MAXIM MAX6638 Technical data
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 features extended temperature resolution data available in
0.125°C increments.
The MAX6638 provides three system alarms: channel 1
alert (ALERT1), overtemperature (OVERT1), and channel 2 alert (ALERT2) that contain programmable thresholds 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 register. Use the OVERT1 output to activate a cooling fan or
trigger a system shutdown.
Each of the 2-wire serial-interface ports accepts standard System Management Bus (SMBus) write byte, read
byte, send byte, and receive byte commands independently of one another with total collision avoidance handled 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-conversion mode. Each SMBus port can set the conversion
rate with the higher conversion and update rate dominating the average power-supply current. Single-conversion requests have a maximum delay of two
conversion cycles with channel-conversion management 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.
Applications
Graphics Cards
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
MAX6638
Temperature Monitor with
Dual Serial Interface
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3895; Rev 1; 1/06
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.
PART
TEMP
RANGE
PINPACKAGE
PKG
CODE
MAX6638ATE+
16 TQFN-EP*
(4mm x 4mm)
T1644-4
SMBus is a trademark of Intel Corporation.
Typical Operating Circuit appears at end of data sheet.
15
16
14
13
6
5
7
DXP
8
V
CC
SCK1
N.C.
12 4
12 11 9
SDA2
SCK2
GND
N.C.
I.C.
N.C.
MAX6638
DXN SDA1
3
10
N.C.
TQFN-EP
TOP VIEW
OVERT1 ALERT1
ALERT2
+
Pin Configuration
*EP = Exposed paddle.
+Denotes lead-free package.
-40°C to +125°C
MAX6638
Temperature Monitor with
Dual Serial Interface
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= 3.0V to 5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC= 3.3V and TA= +85°C.) (Note 1)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
(All voltages referenced to GND, unless otherwise noted.)
V
CC ....................................................................................
-0.3V to +6.0V
DXP.............................................................-0.3V to (V
CC
+ 0.3V)
DXN .......................................................................-0.3V to +0.8V
SCK1, SDA1, SCK2, SDA2, ALERT1,
OVERT1, ALERT2 .....................................................-0.3V to +6V
SDA1, SDA2, ALERT1, OVERT1, ALERT2 ..........-1mA to +50mA
DXN Current .......................................................................±1mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin TQFN (derate 16.9 mW/°C above +70°C) ....1349 mW
ESD Protection (all pins, Human Body Model) ................±2000V
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Supply Voltage V
Operating Current
Standby Supply Current SMBus1 and SMBus2 static 3 10 µA
TEMPERATURE MEASUREMENT
Remote Diode-Source Current I
Remote Temperature Error
Local Temperature Error
Supply Sensitivity of Temperature
Error
POWER-ON RESET
Power-On-Reset Threshold VCC falling 1.9 V
POR Threshold Hysteresis 90 mV
Undervoltage-Lockout Threshold VCC falling 2.30 2.60 2.95 V
Undervoltage-Lockout Hysteresis 90 mV
ANALOG-TO-DIGITAL CONVERTER
Conversion Time
ALERT1, OVERT1, ALERT2, SDA1, SDA2
Output Low Voltage V
Leakage Current I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CC
RJ
OL
LEAK
During conversion 600 950
ADC not converting 80
High level 80 100 120
Low level 8 10 12
VCC = 3.3V, TA = +85°C to +100°C,
T
= +85°C to +145°C
RJ
VCC = 3.3V, TA = +25°C to +100°C,
T
= +25°C to +145°C
RJ
= 3.3V, TA = +0°C to +125°C,
V
CC
T
= 0°C to +145°C
RJ
VCC = 3.3V, TA = +25°C to +85°C -2.0 +2.0
= 3.3V, TA = 0°C to +125°C -3.5 +3.5
V
CC
Nonoverlapping single conversion from
stop bit to conversion complete
IOL = 6mA 0.6 V
VOH = 5.5V ±1 µA
3.0 5.5 V
-1.0 +1.0
-2.0 +2.0
-3.0 +3.0
±0.2 °C/V
23 32 39 ms
µA
µA
°C
°C
MAX6638
Temperature Monitor with
Dual Serial Interface
_______________________________________________________________________________________ 3
Note 1: All parameters are tested at a single temperature. Specifications over temperature are guaranteed by design.
Note 2: Timing specifications are guaranteed by design.
Note 3: Each serial interface resets when its SCK_ is low for more than t
TIMEOUT
.
Note 4: A transition must internally provide at least a hold time to bridge the unidentified region (300ns max) of SCK_’s falling edge.
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 3.0V to 5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC= 3.3V and TA= +85°C.) (Note 1)
SMBus INTERFACE (SCK1, SCK2, SDA1, SDA2)
Logic Input Low Voltage V
Logic Input High Voltage V
Input Leakage Current I
Input Capacitance C
SMBus-COMPATIBLE TIMING (Figure 5) (Note 2)
Serial-Clock Frequency f
Bus Free Time Between STOP and
START Condition
START Condition Setup Time 4.7 µs
Rep eat S TART C ond i ti on S etup Ti m et
START Condition Hold Time t
STOP Condition Setup Time t
Clock Low Period t
Clock High Period t
Data Setup Time t
Data Hold Time t
SMBus Rise Time t
SMBus Fall Time t
SMBus Timeout t
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
IL
IH
LEAK
IN
SCK
t
BUF
SU:STA
HD:STA
SU:STO
LOW
HIGH
SU:DAT
HD:DAT
R
F
TIMEOUT
2.1 V
VIN = GND or V
(Note 3) 100 kHz
90% of SCK_ to 90% of SDA_ 50 ns
10% of SDA_ to 90% of SCK_ 4 µs
90% of SCK_ to 90% of SDA_ 4 µs
10% to 10% 4.7 µs
90% to 90% 4.0 µs
(Note 4) 300 ns
SDA_ low period for interface reset 30 45 60 ms
CC
5pF
4.7 µs
250 ns
0.8 V
±1 µA
1µs
300 ns
MAX6638
Temperature Monitor with
Dual Serial Interface
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
7
6
5
4
3
SUPPLY CURRENT (µA)
2
1
0
TA = +85°C
3.0 5.5
SUPPLY VOLTAGE (V)
REMOTE TEMPERATURE ERROR
vs. REMOTE DIODE TEMPERATURE
0.8
0.6
0.4
0.2
0
-0.2
-0.4
REMOTE TEMPERATURE ERROR (°C)
-0.6
-0.8
0406020
REMOTE DIODE TEMPERATURE (°C)
TA = +25°C
TA = -40°C
100 120 140
80
AVERAGE SUPPLY CURRENT
vs. CONVERSION RATE
600
500
MAX6638 toc01
400
300
200
SUPPLY CURRENT (µA)
100
0
5.04.54.03.5
020
CONVERSION RATE (Hz)
15105
MAX6638 toc02
SUPPLY CURRENT (µA)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
0
MAX6638 toc04
-0.5
-1.0
-1.5
-2.0
LOCAL TEMPERATURE ERROR (°C)
-2.5
-3.0
0608020 40 100 120 140
DIE TEMPERATURE (°C)
MAX6638 toc05
OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
700
TA = +85°C
650
600
550
500
450
400
3.0 5.5
TA = -40°C
SUPPLY VOLTAGE (V)
TA = +25°C
5.04.54.03.5
TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
6
LOCAL
4
2
TEMPERATURE ERROR (°C)
0
-2
0.01 100.1 1 100 1,000 10,000
POWER-SUPPLY NOISE FREQUENCY (kHz)
REMOTE
MAX6638 toc03
MAX6638 toc06
LOCAL TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
0
-1
-2
-3
-4
LOCAL TEMPERATURE ERROR (°C)
-5
-6
0.01 1 100.1 100 1,000 10,000
COMMON-MODE NOISE FREQUENCY (kHz)
MAX6638 toc07
REMOTE TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
2
0
-2
-4
-6
REMOTE TEMPERATURE ERROR (°C)
-8
0.01 10.1 10 100
DXP-DXN CAPACITANCE (nF)
MAX6638 toc08
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/undertemperature ALERT_ open-drain output with independently 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 overwritten 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 assertion for temperatures exceeding the set-point limit. The
temperature conversion results of the two temperature
channels are in integer format. The MSBs of the temperature 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.
MAX6638
Temperature Monitor with
Dual Serial Interface
_______________________________________________________________________________________ 5
Pin Description
Table 1. Temperature Data Format
(RLTS1, RRTS1, RLTS2, RRTS2)
PIN NAME FUNCTION
1V
2 DXP
3DXN
4 OVERT1 Digital Open-Drain Output. OVERT1 indicates an overtemperature condition on channel 1.
5, 7, 12, 13 N.C. No Connection. Not connected internally.
6 I.C. Internally Connected. I.C. must be connected to GND.
8 GND Power-Supply Ground
9 ALERT1 Digital Open-Drain Output. ALERT1 indicates alert condition on channel 1.
10 SDA1 SMBus Data Channel 1. Open-drain output.
11 SCK1 SMBus Clock Channel 1
14 ALERT2 Digital Open-Drain Output. ALERT2 indicates alert condition on channel 2.
15 SDA2 SMBus Data Channel 2. Open-drain output.
16 SCK2 SMBus Clock Channel 2
EP GND Ground. Connect to ground.
CC
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.
TEMPERATURE
(°C)
+145 91 1001 0001
+130 82 1000 0010
+128 80 1000 0000
+25 19 0001 1001
0 00 0000 0000
< 0 00 0000 0000
Diode fault FF 1111 1111
DIGITAL OUTPUT
(hex)
DIGITAL OUTPUT
(bin)
MAX6638
Temperature Monitor with
Dual Serial Interface
6 _______________________________________________________________________________________
Functional Diagram
V
CC
DXP
DXN
ALERT1
OVERT1
ALERT2
S
Q
R
S
Q
R
S
Q
R
MAX6638
MUX
REMOTE
LOCAL
ADC
REGISTER BANK1
COMMAND BYTE
REMOTE TEMPERATURE
LOCAL TEMPERATURE
ALERT THRESHOLD
ALERT-RESPONSE ADDRESS
OVERT THRESHOLD
REGISTER BANK2
COMMAND BYTE
REMOTE TEMPERATURE
LOCAL TEMPERATURE
CONTROL
LOGIC
SMBus
8
READ
8
WRITE
7
ADDRESS
DECODER
SMBus
8
READ
8
WRITE
7
ADDRESS
DECODER
SDA1
SCK1
SDA2
SCK2
ALERT THRESHOLD
ALERT-RESPONSE ADDRESS
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