ADM1033ARQZ-REEL データシートの表示（PDF） - ON Semiconductor

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ADM1033ARQZ-REEL

Thermal Monitor and Fan Speed (RPM) Controller

ON Semiconductor 

ADM1033

Functional Description

The ADM1033 is a local− and remote−temperature

monitor and fan controller for use in a variety of

applications, including microprocessor−based systems. The

device accurately monitors remote and ambient temperature

and uses that information to quietly control the speed of a

cooling fan. Whenever a fan stalls, the device asserts a

FAN_FAULT output.

The ADM1033 features a THERM I/O. As an input, this

measures assertions on the THERM pin. As an output, it

asserts a low signal to indicate when the measured

temperature exceeds the programmed THERM temperature.

The ADM1033 communicates over an SMBus 2.0 interface.

Its LOCATION input determines which version of SMBus to

use, as well as the SMBus address (in fixed and discoverable

mode) and the LOCATION bits in the UDID (in

ARP−capable mode).

Internal Registers

Table 1 gives a brief description of the ADM1033’s

principal internal registers. For more detailed information

on the function of each register, refer to Table 31.

Serial Bus Interface

The ADM1033 communicates with the master via the

2−wire SMBus 2.0 interface. It supports two versions of

SMBus 2.0, determined by the value of the LOCATION

input’s resistors.

The first version is fully ARP−capable. This means that it

supports address resolution protocol (ARP), allowing the

master to dynamically address the device on powerup. It

responds to ARP commands such as “Prepare to ARP.”

The second SMBus version, fixed and discoverable, is

backwards compatible with SMBus 1.0 and 1.1. In this mode,

the ADM1033 powers up with a fixed address, which is

determined by the state of the LOCATION pin on powerup.

NOTE: When using the ADM1033, Addresses 0xC2 and

0xCA should not be used by any other device on the bus.

Location Input

The LOCATION input is a resistor divider input. It has

multiple functions and can specify the SMBus version (in

fixed and discoverable or ARP−capable modes); the SMBus

address (in fixed and discoverable mode); and the LLL bits

(in UDID in ARP−capable mode).

The voltage of this 8−level input is set by a potential

divider. The voltage on LOCATION is sampled on powerup

and digitized by the on−chip ADC to determine the

LOCATION input value. Because the LOCATION input is

sampled only at powerup, changes made while power is

applied have no effect.

VCC

R1

PIN 13

ADM1033

LOCATION

R2

GND

Figure 15. Bootstrapping the LOCATION Input

SMBus 2.0 ARP−Capable Mode

In ARP−capable mode, the ADM1033 supports features

such as address resolution protocol (ARP) and unique device

identifier (UDID). The UDID is a 128−bit message that

describes the ADM1033’s capabilities to the master. The

UDID also includes a vendor specific ID for functionally

equivalent devices.

VCC

ARP

LOCATION = 111 1.5kΩ

ARP

LOCATION = 110 1kΩ

ARP

LOCATION = 101 1kΩ

ARP

LOCATION = 100 1kΩ

FD

ADDRESS = 53h 1kΩ

FD

ADDRESS = 52h 1kΩ

FD

ADDRESS = 51h 1.5kΩ

FD

ADDRESS = 50h

GND

ADM1033 1

ADM1033 2

ADM1033 3

ADM1033 4

ADM1033 5

ADM1033 6

ADM1033 7

ADM1033 8

Figure 16. Setting Up Multiple ADM1033 Addresses

in SMBus 2.0 ARP−Capable Mode

In SMBus 2.0 mode, this vendor specific ID is generated

by an on−chip random number generator. This should enable

two adjacent ADM1033s in the same system to powerup

with a different vendor specific ID, allowing the master to

identify the two separate ADM1033’s and assign a different

address to each.

The state of the LOCATION input on powerup is also

reflected in the UDID. This is useful when there is more than

one ADM1033 in the system, so the master knows which one

it is communicating with. The complete UDID is listed in

Table 3.

The SMBus 2.0 master issues both general and directed

ARP commands. A general command is directed at all ARP

devices. A directed command is targeted at a single device

once an address has been established. The PEC byte must be

used for ARP commands. (Refer to the Packet Error

Checking (PEC) section.)

The ADM1033 responds to the following commands:

• Prepare to ARP (general)

• Reset device (general and directed)

• Get UDID (general and directed)

• Assign address (general)

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