MAX6664AEE+ Maxim Integrated Products, MAX6664AEE+ Datasheet - Page 12

• Manufacturer Part Number: MAX6664AEE+
• Description: IC TEMP MON FAN CNTRL 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX6664AEE+

• Function: Fan Control, Temp Monitor
• Topology: ADC, Multiplexer, Register Bank, Tachometer
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 1 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 11 bit
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

measurement rate, which is controlled by bits [4:2] of
the fan-filter register (23h). Table 5 shows the effect of
the temperature measurement rate control bits. As an
example, assume that the temperature measurement
rate is 2Hz, or 0.5s per monitoring cycle, and the fan-fil-
ter rate is 0.416% per monitoring cycle. For the fan drive
to change from 50% to 100% requires 50% / 0.416% =
120 temperature monitoring cycles. Thus, for a tempera-
ture-monitoring cycle of 0.5s, the time required for the
drive to change from 50% to 100% is 60s.
The fan speed is measured by using the relatively slow
tachometer signal from the fan to gate an 11.25kHz
Temperature Monitors and
PWM Fan Controllers
Table 12. Spin-Up Time; Bits [2:0] Fan
Characteristics Register (20h)—POR = 101
Table 13. Fan Filter Ramp Rate; Bits [6:5]
Fan Filter Register (23h)—POR = 10;
Table 14. N Factor for Speed-Range Adjustment (Assuming Two Tachometer Pulses
per Revolution)
12
BIT 6
0
0
1
1
BIT 2
FAN CHARACTERISTICS REGISTER (20h) POR = 01
______________________________________________________________________________________
0
0
0
0
1
1
1
1
BIT 7
BIT 5
0
0
1
1
0
1
0
1
BIT 1
0
0
1
1
0
0
1
1
(x100% / 240)
RAMP RATE
Fan-Speed Measurement
1
2
4
8
BIT 0
0
1
0
1
0
1
0
1
(% DUTY CYCLE)
BIT 6
RAMP RATE
0
1
0
1
0.416
0.833
1.667
3.333
SPIN-UP
TIME (s)
0.2
0.4
0.6
0.8
1
2
4
8
clock frequency into a fan-speed counter. The mea-
surement is initialized on the starting edge of a PWM
output if fan-speed measurement is enabled by setting
bit 2 of configuration register 2 (01h) to 1. Counting
begins on the leading edge of the second tachometer
pulse and lasts for two tachometer periods or until the
counter overranges (255). The measurement repeats
unless monitoring is disabled by resetting bit 2 in the
configuration register 2 (01h). The measured result is
stored in the fan-speed reading register (08h).
The fan-speed count is given by:
The fan-speed count is given by:
where RPM = fan speed in RPM.
N determines the speed range and is programmed by
bits [7:6] in the fan characteristics register (20h) as
shown in Table 14. When the speed falls below the value
in the speed range column, a fan failure is detected.
The TACH/AIN input can be either a digital signal (from
the fan’s tachometer output) or an analog signal,
depending on the setting of bit 2 of the configuration
register 1 (00h). The default setting is zero, which sets
up TACH/AIN as a digital input. For the analog input
(Figure 4), the detected voltage threshold is typically at
250mV, which is appropriate for sensing the voltage of
a sense resistor connected to the ground lead of a 2-
wire fan. The AIN input only responds to pulse widths
greater than 10µs.
Figure 4. Simplified Tachometer Analog Input Structure
0.1µF
INPUT
TACH
N
1
2
4
8
VREF 2
100Ω
Count
VREF 1
=
SPEED RANGE (FAIL SPEED)
RPM
675 000
CLK
,
×
N
FF
(RPM)
2647
1324
662
331
MAX6653
MAX6663
MAX6664