ADM1033
http://onsemi.com
8
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 5 gives a brief description of the ADM1033’s
principal internal registers. For more detailed information
on the function of each register, refer to Table 35.
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).
Figure 15. Bootstrapping the LOCATION Input
ADM1033
PIN 13
V
CC
GND
R1
R2
LOCATION
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.
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.
Figure 16. Setting Up Multiple ADM1033 Addresses
in SMBus 2.0 ARP-capable Mode
ADM1033 1
V
CC
GND
ARP
LOCATION = 111
1.5 kW
ADM1033 2
ADM1033 3
ADM1033 4
ADM1033 5
ADM1033 6
ADM1033 7
ADM1033 8
ARP
LOCATION = 110
1 kW
ARP
LOCATION = 101
1 kW
ARP
LOCATION = 100
1 kW
FD
ADDRESS = 53h
1 kW
FD
ADDRESS = 52h
1 kW
FD
ADDRESS = 51h
1.5 kW
FD
ADDRESS = 50h
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 7.
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.)
