ADM1031ARQ-REEL7 ON Semiconductor, ADM1031ARQ-REEL7 Datasheet - Page 13

• Manufacturer Part Number: ADM1031ARQ-REEL7
• Description: IC SENSOR 2-TEMP/FAN CTRL 16QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1031ARQ-REEL7

• Rohs Status: RoHS non-compliant
• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 100°C, External Sensor
• Output Type: SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP

T
increases the T
speed) value, since T
that the PWM duty cycle vs. temperature slope remains
exactly the same. Changing the T
control slope. The T
Fan Spin−Up
section, once the temperature being measured exceeds the
T
(default = 33% duty cycle). However, the problem with fans
being driven by PWM is that 33% duty cycle is not enough
to reliably start the fan spinning. The solution is to spin the
fan up for a predetermined time, and once the fan has spun
up, its running speed can be reduced in line with the
temperature being measured.
and 8 seconds. Bits <2:0> of Fan Characteristics Register 1
(Register 0×20) and Fan Characteristic Register 2 (Register
0×21) program the fan spin−up times.
MIN
MIN
Figure 23 shows how, for a given T
As mentioned in the How Does the Control Loop Work?
The ADM1031 allows fan spin−up times between 200 ms
Figure 22. PWM Duty Cycle vs. Temperature Slope
100
Figure 23. Effect of Increasing T
value programmed, the fan turns on at minimum speed
100
93
87
80
73
66
60
53
47
40
33
value affects the loop. Increasing the T
93
87
80
73
66
60
53
47
40
33
T
T
MIN
0
MIN
0
5 10
MAX
20
20
MIN
MAX
(temperature at which the fan runs full
Control Loop
can be changed in increments of 4°C.
TEMPERATURE (°C)
(T
TEMPERATURE (°C)
= T
RANGE
MIN
40
40
MIN
+ T
)
RANGE
value merely shifts the
RANGE
T
T
T
T
T
T
MAX
RANGE
RANGE
RANGE
RANGE
RANGE
60
MIN
60
T
MAX
= T
T
. Note, however,
RANGE
Value on
= 5°C
= 10°C
= 20°C
= 40°C
= 80°C
= T
MIN
, changing the
MIN
+ T
= 40°C
MIN
+ T
RANGE
80
80
RANGE
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value
13
have been chosen, the ADM1031 device can be
programmed. The ADM1031 is placed into automatic fan
speed control mode by setting Bit 7 of Configuration
Register 1 (Register 0×00). The device powers up in
automatic fan speed control mode by default. The control
mode offers further flexibility in that the user can decide
which temperature channel/channels control each fan.
set to 1, increased flexibility is offered. The local and remote
temperature channels can have independently programmed
control loops with different control parameters. Whichever
control loop calculates the fastest fan speed based on the
temperature being measured, drives the fans.
cycle is determined by two independent control loops. This
is the type of auto mode fan behavior seen when Bit 5 and
Bit 6 of Configuration Register 1 are set to 11. Figure 24
shows the control loop for the local temperature channel. Its
T
value is 40°C. The local temperature’s T
Figure 25 shows the control loop for the remote temperature
channel. Its T
T
value is 80°C.
Both control loops calculate a PWM duty cycle of 66%.
Therefore, the fan is driven at 66% duty cycle. If both
temperature channels measure 20°C, the local channel
calculates 33% PWM duty cycle, while the Remote 1
channel calculates 50% PWM duty cycle. Thus, the fans are
driven at 50% PWM duty cycle. Consider the local
Table 5. Fan Spin−Up Times
Table 6. Auto Mode Fan Behavior
MIN
RANGE
Bits 6, 5
Bits 2:0
Once the automatic fan speed control loop parameters
When Bit 5 and Bit 6 of Configuration Register 1 are both
Figure 24 and Figure 25 show how the fan’s PWM duty
Consider if both temperature channels measure 40°C.
000
001
010
100
101
011
110
111
00
01
10
11
value has been programmed to 20°C, and its T
= 80°C. Therefore, the remote temperature’s T
Remote Temperature 1 Controls Fan 1
Remote Temperature 2 Controls Fan 2
Remote Temperature 1 Controls Fan 1 and 2
Remote Temperature 2 Controls Fan 1 and 2
Maximum Speed Calculated by Local and Remote
Temperature Channels Controls Fans 1 and 2
200 ms
400 ms
600 ms
800 ms
1 sec
2 sec (Default)
4 sec
8 sec
Control Operation (Configuration Register 1)
MIN
(Fan Characteristics Registers 1, 2)
value has been set to 0°C, while its
Spin−Up Time
MAX
is thus 60°C.
RANGE
MAX