Datasheet

ManualsBrandsANALOG DEVICES ManualsPMICsADT7408CCPZ-REEL7

±2°C Accurate, 12-Bit Digital

Temperature Sensor

ADT7408

Rev. 0

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FEATURES

12-bit temperature-to-digital converter

±2°C accuracy

Operation from −20°C to +125°C

Operation from 3 V to 3.6 V

240 μA typical average supply current

Selectable 1.5°C, 3°C, 6°C hysteresis

SMBus-/I

C®-compatible interface

Dual-purpose event pin: comparator or interrupt

8-lead LFCSP_VD, 3 mm × 3 mm (JEDEC MO-229 VEED-4)

package

Complies with JEDEC standard JC-42.4 memory module

Thermal sensor component specification

APPLICATIONS

Memory module temperature monitoring

Isolated sensors

Environmental control systems

Computer thermal monitoring

Thermal protection

Industrial process control

Power system monitors

FUNCTIONAL BLOCK DIAGRAM

12- / 10-Bit

ADDRESS

POINTER

EVENT#

∑-∆

DIGITAL COMPARATOR

DECIMATOR

SMBus/I²C INTERFACE

ADT7408

SDA

SCL

FACTORY

RESERVED

TEMPERATURE

MANUFACTURER’S

ID REGISTER

CRITICAL TEMP

ALARM TEMP

LOWER

BOUNDARY TRIP

ALARM TEMP

UPPER

BOUNDARY TRIP

CONFIGURATION

CAPABILITY

REFERENCE

TEMPERATURE

SENSOR

CLK

AND TIMING

GENERATION

–

LPF

1-BIT

DAC

–

05716-001

Figure 1.

GENERAL DESCRIPTION

The ADT7408 is the first digital temperature sensor that complies

with JEDEC standard JC-42.4 for the mobile platform memory

module. The ADT7408 contains a band gap temperature sensor

and a 12-bit ADC to monitor and digitize the temperature to a

resolution of 0.0625°C.

There is an open-drain EVENT# output that is active when the

monitoring temperature exceeds a critical programmable limit or

when the temperature falls above or below an alarm window.

This pin can operate in either comparator or interrupt mode.

There are three slave device address pins that allow up to eight

ADT7408s to be used in a system that monitors temperature of

various components and subsystems.

The ADT7408 is specified for operation at supply voltages from

3.0 V to 3.6 V. Operating at 3.3 V, the average supply current is

less than 240 µA typical. The ADT7408 offers a shutdown mode

that powers down the device and gives a shutdown current of 3 μA

typical. The ADT7408 is rated for operation over the −20°C to

+125°C temperature range. The ADT7408 is available in a lead-

free, 8-lead LFCSP_VD, 3 mm × 3 mm (JEDEC MO-229 VEED-4)

package.

Summary of content (24 pages)

PAGE 1
±2°C Accurate, 12-Bit Digital Temperature Sensor ADT7408 FEATURES FUNCTIONAL BLOCK DIAGRAM 12-bit temperature-to-digital converter ±2°C accuracy Operation from −20°C to +125°C Operation from 3 V to 3.6 V 240 μA typical average supply current Selectable 1.5°C, 3°C, 6°C hysteresis SMBus-/I2C®-compatible interface Dual-purpose event pin: comparator or interrupt 8-lead LFCSP_VD, 3 mm × 3 mm (JEDEC MO-229 VEED-4) package Complies with JEDEC standard JC-42.
PAGE 2
ADT7408 TABLE OF CONTENTS Features .............................................................................................. 1 Address Pointer Register (Write Only).................................... 10 Applications....................................................................................... 1 Capability Register (Read Only) .............................................. 10 Functional Block Diagram ..............................................................
PAGE 3
ADT7408 SPECIFICATIONS All specifications TA = −20°C to +125°C, VDD = 3.0 V to 3.6 V, unless otherwise noted. Table 1.
PAGE 4
ADT7408 TIMING CHARACTERISTICS TA = −20°C to +125°C, VDD = 3.0 V to 3.6 V, unless otherwise noted. Table 2. Parameter 1 SCL Clock Frequency Bus Free Time Between a Stop (P) and Start (S) Condition Hold Time After (Repeated) Start Condition Symbol fSCL tBUF tHD:STA Min 10 4.7 4.
PAGE 5
ADT7408 ABSOLUTE MAXIMUM RATINGS Table 3. Parameter VDD to VSS SDA Input Voltage to VSS SDA Output Voltage to VSS SCL Input Voltage to VSS EVENT# Output Voltage to VSS Operating Temperature Range Storage Temperature Range Maximum Junction Temperature, TJMAX Thermal Resistance1 θJA, Junction-to-Ambient (Still Air) IR Reflow Soldering Profile Rating –0.3 V to +7 V –0.3 V to VDD + 0.3 V –0.3 V to VDD + 0.3 V –0.3 V to VDD + 0.3 V –0.3 V to VDD + 0.
PAGE 6
ADT7408 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS A1 2 A2 3 VSS 4 ADT7408 TOP VIEW (Not to scale) 8 VDD 7 EVENT# 6 SCL 5 SDA 05716-004 A0 1 Figure 4. Pin Configuration Table 4. Pin Function Descriptions Pin No. 1 2 3 4 5 Mnemonic A0 A1 A2 VSS SDA 6 SCL 7 8 EVENT# VDD Description SMBus/I2C Serial Bus Address Selection Pin. Logic input. Can be set to VSS or VDD. SMBus/I2C Serial Bus Address Selection Pin. Logic input. Can be set to VSS or VDD. SMBus/I2C Serial Bus Address Selection Pin.
PAGE 7
ADT7408 TYPICAL PERFORMANCE CHARACTERISTICS 5.0 0.4 VDD = 3.3V 4.0 0.2 0.1 0 –0.1 –0.2 –0.4 –40 05716-015 –0.3 –20 0 20 40 60 80 100 120 3.5 3.0 2.5 2.0 1.5 1.0 05716-016 SHUTDOWN CURRENT (µA) TEMPERATURE ERROR (°C) TA = 85°C 4.5 0.3 0.5 0 3.0 140 3.1 3.2 Figure 5. Temperature Accuracy 0.25 300 250 AVERAGE 3.3V 200 150 100 05716-017 50 20 40 60 80 100 120 140 TEMPERATURE (°C) 250 225 200 175 05716-019 AVERAGE SUPPLY CURRENT (µA) TA = 85°C 275 3.2 3.3 3.4 3.5 3.
PAGE 8
ADT7408 THEORY OF OPERATION CIRCUIT INFORMATION MODES OF OPERATION The ADT7408 is a 12-bit digital temperature sensor presented in 13 bits, including the sign bit format (see the bit map in the Temperature Value Register (Read Only) section). Its output is twos complement in that Bit D12 is the sign bit and Bit D0 to Bit D11 are data bits.
PAGE 9
ADT7408 SMBus/I2C slave address selection pins allow up to eight such devices to co-exist on the same bus. This means that up to eight memory modules can be supported, given that each module has one slave device address slot. After initial power-on, the configuration registers are set to the default values. Software can write to the configuration register to set bits as per the bit definitions in the Registers section. Rev.
PAGE 10
ADT7408 REGISTERS ADDRESS POINTER REGISTER (WRITE ONLY) The ADT7408 contains 16 accessible registers, shown in Table 5. The address pointer register is the only register that is eight bits; the other registers are 16 bits wide. On power-up, the address pointer register is loaded with 0x00 and points to the capability register. This 8-bit write only register selects which of the 16-bit registers is accessed in subsequent read/write operations.
PAGE 11
ADT7408 CONFIGURATION REGISTER (READ/WRITE) This 16-bit read/write register stores various configuration modes for the ADT7408, as shown in Table 8 and the following bit map. Note that RFU means reserved for future use. MSB D15 RFU D14 RFU D13 RFU D12 RFU D11 RFU D10 D9 Hysteresis D8 Shutdown mode D7 Critical lock bit D6 Alarm lock bit D5 Clear event D4 Event output status D3 Event output control D2 Critical event only D1 Event polarity LSB D0 Event mode Table 8.
PAGE 12
ADT7408 Description Hysteresis enable 00: Disable hysteresis 01: Enable hysteresis at 1.5°C 10: Enable hysteresis at 3°C 11: Enable hysteresis at 6°C TH TH – HYST TL TL – HYST BELOW WINDOW BIT 05716-006 Bit D10:D9 ABOVE WINDOW BIT Figure 11. Hysteresis Rev.
PAGE 13
ADT7408 TEMPERATURE TRIP POINT REGISTERS There are three temperature trip point registers. They are the alarm temperature upper boundary trip register, the alarm temperature lower boundary trip register, and the critical temperature trip register. Alarm Temperature Upper Boundary Trip Register (Read/Write) The value is the upper threshold temperature value for alarm mode. The data format is twos complement with one LSB = 0.25oC. RFU (reserved for future use) bits are not supported and always report 0.
PAGE 14
ADT7408 Table 9. Temperature Register Trip Status Description Bit D13 Below alarm window D14 Above alarm window D15 Above critical trip Definition Below alarm window D13 Temperature Alarm Status 0 Temperature is equal to or above the alarm window lower boundary temperature. 1 Temperature is below the alarm window lower boundary temperature. Above alarm window D14 Temperature Alarm Status 0 Temperature is equal to or below the alarm window upper boundary temperature.
PAGE 15
ADT7408 TEMPERATURE DATA FORMAT The values used in the temperature register and three temperature trip point registers are in twos complement format. The temperature register has a 12-bit resolution with 256°C range with 1 LSB = 0.0625°C (256°C/212); see Table 10. The temperature data in the three temperature trip point registers (alarm upper, alarm lower, and critical) is a 10-bit format with 256°C range with 1 LSB = 0.
PAGE 16
ADT7408 EVENT PIN FUNCTIONALITY Critical Trip Figure 12 shows the three differently defined outputs of EVENT# corresponding to the temperature change. EVENT# can be programmed to be one of the three output modes in the configuration register. The device can be programmed in such a way that the EVENT# output is triggered only when the temperature exceeds critical trip point. The critical temperature setting is programmed in the critical temperature register.
PAGE 17
ADT7408 SERIAL INTERFACE The serial bus protocol operates as follows: 2 Control of the ADT7408 is carried out via the SMBus-/I Ccompatible serial interface. The ADT7408 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 follows.
PAGE 18
ADT7408 SMBUS/I2C COMMUNICATIONS The data byte has the most significant bit first. At the end of a read, the ADT7408 accepts either acknowledge (ACK) or no acknowledge (NO ACK) from the master. No acknowledge is typically used as a signal for the slave that the master has read its last byte. It typically takes the ADT7408 100 ms to measure the temperature. The data registers in the ADT7408 are selected by the pointer register.
PAGE 19
ADT7408 The write operation consists of the serial bus address followed by the pointer byte. No data is written to any of the data registers. Because the location latched in the pointer register is correct, then the read consists of an address byte, followed by retrieving the two data bytes (see Figure 16).
PAGE 20
ADT7408 1 9 1 9 SCL SDA A6 A5 A4 START BY MASTER A3 A2 A1 A0 R/W D15 D14 D13 ACK BY TS FRAME 1 SERIAL BUS ADDRESS BYTE 1 D12 D11 D10 D9 ACK BY MASTER FRAME 2 POINTER BYTE 9 D8 1 9 SCL (CONTINUED) SDA A6 (CONTINUED) REPEAT START BY MASTER A5 A4 A3 A2 A1 A0 D15 R/W D14 D13 D12 D11 D10 D9 ACK BY TS FRAME 3 SERIAL BUS ADDRESS BYTE FRAME 4 POINTER BYTE 1 D8 ACK BY MASTER 9 SCL (CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0 NO ACK BY MASTER STOP BY MASTER FRAME 5
PAGE 21
ADT7408 APPLICATION INFORMATION SELF-HEATING EFFECTS The temperature measurement accuracy of the ADT7408 might be degraded in some applications due to self-heating. Errors can be introduced from the quiescent dissipation and power dissipated when converting. The magnitude of these temperature errors is dependent on the thermal conductivity of the ADT7408 package, the mounting technique, and the effects of airflow. At 25°C, static dissipation in the ADT7408 is typically 778 μW operating at 3.3 V.
PAGE 22
ADT7408 OUTLINE DIMENSIONS 3.00 BSC SQ 0.60 MAX 0.50 0.40 0.30 1 8 PIN 1 INDICATOR 0.90 MAX 0.85 NOM SEATING PLANE TOP VIEW 2.75 BSC SQ 0.50 BSC 1.50 REF 5 1.89 1.74 1.59 4 1.60 1.45 1.30 0.70 MAX 0.65 TYP 12° MAX PIN 1 INDICATOR 0.05 MAX 0.01 NOM 0.30 0.23 0.18 0.20 REF Figure 20.
PAGE 23
ADT7408 NOTES Rev.
PAGE 24
ADT7408 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. © 2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05716-0-3/06(0) Rev.