ADM1034ARQZ-R7 ON Semiconductor, ADM1034ARQZ-R7 Datasheet - Page 25

• Manufacturer Part Number: ADM1034ARQZ-R7
• Description: IC THERM/FAN SPEED CTLR 16-QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1034ARQZ-R7

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: 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
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

looks like if all eight points are used on the one curve for both
fans.
programmed to run at discrete speeds. The ADM1034 spins
the fan at its new speed once a threshold is crossed.
Speeds option is chosen. At temperature T1, the fan runs at
Fan Speed 1. As the temperature increases, the fan speed
increases until it reaches Fan Speed 2 at T2.
point in the look−up table, the fan speed remains at the
highest speed until the temperature drops below the T7
temperature value. When the look−up table is split in two,
the same applies.
succession, the fan speed moves to the next highest
programmed temperature as the temperature increases.
Similarly, when the temperature decreases, it ignores
programmed higher temperatures and jumps to the next lower
temperature. Therefore, the temperature−to−fan speed profile
for increasing and decreasing temperature can be different.
option to use between two and eight points for each fan
(eight points only if the same curve is to be used for both
fans). If the user just wants to program a transfer curve (and
Figure 41. Programming the Look−Up Table in Linear
TACH COUNT 8
TACH COUNT 7
TACH COUNT 6
TACH COUNT 5
TACH COUNT 4
TACH COUNT 3
TACH COUNT 2
TACH COUNT 1
TACH COUNT 8
TACH COUNT 7
TACH COUNT 6
TACH COUNT 5
TACH COUNT 4
TACH COUNT 3
TACH COUNT 2
TACH COUNT 1
Figure 40 and Figure 41 show what the look−up table
Figure 40 shows the transfer curve when the fan is
Figure 41 shows the transfer curve if the Linear Fan
Once the temperature exceeds the highest temperature
If the temperatures in T1 to T8 are not programmed in
When programming the look−up table, the user has the
Figure 40. Programming the Look−Up Table in
FAN SPEED
FAN SPEED
Discreet Fan Speeds Mode
T1
T1
Fan Speeds Mode
T2
T2
T3
T3
T4
T4
T5
T5
T6
T6
T7
T7
TEMPERATURE
TEMPERATURE
T8
T8
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25
knows the starting temperature, minimum speed, maximum
temperature, and maximum speed), then all the user needs
to program are four parameters: T1, T2, FS1, and FS2. The
remainder of the look−up temperature thresholds should
remain at their default values of +191°C. If required, the FS3
should be programmed with the same value as FS2 to give
the flat curve, if required. Or, the fan speeds can be left at the
default value of 0. However, it is normal to program a
THERM limit as well. Once this temperature is exceeded
and the boost bit is set, the fans run to full speed. This
overrides the look−up table.
Setting Up the Size of the Look−Up Table
are used for each fan.
the table are used for both fans.
Setting Up the Look−Up Table in Linear Mode
the TACH count decreases linearly (and therefore the fan
speed increases) with temperature.
speed increases with temperature to FS
T
When Discrete/Linear Speed (Bit 2) is set to 0, the fan runs
at a new speed once the temperature threshold is exceeded.
Table 26. Look−Up Table Register Address
X+1
TACH COUNT 2 TO 8
x
1
2
3
4
5
6
7
8
When 4:8 Look−Up (Bit 3)is set to 0 (default), four points
When 4:8 Look−Up (Bit 3) is set to 1, all eight points on
When Discrete/Linear Speed (Bit 2) is set to 1 (default),
Example: At temperature T
Alternatively, the fan can be run at discrete fan speeds.
.
TACH COUNT 1
Figure 42. Programming Two Points on the
FAN SPEED
Temperature, x
0x22
0x23
0x24
0x25
0x26
0x27
0x28
0x29
Look−Up Table
T1
TEMPERATURE
X
, the fans run at FS
FSx, LSB
0x2A
0x2C
0x2E
0x30
0x32
0x34
0x36
0x38
T2
X+1
at temperature
FSx, MSB
T (3 TO 8) = °C
0x2B
0x2D
0x2F
0x31
0x33
0x35
0x37
0x39
X
and fan