Rainbow Electronics MAX1669 - Manual (Page 7)

MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
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_______________Detailed Description
The MAX1669 temperature sensor is designed to work
with an external microcontroller (µC) or other intelligent
devices in computer fan-control applications. The µC is
typically a power-management or keyboard controller,
generating SMBus serial commands by “bit-banging’’
general-purpose input/output (GPIO) pins or through a
dedicated SMBus interface block.
Essentially an 8-bit serial analog-to-digital converter
(ADC) with a sophisticated front end, the temperature
measurement channel contains a switched-current
source, a multiplexer, and an integrating ADC.
Temperature data from the ADC is loaded into a data
register, where it is automatically compared with data
previously stored in over/undertemperature alarm regis-
ters and the critical register (Figure 1).
MUX
REMOTE-TEMPERATURE
DATA REGISTER
HIGH-TEMPERATURE
THRESHOLD
LOW-TEMPERATURE
THRESHOLD
DIGITAL COMPARATOR
TEMPERATURE
TEMPERATURE SENSOR
T CRIT
COMMAND-BYTE
(INDEX) REGISTER
SMBDATA
SMBCLK
ADDRESS
DECODER
READ WRITE
CONTROL
LOGIC
CONTROL
LOGIC
SMB
ADD2
ADD1
ADD0
STATUS BYTE REGISTER
CONFIGURATION
BYTE REGISTER
ALERT RESPONSE
ADDRESS REGISTER
ADC
DXP
DXN
GND
V
CC
8
8
8
8 8
ALERT
MAX1669
S Q
R
CONTROL
LOGIC
OVERT
Q
R
S
GENERAL-PURPOSE
I/O CONTROLLER
-5°C
I/O1
I/O2
Figure 1. MAX1669 Temperature Sensor Functional Diagram