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DS75LX

Digital Thermometer and Thermostat

with Extended Addressing

www.maxim-ic.com

GENERAL DESCRIPTION

This low-voltage (1.7V to 3.7V) digital thermometer

and thermostat provides 9, 10, 11, or 12-bit digital

temperature readings over a -55°C to +125°C range

with ±2°C accuracy over a -25°C to +100°C range. At

power-up, the DS75LX defaults to 9-bit resolution for

software compatibility with the LM75. Communication

with the DS75LX is achieved through a simple 2-wire

serial interface. Three tri-state address pins allow up

to 27 DS75LX devices to operate on the same 2-wire

bus, which greatly simplifies distributed temperature-

sensing applications.

The DS75LX thermostat has a dedicated open-drain

output (O.S.) and programmable fault tolerance,

which allow the user to define the number of

consecutive error conditions that must occur before

O.S. is activated. There are two thermostatic

operating modes that control thermostat operation

based on user-defined trip-points (T

and T

HYST

APPLICATIONS

Any Thermally Sensitive System

Cellular Base Stations

Telecom Switches and Routers

Servers

PIN CONFIGURATIONS

FEATURES

 1.7V to 3.7V Operating Range

 Tri-State Address Pins Allow Up to 27 Unique

Bus Addresses

 Temperature Measurements Require No

External Components

 Measures Temperatures from -55°C to +125°C

(-67°F to +257°F)

 ±2°C Accuracy from -25°C to +100°C

 Thermometer Resolution Is User-

Configurable from 9 (Default) to 12 Bits (0.5°C

to 0.0625°C Resolution)

 9-Bit Conversion Time is 25ms (max)

 Thermostatic Settings are User-Definable

 Data is Read/Written Through 2-Wire Serial

Interface (SDA and SCL Pins)

 Data Lines Filtered Internally for Noise

Immunity (50ns Deglitch)

 Bus Timeout Feature Prevents Lockup

Problems on 2-Wire Interface

 Multidrop Capability Simplifies Distributed

Temperature-Sensing Applications

 Pin/Software Compatible with the LM75

 Available in 8-Pin μSOP (μMAX

) and SO

Packages

ORDERING INFORMATION

PART TEMP RANGE

PACKAGE

DS75LXS+ -55°C to +125°C

8 SO

(150 mils)

DS75LXS+T&R -55°C to +125°C

8 SO

(150 mils),

2500 Piece

DS75LXU+ -55°C to +125°C

8 µSOP

(µMAX)

DS75LXU+T&R -55°C to +125°C

8 µSOP

(µMAX),

3000 Piece

+ Denotes lead-free package.

T&R denotes tape-and-reel.

Note: A “+” symbol will also be marked on the package near the

pin 1 indicator.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

SO (150 mils)

GND

O.S.

DS75

SOP/

MAX

GND

O.S.

DS75

Summary of content (13 pages)

PAGE 1
DS75LX Digital Thermometer and Thermostat with Extended Addressing www.maxim-ic.com GENERAL DESCRIPTION FEATURES This low-voltage (1.7V to 3.7V) digital thermometer and thermostat provides 9, 10, 11, or 12-bit digital temperature readings over a -55°C to +125°C range with ±2°C accuracy over a -25°C to +100°C range. At power-up, the DS75LX defaults to 9-bit resolution for software compatibility with the LM75. Communication with the DS75LX is achieved through a simple 2-wire serial interface.
PAGE 2
DS1386/DS1386P ABSOLUTE MAXIMUM RATINGS Voltage Range on VDD, Relative to Ground Voltage Range on Any Other Pin, Relative to Ground Operating Temperature Range Storage Temperature Range Soldering Temperature -0.3V to +4.0V -0.3V to +6.0V -55°C to +125°C -55°C to +125°C See IPC/JEDEC J-STD-020 These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied.
PAGE 3
SCL Frequency fSCL DS75LX: Digital Thermometer and Thermostat with Extended Addressing 400 kHz AC ELECTRICAL CHARACTERISTICS (continued) (1.7V ≤ VDD ≤ 3.7V, TA = -55°C to +125°C.
PAGE 4
DS75LX: Digital Thermometer and Thermostat with Extended Addressing BLOCK DIAGRAM PRECISION REFERENCE OVERSAMPLING MODULATOR DIGITAL DECIMATOR VDD SCL SDA A0 A1 A2 CONFIGURATION REGISTER ADDRESS AND I/O CONTROL TEMPERATURE REGISTER RP O.S. TOS AND THYST REGISTERS GND Figure 1.
PAGE 5
DS75LX: Digital Thermometer and Thermostat with Extended Addressing OPERATION—MEASURING TEMPERATURE The DS75LX measures temperature using a bandgap temperature-sensing architecture. An on-board delta-sigma analog-to-digital converter (ADC) converts the measured temperature to a digital value that is calibrated in degrees celsius; for Fahrenheit applications a lookup table or conversion routine must be used. The DS75LX is factorycalibrated and requires no external components to measure temperature.
PAGE 6
DS75LX: Digital Thermometer and Thermostat with Extended Addressing Shutdown Mode For power-sensitive applications, the DS75LX offers a low-power shutdown mode. The SD bit in the configuration register controls shutdown mode. When SD is changed to 1, the conversion in progress is completed and the result is stored in the temperature register after which the DS75LX goes into a low-power standby state. The O.S. output is cleared if the thermostat is operating in interrupt mode, and O.
PAGE 7
DS75LX: Digital Thermometer and Thermostat with Extended Addressing Figure 3. O.S. Output Operation Example In this example the DS75LX is configured to have a fault tolerance of 2. TOS Temperature THYST Inactive O.S. Output - Comparator Mode Active Inactive O.S.
PAGE 8
DS75LX: Digital Thermometer and Thermostat with Extended Addressing Table 2. Configuration Register Bit Descriptions BIT NAME 0 Reserved R1 Conversion Resolution Bit 1 R0 Conversion Resolution Bit 0 F1 Thermostat Fault Tolerance Bit 1 F0 Thermostat Fault Tolerance Bit 0 POL Thermostat Output (O.S.) Polarity TM Thermostat Operating Mode SD Shutdown DESCRIPTION Power-Up State = 0 The master can write to this bit, but it always reads out as a 0. Power-Up State = 0 Sets conversion resolution (see Table 3).
PAGE 9
DS75LX: Digital Thermometer and Thermostat with Extended Addressing Table 5. Pointer Definition REGISTER Temperature Configuration THYST TOS P1 0 0 1 1 P0 0 1 0 1 2-WIRE SERIAL DATA BUS The DS75LX communicates over a standard bidirectional, 2-wire serial data bus that consists of a serial clock (SCL) signal and serial data (SDA) signal. The DS75LX interfaces to the bus through the SCL input pin and opendrain SDA I/O pin. All communication is MSb first.
PAGE 10
DS75LX: Digital Thermometer and Thermostat with Extended Addressing Figure 5. Start, Stop, and ACK Signals SDA … SCL … ACK (or NACK) STOP From Receiver Condition START Condition Figure 6. Address Byte BIT 7 a6 BIT 6 a5 BIT 5 a4 BIT 4 a3 BIT 3 a2 BIT 2 a1 BIT 1 a0 BIT 0 R/W̄¯ The Address Pins A0–A2 are tri-state inputs. These can be low, high, or floating in any combination, resulting in 27 address possibilities. These map into the address byte according to Table 6. Figure 7.
PAGE 11
DS75LX: Digital Thermometer and Thermostat with Extended Addressing Table 6.
PAGE 12
DS75LX: Digital Thermometer and Thermostat with Extended Addressing Writing to the DS75LX To write to the DS75LX, the master must generate a START followed by an address byte containing the DS75LX bus address. The value of the R/W̄¯ bit must be a 0, which indicates that a write is about to take place. The DS75LX responds with an ACK after receiving the address byte. This must be followed by a pointer byte from the master, which tells the DS75LX which register is being written to.
PAGE 13
1 START S 1 0 0 1 Address Byte 1 0 A 1 1 0 0 1 Address Byte 1 0 A SCL 1 13 of 13 1 0 0 1 Address Byte 1 0 A 0 ACK (DS75LX) W 0 0 1 START S 1 0 0 1 Address Byte 1 0 A 0 ACK (DS75LX) W 0 0 0 0 0 0 0 Pointer Byte 0 0 Pointer Byte 0 Pointer Byte 0 0 0 A S 1 SCL 1 START S 1 0 0 1 Address Byte 1 0 A Data Byte (from DS75LX) P NACK STOP (Master) D7 D6 D5 D4 D3 D2 D1 D0 N ACK (DS75LX) R 0 0 1 Address Byte 1 An address byte value of 1110010 co