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PDF MAX6638 Data sheet ( Hoja de datos )
| Número de pieza | MAX6638 | |
| Descripción | Temperature Monitor | |
| Fabricantes | Maxim Integrated Products | |
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19-3895; Rev 1; 1/06
Temperature Monitor with
Dual Serial Interface
General Description
The MAX6638 thermal-management sensor includes
internal (local) and external (remote) digital temperature
sensors and two independent SMBus™ serial ports. The
remote temperature accuracy is ±1.0°C, and the local
temperature accuracy is ±2°C. The MAX6638 also fea-
tures extended temperature resolution data available in
0.125°C increments.
The MAX6638 provides three system alarms: channel 1
alert (ALERT1), overtemperature (OVERT1), and chan-
nel 2 alert (ALERT2) that contain programmable thresh-
olds set independently by each of the SMBus serial
ports (SMBus1 and SMBus2). Each alert output asserts
when any of four temperature conditions is violated:
local overtemperature, remote overtemperature, local
undertemperature, or remote undertemperature. The
overtemperature signal asserts when the temperature
rises above the value in the overtemperature limit regis-
ter. Use the OVERT1 output to activate a cooling fan or
trigger a system shutdown.
Each of the 2-wire serial-interface ports accepts stan-
dard System Management Bus (SMBus) write byte, read
byte, send byte, and receive byte commands indepen-
dently of one another with total collision avoidance han-
dled by the MAX6638. Each SMBus can operate its own
unique serial-data rate to access any register in the
MAX6638 for data reads or data writes. The MAX6638
manages all dual-port data register access functions
providing a seamless, conflict-free integration into a
multimaster architecture for thermal management.
The MAX6638 performs measurements autonomously,
at the programmed conversion rate, or in a single-con-
version mode. Each SMBus port can set the conversion
rate with the higher conversion and update rate domi-
nating the average power-supply current. Single-con-
version requests have a maximum delay of two
conversion cycles with channel-conversion manage-
ment and cycling regulated by the dual-port controller.
The MAX6638 operating temperature range is -40°C to
+125°C and measures temperatures between 0°C and
+145°C. The MAX6638 is available in a 16-pin, 4mm x
4mm TQFN with exposed paddle package.
Graphics Cards
Applications
Notebook Computers
Computer Motherboard Systems
Desktop Computers
Workstations
Features
♦ Two Independent SMBus/I2C*-Compatible
Interfaces with Collision Avoidance
♦ High Accuracy
±1.0°C from +85°C to +100°C (Remote)
♦ Remote and Local Temperature Measurements
♦ Three Programmable Output Alarms: ALERT1,
OVERT1, and ALERT2
♦ Programmable Conversion Rates
♦ 11-Bit Low-Noise Integrating ADC
♦ No Calibration Required
♦ Autoscan Conversions
Ordering Information
PART
TEMP
RANGE
PIN-
PACKAGE
16 TQFN-EP*
MAX6638ATE+ -40°C to +125°C (4mm x 4mm)
PKG
CODE
T1644-4
*EP = Exposed paddle.
+Denotes lead-free package.
Pin Configuration
TOP VIEW
12 11 10 9
N.C. 13
ALERT2 14
SDA2 15
MAX6638
SCK2 16 +
1234
8 GND
7 N.C.
6 I.C.
5 N.C.
TQFN-EP
Typical Operating Circuit appears at end of data sheet.
SMBus is a trademark of Intel Corporation.
*Purchase of I2C components from Maxim Integrated Products,
Inc., or one of its sublicensed Associated Companies, conveys
a license under the Philips I2C Patent Rights to use these com-
ponents in an I2C system, provided that the system conforms to
the I2C Standard Specification as defined by Philips.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
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Temperature Monitor with
Dual Serial Interface
Pin Description
PIN
1
2
3
4
5, 7, 12, 13
6
8
9
10
11
14
15
16
EP
NAME
VCC
DXP
DXN
OVERT1
N.C.
I.C.
GND
ALERT1
SDA1
SCK1
ALERT2
SDA2
SCK2
GND
FUNCTION
Supply Voltage. Bypass VCC to GND with a 0.1µF capacitor. A 47Ω series resistor is recommended for
additional noise filtering, but not required.
Combined Current Source and ADC Positive Input for Remote Diode. If a remote-sensing junction is not
used, connect DXP to DXN.
Combined Current Sink and ADC Negative Input for Remote Diode. DXN is internally biased to a diode
voltage above ground.
Digital Open-Drain Output. OVERT1 indicates an overtemperature condition on channel 1.
No Connection. Not connected internally.
Internally Connected. I.C. must be connected to GND.
Power-Supply Ground
Digital Open-Drain Output. ALERT1 indicates alert condition on channel 1.
SMBus Data Channel 1. Open-drain output.
SMBus Clock Channel 1
Digital Open-Drain Output. ALERT2 indicates alert condition on channel 2.
SMBus Data Channel 2. Open-drain output.
SMBus Clock Channel 2
Ground. Connect to ground.
Detailed Description
The MAX6638 temperature monitor features dual-port
SMBus access for use in thermal management of
graphics processing unit (GPU) and CPU systems.
Each of the two SMBus serial ports can be accessed
independently by two thermal-monitoring systems with
all dual-port collision-avoidance logic controlled by the
MAX6638. Each SMBus thermal-monitoring channel
(channels 1 and 2) has a corresponding over/under-
temperature ALERT_ open-drain output with indepen-
dently configurable limit registers. Channel 1 includes
an overtemperature indicator (OVERT1) with an initial
set-point limit that is always activated after a power-on
reset (POR). The initial OVERT1 set point can be over-
written after POR by SMBus1 serial programming. The
overtemperature alarm OVERT1 asserts if the set-point
limit is exceeded.
ADC and Multiplexer
The MAX6638 converts temperatures to digital data
either at a programmed rate or in single conversions.
Either SMBus controller can set the programmed rate
with the higher rate setting taking precedence. The
MAX6638 begins conversions at the maximum rate
after POR to provide the OVERT1 output signal asser-
tion for temperatures exceeding the set-point limit. The
temperature conversion results of the two temperature
channels are in integer format. The MSBs of the tem-
perature data are in 8-bit registers (addresses 00h and
01h; see Table 1) that represent the data as 8 bits with
the full-scale reading to indicate a diode fault. The
remaining 3 bits of temperature data are available in
the extended data-registers format with the LSB equal
to +0.125°C (addresses 11h and 10h; see Table 2).
The converted readings are stored in SMBus reading
registers along with the limit-value registers and other
control functions.
Table 1. Temperature Data Format
(RLTS1, RRTS1, RLTS2, RRTS2)
TEMPERATURE
(°C)
+145
+130
+128
+25
0
<0
Diode fault
DIGITAL OUTPUT DIGITAL OUTPUT
(hex)
(bin)
91 1001 0001
82 1000 0010
80 1000 0000
19 0001 1001
00 0000 0000
00 0000 0000
FF 1111 1111
_______________________________________________________________________________________ 5
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Temperature Monitor with
Dual Serial Interface
lack the complex logic needed to be a bus master.
Upon receiving an ALERT_ interrupt signal, the host
master can broadcast a receive-byte transmission to
the alert-response slave address (0001 100). Following
such a broadcast, any slave device generating an
interrupt attempts to identify itself by putting its own
address on the bus.
The alert response can activate several different slave
devices simultaneously. If more than one slave
attempts to respond, bus arbitration rules apply, and
the device with the lower address code wins. The los-
ing device does not generate an acknowledge
response and continues to hold the ALERT_ line low
until cleared. Successful completion of the read alert-
response protocol clears the interrupt latch, provided
the condition that caused the alert no longer exists.
Overtemperature Limit Output
OVERT1 asserts when the temperature rises to a value
stored in one of the OVERT1 limit registers (19h and
20h). It deasserts when the temperature drops below
the stored limit, minus hysteresis. OVERT1 can be used
to activate a cooling fan, send a warning, invoke clock
throttling, or trigger a system shutdown to prevent com-
ponent damage.
Command-Byte Functions
The 8-bit command-byte register (Table 3) is the mas-
ter index that points to the various other registers within
the MAX6638. The register’s POR state is 0000 0000,
so a receive-byte transmission (a protocol that lacks
the command byte) that occurs immediately after POR
returns the current local-temperature data.
One-Shot Conversion Cycle
The one-shot command immediately forces a new con-
version cycle to begin. If the MAX6638 receives a one-
shot command while the MAX6638 is in standby mode
(RUN = 1), a new conversion begins, after which the
device returns to standby mode. If during a conversion
the MAX6638 receives a one-shot command, the
MAX6638 ignores the command; however, the results of
the conversion in progress update the data registers
accordingly.
Configuration-Byte Functions
The configuration-byte register (Tables 3 and 5) is a
read-write register with several functions. Bit 7 masks
interrupts. Bit 6 puts the MAX6638 into a standby (STOP)
mode or autonomous (RUN) mode. The MAX6638 enters
standby mode when both SMBus controllers set the cor-
responding configuration bits.
Status-Byte Functions
The status-byte register (Tables 3 and 4) indicates
when any temperature threshold is exceeded. This byte
also indicates whether the ADC is converting and if
there is a fault detected in the external sense diode.
After POR, the state of the flag bits are zero, assuming
no alarm conditions are present. The status byte clears
with any successful read of the status byte, after com-
pletion of a conversion and if the fault condition no
longer exists. Note that the ALERT_ interrupt latch does
not automatically clear when the status-flag bit indicat-
ing the ALERT_ clears.
Registers
The internal registers of the MAX6638 are all 8-bit data
word width and are all accessible through SMBus by
read and write operations.
______________________________________________________________________________________ 11
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| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet MAX6638.PDF ] | |
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