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PDF MAX6648 Data sheet ( Hoja de datos )
| Número de pieza | MAX6648 | |
| Descripción | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms | |
| Fabricantes | Maxim Integrated | |
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19-2545; Rev 1; 10/02
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
General Description
The MAX6648/MAX6692 are precise, two-channel digi-
tal temperature sensors. They accurately measure the
temperature of their own die and a remote PN junction,
and report the temperature in digital form using a 2-wire
serial interface. The remote PN junction is typically the
emitter-base junction of a common-collector PNP on a
CPU, FPGA, or ASIC.
The 2-wire serial interface accepts standard System
Management Bus (SMBus)™ write byte, read byte,
send byte, and receive byte commands to read the
temperature data and to program the alarm thresholds.
To enhance system reliability, the MAX6648/MAX6692
include an SMBus timeout. A fault queue prevents the
ALERT and OVERT outputs from setting until a fault has
been detected one, two, or three consecutive times
(programmable).
The MAX6648/MAX6692 provide two system alarms:
ALERT and OVERT. ALERT asserts when any of four tem-
perature conditions are violated: local overtemperature,
remote overtemperature, local undertemperature, or
remote undertemperature. OVERT asserts when the tem-
perature rises above the value in either of the two OVERT
limit registers. The OVERT output can be used to activate
a cooling fan, or to trigger a system shutdown.
Measurements can be done autonomously, with the
conversion rate programmed by the user, or in a single-
shot mode. The adjustable conversion rate allows the
user to optimize supply current and temperature
update rate to match system needs.
Remote accuracy is ±0.8°C maximum error between
+25°C and +125°C with no calibration needed. The
MAX6648/MAX6692 operate from -55°C to +125°C, and
measure temperatures between 0°C and +125°C. The
MAX6648 is available in an 8-pin µMAX package, and the
MAX6692 is available in 8-pin µMAX and SO packages.
Applications
Desktop Computers
Notebook Computers
Servers
Thin Clients
Workstations
Test and Measurement
Multichip Modules
Features
o Dual Channel: Measures Remote and Local
Temperature
o 0.125°C Resolution
o High Accuracy: ±0.8°C (max) from +25°C to
+125°C (Remote), and ±2°C (max) from +60°C to
+100°C (Local)
o Two Alarm Outputs: ALERT and OVERT
o Two Default OVERT Thresholds Available
MAX6648: +110°C
MAX6692: +85°C
o Programmable Conversion Rate
o SMBus-Compatible Interface
o SMBus Timeout
o Programmable Under/Overtemperature Alarm
Thresholds
Ordering Information
PART
TEMP RANGE PIN-
MEASURED
PACKAGE TEMP RANGE
MAX6648MUA -55°C to +125°C 8 µMAX 0°C to +125°C
MAX6692MUA -55°C to +125°C 8 µMAX 0°C to +125°C
MAX6692MSA -55°C to +125°C 8 SO
0°C to +125°C
Typical Operating Circuit
0.1µF
3.3V
200Ω
VCC
DXP SDA
DXN
2200pF
MAX6648 SCLK
MAX6692
ALERT
OVERT
µP GND
10kΩ EACH
DATA
CLOCK
INTERRUPTED TO µP
TO FAN DRIVER OR
SYSTEM SHUTDOWN
SMBus is a trademark of Intel Corp.
Pin Configuration and Functional Diagram appear at end of
data sheet.
________________________________________________________________ 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  
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
Pin Description
PIN NAME
FUNCTION
1
VCC
Supply Voltage Input, 3V to 5.5V. Bypass VCC to GND with a 0.1µF capacitor. A 200Ω series
resistor is recommended but not required for additional noise filtering.
Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel. DO
2 DXP NOT LEAVE DXP FLOATING; tie DXP to DXN if no remote diode is used. Place a 2200pF
capacitor between DXP and DXN for noise filtering.
3
DXN
Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally biased to one
diode drop above ground.
4
OVERT
Overtemperature Alert/Interrupt Output, Open Drain. OVERT is logic low when the temperature is
above the software-programmed threshold.
5
GND
Ground
SMBus Alert (Interrupt) Output, Open Drain. ALERT asserts when temperature exceeds user-set
6
ALERT
limits (high or low temperature). ALERT stays asserted until acknowledged by either reading the
status register or by successfully responding to an alert response address, provided that the fault
condition no longer exists. See the ALERT Interrupts section.
7
SDA
SMBus Serial-Data Input/Output, Open Drain
8
SCLK
SMBus Serial-Clock Input
Detailed Description
The MAX6648/MAX6692 are temperature sensors
designed to work in conjunction with a microprocessor
or other intelligence in thermostatic, process-control, or
monitoring applications. Communication with the
MAX6648/MAX6692 occurs through the SMBus-com-
patible serial interface and dedicated alert pins. ALERT
asserts if the measured local or remote temperature is
greater than the software-programmed ALERT high
limit or less than the ALERT low limit. ALERT also
asserts if the remote-sensing diode pins are shorted or
unconnected. The overtemperature alarm, OVERT,
asserts if the software-programmed OVERT limit is
exceeded. OVERT can be connected to fans, a system
shutdown, a clock throttle control, or other thermal-
management circuitry.
The MAX6648/MAX6692 convert temperatures to digital
data either at a programmed rate or in single conver-
sions. Temperature data is represented as 10 bits plus
sign, with the LSB equal to 0.125°C. The “main” tempera-
ture data registers (at addresses 00h and 01h) are 8-bit
registers that represent the data as 7 bits with the final
MSB indicating the diode fault status (Table 1). The
remaining 3 bits of temperature data are available in the
“extended” registers at addresses 11h and 10h (Table 2).
ADC and Multiplexer
The averaging ADC integrates over a 60ms period
(each channel, typically), with excellent noise rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes. The ADC and
associated circuitry measure each diode’s forward volt-
age and compute the temperature based on this volt-
age. Both channels are automatically converted once
the conversion process has started, either in free-run-
ning or single-shot mode. If one of the two channels is
not used, the device still performs both measurements,
and the user can ignore the results of the unused chan-
Table 1. Main Temperature Data Register
Format (00h, 01h)
TEMP (°C)
130
127
126
25
0
<0
-1
-25
Diode fault
(short or open)
DIGITAL OUTPUT
0 111 1111
0 111 1111
0 111 1111
0 001 1001
0 000 0000
0 000 0000
0 000 0000
0 000 0000
1 000 0000
_______________________________________________________________________________________ 5
5 Page 
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
Table 7. Status Register Bit Assignments (02h)
BIT NAME
7 (MSB) BUSY
6 LHIGH
5 LLOW
4 RHIGH
3 RLOW
2 FAULT
1 EOT
0 IOT
POR
STATE
0
0
0
0
0
0
0
0
FUNCTION
A/D is busy converting when 1.
Local (internal) high-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
Local (internal) low-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
Remote (external) high-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
Remote (external) low-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
A 1 indicates DXN and DXP are either shorted or open; cleared by POR or readout of the status
byte if the fault condition no longer exists.
A 1 indicates the remote (external) junction temperature exceeds the external OVERT threshold.
A 1 indicates the local (internal) junction temperature exceeds the internal OVERT threshold.
POR and UVLO
To prevent ambiguous power-supply conditions from
corrupting the data in memory and causing erratic
behavior, a POR voltage detector monitors VCC and
clears the memory if VCC falls below 2.0V (typ). When
power is first applied and VCC rises above 2.0V (typ),
the logic blocks begin operating, although reads and
writes at VCC levels below 3V are not recommended. A
second VCC comparator, the ADC UVLO comparator
prevents the ADC from converting until there is suffi-
cient headroom (VCC = 2.8V typ).
Power-up defaults include:
Power-Up Defaults
• Interrupt latch is cleared.
• ADC begins autoconverting at a 4Hz rate.
• Command byte is set to 00h to facilitate quick local
temperature receive byte queries.
• Local (internal) THIGH limit set to +85°C.
• Local (internal) TLOW limit set to 0°C.
• Remote (external) THIGH limit set to +85°C.
• Remote (external) TLOW limit set to 0°C.
• OVERT internal limit is set to +85°C; every external
limit is set to +110°C (MAX6648).
• OVERT limits are set to +85°C (MAX6692).
Table 8. Conversion-Rate Control Byte
(04h)
DATA
00h
01h
02h
03h
04h
05h
06h
07h
08h-FFh
CONVERSION
RATE (Hz)
0.0625
0.125
0.25
0.5
1
2
4
4
Reserved
Applications Information
Remote-Diode Selection
The MAX6648/MAX6692 can directly measure the die
temperature of CPUs and other ICs that have on-board
temperature-sensing diodes (see Typical Operating
Circuit), or they can measure the temperature of a dis-
crete diode-connected transistor.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX6648.PDF ] | |
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