ADM1030ARQ-REEL ON Semiconductor, ADM1030ARQ-REEL Datasheet - Page 12

• Manufacturer Part Number: ADM1030ARQ-REEL
• Description: IC SNSR TEMP/FAN PWM CTRL 16QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1030ARQ-REEL

• 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

ADM1030
AUTOMATIC FAN SPEED CONTROL
The ADM1030 has a local temperature channel and a remote
temperature channel, which may be connected to an on-chip
diode-connected transistor on a CPU. These two temperature
channels may be used as the basis for an automatic fan speed
control loop to drive a fan using Pulsewidth Modulation (PWM).
HOW DOES THE CONTROL LOOP WORK?
The Automatic Fan Speed Control Loop is shown in Fig-
ure 6 below.
In order for the fan speed control loop to work, certain loop
parameters need to be programmed into the device.
1. T
2. T
3. T
4. A hysteresis value of 5 C is included in the control loop to
Figure 7 shows the different control slopes determined by the
T
T
can be seen how changing the T
duty cycle versus temperature slope.
RANGE
MIN
and run at minimum speed. The fan will only turn on once
the temperature being measured rises above the T
programmed. The fan will spin up for a predetermined time
(default = 2 secs). See Fan Spin-Up section for more details.
will automatically adjust the fan speed. As the temperature
increases beyond T
increased accordingly. The T
the fan speed versus temperature slope of the control loop.
mum speed. At this temperature, the PWM duty cycle
driving the fan will be 100%. T
T
T
a register on-chip.
prevent the fan continuously switching on and off if the tem-
perature is close to T
such time as the temperature drops 5 C below T
SPEED
FAN
MIN
RANGE
MAX
RANGE
RANGE
MAX
MIN
was set to 0 C to start all slopes from the same point. It
. The temperature at which the fan should switch on
value chosen, and programmed into the ADM1030.
. The temperature at which the fan will be at its maxi-
. The temperature range over which the ADM1030
Figure 6. Automatic Fan Speed Control
. Since this parameter is the sum of the T
parameters, it does not need to be programmed into
SPIN UP FOR 2 SECONDS
MIN
MIN
, the PWM_OUT duty cycle will be
. The fan will continue to run until
TEMPERATURE
T
MIN
RANGE
RANGE
MAX
parameter actually defines
value affects the PWM
is given by T
T
MAX
= T
MIN
+ T
Rev. 2 | Page 12 of 29 | www.onsemi.com
MIN
MIN
RANGE
MIN
MIN
.
and
value
+
–12–
Figure 8 shows how, for a given T
value affects the loop. Increasing the T
the T
since T
Duty Cycle vs Temperature slope remains exactly the same.
Changing the T
T
FAN SPIN-UP
As was previously mentioned, once the temperature being mea-
sured exceeds the T
at minimum speed (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 may be reduced in line with the
temperature being measured.
The ADM1030 allows fan spin-up times between 200 ms and
8 seconds. Bits <2:0> of Fan Characteristics Register 1 (Register
0x20) program the fan spin-up time.
Figure 7. PWM Duty Cycle vs. Temperature Slopes (T
Figure 8. Effect of Increasing T
MIN
100
100
93
87
80
73
66
60
53
47
40
33
93
87
80
73
66
60
53
47
40
33
T
T
MIN
MIN
0
0
MAX
may be changed in increments of 4 C.
MAX
5
(temperature at which the fan runs full speed) value,
10
= T
MIN
MIN
20
20
+ T
value merely shifts the control slope. The
MIN
RANGE
value programmed, the fan will turn on
TEMPERATURE –
TEMPERATURE –
. Note, however, that the PWM
40
40
RANGE
MIN
Value on Control Loop
MIN
, changing the T
�
�
C
C
value will increase
T
T
MAX
MAX
60
60
= T
= T
MIN
MIN
+ T
+ T
RANGE
RANGE
MIN
REV. A
RANGE
80
80
)