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

12 V

TACH

OUTPUT

PULL-UP

TYP < 1 kW

OR TOTEM-POLE

R1

10 kW

TACH1

OR

TACH 2

ZD1*

ZENER

VCC

FAN SPEED

COUNTER

* Choose ZD1 Voltage Approx. 0.8  VCC

Figure 27. Fan with Strong Tach. Pull-up to > VCC or

Totem-pole Output, Clamped with Zener and Resistor

12 V

VCC

< 1 kW

TACH

OUTPUT

R1*

TACH1

OR

TACH 2

R2*

FAN SPEED

COUNTER

* See Text

Figure 28. Fan with Strong Tach. Pull-up to > VCC or

Totem-pole Output, Attenuated with R1/R2

Fan Speed Control

Fan speed is controlled using pulsewidth modulation

(PWM). The PWM outputs (Pins 1 and 24) give a pulse

output with a programmable frequency (default 250 Hz) and

a duty-cycle defined by the contents of the relevant fan speed

register, or by the automatic fan speed control when this

mode is enabled. The speed at which a fan runs is determined

by fault conditions and the settings of various control and

mask registers.

A fan can only be driven if it is defined as being supported

by the controller in register 02h. The ADM1029 supports up

to two fans, so Bits 0 and 1 of this register are permanently

set. This register is read-only.

A fan will only be driven if it is defined as being supported

by the system in register 03h. If Bit 0 of this register is set,

it indicates that Fan 1 is installed. This is the power-on

default. If Bit 1 is set, it indicates that Fan 2 is installed. This

bit is set by the state of Pin 18 at power-up. This register is

read/write and the default/power-on setting can be

overwritten. If a fan is not supported in register 03h it will

not be driven, even if it is physically installed.

The PWM outputs are open-drain outputs. They require

pull-up resistors and must be amplified and buffered to drive

the fans.

Minimum Speed

The normal operating fan speed is set by the four LSBs of

the Fan 1 and Fan 2 Minimum/Alarm Speed Registers

(addresses 60h, 61h). These bits also set the minimum speed

at which a fan will run in automatic control mode. These bits

should be set to 05h. This corresponds to 33% PWM

duty-cycle, which is the lowest speed at which most fans will

run reliably.

Fan(s) will run at minimum speed if there is no fault

condition, automatic fan speed is disabled, and there are no

other overriding conditions.

Alarm Speed

Alarm speed is set by the four MSBs of the Fan 1 and

Fan 2 Minimum/Alarm Speed Registers (addresses 60h,

61h). Fan(s) will run at alarm speed if any of the following

conditions occurs, assuming the condition has not been

masked out using the Fan Event Mask Registers:

 Setting Bit 0 of register 07h forces Fan 1 to run at alarm

speed (Set Fan x Alarm Speed Register).

 Setting Bit 1 of register 07h forces Fan 2 to run at alarm

speed (Set Fan x Alarm Speed Register).

If monitoring is disabled by clearing Bit 4 of the

Configuration Register, all fans controlled by the

ADM1029 will run at alarm speed.

 When a GPIO pin is configured as an input by setting

Bit 0 of the corresponding GPIO Behavior Register,

and Bit 4 of the GPIO Behavior Register is also set, all

fans controlled by the ADM1029 will go to alarm speed

when the logic input is asserted (high or low, depending

on the polarity bit, Bit 1 of the corresponding GPIO

Behavior Register).

 If Bit 7 of a Fan Fault Action Register is set

(18h − Fan 1, 19h − Fan 2) the corresponding fan will

go to alarm speed when CFAULT is pulled low by an

external source.

 If a tach measurement exceeds the set limit, all fans

controlled by the ADM1029 will run at alarm speed.

 If a fan fault input pin is asserted (low), all fans

controlled by the ADM1029 will run at alarm speed.

 If Bit 1 of a Temp. Fault Action Register is set

(40h − Local Sensor, 41h − Remote 1, 42h − Remote 2),

all fans controlled by the ADM1029 will go to alarm

speed if the corresponding temperature high limit is

exceeded.

 If Bit 5 of a Temp. Fault Action Register is set, all fans

controlled by the ADM1029 will go to alarm speed if a

temperature input crosses the corresponding

temperature low limit, the direction depending on the

setting of Bit 3 of the Temp. Control register.

(0 = alarm when input goes below low limit, 1 = alarm

when input goes above low limit).

 If Bit 1 of an AIN Behavior Register is set

(50h − AIN0, 51h − AIN1), all fans controlled by the

ADM1029 will go to alarm speed if the corresponding

AIN high limit is exceeded.

 If Bit 5 of an AIN Behavior Register is set, all fans

controlled by the ADM1029 will go to alarm speed if

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