ADM1034ARQZ-R7 ON Semiconductor, ADM1034ARQZ-R7 Datasheet - Page 24

• 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

Fan Response Register
the current fan speed, comparing it with the programmed fan
speed, and then updating the drive signal applied to the fan.
The rate at which the ADM1034 looks at and updates the
drive signal is determined by the fan response register.
Different fans have different inertias and respond to a
changing drive signal more or less quickly than others. The
fan response register allows the user to tailor the ADM1034
to a particular fan to prevent situations like overshoot.
can make to the drive signal per second. Table 23 lists the
available options.
Look−Up Table: Modes of Operation
operation used to determine the behavior of the system:
•
•
Manual Mode
The software can program the required fan speed value or
the target fan speed to the ADM1034, which then outputs
that fan speed.
Table 23. Fan Response Codes
Table 24. Conversion Rates
The ADM1034 fan speed controller operates by reading
The user programs the number of updates the ADM1034
The ADM1034 look−up table has two different modes of
In manual mode, the ADM1034 is under software control.
Manual mode
Look−up table
Code
<6:4>
<2:0>
Bit #
000
001
010
011
100
101
110
111
7
3
1.25 updates/second
2.5 updates/second = default
5 updates/second
10 updates/second
20 updates/second
40 updates/second
80 updates/second
160 updates/second
Fan 2 Response
Fan 1 Response
Update Rate
Function
Reserved
Reserved
http://onsemi.com
24
Programming Target Fan Speed
TACH count for N poles or a TACH count for one full
rotation of the fan, assuming the number of poles is
programmed correctly in the Configuration 3 Register
(Address 0x03).
Example 1: If the desired speed for Fan 1 is 5000 rpm,
program the following value to the TACH count registers:
Example 2: If the desired speed for Fan 2 is 3500 rpm,
program the following value to the TACH pulse period
registers:
Look−Up Table
temperature−to−fan speed profile. There are 24 registers in
the look−up table; 8 for temperature and 16 for target fan
speed (each target fan speed is two registers). In total, there
are eight available points. In the default configuration, four
of these are for Fan 1 and four are for Fan 2. However, it can
be configured such that eight points are available and both
fans run from the same table.
table. The ADM1034 can be programmed to make the fan
speed run at discrete speeds and jump to the new fan speed
once the temperature threshold is crossed. Or, it can linearly
ramp the TACH count between the two temperature
thresholds.
Table 25. Registers to be Programmed
Fan 1
Fan 1
Fan 2
Fan 2
In this mode, the user programs the target fan speed as a
Use the following steps to program the target fan speed:
where:
The ADM1034 allows the user to program a
There are two options when programming the look−up
Fan
TACH Count = (f x 60)/R
f = clock frequency = 81.92 kHz
R = required RPM value
TACH Count = (f x 60)/5000
TACH Count = 983d = 0x03D7
TACH Count = (f x 60)/3500
TACH Count = 1404d = 0x057C
1. Place the ADM1034 into manual mode. Set Bit 7
2. Program the target TACH count (fan speed) using
(Table/SW) of Configuration Register 1
(Address 0x01) = 0.
the following equation:
Look−Up Table FS1, MSB
Look−Up Table FS2, MSB
Look−Up Table FS1, LSB
Look−Up Table FS2, LSB
Description
Address
0x2C
0x2D
0x2A
0x2B
Value
0xD7
0x7C
0x03
0x05