis intrusion.
PIN
3 ADD0 SMBus Address Select Pin 0. See Table 11.
4 ADD1 SMBus Address Select Pin 1. See Table 11.
8 DXP
Combined Current Source and ADC Positive Input from Remote Diode. Place a 2200pF capacitor
between DXP and DXN for noise filtering.
7 DXN
Combined Current Sink and ADC Negative Input from Remote Diode. DXN is normally biased to a diode
voltage above ground.
6 AGND Analog Ground
5 ADD2 SMBus Address Select Pin 2. See Table 11.
13 SMBCLK SMBus Serial-Clock Input
12 PGND Power Ground
11 FAN
Fan-Control Logic Output. Swings from PGND to V
CC
in PWM mode, or PGND to 0.94 · V
CC
in DAC mode.
10 SYNC
Oscillator Synchronization Input. Connect to AGND to use internal clock. Capture range is 140kHz to
400kHz. The synchronization signal is internally applied to the FAN PWM clock. See Table 5 for synchro-
nized frequencies.
9 V
CC
Supply Voltage Input, +3V to +5.5V. Bypass to AGND with a 0.1µF capacitor.
16
OVERT
Active-Low, Open-Drain Thermostat Output. Activated by T
CRIT
threshold
15
ALERT
Active-Low, Open-Drain SMBus Alert (interrupt) Output
14 SMBDATA Open-Drain SMBus Serial-Data Input/Output