ADM1034 datasheet(24/40 Pages) AD

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ADM1034

Rev. 0 | Page 24 of 40

Once the THERM limits are exceeded, the fans are boosted to

full speed—that is, as long as the Boost Disable Bit (Bit 1) is not

set in Configuration Register 2 (Address 0x02).

To configure THERM as an input, the user must set the

THERM timer bit (Bit 2) of Configuration Register 1 (Address

0x01) to 1. (It no longer operates as an output.) The ADM1034

can then detect when the THERM input is asserted low. This

may be connected to a trip point temperature sensor or to the

FAN_FAULT PROCHOT output of a CPU. With processor core

voltages reducing all the time, the threshold for the AGTL +

PROCHOT output also reduces down as new processors

become available. The default threshold on the input is the

normal CMOS threshold. However, Pin 8 (FAN_FAULT/REF)

can also be reconfigured as a REF input. This is done by setting

Bit 7 (FAN_FAULT/REF) in Configuration Register 4 (Address

0x04). Connect the processor VCCP to this input to provide a

reference for the THERM input. The resulting THERM

threshold is 0.75×VCCP, which is the correct threshold for an

AGTL+ signal.

The ADM1034 also measures assertion times on the THERM

input as a percentage of a time window. This time window is

programmable in Configuration Register 4 (Address 0x04) by

using Bits <6:4> (THERM % Time Window). Values between

0.25 seconds and 8 seconds are programmable. The assertion

time as a percentage of the time window is stored in the

THERM % On-Time Register (Address 0x4E).

A THERM % limit is also associated with this register. Once the

measured percentage exceeds the percentage limit, the THERM

% Exceeded Bit (Bit 4) in Status Register 2 (Address 0x50) is

asserted and an ALERT is generated, that is, if the mask bit is

not set. If the limit is set to 0x00, an ALERT is generated on the

first assertion. If the limit is set to 0xFF, an ALERT is never

generated. This is because 0xFF corresponds to the THERM

input, which is asserted continuously.

Table 24. THERM % On-Time Window

Code

THERM % On-Time Window

000

0.25 s

001

0.5 s

010

1 s

011

2 s

100

4 s

101

8 s

110

8 s

111

8 s

When THERM is configured as an input only, setting the Enable

THERM Events bits in Configuration Register 4 allows Pin 7 to

operate as an I/O.

The user can configure the THERM pin to be pulled low as an

output whenever the local temperature exceeds the local

THERM limit. To do this, set the Enable Local THERM events

bit (Bit 0) of Configuration Register 4 (Address 0x04).

The user can also configure the THERM pin to be pulled low as

an output whenever the Remote 1 temperature exceeds the

Remote 1 THERM limit. Set the Enable Remote 1 THERM

events bit (Bit 1) of Configuration Register 4 (Address 0x04).

The last option is to configure the THERM pin to be pulled low

as an output whenever the Remote 2 temperature exceeds the

Remote 2 THERM limit. Set the Enable Remote 2 THERM

events bit (Bit 2) of Configuration Register 4 (Address 0x04).

THERM % LIMIT REGISTER

The THERM % limit is programmed to Register 0x19. An

ALERT is generated, if THERM is asserted for longer than the

programmed percentage limit. The limit is programmed as a

percentage of the chosen time window.

THERM % limit register is an 8-bit register.

0x00 = 0%

0xFF = 100%

Therefore, 1 LSB = 0.39%.

Example

If a time window of 8 seconds is chosen, and an ALERT is to be

generated if THERM is asserted for more than 1 second,

program the following value to the limit register:

% Limit = 1/8 × 100 = 12.5%

12.5% / 0.39% = 32d = 0x20 = 0010 0000

An ALERT is generated if the THERM limit is exceeded after

the time window has elapsed, assuming it is not masked.

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