MAX31725MTA+T Datasheet MAX31726MTA+T, MAX31725MTA+T, MAX31725MTA+ | P7-P9

MAX31725/MAX31726

±0.5°C Local Temperature Sensors

7Maxim Integrated

Block Diagram

I

2

C BLOCK

DIGITAL LOGIC BLOCK

DATA REGISTER BLOCK

TEMPERATURE CORE BLOCK

POR

BLOCK

0

MSB LSB

DATA POINTER

SERIAL LOGIC

SDA

SCL

ADDRESS

DECODER

0 0 0 0 0 D1 D0

D1 D0

0 0

STEMP

CONFIG

MSB LSB

MS BYTE

MSB LSB

3

MSB LSB

LS BYTE

2

6

2

5

2

4

2

3

2

1

2

0

2

-1

2

-2

2

-3

2

-4

2

-5

2

-6

2

-7

2

-8

ST

HYST

MSB

TEMPERATURE

SENSOR

16-BIT

Σ∆ ADC

LSB

MS BYTE

MSB LSB

LS BYTE

2

6

2

5

2

4

2

3

2

1

2

0

2

-1

2

-2

2

-3

2

-4

2

-5

2

-6

2

-7

2

-8

ST

OS

2

6

2

5

2

4

2

3

2

1

2

0

2

-1

2

-2

2

-3

2

-4

2

-5

2

-6

2

-7

2

-8

T

OS

REGISTER

DIGITAL

COMPARATOR

0 1

1 0

1 1

A0

A1

V

DD

GND

V

DD

A2

(RESET)

TEMP REGISTER

T

HYST

REGISTER

THERMOSTAT

LOGIC

FAULT

QUEUE

BITS

COMPARE/

INTERRUPT

BIT

OS

POLARITY

BIT

OS

N

OS

ACTIVATE

ONE

SHOT

TIMEOUT

DATA

FORMAT

FAULT

QUEUE

[1]

FAULT

QUEUE

[2]

OS

POLARITY

SHUTDOWN

2

VOLTAGE

REFERENCE

DIGITAL CONTROL

ONE-SHOT BIT

SHUTDOWN BIT

MAX31725

MAX31726

( ) MAX31726 ONLY.

COMPARATOR/

INTERRUPT

MAX31725/MAX31726

±0.5°C Local Temperature Sensors

8Maxim Integrated

Detailed Description

The MAX31725/MAX31726 temperature sensors measure

temperature and convert the data into digital form. An

I

2

C-compatible two-wire serial interface allows access

to conversion results. The devices accept standard I

2

C

commands to read the data, set the overtemperature alarm

(OS) trip thresholds, and configure other characteristics.

While reading the temperature register, any changes in

temperature are ignored until the read is completed. The

temperature register is updated for the new temperature

measurement upon completion of the read operation.

OS Output, T

OS

and T

HYST

Limits

In comparator mode, the OS output behaves like a

thermostat (Figure 2). The output asserts when the

temperature rises above the limit set in the T

OS

register.

The output deasserts when the temperature falls below

the limit set in the T

HYST

register. In comparator mode,

the OS output can be used to turn on a cooling fan,

initiate an emergency shutdown signal, or reduce system

clock speed.

In interrupt mode, exceeding T

OS

also asserts OS. OS

remains asserted until a read operation is performed

on any of the registers. Once OS has asserted due to

Figure 2. OS Output Temperature Response Diagram

T

OS

T

HYST

INACTIVE

ACTIVE

INACTIVE

ACTIVE

READ

OPERATION

READ

OPERATION

READ

OPERATION

TEMPERATURE

OS OUTPUT

(COMPARATOR MODE)

OS SET ACTIVE LOW

OS OUTPUT

(INTERRUPT MODE)

OS SET ACTIVE LOW

MAX31725/MAX31726

±0.5°C Local Temperature Sensors

9Maxim Integrated

crossing above T

OS

and is then reset, it is asserted again

only when the temperature drops below T

HYST

. The

output then remains asserted until it is reset by a read.

It is then asserted again if the temperature rises above

T

OS

, and so on. Putting the MAX31725 or MAX31726 into

shutdown mode also resets OS.

I

2

C-Compatible Bus Interface

A standard I

2

C-compatible 2-wire serial interface reads

temperature data from the temperature registers and

reads and writes control bits and alarm threshold data to

and from the alarm and configuration registers.

Each device responds to its own I

2

C slave address, which

is selected using the A0, A1, and A2 pins for the MAX31725

or the A0 and A1 pins for the MAX31726. A0 and A1 can

be connected to the supply voltage, ground, SDA, or

SCL. A2 can be connected to supply voltage or ground to

provide up to 32 unique addresses for the MAX31725 and

up to 16 unique addresses for the MAX31726.

Table 1a and Table 1b show how the A0, A1, and A2

connections determine the slave address.

Table 1a. MAX31725 Slave Address Selection

Table 1b. MAX31726 Slave Address Selection

A2

CONNECTION

A1

CONNECTION

A0

CONNECTION

SLAVE

ADDRESS

BYTE

(hex)

GND GND GND 90h

GND GND V

DD

92h

GND GND SCL 82h

GND GND SDA 80h

GND V

DD

GND 94h

GND V

DD

V

DD

96h

GND V

DD

SCL 86h

GND V

DD

SDA 84h

GND SCL GND B4h

GND SCL V

DD

B6h

GND SCL SCL A6h

GND SCL SDA A4h

GND SDA GND B0h

GND SDA V

DD

B2h

GND SDA SCL A2h

GND SDA SDA A0h

V

DD

GND GND 98h

V

DD

GND V

DD

9Ah

V

DD

GND SCL 8Ah

V

DD

GND SDA 88h

V

DD

V

DD

GND 9Ch

V

DD

V

DD

V

DD

9Eh

V

DD

V

DD

SCL 8Eh

V

DD

V

DD

SDA 8Ch

V

DD

SCL GND BCh

V

DD

SCL V

DD

BEh

V

DD

SCL SCL AEh

V

DD

SCL SDA ACh

V

DD

SDA GND B8h

V

DD

SDA V

DD

BAh

V

DD

SDA SCL AAh

V

DD

SDA SDA A8h

A1

CONNECTION

A0

CONNECTION

SLAVE

ADDRESS BYTE

(hex)

GND GND 98h

GND V

DD

9Ah

GND SCL 8Ah

GND SDA 88h

V

DD

GND 9Ch

V

DD

V

DD

9Eh

V

DD

SCL 8Eh

V

DD

SDA 8Ch

SCL GND BCh

SCL V

DD

BEh

SCL SCL AEh

SCL SDA ACh

SDA GND B8h

SDA V

DD

BAh

SDA SCL AAh

SDA SDA A8h

MAX31725MTA+T

MAX31725MTA+T

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