General Description
The MAX6683 system supervisor monitors multiple
power-supply voltages, including its own, and also features an on-board temperature sensor. The MAX6683
converts voltages to an 8-bit code and temperatures to
an 11-bit (10-bit-plus-sign) code using an analog-todigital converter (ADC). A multiplexer automatically
sequences through the voltage and temperature measurements. The digitized signals are then stored in registers and compared to the over/underthreshold limits
programmed over the SMBus™/I2C™-compatible 2wire serial interface.
When a temperature measurement exceeds the programmed threshold, or when an input voltage falls outside the programmed voltage limits, the MAX6683
generates a latched interrupt output ALERT. Three
interrupt modes are available for temperature excursions. These are default mode, one-time interrupt
mode, and comparator mode. The ALERT output is
cleared, except for temperature interrupts generated in
comparator mode, by reading the Interrupt Status register (Table 5). The ALERT output can also be masked
by writing to the appropriate bits in the Interrupt Mask
register (Table 6) or by setting bit 1 of the Configuration
register (Table 4) to zero. The MAX6683 SMBus/I2Ccompatible interface also responds to the SMB alert
response address.
Applications
Workstations
Servers
Networking
Telecommunications
Features
♦ Monitors Local Temperature
♦ Monitors Three External Voltages (1.8V, 2.5V, 5V
Nominal)
♦ Monitors V
CC
(3.3V Nominal)
♦ User-Programmable Voltage and Temperature
Thresholds
♦ Alert Function with Ability to Respond to SMB
Alert Response Address
♦ +2.7V to +5.5V Supply Range
♦ -40°C to +125°C Temperature Range
♦ 60Hz or 50Hz Line-Frequency Rejection
♦ Tiny 10-Pin µMAX Package
♦ MAX6683EVKIT Available
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
19-2226; Rev 0; 10/01
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.
Ordering Information
SMBus is a trademark of Intel Corp.
I
2
C is a trademark of Philips Corp.
I2C/SMBus
CONTROLLER
CPU
V
CC
V
CC =
+3.3V
SCL
SDA
ADD
1.8V
IN
2.5V
IN
5V
IN
N.C.
GND
TO 1.8V
1.8V
TO 2.5V
TO 5V
0.1µF
10kΩ
ALERT
Typical Application Circuit
PART TEMP. RANGE PIN-PACKAGE
MAX6683AUB -40°C to +125°C 10 µMAX
TOP VIEW
1
1.8V
IN
2
2.5V
IN
3
5V
IN
4
GND ALERT
5
10
V
CC
9
MAX6683
SCL
8
SDA
7
ADDN.C.
6
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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
All Pins...................................................................-0.3V to +6.0V
SDA, ALERT Current ...........................................-1mA to +50mA
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
Junction Temperature......................................................+150°C
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V, TA= +25°C.)
POWER SUPPLY
Supply Voltage V
Supply Current
Power-On Reset (POR) Voltage VCC, rising or falling edge 2 V
TEMPERATURE
Resolution Read word mode 0.125 °C
Supply Sensitivity PSS 0.7
ADC CHARACTERISTICS
Total Unadjusted Error TUE VIN > 10LSBs ±1.5 %
Differential Nonlinearity DNL VIN > 10LSBs ±1 LSB
Supply Sensitivity PSS ±1 LSB/V
Input Resistance R
Total Monitoring Cycle Time t
SCL, SDA, ADD
Logic Input Low Voltage V
Logic Input High Voltage V
Input Leakage Current I
Output Low Voltage V
ALERT
Output Low Voltage V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CC
I
CC
I
SD
LEAK
OL
OLA
Operating 200 500
Shutdown mode, interface inactive 10
T
= +25°C, VCC = +3.3V ±2
A
-20°C ≤ TA ≤ +85°C, VCC = +3.3V ±3Accuracy
-40°C ≤ T
1.8VIN, 2.5VIN, 5V
IN
(Note 1) 200 300 ms
c
IL
V
IH
CC
VCC > 3.6V 2.6
VIN = 0 or 5V ±1µA
I
SINK
I
SINK
I
SINK
≤ +125°C, VCC = +3.3V ±5
A
≤ 3.6V 2.0
= 3mA 400 mV
= 1.2mA, VCC > 2.7V 0.3
= 3.2mA, VCC > 4.5V 0.4
2.7 5.5 V
±1.5
IN
100 150 200 kΩ
0.8 V
µA
°C
°C/V
V
V
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
_______________________________________________________________________________________ 3
Note 1: Total monitoring time includes temperature conversion and four analog input voltage conversions.
Note 2: A master device must provide at least a 300ns hold time for the SDA signal, referred to V
IL
of the SCL signal, to bridge the
undefined region of SCL’s falling edge.
Note 3: C
b
= total capacitance of one bus line in pF. Rise and fall times are measured between 0.3 ✕VCCto 0.7 ✕VCC.
Note 4: Input filters on SDA, SCL, and ADD suppress noise spikes <50ns.
ELECTRICAL CHARACTERISTICS (continued)
(TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V, TA= +25°C.)
TIMING (Figures 3 and 4)
Serial Clock Frequency f
Bus Free Time Between Stop
and Start
Start Condition Hold Time tHD:
Stop Condition Hold Time tSU:
Clock Low Time T
Clock High Time T
Data Setup Time tSU:
Data Hold Time tHD:
Receive SCL/SDA Minimum
Rise Time
Receive SCL/SDA Maximum
Rise Time
Receive SCL/SDA Minimum Fall
Time
Receive SCL/SDA Maximum Fall
Time
Transmit SDA Fall Time t
Pulse Width of Spike
Suppressed
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SCL
T
BUF
STA
STO
LOW
HIGH
DAT
(Note 2) 0 0.9 µs
(Note 3)
R
(Note 3) 300 ns
R
(Note 3)
F
(Note 3) 300 ns
F
Cb = 400pF, I
F
(Note 4) 50 ns
SINK
= 3mA
t
t
t
t
t
SP
DAT
0 400 kHz
1.3 µs
0.6 µs
0.6 µs
1.3 µs
0.6 µs
100 ns
20 +
0.1C
b
20 +
0.1C
b
20 +
0.1C
b
300 ns
ns
ns
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= +3.3V, ADD = GND, TA= +25°C, unless otherwise noted.)
0
100
50
200
150
300
250
350
2.5 3.5 4.03.0 4.5 5.0 5.5
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6683 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
INTERFACE INACTIVE
A
C
D
E
B
A: TA = +125°C
B: T
A
= +85°C
C: T
A
= +25°C
D: T
A
= 0°C
E: T
A
= -40°C
450
250
1 100 1000
SUPPLY CURRENT
vs. SCL CLOCK FREQUENCY
300
275
325
350
375
400
425
MAX6683 toc02
CLOCK FREQUENCY (kHz)
SUPPLY CURRENT (µA)
10
VCC = +5V
SCL = 3Vp-p
-4
-3
-2
-1
0
1
2
3
4
2.5 3.53.0 4.0 4.5 5.0 5.5
TEMPERATURE ERROR
vs. SUPPLY VOLTAGE
MAX6683 toc03
SUPPLY VOLTAGE (V)
TEMPERATURE ERROR (°C)
TA = +85°C
TA = 0°C
TA = -40°C
6
0
1 100 1k10 10k
TEMPERATURE ERROR
vs. SUPPLY NOISE FREQUENCY
MAX6683 toc04
SUPPLY NOISE FREQUENCY (Hz)
TEMPERATURE ERROR (°C)
1
2
3
4
5
VCC = +5V
BYPASS CAP REMOVED
200mVp-p
-5
-2
-3
-4
0
-1
4
3
2
1
5
-50 -25 0 25 50 75 100 125
TEMPERATURE ERROR
vs. TEMPERATURE
MAX6683 toc05
TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
Detailed Description
The MAX6683 is a voltage and temperature monitor
designed to communicate through an SMBus/I2C interface with an external microcontroller (µC). A µC with no
built-in I2C or SMBus capabilities can generate SMBus
serial commands by “bit-banging” general-purpose
input-output (GPIO) pins.
The MAX6683 can monitor external supply voltages of
typically 1.8V, 2.5V, 5V, as well as its own supply voltage and temperature. This makes it ideal for supervisor
and thermal management applications in telecommunications, desktop and notebook computers, workstations, and networking equipment. Voltage inputs are
converted to an 8-bit code and temperature is converted to an 11-bit code. The high-order 8 bits of the temperature conversion can be read using a read byte
operation through the I2C interface. The full 11-bit temperature conversion is read using a read word operation and disregarding the lower 5 bits of the low byte.
By setting bit 5 of the Configuration Register to 1, the
temperature conversion can be reduced to 9 bits with a
four-fold reduction in conversion time. In this case, the
lower 7 bits of the low byte should be disregarded; 8bit temperature data has a resolution of 1°C/LSB, while
11-bit temperature data has a resolution of 0.125°C/
LSB. Setting bit 5 of the Configuration Register to 1
reduces the monitoring cycle time by a factor of 4. In
this case, a read word operation for temperature data
yields a 9-bit code in which the lower 7 bits of the low
byte should be disregarded. The LSB of the 9-bit temperature data has a value of 0.5°C.
Each input voltage is scaled down by an on-chip resistive voltage-divider so that its output, at the nominal
input voltage, is 3/4 of the ADC’s full-scale range, or a
decimal count of 192 (Table 3). Input voltages other
than the nominal values may be used; ensure that they
fall within the usable ranges of pins to which they are
applied. Attenuate voltages greater than 6V with an
external resistive voltage-divider.
Writing a 1 to bit 0 of the Configuration Register starts
the monitoring function. The device performs a sequential sampling of all the inputs, starting with the internal
temperature sensor and continuing with 2.5VIN, 1.8VIN,
5VIN, and VCC. If the master terminates the conversion,
the sequential sampling does not stop until the sampling cycle is completed and the results are stored.
When it starts again, it always starts with the temperature measurement.
An interrupt signal is generated when a temperature
measurement goes above the hot limit or when a voltage measurement is either above the high limit or
below the low limit. This causes the open-drain output
ALERT to go to the active-low state and set each corresponding interrupt status bit (bits 0 through 4) to 1
(Table 5). The interrupt is cleared by reading the
Interrupt Status Register except for temperature interrupts generated in comparator mode. Reading the
Interrupt Status Register also clears the register itself,
except for temperature interrupt bits set in comparator
mode.
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
_______________________________________________________________________________________ 5
Pin Description
PIN NAME FUNCTION
1 1.8V
2 2.5V
35VINAnalog Input. Monitors 5V nominal supply.
4 N.C. No Connect. Not internally connected. Connect to GND to improve thermal conductivity.
5 GND Ground
6 ALERT
7 ADD
8 SDA SMBus/I2C-Compatible Serial Data Interface
9 SCL SMBus/I2C-Compatible Clock Input
10 V
Analog Input. Monitors 1.8V nominal supply.
IN
Analog Input. Monitors 2.5V nominal supply.
IN
SMBus Alert (Interrupt) Output, Open Drain. Alerts the master that a temperature or voltage limit has been
violated.
2
SMBus/I
transaction, and the 2LSBs of the Slave Address register are detemined by ADD’s connection to GND, SDA,
SCL, or V
Supply Voltage Input, +2.7V to +5.5V. Also serves as a voltage monitor input. Bypass VCC to GND with a
CC
0.1µF capacitor.
C-Compatible Address Select Input. ADD is sampled at the beginning of each SMBus/I2C
.
CC
MAX6683
Unless the fault is removed, the ALERT output only
remains cleared until the end of the next conversion
cycle where it is again asserted. The ALERT output can
also be masked by writing to the appropriate bits in the
Interrupt Mask Register (Table 6) or by setting bit 1 of
the Configuration Register (Table 4) to zero.
The 2-wire serial interface accepts both I2C and standard SMBus Write Byte, Read Byte, Read Word, Send
Byte, and Receive Byte commands to program the
alarm thresholds and to read voltage and temperature
data. Voltage data is scaled so that when the nominal
voltage is present at an input (e.g., 1.8V for the 1.8V
IN
input), the conversion result is equal to 3/4 of the ADC
full-scale range or a decimal count of 192 (Table 1).
When using the Read Byte command, the temperature
data format is 7 bits plus sign with the LSB equal to
1°C, in two's complement format. When using the Read
Word command, the temperature data format is 10 bits
plus sign, with the LSB equal to 0.125°C, in two’s complement format. See Table 2 for the temperature data
format.
The MAX6683 has only one address input, ADD.
Connect ADD to GND, V
CC
, SDA, or SCL to select one
of four different address codes. Whenever an
SMBus/I2C transaction is initiated, the 2LSBs of the
Slave Address Register are determined by connection,
setting the chip address to one of four possible values.
In addition, an address code can also be directly writ-
Temperature Sensor and System Monitor
in a 10-Pin µMAX
6 _______________________________________________________________________________________
Table 1. Register Map
ADDRESS READ/WRITE POWER-ON DEFAULT DESCRIPTION
20h R — Data register for 2.5 VIN measurement
21h R — Data register for 1.8VIN measurement
22h R — Data register for 5VIN measurement
23h R — Data register for VCC measurement
27h R — Data register for temperature measurement
2Bh R/W 1101 0011 (1.1 × 2.5V) High limit for 2.5V
2Ch R/W 1010 1101 (0.9 × 2.5V) Low limit for 2.5V
2Dh R/W 1101 0011 (1.1 × 1.8V) High limit for 1.8V
2Eh R/W 1010 1101 (0.9 × 1.8V) Low limit for 1.8V
2Fh R/W 1101 0011 (1.1 × 5V) High limit for 5V
30h R/W 1010 1101 (0.9 × 5V) Low limit for 5V
31h R/W 1101 0011 (1.1 × 3.3V) High limit for V
32h R/W 1010 1101 (0.9 × 3.3V) Low limit for V
39h R/W 0101 0000 (+80°C) Hot temperature limit
3Ah R/W 0100 0001 (+65°C) Hot temperature hysteresis
40h R/W 0000 1000 Configuration Register
41h R 0000 0000 Interrupt Status Register
43h R/W 0000 0000 Interrupt Mask Register
48h R/W 0010 1XXY
4Bh R/W 0000 0000 Temperature Configuration Register
Device Address Register. The values of XX are
dependent on the status of the ADD pin.
Power-On Default ADD Connection
0010 100Y To GND
0010 101Y To V
0010 110Y To SDA
0010 111Y To SCL
Y (bit 0) is the SMBus read/write bit. When the 7-bit chip
address is read back from the Serial Address Register,
an 8-bit word is presented with a zero in bit 0 (Y).
IN
IN
IN
IN
IN
IN
CC
CC
CC
ten to the Serial Address Register. This code overwrites
the code set by connection of the ADD pin, until the
MAX6683 is taken through a POR cycle.
ADC and Multiplexer
The ADC integrates over a 66ms period, an integral
multiple of the line period with excellent noise rejection.
The internal oscillator is trimmed to produce a 66ms
conversion time for temperature and 33ms for each
voltage. This is equivalent to 4 and 2 cycles of 60Hz,
respectively, and provides protection against noise
pickup from the main supply. The internal oscillator frequency can be changed to provide the same protection
against 50Hz by setting bit 7 in the Configuration
Register to 1 (Table 4). The multiplexer automatically
sequences through the inputs, measuring voltages and
temperature.
Low-Power Shutdown Mode
Setting bit 0 in the Configuration Register to zero stops
the monitoring loop and puts the MAX6683 into lowpower shutdown mode. In this mode, the SMBus/I2C
interface remains active, and the supply current drops
to 10µA or less.
Power-On Reset
The MAX6683 POR supply voltage is typically 2V.
Below this supply voltage, all registers are reset, the
device is put into shutdown mode, and the SMBus/I
2
C
interface is inactive.
Alarm Threshold Registers
Two registers, a hot temperature limit (T
HOT
) at 39h and
a hot temperature hysteresis (T
HYST
) at 3Ah, store
alarm threshold data (Table 1). If a measured temperature exceeds the value of T
HOT
, an ALERT is asserted.
Alerts are cleared and reasserted depending on
the interrupt mode selected in the Temperature
Configuration Register (see
ALERT
Interrupts).
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
_______________________________________________________________________________________ 7
Table 3. Voltage Data Format
Table 2. Temperature Data Format
(Two's Complement)
HIGH BYTE
TEMPERATURE
(°C)
+125 0111 1101 7D
+25 0001 1001 19
+1 0000 0001 01
0 0000 0000 00
-1 1111 1111 FF
-25 1110 0111 E7
-40 1101 1000 D8
LOW BYTE
0.875 1110 0000 D0
0.125 0010 0000 20
DIGITAL OUTPUT
(BINARY)
DIGITAL OUTPUT
(HEX)
ADC OUTPUT
CODE
LSB weight 9.375mV (1.8V/192) 13mV (2.5V/192) 26mV (5V/192) 17.2mV (3.3V/192)
0 < 9.375mV < 13mV < 26mV —
1 9.375mV to 18.75mV 13mV to 26mV 26mV to 52mV —
2 18.75mV to 28.125mV 26mV to 39mV 52mV to 78mV —
—————
64 (1/4 scale) 600mV to 609.4mV 833mV to 846mV 1.664V to 1.692V —
—————
128 (1/2 scale) 1.2V to 1.2094V 1.667V to 1.680V 3.330V to 3.560V —
—————
192 (3/4 scale) 1.8V to 1.737V 2.5V to 2.513V 5V to 5.026V 3.3V to 3.317V
—————
253 2.372V to 2.381V 3.294V to 3.307V 6.566V to 6.640V 4.348V to 4.366V
254 2.381V to 2.391V 3.572V to 3.586V 6.615V to 6.640V 4.366V to 4.383V
255 = 2.391V = 3.586V = 6.640V = 4.383V
INPUT VOLTAGE
AT 1.8V
IN
INPUT VOLTAGE
AT 2.5V
IN
INPUT VOLTAGE
AT 5V
IN
VCC = +3.3V
MAX6683
The POR state of the T
HOT
register is 0101 0000 or
+80°C. The POR state of the T
HYST
register is 0100
0001 or +65°C.
High and low limits for the voltage inputs are stored in
registers 2Bh through 32h. If a measured voltage is less
than V
LOW
or greater than V
HIGH
, an ALERT is asserted.
The POR states of the high and low voltage limits are
1.1 and 0.9 times the nominal voltage for each input.
Interrupt Status Byte Functions
The Interrupt Status Register records temperature or
voltage fault conditions whenever a limit is exceeded
(Table 5). Bits 0 through 3 correspond to the 2.5V, 1.8V,
5V, and VCCvoltage inputs and bit 4 corresponds to
the temperature. If a threshold has been crossed, the
appropriate bit contains a 1. In the default and one-time
interrupt modes, reading the status register clears the
register until a new out-of-range condition is detected.
Temperature Sensor and System Monitor
in a 10-Pin µMAX
8 _______________________________________________________________________________________
Table 4. Configuration Register (Address 40h, Power-On Default = 08h)
Table 5. Interrupt Status Register (Address 41h, Power-Up Default = 00h)
BIT NAME READ/WRITE DESCRIPTION
This bit controls the monitoring loop. Setting the bit to zero stops the
0 Start/Stop R/W
1 ALERT Enable R/W
2 Reserved ——
3 ALERT Clear R/W
4
5 Short Cycle R/W This bit reduces the conversion time by a factor of 4 when it is set to 1.
6 Reserved ——
7 Reset R/W
Line Frequency
Select
R/W
monitoring loop and puts the device into shutdown mode. The I
interface is still active during the shutdown mode. Setting the bit to 1 starts the
monitoring cycle. All high/low limits should be set before setting this bit to 1.
This bit is used to enable or disable the ALERT output. Setting the bit to 1
enables the ALERT output; setting the bit to 0 disables the ALERT output.
This bit is used to clear the ALERT output when it is set to high. It does not
affect the Interrupt Status Register. The monitoring loop does not start until the
bit is set to zero.
This bit controls the internal clock frequency. Setting the bit to 1 changes the
clock frequency to 51.2kHz from 61.4kHz. This can improve the measurement
accuracy when the power-line frequency is at 50Hz.
This bit is used as a reset signal for the register initialization. The 1 of this bit
resets all the register values into the power-up default mode, including bit 7
itself.
2
C/SMBus
BIT NAME READ/WRITE DESCRIPTION
0 2.5VIN-Error R A 1 i nd i cates ei ther a hi g h or l ow l i m i t has b een exceed ed at the 2.5V
1 1.8VIN-Error R A 1 i nd i cates ei ther a hi g h or l ow l i m i t has b een exceed ed at the 1.8V
25V
3V
4 Temp-Error R
5, 6, 7 Reserved ——
-Error R A 1 i nd i cates ei ther a hi g h or l ow l i m i t has b een exceed ed at the 5V
IN
-Error R A 1 i nd i cates ei ther a hi g h or l ow l i m i t has b een exceed ed at the V
CC
A 1 indicates either a high or low limit has been exceeded at the internal
temperature sensor. The conditions that generate and clear this bit depend
on the temperature interrupt mode selected by bits 0 and 1 in the
Temperature Configuration Register.
IN
C C
i np ut.
IN
i np ut.
i np ut.
I N
i np ut.
ALERT
Interrupts
An out-of-range voltage or temperature causes the
ALERT output signal to be asserted. However, if the
assertion is caused by an out-of-range temperature, the
ALERT output can operate in one of three different
modes: default, one-time interrupt, or comparator
mode. In the default and one-time interrupt modes, the
ALERT signal and Interrupt Status Register are cleared
by reading the Interrupt Status Register (Table 5). In
comparator mode, ALERT is only cleared when the fault
condition is removed. Reading the Interrupt Status
Register clears all but bit 4 of the Status Register if the
fault condition is not removed. Reading the Interrupt
Status Register with the fault condition removed clears
the entire register. Unless the fault is removed, ALERT
is reasserted after the next conversion cycle. The
ALERT output can also be masked by writing to the
appropriate bits in the Interrupt Mask Register (Table 6)
or by setting bit 1 of the Configuration Register (Table
4) to zero.
The interrupt does not halt conversions. New temperature and voltage data continue to be available over the
SMBus interface after ALERT is asserted. The three
temperature ALERT modes are shown in Figure 1 and
are selected through the Temperature Configuration
Register (Table 7). The ALERT output pin is open drain,
so the device can share a common interrupt line.
Default Mode
An interrupt is initiated when temperature exceeds
T
HOT
(address 39h). The interrupt is cleared only by
reading the Interrupt Status Register. An interrupt continues to be generated on subsequent measurements
until the temperature goes below T
HYST
(address 3Ah).
One-Time Interrupt Mode
An interrupt is initiated when temperature exceeds
T
HOT
(address 39h). The interrupt is cleared only by
reading the Interrupt Status Register. The next interrupt
is then initiated when temperature falls below the T
HYST
(address 3Ah).
Comparator Mode
An interrupt is initiated when temperature exceeds
T
HOT
(address 39h). The ALERT output remains assert-
ed low until the temperature goes below T
HOT
. Reading
the Interrupt Status Register does not clear the ALERT
output or interrupt status bit in the register. The inter-
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
_______________________________________________________________________________________ 9
Table 7. Temperature Configuration Register (Address 4Bh, Power-Up Default = 00h)
Table 6. Interrupt Mask Register (Address 43h, Power-Up Default = 00h)
BIT NAME READ/WRITE DESCRIPTION
0 2.5V R/W
1 1.8V R/W
2 5V R/W
3 3.3V R/W
4 Temp. R/W
5, 6, 7 Reserved ——
BIT NAME READ/WRITE DESCRIPTION
0, 1
2−7 Reserved ——
Hot Temperature
Interrupt Select
R/W
Setting the bit to 1 disables the Interrupt Status Register bit (bit 0) and the
CC
IN
IN
input.
IN
input.
input.
input.
ALERT output for the 2.5V
Setting the bit to 1 disables the Interrupt Status Register bit (bit 1) and the
ALERT output for the 1.8V
Setting the bit to 1 disables the Interrupt Status Register bit (bit 2) and the
ALERT output for the 5V
Setting the bit to 1 disables the Interrupt Status Register bit (bit 3) and the
ALERT output for the V
Setting the bit to 1 disables the Interrupt Status Register bit (bit 4) and the
ALERT output for temperature.
Bit 1, bit 0 = 00: Default mode
Bit 1, bit 0 = 01: One-time interrupt mode
Bit 1, bit 0 = 10: Comparator mode
Bit 1, bit 0 = 11: Default mode
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
10 ______________________________________________________________________________________
Figure 1. Alert Response to Temperature Interrupts
Figure 2. SMBus Protocols
TEMPERATURE
MONITORING CYCLE
INTERRUPT
STATUS READ
T
HOT
T
HYST
ALERT
ALERT
ALERT
Write Byte Format
S COMMANDW/R
Read Byte Format
Send Byte Format Receive Byte Format
Read Word Format
S COMMAND A
S = Start condition
P = Stop condition
ADDRESS ACK
7 bits
Slave Address: equivalent to chip-select line of
a 3-wire interface
ADDRESS ACK S ACK
7 bits
Slave Address: equi valent to chip-select line of
a 3-wire interface
ADDRESS
7 bits
ADDRESS ACK S ACK ACK
7 bits
W/R
W/R
0
W/R
0
Shaded = Slave transmission
A = Not acknowledged
0
ACK
0
Command Byte: selects
which register you are
reading from
ACK
COMMAND ACK PS ACK
8 bits
Data Byte: writes data to the
register commanded by the
last Read Byte or Write Byte
transmission
ACK
8 bits
ACK
8 bits
Command Byte: selects which
register you are writing to
8 bits
ADDRESS
7 bits
ADDRESS
7 bits
Slave Address: repeated
due to change in dataflow direction
ADDRESS
7 bits
W/R
1
DEFAULT MODE
ONE-TIME
INTERRUPT MODE
COMPARATOR MODE
DATA ACK P
8 bits
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
W/R
1
W/R
1
DATA_LOW_byte
8 bits
DATA
8 bits
Data Byte: reads from
the register set by the
command byte
DATA PS
8 bits
Data Byte: reads data from
the register commanded
by the last Read Byte or
Write Byte transmission;
also used for SMBus alert
Response return address
DATA_HIGH_byte
8 bits
PS COMMAND A
A
P
rupt continues to be generated on subsequent measurements until the temperature falls below T
HOT
.
SMBus/I2C-Compatible Digital Interface
From a software prospective, the MAX6683 appears as a
set of byte-wide registers that contain voltage and temperature data, alarm threshold values, or control bits.
The device employs five standard SMBus protocols:
write byte, read byte, read word, send byte, and
receive byte (Figures 2, 3, 4).
Slave Address
The device address can be set to one of four different
values by pin strapping ADD to GND, SDA, SCL, or
VCC, so more than one MAX6683 can reside on the
same bus without address conflicts (Table 1). The
address pin state is checked at the beginning of each
SMBus/I2C transaction and is insensitive to glitches on
VCC. Any address code can also be written to the Serial
Address Register and overwrites the code set by connecting the ADD pin until the MAX6683 is taken through
a POR cycle.
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
______________________________________________________________________________________ 11
Figure 3. SMBus Write Timing Diagram
Figure 4. SMBus Read Timing Diagram
AB CDEFG HIJ
t
LOWtHIGH
SMBCLK
SMBDATA
t
t
HD:STA
SU:STA
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
AB CDEFG HIJ
t
LOWtHIGH
SMBCLK
t
SU:DAT
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
t
HD:DAT
K
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
K
t
SU:STO
L
t
BUF
L
M
M
SMBDATA
t
t
HD:STA
SU:STA
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
t
SU:DAT
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW
t
t
SU:STO
BUF
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
MAX6683
The MAX6683 also responds to the SMBus alert
response address (see Alert Response Address).
Alert Response Address
The SMBus alert response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex, expensive logic needed to be a bus
master. Usually the ALERT outputs of several slave
devices are wire-ORed to the same interrupt input of
the host master. Upon receiving an interrupt signal, the
host master can broadcast a receive byte transmission
(Figure 2) with the alert response address (0001 100).
A read operation is denoted by a 1 in the eighth
address bit. Then, any slave device that generated an
interrupt attempts to identify itself by putting its own
address on the bus.
The alert response can activate several different slave
devices simultaneously, similar to the I2C general call. If
more than one slave attempts to respond, bus arbitration rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledge signal and continues to hold the interrupt
line low until serviced. The MAX6683 does not automatically clear its ALERT when it responds to an alert
response address. The host master must then clear or
mask the ALERT by reading the Interrupt Status
Register, writing to the Interrupt Mask Register, or setting bit 1 of the Configuration Register to zero before it
can identify other slaves generating an interrupt.
Command Byte Functions
The 8-bit Command Byte Register (Table 1) is the master index that points to the other data, configuration,
limits, and address registers within the MAX6683. The
functions of those other registers are described below.
Configuration Byte Functions
The Configuration Register (Table 4) is a read-write register with several functions:
• Bit 0 puts the MAX6683 into software standby mode
(STOP) or autoconvert (START) mode. The 2-wire
interface is still active in the standby mode. All voltage and temperature limits should be set before
setting this bit to 1.
• Bit 1 enables and disables the ALERT output.
Setting this bit to 1 enables the ALERT output.
• Bit 2 is reserved.
• Bit 3 clears the ALERT output and stops the moni-
toring loop when set to 1. Clearing the output does
not affect the contents of the Interrupt Status
Registers.
• Bit 4 sets the analog-to-digital conversion speed to
minimize interference from power-line frequencies.
Setting this bit to 1 can improve accuracy when the
power-line frequency is 50Hz. When the power-line
frequency is 60Hz, bit 4 should be zero.
• Bit 5 reduces the oversampling ratio in the ADC
from 8 to 2. This reduces the monitoring cycle time
by a factor of 4 to typically 50ms at the cost of
reduced noise rejection.
• Bit 6 is reserved.
• Bit 7 resets all register values to their power-up
default values. To reset all registers, set bit 7 to 1.
This also resets bit 7 to its power-up value of zero.
Read Temperature
The MAX6683 reads out temperature in an 8-, 9-, or 11-bit
two's complement format. To obtain the 8-bit temperature
data (7 bits plus sign), execute a Read Byte command to
the Temperature Data Register (address 27h).
To obtain the 11-bit temperature data (10 bits plus
sign), execute a Read Word command to the
Temperature Data Register (address 27h). When performing a Read Word operation, the MAX6683 writes
the 11 bits of data to the bus in two 8-bit words. The
Temperature Sensor and System Monitor
in a 10-Pin µMAX
12 ______________________________________________________________________________________
Figure 5. Read Temperature Format
UPPER BYTE
D10 D9 D8 D7 D6 D5 D4
11-BIT READ FORMAT
UPPER BYTE
D8 D7 D6 D5 D4 D3 D2
9-BIT READ FORMAT
LOWER BYTE
D3
D1
D2 D1 D0 X X
LOWER BYTE
X
X
X
D0
X
X
X
X = DON'T CARE
X
X
X
X
upper byte contains the MSBs, while the lower byte
contains the 3LSBs (Figure 5). D9–D3 of the upper byte
represent the whole decimal number of the temperature
conversion and D10 is sign. D2–D0 of the lower byte
represent 1/2, 1/4, 1/8 of a degree, respectively, and
the remaining bits are disregarded.
Nine-bit temperature data (8 bits plus sign) is obtained
by setting bit 5 of the Configuration Register (address
40h) to 1, reducing the conversion time by a factor of
four, and executing a Read Word command to the
Temperature Data Register (address 27h). The upper
byte contains the MSBs, while the lower byte contains
the LSB (Figure 5). D7–D1 of the upper byte represent
the whole decimal number of the temperature conversion and D0 is sign. D0 of the lower byte represents 1/2
of a degree, and the remaining bits are disregarded.
Applications Information
Sensing Circuit Board and
Component Temperatures
Temperature sensor ICs like the MAX6683 that sense
their own die temperatures must be mounted on or
close to the object whose temperature they are intended to measure. Because there is a good thermal path
between the 10-pin µMAX package’s metal leads and
the IC die, the MAX6683 can accurately measure the
temperature of the circuit board to which it is soldered.
If the sensor is intended to measure the temperature of
a heat-generating component on the circuit board, it
should be mounted as close as possible to that component and should share supply and ground traces (if
they are not noisy) with that component where possible.
This maximizes the heat transfer from the component to
the sensor.
The thermal path between the plastic package and the
die is not as good as the path through the leads, so the
MAX6683, like all temperature sensors in plastic packages, is less sensitive to the temperature of the surrounding air than to the temperature of the leads.
Wiring and circuits must be kept insulated and dry to
avoid leakage and corrosion, especially if they operate
at cold temperatures where condensation can occur.
Chip Information
TRANSISTOR COUNT: 13,446
PROCESS: BiCMOS
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
______________________________________________________________________________________ 13
Functional Diagram
V
CC
1.8V
2.5V
5.0V
IN
IN
IN
INPUT VOLTAGE
SCALING AND
MULTIPLEXER
TEMPERATURE
SENSOR
ADC
VOLTAGE
REFERENCE
DATA AND
CONTROL
LOGIC
I2C/SMBus-
COMPATIBLE
INTERFACE
SDA
SCL
ALERT
ADD
MAX6683
Temperature Sensor and System Monitor
in a 10-Pin µMAX
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Package Information
10LUMAX.EPS
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