ADM1029(2012) Просмотр технического описания (PDF) - ON Semiconductor

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ADM1029
(Rev.:2012)

Dual PWM Fan Controller and Temperature Monitor for High Availability Systems

ON Semiconductor 

ADM1029

1. Place the ADM1029 as close as possible to the

remote sensing diode. Provided that the worst

noise sources such as clock generators,

data/address buses, and CRTs are avoided, this

distance can be 4 to 8 inches.

2. Route the D+ and D– tracks close together, in

parallel, with grounded guard tracks on each side.

Provide a ground plane under the tracks if

possible.

3. Use wide tracks to minimize inductance and

reduce noise pickup. Ten mil track minimum

width and spacing is recommended.

GND

D+

D−

GND

10 MIL

10 MIL

10 MIL

10 MIL

10 MIL

10 MIL

10 MIL

Figure 22. Arrangement of Signal Tracks

4. Try to minimize the number of copper/solder

joints, which can cause thermocouple effects.

Where copper/solder joints are used, make sure

that they are in both the D+ and D– path and at the

same temperature.

Thermocouple effects should not be a major

problem as 1C corresponds to about 240 mV, and

thermocouple voltages are about 3 mV/C of

temperature difference. Unless there are two

thermocouples with a big temperature differential

between them, thermocouple voltages should be

much less than 200 mV.

5. Place 0.1 mF bypass and 1000 pF input filter

capacitors close to the ADM1029.

6. If the distance to the remote sensor is more than

8 inches, the use of twisted pair cable is

recommended. This will work up to about

6 to 12 feet.

7. For really long distances (up to 100 feet), use

shielded twisted pair such as Belden #8451

microphone cable. Connect the twisted pair to D+

and D– and the shield to GND close to the

ADM1029. Leave the remote end of the shield

unconnected to avoid ground loops.

Because the measurement technique uses switched

current sources, excessive cable and/or filter capacitance

can affect the measurement. When using long cables, the

filter capacitor may be reduced or removed.

Cable resistance can also introduce errors. 1 W series

resistance introduces about 0.5C error.

Temperature-related Registers

Table 7 is a list of registers on the ADM1029 that are

specific to temperature measurement and control.

Table 7. TEMPERATURE-SPECIFIC REGISTERS

Address

Description

0x06

0x30

0x31

0x32

0x40

0x41

0x42

0x48

0x49

0x4A

0x80

0x81

0x82

0x88

0x89

0x8A

0x90

0x91

0x92

0x98

0x99

0x9A

0xA0

0xA1

0xA2

Temp Devices Installed

Local Temp Offset

Remote 1 Temp Offset

Remote 2 Temp Offset

Local Temp Fault Action

Remote 1 Temp Fault Action

Remote 2 Temp Fault Action

Local Temp Cooling Action

Remote 1 Temp Cooling Action

Remote 2 Temp Cooling Action

Local Temp TMIN

Remote 1 Temp TMIN

Remote 2 Temp TMIN

Local Temp TRANGE/THYST

Remote 1 Temp TRANGE/THYST

Remote 2 Temp TRANGE/THYST

Local Temp High Limit

Remote 1 Temp High Limit

Remote 2 Temp High Limit

Local Temp Low Limit

Remote 1 Temp Low Limit

Remote 2 Temp Low Limit

Local Temp Value

Remote 1 Temp Value

Remote 2 Temp Value

The flowchart in Figure 23 shows how to configure the

ADM1029 to measure temperature. It also shows how to

configure the ADM1029’s behavior for out-of-limit

temperature measurements.

Fan Interfacing

The ADM1029 can be interfaced to many types of fan. It

can be used to control the speed of a simple two-wire fan. It

can measure the speed of a fan with a tach output, and it can

accept a logic input from fans with a FAULT output. By

means of a shorting link in the fan connector it can also

determine if a fan is present or not and if fans have been

hot-swapped.

The ADM1029 can control or monitor one or two fans.

Bits 0 and 1 of the Fans Supported In System Register (03h)

tell the ADM1029 how many fans it should be

controlling/monitoring.

In the following descriptions “installed” means that the

corresponding bit of register 03h is set and the ADM1029

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