Rainbow Electronics MAX6626 User Manual

Page 1

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.

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.

Applications

Fan Control Temperature Alarms System Temperature Control Industrial Equipment

Features

♦ 9-Bit Temperature-to-Digital Converter (MAX6625)

♦ 12-Bit Temperature-to-Digital Converter (MAX6626)

♦ Accuracy

±1°C (T

= +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

♦ I

C-Compatible Serial Interface

♦ Up to Four Devices on a Single Bus

♦ Versatile Alarm Output with Programmable Trip

Temperature and Hysteresis

♦ Low-Power Shutdown Mode

♦ Space-Saving 6-Pin SOT23 Package

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with

I2C-Compatible Serial Interface in a SOT23

________________________________________________________________ Maxim Integrated Products 1

Pin Configuration

0.1µF

MAX6625 MAX6626

SCL

TO I

MASTER

10k (OMIT FOR MAX6625R AND MAX6626R)

SDA

OT OUTPUT

Typical Operating Circuit

19-1841; Rev 2; 7/02

*For device options, see Selector Guide at end of data sheet.

Requires special solder temperature profile described in the Absolute Maximum Ratings section.

Ordering Information

I2C is a trademark of Philips Corp.

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 PIN-PACKAGE

M A X6 6 2 5 P M U T - T * -55°C to +125°C 6 SOT23-6

MAX6625RMUT-T* -55°C to +125°C 6 SOT23-6

M A X6 6 2 6 P M U T - T * -55°C to +125°C 6 SOT23-6

MAX6626RMUT-T* -55°C to +125°C 6 SOT23-6

TOP VIEW

SDA

GND

16V

MAX6625

MAX6626

SOT23-6

5 ADD

OTSCL

Page 2

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(+3V ≤ VS≤ +5.5V, T

A =

-55°C to +125°C, unless otherwise noted.)

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.

VSto GND ................................................................-0.3V to +6V

OT, SCL, SDA to GND.............................................-0.3V to +6V

ADD to GND .................................................-0.3V to (V

+ 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.

Power-Supply Voltage V

ADC Resolution

Temperature Resolution

Accuracy (Notes 2, 3)

Power-Supply Sensitivity VS = +3V to +5.5V 1 °C/V

Conversion Time t

OT Pullup Resistor R

OT Saturation Voltage (Note 4) V

OT Delay (Programmable through fault queue) 1 × t

HIGH

LOW

I2C-COMPATIBLE I/O: SCL, SDA, ADD

Input High Voltage V

Input Low Voltage V

Input Hysteresis 0.2 V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Default Temperature T

I2C-compatible active 1 mA

I2C-compatible inactive 250 µAQuiescent Current I

Shutdown mode 1 µA

MAX6625 9

MAX6626 12

MAX6625 0.5

MAX6626 0.0625 TA = +25°C, VS = +3V to +3.6V ±1

0°C = TA ≤ +50°C, VS = +3.0V to +3.6V ±1.5

0°C = T

MAX6625R, MAX6626R only 25 50 kΩ

HIGH

LOW

= 4mA 0.8 V

OUT

VS < +3.6V 2

VS > +3.6V 3

≤ +70°C, VS = +3.0V to +3.6V ±2.0

3 5.5 V

133 ms

6 × t

80 °C

75 °C

0.8 V

Bits

°C/LSB

°C

Page 3

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with

I2C-Compatible Serial Interface in a SOT23

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(+3V ≤ VS≤ +5.5V, T

A =

-55°C to +125°C, unless otherwise noted.)

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: C

= 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.

Figure 1. Serial Bus Timing

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Input High Leakage Current I

Input Low Leakage Current I

Input Capacitance C

Output Low Voltage V

Output High Current I

I2C-COMPATIBLE TIMING

Serial Clock Frequency f

Bus Free Time Between STOP and START Conditions

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 (Note 5) t

Maximum Receive SCL/SDA Rise Time (Note 6)

Minimum Receive SCL/SDA Rise Time (Note 6)

Maximum Receive SCL/SDA Fall Time (Note 6)

Minimum Receive SCL/SDA Fall Time (Note 6)

Transmit SDA Fall Time (Note 6)

Pulse Width of Suppressed Spike (Note 7)

SCL

BUF

HD:STA

SU:STO

LOW

HIGH

SU:DAT

HD:DAT

= +5V ±1 µA

= 0 ±1 µA

= 3mA 0.4 V

VOH = 5V 1 µA

CB = 400pF, IO = 3mA

10 pF

DC 400 kHz

1.3 µs

0.6 µs

1.3 µs

0.6 µs

100 ns

0 0.9 µs

300 ns

20 +

0.1C

300 ns

20 +

0.1C

20 +

0.1C

250 ns

50 ns

SCL

SDA

HD:STA

LOW

SU:DAT

HIGH

HD:DAT

SU:STO

BUF

Page 4

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VS = +3.3V, TA = +25°C, unless otherwise noted.)

Pin Description

100

-5 50101520

RESPONSE TO THERMAL SHOCK

TEMPERATURE vs. TIME

MAX6625 toc01

TIME (s)

OUTPUT TEMPERATURE (°C)

DEVICE IMMERSED IN +85°C FLUORINERT BATH

120

100

160

140

180

200

-55 5 35-25 65 95 125

STATIC QUIESCENT SUPPLY CURRENT

vs. TEMPERATURE

MAX6625 toc02

TEMPERATURE (°C)

INPUT CURRENT (µA)

120

100

160

140

180

200

-55 5 35-25 65 95 125

DYNAMIC QUIESCENT SUPPLY CURRENT

vs. TEMPERATURE

MAX6625 toc03

TEMPERATURE (°C)

INPUT CURRENT (µA)

-5

-2

-3

-4

-1

-50 -25 0 25 50 75 100 125

TEMPERATURE ERROR vs.

TEMPERATURE

MAX6625 toc04

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

MAXIMUM LIMIT

±5 SIGMA RANGE

MINIMUM LIMIT

PIN NAME FUNCTION

1 SDA I2C-Compatible Serial Bidirectional Data Line

2 GND Power-Supply Ground

3 SCL I2C-Compatible Clock Input

4 OT Temperature Alarm Output

5 ADD I2C-Compatible Address Set Pin: Ground (0), VS (1), SDA (2), SCL (3); see Table 1.

6VSPower-Supply Input, +3V to +5.5V. Bypass VS to GND with a 0.1µF capacitor.

Page 5

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with

I2C-Compatible Serial Interface in a SOT23

_______________________________________________________________________________________ 5

Detailed Description

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 I2C-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-

tions as a slave on the I

C-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 I2C-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

C-compatible

address for each state.

Figure 2. Functional Block Diagram

BANDGAP

ADDRESS POINTER

REFERENCE

TEMP SIGNAL

TEMPERATURE REGISTER

CONFIGURATION REGISTER

SERIAL BUS INTERFACE

HIGH

LOW

ADC

MAX6625 MAX6626

SET-POINT

COMPARATOR

FAULT QUEUE

COUNTER

MAX665_ R

ONLY

+Vs

GND SDA SCL ADD

Page 6

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23

6 _______________________________________________________________________________________

Figure 3. I2C-Compatible Timing Diagram

ADDRESS

BYTE

ADDRESS

BYTE

ADDRESS

BYTE

(a) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FROM CONFIGURATION REGISTER

(b) CONFIGURATION REGISTER WRITE

HIGH

AND T

LOW

WRITE

POINTER

BYTE

POINTER

BYTE

POINTER

BYTE

MOST-SIGNIFICANT

DATA BYTE

LEAST-SIGNIFICANT

DATA BYTE

CONFIGURATION

BYTE

ADDRESS

BYTE

DATA

BYTE

ACK BY

MAX6625

ACK BY

MAX6625

ACK BY

MAX6625

ACK BY

MAX6625

ACK BY

MAX6625

ACK BY

MAX6625

ACK BY

MAX6625

START

MASTER

START

MASTER

START

MASTER

REPEAT

START

MASTER

ACK BY

MASTER

STOP

COND BY

MASTER

ACK BY

MAX6625

ACK BY

MAX6625

STOP

COND BY

MASTER

STOP

COND BY

MASTER

ACK BY

MAX6625

Page 7

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with

I2C-Compatible Serial Interface in a SOT23

_______________________________________________________________________________________ 7

Figure 4. I2C-Compatible Timing Diagram

ADDRESS

BYTE

ADDRESS BYTE

ADDRESS

BYTE

ADDRESS

BYTE

DATA

BYTE

(a) TYPICAL 2-BYTE READ FROM PRESET POINTER LOCATION SUCH AS TEMP, T

HIGH

, T

LOW

(b) TYPICAL POINTER SET FOLLOWED BY IMMEDIATE READ FOR 2-BYTE REGISTER SUCH AS TEMP, T

HIGH

, T

LOW

MOST-SIGNIFICANT

DATA BYTE

LEAST-SIGNIFICANT

DATA BYTE

POINTER BYTE

MOST-SIGNIFICANT

DATA BYTE

LEAST-SIGNIFICANT

DATA BYTE

ACK BY

MAX6625

ACK BY

MASTER

ACK BY

MAX6625

ACK BY

MAX6625

ACK BY

MASTER

ACK BY

MAX6625

ACK BY

MASTER

START

MASTER

START

MASTER

REPEAT

START

MASTER

START

MASTER

STOP

COND BY

MASTER

STOP

COND BY

MASTER

STOP

COND BY

MASTER

NO ACK BY

MASTER

ACK BY

MASTER

ACK BY

MASTER

Page 8

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23

8 _______________________________________________________________________________________

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 (T

HIGH

), and low-temperature (T

LOW

) 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

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.

Temperature Conversion

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.

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

Figure 5. MAX6625/MAX6626 Programmers Model

Table 1. Address Selection

SDA

SCL

INTERFACE

TEMPERATURE

(READ ONLY)

POINTER = 00000000

SET-POINT

HIGH

(READ-WRITE)

ADD CONNECTION I2C-COMPATIBLE ADDRESS

GND 100 1000

SDA 100 1010

SCL 100 1011

POINTER = 00000011

100 1001

DATA

POINTER REGISTER

(SELECTS REGISTER FOR

COMMUNICATION)

ADDRESS

(READ-WRITE, SETS OPERATING MODES)

CONFIGURATION

POINTER = 00000001

SET-POINT

LOW

(READ-WRITE)

POINTER = 00000010

Page 9

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with

I2C-Compatible Serial Interface in a SOT23

_______________________________________________________________________________________ 9

Table 2. Pointer Register

D7 to D2: Will read all zeros, cannot be written.

PART D15

D14

D13

D12

D11

D10D9D8D7D6D5D4D3D2–D0

MAX6625

0000 0

MAX6625

MSB

Bit

Table 4. Temperature Register

D2 D1 D0

Fault

Mode

Shutdown

Table 5. Configuration Register

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.

D4 D3 NUMBER OF FAULTS

0 0 1 (Default)

01 2

10 4

11 6

Table 6. Fault Queue Depth

D1 D0 REGISTER

0 0 Temperature (Default)

0 1 Configuration

10T

LOW

11T

HIGH

Table 3. Register Select

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.

1LSB = 0.5°C for the MAX6625. 1LSB = 0.0.0625°C for the MAX6626. Temperature is stored in two’s-complement format.

D7 D6 D5 D4 D3 D2 D1 D0

00000 0

(see Table 3)

MSB

(Sign)

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB

Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB

D6 D5 D4 D3

Comparator

Queue

Depth

Polarity

or Interrupt

Page 10

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23

10 ______________________________________________________________________________________

Table 7. T

HIGH

and T

LOW

Registers

D6 to D0: Will read all zeros, cannot be written. D15: MSB is the sign bit. Default: T

HIGH

= +80°C (5000H), T

LOW

= +75°C (4B00H).

LSB = 0.5°C.

DIGITAL OUTPUT CODE

MAX6625 MAX6626

BINARY BINARY

TEMPERATURE

(°C)

MSB LSB

HEX

MSB LSB

HEX

+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

Table 8. Output Code vs. Temperature

*8000H is the default value at power-up and after coming out of shutdown.

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

Page 11

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with

C-Compatible Serial Interface in a SOT23

______________________________________________________________________________________ 11

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 T

HIGH

or below T

LOW

. 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 T

HIGH

, T

LOW

, 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 T

LOW

Comparator Mode

In comparator mode, OT is asserted when the number of consecutive conversions exceeding the value in the T

HIGH

OT deasserts when the number of consecutive conversions less than the value in the T

LOW

to the depth of the fault queue. T

HIGH

minus T

LOW

the effective hysteresis of the OT output.

For example, if T

HIGH

is set to +100°C, T

LOW

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 T

HIGH

or a T

LOW

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 T

HIGH

fault. After a T

HIGH

fault, the IC looks for a T

LOW

fault. After a T

LOW

fault,

the IC looks for a T

HIGH

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 T

HIGH

fault. The activation of

any fault is subject to the depth of the fault queue.

Figure 6. OT Alarm Output and Reset Diagram

HIGH

DIE

TEMPERATURE

LOW

(COMPARATOR MODE)

(INTERRUPT MODE)

TEMPERATURE RESPONSE SHOWN WITH OT SET FOR

** *

ACTIVE LOW

TIME

*THIS ASSUMES DEASSERTION OF OT BY A MASTER THROUGH THE SERIAL INTERFACE. SEE INTERRUPT MODE SECTION.

Page 12

MAX6625/MAX6626

9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23

12 ______________________________________________________________________________________

Example 1: If T

HIGH

is set to +100°C, T

LOW

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 I2C-compatible interface, OT will deassert. OT will assert again when four consecutive conversions are less than +80°C.

Example 2: If T

HIGH

is set to +100°C, T

LOW

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

fault.

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.

Thermal Considerations

The MAX6625/MAX6626 supply current is less than 1mA when the I

C-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

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:

∆T

= P

where PDis the power dissipated by the MAX6625/ MAX6626, and θJAis 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 V

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.

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.

Figure 7. Fan Controller

Figure 8. Simple Thermostat

+3V TO +5V

MAX6625R MAX6626R

+12V

12V 300mA FAN MOTOR

LOGIC LEVEL MOSFET

+3V to +5V

MAX6625P MAX6626P

RELAY 5VDC, 20mA 125VAC, 1A

2N3904

HEATER

HEATER SUPPLY

Page 13

9-Bit/12-Bit Temperature Sensors with

I2C-Compatible Serial Interface in a SOT23

MAX6625/MAX6626

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

TRANSISTOR COUNT: 7513

PROCESS: BiCMOS

Chip Information

Selector Guide

Package Information

(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.)

PART

M A X 6 62 5P M U T Open Drain 9 AAHY

MAX6625RMUT Internal Pullup 9 AAHZ

M A X 6 62 6P M U T Open Drain 12 AANP

MAX6626RMUT Internal Pullup

ALARM

OUTPUT

RESOLUTION

(bits)

TOP

MARK

AANQ

6LSOT.EPS