Datasheet

ManualsBrandsANALOG DEVICES ManualsLinear ICsDigital temperature sensor Case type MSOP8 Type (misc.) Digital temperature sensor

±1°C Accurate, 12-Bit Digital

Temperature Sensor

ADT75

Rev. 0

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FEATURES

12-bit temperature-to-digital converter

B grade accuracy ±1.0°C from 0°C to 70°C

A grade accuracy ±2.0°C from –25°C to +100°C

SMBus/I

C-compatible interface

Operation from −55°C to +125°C

Operation from 3 V to 5.5 V

Overtemperature indicator

Shutdown mode for low power consumption

Power consumption 79 μW typically at 3.3 V

Small, low cost 8-pin MSOP in Pb-Sn and Pb-free packages

Standard 8-pin SOIC Pb-free package

APPLICATIONS

Isolated sensors

Environmental control systems

Computer thermal monitoring

Thermal protection

Industrial process control

Power-system monitors

Hand-held applications

PRODUCT HIGHLIGHTS

1. On-chip temperature sensor allows an accurate

measurement of the ambient temperature. The measurable

temperature range is −55°C to +125°C.

2. Supply voltage is 3.0 V to 5.5 V.

3. Space-saving, 8-lead MSOP and 8-lead SOIC.

4. Temperature accuracy is ±1°C maximum.

5. Temperature resolution is 0.0625°C.

6. Shutdown mode reduces the current consumption to

3 A typical.

7. Connect up to eight ADT75s to a single SMBus/I

C bus.

FUNCTIONAL BLOCK DIAGRAM

CLK AND

TIMING

GENERATION

LPF

Σ-Δ

DIGITAL

COMPARATOR

OS/ALER

GND

SDA

SCL

TEMPERATURE

SENSOR

TEMPERATURE

SENSOR

CONFIGURATION

HYST

SETPOINT

POINTER

SMBus/I

C INTERFACE

1-BIT

12-BIT

DECIMATOR

1-BIT

DAC

REFERENCE

–

05326-001

Figure 1.

Summary of content (24 pages)

PAGE 1
±1°C Accurate, 12-Bit Digital Temperature Sensor ADT75 FEATURES PRODUCT HIGHLIGHTS 12-bit temperature-to-digital converter B grade accuracy ±1.0°C from 0°C to 70°C A grade accuracy ±2.0°C from –25°C to +100°C SMBus/I2C-compatible interface Operation from −55°C to +125°C Operation from 3 V to 5.5 V Overtemperature indicator Shutdown mode for low power consumption Power consumption 79 μW typically at 3.3 V Small, low cost 8-pin MSOP in Pb-Sn and Pb-free packages Standard 8-pin SOIC Pb-free package 1.
PAGE 2
ADT75 TABLE OF CONTENTS Features .............................................................................................. 1 Temperature Data Format......................................................... 11 Applications....................................................................................... 1 One-Shot Mode .......................................................................... 12 Product Highlights ...........................................................................
PAGE 3
ADT75 GENERAL DESCRIPTION The ADT75 is a complete temperature monitoring system in 8-lead MSOP and SOIC packages. It contains a bandgap temperature sensor and 12-bit ADC to monitor and digitize the temperature to a resolution of 0.0625°C. The ADT75 is pin and register compatible with the LM75 and AD7416. The ADT75 is guaranteed to operate at supply voltages from 3 V to 5.5 V. Operating at 3.3 V, the average supply current is typically 200 μA.
PAGE 4
ADT75 SPECIFICATIONS A GRADE TA = TMIN to TMAX, VDD = 3.0 V to 5.5 V. All specifications for −55°C to +125°C, unless otherwise noted. Table 1. Parameter TEMPERATURE SENSOR AND ADC Accuracy at VDD = 3.0 V to 5.5 V Accuracy at VDD = 3.0 V to 3.6 V Accuracy at VDD = 4.5 V to 5.
PAGE 5
ADT75 B GRADE TA = TMIN to TMAX, VDD = 3.0 V to 5.5 V. All specifications for −55°C to +125°C, unless otherwise noted. Table 2. Parameter TEMPERATURE SENSOR AND ADC Accuracy at VDD = 3.0 V to 5.5 V Accuracy at VDD = 3.0 V to 3.6 V Accuracy at VDD = 4.5 V to 5.
PAGE 6
ADT75 TIMING SPECIFICATIONS AND DIAGRAM Measure the SDA and SCL timing with the input filters turned on to meet the fast mode I2C specification. Switching off the input filters improves the transfer rate but has a negative affect on the EMC behavior of the part. TA = TMIN to TMAX, VDD = +2.7 V to +5.5 V, unless otherwise noted. Table 3.
PAGE 7
ADT75 ABSOLUTE MAXIMUM RATINGS Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 1.2 WMAX = (TJMAX − TA)/θJA 205.9°C/W 43.74°C/W WMAX = (TJMAX − TA)/θJA 157°C/W 56°C/W 1.0 0.
PAGE 8
ADT75 SDA 1 SCL 2 OS/ALERT 3 GND 4 ADT75 TOP VIEW (Not to Scale) 8 VDD 7 A0 6 A1 5 A2 05326-004 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Figure 4. Pin Configuration Table 5. Pin Function Descriptions Pin No. 1 Mnemonic SDA 2 SCL 3 OS/ALERT 4 5 6 7 8 GND A2 A1 A0 VDD Description SMBus/I2C Serial Data Input/Output. Serial data that is loaded into and read from the ADT75 registers is provided on this pin. Open-drain configuration; needs a pull-up resistor. Serial Clock Input.
PAGE 9
ADT75 TYPICAL PERFORMANCE CHARACTERISTICS 7 1.0 TA = 30°C 0.8 0.6 0.4 SHUTDOWN CURRENT (μA) TEMPERATURE ERROR (°C) 6 VDD = 3.3V 0.2 0 –0.2 VDD = 5V –0.4 5 4 3 2 –0.6 –35 –15 5 25 45 65 85 105 05326-026 –1.0 –55 1 05326-023 –0.8 0 3.0 125 3.5 4.0 Figure 5. Temperature Accuracy at 3.3 V and 5 V 5.0 5.5 Figure 8. Shutdown Current vs. Supply Voltage at 30°C 0.05 TA = 25°C A 0.1μF CAPACITOR IS CONNECTED AT THE VDD PIN. CONVERTING @ 5.5V 450 0.04 CONVERTING @ 3.
PAGE 10
ADT75 THEORY OF OPERATION CIRCUIT INFORMATION FUNCTIONAL DESCRIPTION The ADT75 is a 12-bit digital temperature sensor with the 12th bit acting as the sign bit. An on-board temperature sensor generates a voltage precisely proportional to absolute temperature that is compared to an internal voltage reference and input to a precision digital modulator. Overall accuracy for the ADT75 A Grade is ±2°C from −25°C to +100°C and accuracy for the ADT75 B Grade is ±1°C from 0°C to +70°C.
PAGE 11
ADT75 Configuration register functions consist of Table 6. 12-Bit Temperature Data Format • Switching between normal operation and full power-down. • Switching between comparator and interrupt event modes. • Setting the OS/ALERT pin active polarity. • Setting the number of faults that activate the OS/ALERT pin. • Enabling the one-shot mode. • Enabling the SMBus alert function mode on the OS/ALERT pin. Temperature −55°C −50°C −25°C −0.0625°C 0°C +0.
PAGE 12
ADT75 TEMPERATURE ONE-SHOT MODE 82°C Setting Bit D5 of the configuration register enables the one-shot mode. When this mode is enabled, the ADT75 goes immediately into shutdown mode and the current consumption is reduced to typically 3 μA when VDD is 3.3 V and 5.5 μA when VDD is 5 V. A one-shot temperature measurement is initiated when Address 0x04 is written to the address pointer register, which is writing to the one-shot register.
PAGE 13
ADT75 REGISTERS Address Pointer Register The ADT75 contains six registers: four are data registers, one is the address pointer register, and the final register is the one-shot register. The configuration register is the only data register that is 8 bits wide while the rest are 16 bits wide. The temperature value register is the only data register that is read only. Both a read and write can be performed on the rest of the data registers and on the one-shot register.
PAGE 14
ADT75 Temperature Value Register This 16-bit read only register stores the temperature measured by the internal temperature sensor. The temperature is stored in twos complement format with the MSB being the temperature sign bit. When reading from this register, the eight MSBs (Bit D15 to Bit D8) are read first and then the eight LSBs (Bit D7 to Bit D0) are read. The control register settings are the default settings on power up.
PAGE 15
ADT75 Table 11. Bit D0 Shutdown D1 Cmp/Int D2 OS/ALERT D4:D3 Fault Queue D5 One-Shot D6 Reserved D7 OS/SMBus Alert Mode Function Shutdown Bit. Setting this bit to 1 puts the ADT75 into shutdown mode. All circuitry except the SMBus/I2C interface is powered down. To power up the part again, write 0 to this bit. This bit selects between comparator and interrupt mode. D1 0 Over Temperature Interrupt Modes Comparator mode 1 Interrupt mode This bit selects the output polarity of the OS/ALERT pin.
PAGE 16
ADT75 SERIAL INTERFACE The serial bus protocol operates as follows: 2 Control of the ADT75 is carried out via the SMBus/I Ccompatible serial interface. The ADT75 is connected to this bus as a slave and is under the control of a master device. 1. The master initiates data transfer by establishing a start condition, defined as a high to low transition on the serial data line SDA, while the serial clock line SCL remains high. This indicates that an address/data stream is going to follow.
PAGE 17
ADT75 WRITING DATA Writing Data to a Register Depending on the register being written to, there are two different writes for the ADT75. The configuration register is 8-bits wide so only one byte of data can be written to this register. Writing a single byte of data to the configuration register consists of the serial bus address, the data register address written to the address pointer register, followed by the data byte written to the selected data register. This is shown in Figure 15.
PAGE 18
ADT75 1 9 1 9 SCL 1 SDA 0 0 1 A2 A1 A0 P7 R/W START BY MASTER P6 P5 P4 P3 P2 P1 P0 ACK. BY ADT75 ACK. BY ADT75 FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE 1 1 9 9 SCL (CONTINUED) D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 ACK. BY ADT75 ACK. BY ADT75 STOP BY MASTER FRAME 4 DATA BYTE FRAME 3 DATA BYTE 05326-015 SDA (CONTINUED) Figure 16.
PAGE 19
ADT75 OS/ALERT OUTPUT OVERTEMPERATURE MODES Interrupt Mode The ADT75 has two overtemperature modes, comparator mode and interrupt mode. The OS/ALERT pin defaults on power up as an OS pin; the comparator mode is the default power up overtemperature mode. The OS/ALERT output pin becomes active when the temperature measured exceeds the temperature limit stored in the TOS setpoint register. How this pin reacts after this event depends on the overtemperature mode selected.
PAGE 20
ADT75 SMBus ALERT 1. SMBALERT is pulled low. The OS/ALERT pin can behave as a SMBus alert pin when the SMBus alert function is enabled by setting Bit D7 in the configuration register. The interrupt mode must also be selected (Bit D1 in the configuration register). The OS/ALERT pin is an open-drain output and requires a pull-up to VDD. Several SMBus alert outputs can be wire-AND’ed together, so that the common line goes low if one or more of the SMBus alert outputs goes low.
PAGE 21
ADT75 APPLICATION INFORMATION THERMAL RESPONSE TIME SUPPLY DECOUPLING The time required for a temperature sensor to settle to a specified accuracy is a function of the thermal mass of the sensor and the thermal conductivity between the sensor and the object being sensed. Thermal mass is often considered equivalent to capacitance. Thermal conductivity is commonly specified using the symbol Q, and can be thought of as thermal resistance.
PAGE 22
ADT75 TEMPERATURE MONITORING The ADT75 is ideal for monitoring the thermal environment within electronic equipment. For example, the surface-mounted package accurately reflects the exact thermal conditions that affect nearby integrated circuits. The ADT75 measures and converts the temperature at the surface of its own semiconductor chip. When the ADT75 is used to measure the temperature of a nearby heat source, the thermal impedance between the heat source and the ADT75 must be considered.
PAGE 23
ADT75 OUTLINE DIMENSIONS 3.20 3.00 2.80 5.00 (0.1968) 4.80 (0.1890) 8 8 3.20 3.00 2.80 1 5 4.00 (0.1574) 3.80 (0.1497) 1 5.15 4.90 4.65 4 0.25 (0.0098) 0.10 (0.0040) 0.65 BSC 0.38 0.22 COPLANARITY 0.10 0.23 0.08 0.80 0.60 0.40 8° 0° 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE 1.10 MAX 0.15 0.00 6.20 (0.2440) 4 5.80 (0.2284) 1.27 (0.0500) BSC PIN 1 0.95 0.85 0.75 5 0.50 (0.0196) × 45° 0.25 (0.0099) 8° 0.25 (0.0098) 0° 1.27 (0.0500) 0.40 (0.
PAGE 24
ADT75 NOTES Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. © 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05326-0-10/05(0) Rev.