MAXIM MAX6625RMUT-T

19-1841; Rev 2; 7/02
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
Features
♦ 9-Bit Temperature-to-Digital Converter (MAX6625)
The MAX6625/MAX6626 feature a shutdown mode that
saves power by turning off everything but the power-on
reset and the I2C-compatible interface. Four separate
addresses can be configured with the ADD pin, allowing
up to four MAX6625/MAX6626 devices to be placed on
the same bus. The MAX6625P/MAX6626P OT outputs are
open drain, and the MAX6625R/MAX6626R OT outputs
include internal pullup resistors.
The MAX6625 has a 9-bit internal ADC and can function
as a replacement for the LM75 in most applications. The
MAX6626 has a 12-bit internal ADC. Both devices come
in the space-saving 6-pin SOT23 package.
♦ Up to Four Devices on a Single Bus
Applications
Fan Control
Temperature Alarms
System Temperature Control
Industrial Equipment
♦ 12-Bit Temperature-to-Digital Converter (MAX6626)
♦ Accuracy
±1°C (TA = +25°C)
±1.5°C (0°C to +50°C)
±2°C (0°C to +70°C)
±3°C (-40°C to +85°C)
±4°C (-55°C to +125°C)
♦ 133ms Conversion Time
♦ I2C-Compatible Serial Interface
♦ Versatile Alarm Output with Programmable Trip
Temperature and Hysteresis
♦ Low-Power Shutdown Mode
♦ Space-Saving 6-Pin SOT23 Package
Ordering Information
PART
TEMP. RANGE
MA X6 62 5PMUT -T *
-55°C to +125°C
PIN-PACKAGE
6 SOT23-6
MAX6625RMUT-T*
-55°C to +125°C
6 SOT23-6
MA X6 62 6PMUT -T *
-55°C to +125°C
6 SOT23-6
MAX6626RMUT-T*
-55°C to +125°C
6 SOT23-6
*For device options, see Selector Guide at end of data sheet.
Requires special solder temperature profile described in the
Absolute Maximum Ratings section.
Typical Operating Circuit
Pin Configuration
VS
1k
0.1µF
6
4
TOP VIEW
1k
10k
(OMIT FOR MAX6625R
AND MAX6626R)
SDA 1
OT OUTPUT
MAX6625
MAX6626
1
3
GND 2
SDA
SCL
MAX6625
MAX6626
2
VS
5
ADD
4
OT
TO I2C
MASTER
SCL 3
5
6
SOT23-6
I2C is a trademark of Philips Corp.
________________________________________________________________ Maxim Integrated Products
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
MAX6625/MAX6626
General Description
The MAX6625/MAX6626 combine a temperature sensor,
a programmable overtemperature alarm, and an I2C™compatible serial interface into single compact packages.
They convert their die temperatures into digital values
using internal analog-to-digital converters (ADCs). The
result of the conversion is held in a temperature register,
readable at any time through the serial interface. A dedicated alarm output, OT, activates if the conversion result
exceeds the value programmed in the high-temperature
register. A programmable fault queue sets the number of
faults that must occur before the alarm activates, preventing spurious alarms in noisy environments. OT has programmable output polarity and operating modes.
MAX6625/MAX6626
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
ABSOLUTE MAXIMUM RATINGS
VS to GND ................................................................-0.3V to +6V
OT, SCL, SDA to GND.............................................-0.3V to +6V
ADD to GND .................................................-0.3V to (VS + 0.3V)
Current into Any Pin............................................................±5mA
OT Sink Current.................................................................. 20mA
Continuous Power Dissipation
6-Pin SOT23 (derate 9.1mW/°C above +70°C)............727mW
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-60°C to +150°C
Lead Temperature .............................................................Note 1
ESD Rating (Human Body Model)......................................2000V
Note 1: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during board-level solder attach and rework. This limit permits only the use of the solder profiles recommended in the industry-standard specification, IPC/JEDEC J-STD-020A, paragraph 7.6, Table 3 for IR/VPR and Convection
Reflow. Preheating is required. Hand or wave soldering is not allowed.
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.
ELECTRICAL CHARACTERISTICS
(+3V ≤ VS ≤ +5.5V, TA = -55°C to +125°C, unless otherwise noted.)
PARAMETER
Power-Supply Voltage
SYMBOL
CONDITIONS
VS
MIN
TYP
3
I2C-compatible active
Quiescent Current
IC
ADC Resolution
I2C-compatible inactive
Power-Supply Sensitivity
1
mA
µA
1
µA
MAX6625
9
MAX6626
12
Bits
0.5
°C/LSB
0.0625
±1
0°C = TA ≤ +50°C, VS = +3.0V to +3.6V
±1.5
0°C = TA ≤ +70°C, VS = +3.0V to +3.6V
±2.0
VS = +3V to +5.5V
Conversion Time
tC
OT Pullup Resistor
RP
MAX6625R, MAX6626R only
OT Saturation Voltage (Note 4)
VL
IOUT = 4mA
OT Delay
V
Shutdown mode
MAX6626
TA = +25°C, VS = +3V to +3.6V
Accuracy (Notes 2, 3)
UNITS
5.5
250
MAX6625
Temperature Resolution
MAX
°C/V
1
133
(Programmable through fault queue)
°C
ms
25
50
kΩ
0.8
V
1 × tC
6 × tC
ms
THIGH Default Temperature
THIGH
80
°C
TLOW Default Temperature
TLOW
75
°C
I2C-COMPATIBLE I/O: SCL, SDA, ADD
Input High Voltage
VIH
Input Low Voltage
VIL
Input Hysteresis
2
VS < +3.6V
2
VS > +3.6V
3
V
0.8
0.2
_______________________________________________________________________________________
V
V
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
(+3V ≤ VS ≤ +5.5V, TA = -55°C to +125°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input High Leakage Current
IIH
VIN = +5V
±1
µA
Input Low Leakage Current
IIL
VIN = 0
±1
µA
Input Capacitance
CIN
Output Low Voltage
VOL
IOL = 3mA
0.4
V
Output High Current
IOH
VOH = 5V
1
µA
400
kHz
10
pF
I2C-COMPATIBLE TIMING
Serial Clock Frequency
fSCL
DC
Bus Free Time Between STOP
and START Conditions
tBUF
1.3
µs
START Condition Hold Time
tHD:STA
0.6
µs
STOP Condition Setup Time
tSU:STO
0.6
µs
Clock Low Period
tLOW
1.3
µs
Clock High Period
tHIGH
0.6
µs
Data Setup Time
tSU:DAT
100
Data Hold Time (Note 5)
tHD:DAT
0
ns
0.9
µs
Maximum Receive SCL/SDA
Rise Time (Note 6)
tR
300
ns
Minimum Receive SCL/SDA
Rise Time (Note 6)
tR
20 +
0.1CB
ns
Maximum Receive SCL/SDA
Fall Time (Note 6)
tF
300
ns
Minimum Receive SCL/SDA
Fall Time (Note 6)
tF
20 +
0.1CB
ns
Transmit SDA Fall Time
(Note 6)
tF
Pulse Width of Suppressed
Spike (Note 7)
20 +
0.1CB
CB = 400pF, IO = 3mA
tSP
250
50
ns
ns
Note 2: Guaranteed by design and characterization to ±5 sigma.
Note 3: Quantization error not included in specifications for temperature accuracy.
Note 4: Output current should be minimized for best temperature accuracy. Power dissipation within the MAX6625/MAX6626 will
cause self-heating and temperature drift; see Thermal Considerations section.
Note 5: A master device must provide a hold time of at least 300ns for the SDA signal in order to bridge the undefined region of
SCL’s falling edge.
Note 6: CB = total capacitance of one bus line in pF. Tested with CB = 400pF.
Note 7: Input filters on SDA, SCL, and ADD suppress noise spikes less than 50ns.
SCL
tF
tR
tLOW
tHIGH
tHD:STA
tSU:DAT
tHD:DAT
tSU:STO
SDA
tBUF
Figure 1. Serial Bus Timing
_______________________________________________________________________________________
3
MAX6625/MAX6626
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VS = +3.3V, TA = +25°C, unless otherwise noted.)
STATIC QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
RESPONSE TO THERMAL SHOCK
TEMPERATURE vs. TIME
60
40
MAX6625 toc02
180
INPUT CURRENT (µA)
80
20
160
140
120
100
DEVICE IMMERSED IN +85°C
FLUORINERT BATH
80
0
-5
0
5
10
15
-55
20
-25
5
35
65
95
TIME (s)
TEMPERATURE (°C)
DYNAMIC QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE ERROR vs.
TEMPERATURE
5
MAX6625 toc03
200
4
TEMPERATURE ERROR (°C)
180
160
140
120
125
MAX6625 toc04
OUTPUT TEMPERATURE (°C)
200
MAX6625 toc01
100
INPUT CURRENT (µA)
MAX6625/MAX6626
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
MAXIMUM LIMIT
3
2
1
±5 SIGMA RANGE
0
-1
-2
-3
100
MINIMUM LIMIT
-4
80
-5
-55
-25
5
35
65
95
125
-50
TEMPERATURE (°C)
-25
0
25
50
75
100
125
TEMPERATURE (°C)
Pin Description
PIN
4
NAME
FUNCTION
I2C-Compatible Serial Bidirectional Data Line
1
SDA
2
GND
Power-Supply Ground
3
SCL
I2C-Compatible Clock Input
4
OT
Temperature Alarm Output
5
ADD
6
VS
I2C-Compatible Address Set Pin: Ground (0), VS (1), SDA (2), SCL (3); see Table 1.
Power-Supply Input, +3V to +5.5V. Bypass VS to GND with a 0.1µF capacitor.
_______________________________________________________________________________________
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
The MAX6625/MAX6626 continuously convert their die
temperatures into digital values using their self-contained delta-sigma ADCs. The resulting data is readable at any time through the I 2 C-compatible serial
interface. A dedicated alarm output asserts if the result
exceeds the value in the programmable high-temperature register. A programmable fault queue sets the
number of faults that must occur before the alarm
asserts, preventing spurious alarms in noisy environments. The alarm output polarity is selectable and
deasserts based on either of two operating modes,
comparator or interrupt. In comparator mode, the OT
output deasserts if the temperature conversion result
falls below the programmable low-temperature register
value (subject to the fault queue conditions) providing
adjustable hysteresis. In interrupt mode, the OT output
deasserts when any register is read through the serial
interface. Each conversion cycle takes about 130ms. At
power-up, the temperature register is set to 8000H until
the first conversion is completed.
The MAX6625/MAX6626 feature a shutdown mode,
accessible through the serial interface, that saves power
by turning off everything but the power-on reset and the
I2C-compatible interface. While in shutdown mode the
temperature register is set to 8000H. The device func-
BANDGAP
REGISTER
tions as a slave on the I2C-compatible bus supporting
Write Byte, Write Word, Read Byte, and Read Word commands. Four separate addresses can be configured with
the ADD pin, allowing up to four MAX6625/MAX6626
devices to be placed on the same bus. Figure 2 shows
the functional block diagram of the MAX6625/MAX6626.
Serial interface
I2C-Compatible Operation
The MAX6625/MAX6626 are readable and programmable through their I 2 C-compatible serial interface.
Figures 3 and 4 show the timing details of the clock
(SCL) and data (SDA) signals. The device functions as
a slave on the I2C-compatible bus and supports Write
Byte, Write Word, Read Byte, and Read Word commands.
Addressing
Four separate addresses can be configured with the
ADD pin, allowing up to four MAX6625/MAX6626s to be
placed on the same bus. The address is selected by
connecting the ADD pin to either of four places: GND
(address 0), VS (address 1), SDA (address 2), or SCL
(address 3). Table 1 shows the full I 2C-compatible
address for each state.
REFERENCE
ADC
TEMP SIGNAL
MAX6625
MAX6626
+Vs
TEMPERATURE REGISTER
ADDRESS
POINTER
REGISTER
THIGH REGISTER
MAX665_ R
ONLY
SET-POINT
COMPARATOR
OT
TLOW REGISTER
CONFIGURATION REGISTER
SERIAL BUS INTERFACE
FAULT
QUEUE
COUNTER
GND
SDA
SCL
ADD
Figure 2. Functional Block Diagram
_______________________________________________________________________________________
5
MAX6625/MAX6626
Detailed Description
6
START
BY
MASTER
START
BY
MASTER
START
BY
MASTER
ADDRESS
BYTE
ADDRESS
BYTE
ADDRESS
BYTE
POINTER
BYTE
ACK BY REPEAT
MAX6625 START
BY
MASTER
ADDRESS
BYTE
ACK BY
MAX6625
ACK BY
MAX6625
ACK BY
MAX6625
POINTER
BYTE
POINTER
BYTE
CONFIGURATION
BYTE
MOST-SIGNIFICANT
DATA BYTE
(c) THIGH AND TLOW WRITE
ACK BY
MAX6625
(b) CONFIGURATION REGISTER WRITE
ACK BY
MAX6625
ACK BY
MAX6625
MAX6625
DATA
BYTE
LEAST-SIGNIFICANT
DATA BYTE
STOP
COND BY
ACK BY MASTER
(a) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FROM CONFIGURATION REGISTER
ACK BY
MAX6625
ACK BY
MAX6625
STOP
COND BY
MASTER
NO
ACK BY
MASTER
STOP
COND BY
MASTER
MAX6625/MAX6626
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
Figure 3. I2C-Compatible Timing Diagram
_______________________________________________________________________________________
_______________________________________________________________________________________
START
BY
MASTER
START
BY
MASTER
START
BY
MASTER
REPEAT
START
BY
MASTER
ADDRESS
BYTE
ADDRESS BYTE
ADDRESS
BYTE
ACK BY
MASTER
ACK BY
MASTER
LEAST-SIGNIFICANT
DATA BYTE
ACK BY
MAX6625
POINTER BYTE
MOST-SIGNIFICANT
DATA BYTE
ACK BY
MAX6625
ACK BY
MASTER
DATA
BYTE
NO
ACK BY
MASTER
(c) TYPICAL 1-BYTE READ FROM CONFIGURATION REGISTER WITH PRESET POINTER
ACK BY
MAX6625
STOP
COND BY
MASTER
(b) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FOR 2-BYTE REGISTER SUCH AS TEMP, THIGH, TLOW
ADDRESS
BYTE
MOST-SIGNIFICANT
DATA BYTE
(a) TYPICAL 2-BYTE READ FROM PRESET POINTER LOCATION SUCH AS TEMP, THIGH, TLOW
ACK BY
MAX6625
LEAST-SIGNIFICANT
DATA BYTE
NO ACK BY
MASTER
NO
ACK BY
MASTER
STOP
COND BY
MASTER
MAX6625/MAX6626
STOP
COND BY
MASTER
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
Figure 4. I2C-Compatible Timing Diagram
7
MAX6625/MAX6626
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
SDA
INTERFACE
SCL
DATA
ADDRESS
POINTER REGISTER
(SELECTS REGISTER FOR
COMMUNICATION)
REGISTER SELECT
TEMPERATURE
(READ ONLY)
POINTER = 00000000
CONFIGURATION
(READ-WRITE, SETS OPERATING MODES)
POINTER = 00000001
THIGH SET-POINT
(READ-WRITE)
POINTER = 00000011
TLOW SET-POINT
(READ-WRITE)
POINTER = 00000010
Figure 5. MAX6625/MAX6626 Programmers Model
Table 1. Address Selection
ADD CONNECTION
I2C-COMPATIBLE ADDRESS
GND
100 1000
VS
100 1001
Temperature Conversion
SDA
100 1010
SCL
100 1011
An on-chip bandgap reference produces a signal proportional to absolute temperature (PTAT), as well as the
temperature-stable reference voltage necessary for the
analog-to-digital conversion. The PTAT signal is digitized by the on-board ADC to a resolution of 0.5°C for
the MAX6625, and 0.0625°C for the MAX6626. The
resulting digital value is placed in the temperature register. The temperature conversion runs continuously
and asynchronously from the I2C-compatible interface
at a rate of 133ms per conversion. When the temperature register is read, the most recently completed conversion result is provided and the currently active
conversion is aborted. When the bus transaction is finished by an I2C-compatible stop condition conversions
resume.
Control Registers
Five registers control the operation of the MAX6625/
MAX6626 (Figure 5 and Tables 2 through 7). The pointer register should be the first addressed and determines which of the other four registers will be acted on.
The other four are the temperature, configuration, hightemperature (THIGH), and low-temperature (TLOW) registers. The temperature register is 9 bits for the
MAX6625 and 12 bits for the MAX6626, read only, and
contains the latest temperature data. The register
length is 16 bits with the unused bits masked to 0. The
digital temperature data contained in the temperature
register is in °C, using a two’s-complement format with
1LSB corresponding to 0.5°C for the MAX6625 and
0.0625°C for the MAX6626 (Table 8).
The configuration register is 8 bits, read/write, and contains the fault queue depth, the temperature alarm
polarity select bit, the interrupt mode select bit, and the
shutdown control bit. The high-temperature register is
9 bits, read/write, and contains the value that triggers
8
the overtemperature alarm. The low-temperature register is 9 bits, read/write, and contains the value to which
the temperature must fall before the overtemperature
alarm is deasserted, if in comparator mode.
Overtemperature Alarm
The dedicated overtemperature output pin, OT, has
programmable polarity and two modes: comparator
and interrupt. Polarity and mode are selected through
the configuration register, and alarm activity is governed by a fault queue. Fault queue depth is also
selected through the configuration register (Tables 5
and 6). The MAX6625P/MAX6626P OT output is open
_______________________________________________________________________________________
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
MAX6625/MAX6626
Table 2. Pointer Register
D7
D6
D5
D4
D3
D2
0
0
0
0
0
0
D1
D0
Register select
(see Table 3)
D7 to D2: Will read all zeros, cannot be written.
Table 3. Register Select
D1
D0
REGISTER
0
0
0
1
Configuration
1
0
TLOW
1
1
THIGH
Temperature (Default)
Table 4. Temperature Register
PART
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2–D0
MAX6625
MSB
(Sign)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
0
0
0
0
0
MAX6625
MSB
(Sign)
Bit
11
Bit
10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
0
D6 to D0, MAX6625: Will read all zeros, cannot be written.
D2 to D0, MAX6626: Will read all zeros, cannot be written.
D15: MSB is the sign bit.
Table 5. Configuration Register
D7
0
D6
0
D5
0
D4
D3
Fault
Queue
Depth
D2
OT
Polarity
D1
Comparator
or Interrupt
Mode
All defaults = 0.
D0: 0 = Normal operation, 1 = Shutdown.
D1: 0 = Comparator mode, 1 = Interrupt mode.
D2: 0 = Active low, 1 = Active high.
D7 to D5: Reserved locations, always write zeros.
1LSB = 0.5°C for the MAX6625.
1LSB = 0.0.0625°C for the MAX6626.
Temperature is stored in two’s-complement format.
Table 6. Fault Queue Depth
D0
Shutdown
D4
D3
NUMBER OF FAULTS
0
0
1 (Default)
0
1
2
1
0
4
1
1
6
_______________________________________________________________________________________
9
MAX6625/MAX6626
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
Table 7. THIGH and TLOW Registers
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
MSB
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
0
0
0
0
0
0
0
D6 to D0: Will read all zeros, cannot be written.
D15: MSB is the sign bit.
Default: THIGH = +80°C (5000H), TLOW = +75°C (4B00H).
LSB = 0.5°C.
Table 8. Output Code vs. Temperature
DIGITAL OUTPUT CODE
MAX6625
TEMPERATURE
(°C)
BINARY
MSB
LSB
MAX6626
HEX
BINARY
MSB
LSB
+125.0000
0111 1101 0000 0000
7D00
0111 1101 0000 0000
7D00
+124.9375
0111 1100 1000 0000
7C80
0111 1100 1111 0000
7CF0
+25.0000
0001 1001 0000 0000
1900
0001 1001 0000 0000
1900
+0.5000
0000 0000 1000 0000
0080
0000 0000 1000 0000
0080
0.0000
0000 0000 0000 0000
0000
0000 0000 0000 0000
0000
-0.5000
1111 1111 1000 0000
FF80
1111 1111 1000 0000
FF80
-25.0000
1110 0111 0000 0000
E700
1110 0111 0000 0000
E700
-55.0000
1100 1001 0000 0000
C900
1100 1001 0000 0000
C900
∗
1000 0000 0000 0000
8000
1000 0000 0000 0000
8000
*8000H is the default value at power-up and after coming out of shutdown.
10
HEX
______________________________________________________________________________________
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
MAX6625/MAX6626
THIGH
DIE
TEMPERATURE
TLOW
OT
(COMPARATOR MODE)
OT
(INTERRUPT MODE)
*
*
*
*THIS ASSUMES DEASSERTION OF OT BY A
MASTER THROUGH THE SERIAL INTERFACE.
SEE INTERRUPT MODE SECTION.
TEMPERATURE RESPONSE
SHOWN WITH OT SET FOR
ACTIVE LOW
TIME
Figure 6. OT Alarm Output and Reset Diagram
drain, and the MAX6625R/MAX6626R output includes
an internal 35kΩ (typ) pullup resistor. Figure 6 shows
the OT alarm operation and reset details.
Fault Queue
A programmable fault queue on the MAX6625/
MAX6626 eliminates spurious alarm activity in noisy
environments. The queue sets the number of consecutive out-of-tolerance temperature readings that must
occur before the OT alarm output is toggled. An out-oftolerance reading is above THIGH or below TLOW. The
fault queue depth defaults to one at power-up and may
be programmed to one, two, four, or six consecutive
conversions. Any time the conversion result is in tolerance, and OT is not asserted, the queue is cleared,
even if it contains some out-of-tolerance counts.
Additionally, the fault queue automatically clears at
power-up, in shutdown, or if a master writes to any of
the THIGH, TLOW, or configuration registers. Whenever
the fault queue is cleared, OT is deasserted.
For example, the fault queue is set to four, two consecutive out-of-tolerance readings have occurred, and the
master writes to the TLOW register. The fault queue is
cleared and begins to look for four new consecutive
out-of-tolerance conversions.
Comparator Mode
In comparator mode, OT is asserted when the number
of consecutive conversions exceeding the value in the
THIGH register is equal to the depth of the fault queue.
OT deasserts when the number of consecutive conversions less than the value in the TLOW register is equal
to the depth of the fault queue. THIGH minus TLOW is
the effective hysteresis of the OT output.
For example, if THIGH is set to +100°C, TLOW is set to
+80°C, and the fault queue depth is set to four, OT will
not assert until four consecutive conversions exceed
+100°C. Then, OT will not deassert until four consecutive conversions are less than +80°C.
Comparator mode allows autonomous clearing of an OT
fault without the intervention of a master and is ideal to
use for driving a cooling fan (Figure 7).
Interrupt Mode
In interrupt mode, the MAX6625/MAX6626 look for a
THIGH or a TLOW fault based on previous fault activity.
The OT pin asserts an alarm for an undertemperature
fault, as well as for an overtemperature fault, depending
on certain conditions. If the fault queue is cleared at
power-up, the IC looks for a THIGH fault. After a THIGH
fault, the IC looks for a TLOW fault. After a TLOW fault,
the IC looks for a THIGH fault, and it will bounce back
and forth if properly deasserted each time. Once either
fault has occurred, it remains active indefinitely until
deasserted by a read of any register, and the device
then begins to look for a fault of the opposite type. Also,
if the fault queue is cleared, OT is deasserted and the
IC once again looks for a THIGH fault. The activation of
any fault is subject to the depth of the fault queue.
______________________________________________________________________________________
11
MAX6625/MAX6626
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
Example 1: If THIGH is set to +100°C, TLOW is set to
+80°C, and the fault queue depth is set to four, OT will
not assert until four consecutive conversions exceed
+100°C. If the temperature is then read through the
I 2 C-compatible interface, OT will deassert. OT will
assert again when four consecutive conversions are
less than +80°C.
Example 2: If THIGH is set to +100°C, TLOW is set to
+80°C, and the fault queue depth is set to four, OT will
not assert until four consecutive conversions exceed
+100°C. If the T HIGH register is then changed to
+120°C, OT deasserts and the IC looks for a new
THIGH fault.
key to accurate temperature monitoring is good thermal
contact between the MAX6625/MAX6626 package and
the monitored device or circuit. In some applications,
the SOT23-6 package may be small enough to fit
underneath a socketed µP, allowing the device to monitor the µP’s temperature directly. Heat flows in and out
of plastic packages primarily through the leads. Short,
wide copper traces leading to the temperature monitor
ensure that heat transfers quickly and reliably. The rise
in die temperature due to self-heating is given by the
following formula:
∆TJ = PD ✕ θJA
Shutdown
The MAX6625/MAX6626 offer a low-power shutdown
mode. Enter shutdown mode by programming the shutdown bit of the control register high. In shutdown, the
temperature register is set to 8000H and the ADC is
turned off, reducing the device current draw to 1µA
(typ). After coming out of shutdown, the temperature
register will continue to read 8000H until the first conversion result appears. The fault queue is held in reset
during shutdown.
where PD is the power dissipated by the MAX6625/
MAX6626, and θJA is the package’s thermal resistance.
The typical thermal resistance is +110°C/W for the
SOT23-6 package. To limit the effects of self-heating,
minimize the output currents. For example, if the
MAX6625/MAX6626 sink 4mA with the maximum OT VL
spec of 0.8V, an additional 3.2mW of power is dissipated within the IC. This corresponds to a 0.35°C rise in
the die temperature.
Thermal Considerations
The MAX6625/MAX6626 supply current is less than
1mA when the I2C-compatible interface is active. When
used to drive high-impedance loads, the devices dissipate negligible power; therefore, the die temperature is
essentially the same as the package temperature. The
Applications
Figure 7 shows the MAX6625/MAX6626 used as a temperature-triggered fan controller. Figure 8 shows the
MAX6625/MAX6626 used as a thermostat to control a
heating element.
+VS
+3V to +5V
+VS
+3V TO +5V
+12V
HEATER
12V 300mA
FAN MOTOR
6
4
OT
MAX6625R
MAX6626R
6
LOGIC LEVEL
MOSFET
4k
RELAY
5VDC, 20mA
125VAC, 1A
MAX6625P
MAX6626P
OT
5
2N3904
2
HEATER
SUPPLY
3
Figure 7. Fan Controller
12
Figure 8. Simple Thermostat
______________________________________________________________________________________
9-Bit/12-Bit Temperature Sensors with
I2C-Compatible Serial Interface in a SOT23
ALARM
OUTPUT
RESOLUTION
(bits)
TOP
MARK
MAX6625PMUT
Open Drain
9
AAHY
MAX6625RMUT
Internal Pullup
9
AAHZ
MAX6626PMUT
Open Drain
12
AANP
MAX6626RMUT
Internal Pullup
12
AANQ
PART
Chip Information
TRANSISTOR COUNT: 7513
PROCESS: BiCMOS
Package Information
6LSOT.EPS
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX6625/MAX6626
Selector Guide