ADM1029ARQZ-R7 datasheet(7/50 Pages) ONSEMI

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TEMPERATURE

– C

0.05

0.00

–0.05

–0.10

–0.15

–0.20

–0.25

–0.30

–0.35

–0.40

–0.45

–0.50

–0.55

–0.60

100

105

120

TPC 13. Local Temperature Error

PRODUCT DESCRIPTION

The ADM1029 is a versatile fan controller and monitor for use

in personal computers, servers, telecommunications equipment,

or any high-availability system where reliable control and moni-

toring of multiple cooling fans is required. Each ADM1029 can

control the speed of one or two fans and can measure the speed

of fans that have a tachometer output. The ADM1029 can also

measure the temperature of one or two external sensing diodes

or an internal temperature sensor, allowing fan speed to be

adjusted to keep system temperature within acceptable limits. The

ADM1029 has FAULT inputs for use with fans that can signal

failure conditions, and inputs to detect whether or not fans are

connected.

The ADM1029 communicates with the host processor over an

System Management (SMBus) serial bus. It supports eight

different serial bus addresses, so that up to eight devices can

be connected to a common bus, controlling up to sixteen fans.

This makes software support and hardware design scalable.

The ADM1029 has an interrupt output (INT) that allows it

to signal fault conditions to the host processor. It also has a

separate, cascadable fault output (CFAULT) that allows the

ADM1029 to signal a fault condition to other ADM1029s.

The ADM1029 has a number of useful features including an

automatic fan speed control option implemented in hardware

with no software requirement, automatic use of backup fans in

the event of fan failure, and supports hot-swapping of failed fans.

FUNCTIONAL DESCRIPTION

SERIAL BUS INTERFACE

Control of the ADM1029 is carried out via the serial bus. The

ADM1029 is connected to this bus as a slave device, under the

control of a master device.

The ADM1029 has a 7-bit serial bus address. The four MSBs of

the address are set to 0101. The three LSBs can be set by the

user to give a total of eight different addresses, allowing up to

eight ADM1029s to be connected to a single serial bus segment.

To minimize device pin count and size, the three LSBs are set

using a single pin (ADD, Pin 15). This is an 8-level input whose

input voltage is set by a potential divider. The voltage on ADD

is sampled immediately after power-up and digitized by the

on-chip ADC to determine the value of the 3 LSBs. Since ADD

is sampled only at power-up, any changes made while power is

on will have no effect.

ADM1029

ADD

VCC

GND

Figure 2. Setting the Serial Address

Table I shows resistor values for setting the 3 LSBs of the serial

bus address. The same principle is used to set the voltage on Pin

18 (TMIN/INSTALL), which controls the automatic fan speed

control function, and also tells the ADM1029 how many fans

should be installed, as described later.

If several ADM1029s are used in a system, their ADD inputs

can tap off a single potential divider, as shown in Figure 3.

ADD

ADDRESS XXXX000

ADDRESS XXXX001

ADDRESS XXXX111

ADDRESS XXXX110

ADDRESS XXXX101

ADDRESS XXXX100

ADDRESS XXXX011

ADDRESS XXXX010

VCC

GND

1.5k

ADM1029 #1

ADM1029 #2

ADM1029 #3

ADM1029 #4

ADM1029 #5

ADM1029 #6

ADM1029 #7

ADM1029 #8

Figure 3. Setting Address of up to Eight ADM1029s

ADM1029

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