ADT7408

ADT7408 (Rev. A)

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• Manufacturer or author: Analog Devices, Inc.
• PDF pages: 22

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±2°C Accurate, 12-Bit Digital Temperature Sensor Data Sheet ADT7408 Rev. A Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Tel: 781.329.4700 ©2006–2016 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com

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 A typical average supply current Selectable 1.5°C, 3°C, 6°C hysteresis SMBus-/I 2C®-compatible interface Dual-purpose event pin: comparator or interrupt 8-lead LFCSP , 3 mm × 3 mm (JEDEC MO-229 WEED-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 REGISTER EVENT# ∑-∆ DIGITAL COMPARATOR DECIMATOR SMBus/I²C INTERFACE ADT7408 Vss SDA SCL FACTORY RESERVED REGISTER TEMPERATURE REGISTER MANUFACTURER’S ID REGISTER CRITICAL TEMP REGISTER ALARM TEMP LOWER BOUNDARY TRIP REGISTER ALARM TEMP UPPER BOUNDARY TRIP REGISTER CONFIGURATION REGISTER CAPABILITY REGISTER REFERENCE TEMPERATURE SENSOR CLK AND TIMING GENERATION 1-BIT VDD 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 A 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 , 3 mm × 3 mm (JEDEC MO-229 WEED-4) package.

Rev. A | Page 2 of 22 TABLE OF CONTENTS

REVISION HISTORY

6/2016—Rev. 0 to Rev. A 3/2006—Revision 0: Initial Version

Rev. A | Page 3 of 22 SPECIFICATIONS All specifications TA = −20°C to +125°C, VDD = 3.0 V to 3.6 V , unless otherwise noted. Table 1. Parameter Symbol Min Typ Max Unit Test Conditions/Comments TEMPERATURE SENSOR AND ADC Local Sensor Accuracy (C Grade) ±0.5 ±2.0 °C 75°C ≤ TA ≤ 95°C, 3.0 V ≤ VDD ≤ 3.6 V active range ±1 ±3.0 °C 40°C ≤ TA ≤ 125°C, 3.0 V ≤ VDD ≤ 3.6 V monitor range ADC Resolution 12 Bits Temperature Resolution 0.0625 °C Temperature Conversion Time 60 125 ms Long Term Drift 0.081 °C Drift over 10 years, if part is operated at 55°C EVENT# OUTPUT (OPEN DRAIN) Output Low Voltage, VOL 0.4 V IOL = 3 mA Pin Capacitance 10 pF High Output Leakage Current IOH 0.1 1 µA EVENT# = 3.6 V Rise Time1 tLH 30 ns Fall Time1 tHL 30 ns RON Resistance (Low Output)1 15 Ω Supply and temperature dependent DIGITAL INPUTS Input Current IIH, IIL −1 +1 µA VIN = 0 V to VDD Input Low Voltage VIL 0.8 V 3.0 V ≤ VDD ≤ 3.6 V Input High Voltage VIH 2.1 V 3.0 V ≤ VDD ≤ 3.6 V SCL, SDA Glitch Rejection1 50 ns Input filtering suppresses noise spikes of less than 50 ns Pin Capacitance1 10 pF DIGITAL OUTPUT (OPEN DRAIN) Output Low Current IOL 6 mA SDA forced to 0.6 V Output Low Voltage VOL 0.4 V 3.0 V ≤ VDD ≤ 3.6 V at IOPULL_UP = 350 µA Output High Voltage VOH 2.1 V Output Capacitance1 COUT 10 pF POWER REQUIREMENTS Supply Voltage VDD 3.0 3.3 3.6 V Average Supply Current IDD 240 500 µA Supply Current IDD_CONV 360 550 µA Device current while converting Shutdown Mode at 3.3 V 3 20 µA Average Power Dissipation PD 790 µW VDD = 3.3 V, normal mode at 25°C 1 Guaranteed by design and characterization, not production tested.

TA = −20°C to +125°C, VDD = 3.0 V to 3.6 V , unless otherwise noted. Hold Time After (Repeated) Start Condition tHD:STA 4.0 μs After this period, the first clock is generated. 1 Guaranteed by design and characterization, not production tested. Figure 2. SMBus/I2C Timing Diagram

1 Power Dissipation PMAX = (TJMAX − TA)/θJA, where TA is the ambient

Figure 3. LFCSP Pb-Free Reflow Profile Based on JEDEC J-STD-20C

8 VDD

7 EVENT#

6 SCL

5 SDA

Figure 4. Pin Configuration Table 4. Pin Function Descriptions 1 A0 SMBus/I 2C Serial Bus Address Selection Pin. Logic input. Can be set to VSS or VDD. 2 A1 SMBus/I 2C Serial Bus Address Selection Pin. Logic input. Can be set to VSS or VDD. 3 A2 SMBus/I 2C Serial Bus Address Selection Pin. Logic input. Can be set to VSS or VDD. 4 V SS Negative Supply or Ground. registers is provided on this pin. Open-drain configuration; it needs a pull-up resistor. out from any register of the ADT7408. Open-drain configuration needs a pull-up resistor. 7 EVENT# Active Low. Open-drain event output pin. Dr iven low on comparator level or alert interrupt. 8 V DD Positive Supply Power. Deco uple the supply to ground.

±4°C from −20°C to +125°C, with excellent transducer linearity. drain output of the ADT7408 is capable of sinking 6 mA. needing correction or calibration by the user. accuracy in an extremely compact circuit. the comparator output in response to input voltage changes. overall noise performance and increasing accuracy. Figure 10. First-Order, Σ-Δ Modulator The conversion clock for the part is internally generated. even when it is in shutdown mode. conversion but waits until communication to the part is finished. mode, and the output polarity via the configuration register. software from the bus host at any time.

Rev. A | Page 9 of 22 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.

The ADT7408 contains 16 accessible registers, shown in Table 5. Table 5. Registers between 0x08 and 0x0F is reserved for factory usage. Table 6. Address Pointer Selected Registers thermal sensor, as shown in Table 7 and the following bit map. Note that RFU means reserved for future use. Table 7. Capability Mode Description 1 Alarm and critical trips capability. 0 Default accuracy ±2°C over the active range and ±3°C over the monitor range. 1 Can read temperature below 0°C and set sign bit accordingly (default). [D15:D5] Reserved for future use; must be 0.

that RFU means reserved for future use. Table 8. Configuration Mode Description 0: comparator output mode (default). When either lock bit (D6 and D7) is set, this bit cannot be altered until unlocked. When either lock bit (D6 and D7) is set, this bit cannot be altered until unlocked. 0: event output on alarm or critical temperature event (default). 1: event only if temperature is above the value in the critical temperature trip register. When either lock bit (D6 and D7) is set, this bit cannot be altered until unlocked. 0: event output disabled (default). When either lock bit (D6 and D7) is set, this bit cannot be altered until unlocked. D4 Event output status (read only). 0: event output condition is not being asserted by this device. 1: event output pin is being asserted by this device due to alarm window or critical trip condition. by writing to the clear event bit. Writing to this bit has no effect on the output status because it is a read function only. D5 Clear event (write only). 1: clears an active event in interrupt mode. is greater than the critical temperature, an event cannot be cleared (see Figure 12). 0: alarm trips are not locked and can be altered (default). 1: alarm trip register settings cannot be altered. can be written with a single write and do not require double writes. 0: critical trip is not locked and can be altered (default). 1: critical trip register settings cannot be altered. can be written with a single write and do not require double writes. is set, this bit cannot be set until unlocked. However, it can be cleared at any time.

01: enable hysteresis at 1.5°C. 10: enable hysteresis at 3°C. 11: enable hysteresis at 6°C. Figure 11. Hysteresis

Rev. A | Page 13 of 22 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 = 0.25°C. RFU (reserved for future use) bits are not supported and always report 0. Interrupts respond to the programmed boundary values. If boundary values are being altered in-system, the user should turn off interrupts until a known state can be obtained to avoid superfluous interrupt activity. The format of this register is shown in the following bit map: Sign MSB LSB D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 Alarm window upper boundary temperature RFU RFU Alarm Temperature Lower Boundary Trip Register (Read/Write) The value is the lower threshold temperature value for alarm mode. The data format is twos complement with one LSB = 0.25oC. RFU bits are not supported and always report 0. Interrupts respond to the programmed boundary values. If boundary values are being altered in-system, the user should turn off interrupts until a known state can be obtained to avoid superfluous interrupt activity. The format of this register is shown in the following bit map: Sign MSB LSB D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 Alarm window upper boundary temperature RFU RFU Critical Temperature Trip Register (Read/Write) The value is the critical temperature. The data format is twos complement with one LSB = 0.25oC. RFU bits are not supported and always report 0. The format of this register is shown in the following bit map: Sign MSB LSB D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 Critical temperature trip point RFU RFU Temperature Value Register (Read Only) This 16-bit, read-only register stores the trip status and the temperature measured by the internal temperature sensor, as shown in Table 9. The temperature is stored in 13-bit, twos complement format with the MSB being the temperature sign bit and the 12 LSBs representing temperature. One LSB = 0.0625oC. The most significant bit has a resolution of 128oC. 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 trip status bits represent the internal temperature trip detection and are not affected by the status of the event or configuration bits, for example, event output control, clear event. If both above and below are 0, then the current temperature is exactly within the alarm window boundaries, as defined in the configuration register. The format and descriptions are shown in Table 9 and the following bit map: Sign MSB LSB D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Above critical trip Above alarm window Below alarm window Temperature

Table 9. Temperature Register Trip Status Description 0 Temperature is equal to or above the alarm window lower boundary temperature. 1 Temperature is below the alarm window lower boundary temperature. 0 Temperature is equal to or below the alarm window upper boundary temperature. 1 Temperature is above the alarm window upper boundary temperature. 0 Temperature is below the critical temperature setting. 1 Temperature is equal to or above the critical temperature setting.

where d is the 12-bit digital output in decimal. code, but the sign is inserted in the final result. Table 10 tabulates some temperature results vs. digital outputs. contains DB2 to DB11. DB0 to DB1 are not in this calculation. register requires a 2-byte read. Table 10. 12-Bit Temperature Data Format

The pointer register selects the data registers in the ADT7408. register requires two data bytes. by retrieving the two data bytes. 16 bits wide, so two bytes of data are written to these registers. start or repeated start is required. Figure 14. Writing to the Address Pointer Register, Followed by Two Bytes of Data

Figure 17. A Write to the Pointer Register Followed by a Repeat Start and an Immediate Data-Word Read

0.203 REF

0.05 MAX

0.02 NOM

0.50 BSC

Figure 20. 8-Lead Frame Chip Scale Package [LFCSP] 2 Temperature accuracy is over the 75°C to 95°C temperature range. I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors). registered trademarks are the prop erty of their respective owners.