10-Bit Digital Temperature Sensor (AD7416) and Four Single-Channel ADCs AD7416/AD7417/AD7418 FUNCTIONAL BLOCK DIAGRAMS 10-bit ADC with 15 μs and 30 μs conversion times Single and 4 single-ended analog input channels On-chip temperature sensor: −40°C to +125°C On-chip track-and-hold Overtemperature indicator Automatic power-down at the end of a conversion Wide operating supply range: 2.7 V to 5.5 V I2C-compatible serial interface Selectable serial bus address allows connection of up to 8 AD7416/AD7417 devices to a single bus AD7416 is a superior replacement for LM75 10-BIT ANALOG-TO-DIGITAL CONVERTER BAND GAP TEMPERATURE SENSOR AD7416 TEMPERATURE VALUE REGISTER SETPOINT COMPARATOR TOTI SETPOINT REGISTER ADDRESS POINTER REGISTER 8 VDD THYST SETPOINT REGISTER 3 OTI FAULT QUEUE COUNTER CONFIGURATION REGISTER 4 GND A0 7 Data acquisition with ambient temperature monitoring Industrial process control Automotive Battery-charging applications Personal computers Figure 1. AD7416 The temperature sensor on the parts can be accessed via multiplexer Channel 0. When Channel 0 is selected and a conversion is initiated, the resulting ADC code at the end of the conversion gives a measurement of the ambient temperature (±1°C @ 25°C). On-chip registers can be programmed with high and low temperature limits, and an open-drain overtemperature indicator (OTI) output is provided, which becomes active when a programmed limit is exceeded. A configuration register allows programming of the sense of the OTI output (active high or active low) and its operating mode (comparator or interrupt). A programmable fault queue counter allows the number of out-of-limit measurements that must occur before triggering the OTI output to be set to prevent spurious triggering of the OTI output in noisy environments. VDD REFIN 5 14 TOTI SETPOINT B REGISTER TEMP SENSOR CHARGE DISTRIBUTION DAC AIN1 7 AIN2 8 MUX AIN3 9 A>B 4 OTI 3 SCL 2 SDA A REF 2.5V GENERAL DESCRIPTION SAMPLING CAPACITOR DATA OUT I2C CLOCK CONTROL LOGIC INTERFACE AIN4 10 AD7417 VBALANCE 1 16 6 15 13 12 11 NC NC GND CONVST A0 A1 A2 01126-002 The AD7417 and AD7418 are 10-bit, 4-channel and single-channel ADCs with an on-chip temperature sensor that can operate from a single 2.7 V to 5.5 V power supply. The devices contain a 15 μs successive approximation converter, a 5-channel multiplexer, a temperature sensor, a clock oscillator, a track-and-hold, and a reference (2.5 V). The AD7416 is a temperature-monitoring only device in an 8-lead package. 2 SCL A2 5 NC = NO CONNECT Figure 2. AD7417 VDD REFIN 7 6 TOTI SETPOINT B REGISTER TEMP SENSOR 3 OTI 2 SCL 1 SDA A CHARGE DISTRIBUTION DAC REF 2.5V AIN 5 A>B MUX SAMPLING CAPACITOR DATA OUT I2C CLOCK CONTROL LOGIC INTERFACE AD7418 VBALANCE 4 8 GND CONVST 01126-003 APPLICATIONS 1 SDA SERIAL BUS INTERFACE A1 6 01126-001 FEATURES Figure 3. AD7418 Rev. I 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. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©1998–2010 Analog Devices, Inc. All rights reserved. AD7416/AD7417/AD7418 TABLE OF CONTENTS Features .............................................................................................. 1 On-Chip Reference .................................................................... 11 Applications....................................................................................... 1 Temperature Measurement ....................................................... 12 General Description ......................................................................... 1 Internal Register Structure........................................................ 12 Functional Block Diagrams............................................................. 1 Serial Bus Interface..................................................................... 14 Revision History ............................................................................... 2 OTI Output ................................................................................. 17 Product Highlights ........................................................................... 3 Fault Queue ................................................................................. 17 Specifications..................................................................................... 4 Power-On Defaults..................................................................... 17 AD7417/AD7418 Specifications................................................. 4 Operating Modes........................................................................ 17 AD7416 Specifications................................................................. 6 CONVST Start Mode................................................................. 18 Absolute Maximum Ratings............................................................ 7 Applications Information .............................................................. 19 ESD Caution.................................................................................. 7 Supply Decoupling ..................................................................... 19 Pin Configurations and Function Descriptions ........................... 8 Power-On Reset.......................................................................... 19 Terminology .................................................................................... 10 Mounting the AD7416/AD7417/AD7418 .............................. 19 Theory of Operation ...................................................................... 11 Fan Controller............................................................................. 19 Circuit Information.................................................................... 11 Thermostat .................................................................................. 19 Converter Details........................................................................ 11 System with Multiple AD7416 Devices................................... 20 Typical Connection Diagram ................................................... 11 Outline Dimensions ....................................................................... 21 Analog Inputs.............................................................................. 11 Ordering Guide .......................................................................... 23 REVISION HISTORY 11/10—Rev. H to Rev. I Changes to Figure 19...................................................................... 16 2/09—Rev. G to Rev. H Updated Format..................................................................Universal Changes to Data Sheet Title, Figure 2 and Figure 3..................... 1 Moved Product Highlights Section................................................ 3 Changes to Table 1............................................................................ 4 Changes to Endnote 1, Table 2........................................................ 6 Added Figure 5 Caption................................................................... 7 Changes to Table 4............................................................................ 8 Changes to Table 5 and Table 6....................................................... 9 Changes to On-Chip Reference Section...................................... 11 Changes to Figure 13...................................................................... 12 Changes to Table 8 and Table 10................................................... 13 Changes to Figure 15, Figure 16, and Figure 17 ......................... 15 Changes to Reading Data From the AD7416/AD7417/AD7418 Section, Figure 18, and Figure 19 ................................................. 16 Change to Mode 1 .......................................................................... 17 Changes to Figure 22 Caption and CONVST Pin Mode Section.............................................................................................. 18 Moved Figure 21 and Figure 22 .................................................... 18 Changes to Power-On Reset Section............................................ 19 Updated Outline Dimensions ....................................................... 21 Changes to Ordering Guide .......................................................... 23 8/04—Data Sheet Changed from Rev. F to Rev. G Changes to Figure 12...................................................................... 12 Changes to Reading Data from the AD7416/AD7417/AD7418 Section.............................................................................................. 13 Changes to Power-On-Reset section ........................................... 14 7/03—Data Sheet Changed from Rev. E to Rev. F Updated Features...............................................................................1 Updated Specifications .....................................................................3 Updated Absolute Maximum Ratings ............................................6 Updated Ordering Guide .................................................................6 Updated Product Highlights............................................................7 Updated Circuit Information...........................................................7 Updated Temperature Measurement section ................................9 10/02—Data Sheet Changed from Rev. D to Rev. E Edits to Specifications Headings .....................................................2 Added Temperature Measurement section....................................8 Edits to Serial Bus Address section .............................................. 10 Edits to Figure 11............................................................................ 12 Edits to CONVST Pin Mode section ........................................... 14 Edits to Power-On-Reset section ................................................. 14 Addition of Figures 16 and 17 ...................................................... 15 Updated Outlines ........................................................................... 16 Rev. I | Page 2 of 24 AD7416/AD7417/AD7418 An I2C® compatible serial interface allows the AD7416/AD7417/ AD7418 registers to be written to and read back. The three LSBs of the AD7416/AD7417 serial bus address can be selected, which allows up to eight AD7416/AD7417 devices to be connected to a single bus. The AD7417 is available in a narrow body, 0.15 inch, 16-lead, small outline package (SOIC) and in a 16-lead, thin shrink, small outline package (TSSOP). The AD7416 and AD7418 are available in 8-lead SOIC and MSOP packages. PRODUCT HIGHLIGHTS 1. 2. 3. The AD7416/AD7417/AD7418 have an on-chip temperature sensor that allows an accurate measurement of the ambient temperature (±1°C @ 25°C, ±2°C overtemperature) to be Rev. I | Page 3 of 24 made. The measurable temperature range is −40°C to +125°C. An overtemperature indicator is implemented by carrying out a digital comparison of the ADC code for Channel 0 (temperature sensor) with the contents of the on-chip TOTI setpoint register. The AD7417 offers a space-saving, 10-bit analog-to-digital solution with four external voltage input channels, an onchip temperature sensor, an on-chip reference, and a clock oscillator. The automatic power-down feature enables the AD7416/ AD7417/AD7418 to achieve superior power performance. At slower throughput rates, the part can be programmed to operate in a low power shutdown mode, allowing further savings in power consumption. AD7416/AD7417/AD7418 SPECIFICATIONS AD7417/AD7418 SPECIFICATIONS VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted. Table 1. Parameter DC ACCURACY Resolution Minimum Resolution for Which No Missing Codes Are Guaranteed Relative Accuracy 2 Differential Nonlinearity2 Gain Error2 Gain Error Match2 Offset Error2 Offset Error Match2 ANALOG INPUTS Input Voltage Range Input Leakage Current 3 Input Capacitance TEMPERATURE SENSOR1 Measurement Error Ambient Temperature 25°C TMIN to TMAX Temperature Resolution CONVERSION RATE Track-and-Hold Acquisition Time 4 Conversion Time Temperature Sensor Channel 1 to Channel 4 REFERENCE INPUT 5,6 REFIN Input Voltage Range Input Impedance Input Capacitance ON-CHIP REFERENCE Reference Error6 Temperature Coefficient6 DIGITAL INPUTS Input High Voltage, VIH Input Low Voltage, VIL Input Leakage Current DIGITAL OUTPUTS Output Low Voltage, VOL Output High Current A Version B Version 1 Unit 10 10 10 10 Bits Bits ±1 ±1 ±3 ±10 ±0.6 ±4 ±0.7 ±1 ±1 ±3 ±10 ±0.6 ±4 ±0.7 LSB max LSB max LSB max LSB max LSB max LSB max LSB max VREF 0 ±1 10 VREF 0 ±1 10 V max V min μA max pF max ±2 ±3 1/4 ±1 ±2 1/4 °C max °C max °C/LSB 400 400 ns max Source impedance < 10 Ω 30 15 30 15 μs max μs max Typically 27 μs Typically 10 μs 2.625 2.375 40 10 2.625 2.375 40 10 V max V min kΩ min pF max 2.5 V + 5% 2.5 V − 5% ±25 80 ±25 80 mV max ppm/°C typ VDD × 0.7 VDD × 0.3 1 VDD × 0.7 VDD × 0.3 1 V min V max μA max 0.4 1 0.4 1 V max μA max Test Conditions/Comments Any channel This specification is typical for VDD of 3.6 V to 5.5 V This specification is typical for VDD of 3.6 V to 5.5 V External reference Internal reference AD7417 only AD7417 only Nominal 2.5 V Rev. I | Page 4 of 24 IOL = 3 mA VOH = 5 V AD7416/AD7417/AD7418 Parameter POWER REQUIREMENTS VDD IDD Normal Operation Power-Down Auto Power-Down Mode 10 SPS Throughput Rate 1 kSPS Throughput Rate 10 kSPS Throughput Rate Power-Down A Version B Version 1 Unit Test Conditions/Comments 5.5 2.7 5.5 2.7 V max V min For specified performance 600 1.5 600 1.5 μA max μA max 6 60 600 3 6 60 600 3 μW typ μW typ μW typ μW max Logic inputs = 0 V or VDD 1 0.7 μA typically VDD = 3 V; see the Operating Modes section Typically 0.15 μW B Version applies to AD7417 only with temperature range of −40°C to +85°C. A Version temperature range is −40°C to +125°C. For VDD = 2.7 V, TA = 85°C maximum and temperature sensor measurement error = ±3°C maximum. 2 See the Terminology section. 3 Refers to the input current when the part is not converting. Primarily due to reverse leakage current in the ESD protection diodes. 4 Sample tested during initial release and after any redesign or process change that may affect this parameter. 5 On-chip reference shuts down when an external reference is applied. 6 The accuracy of the temperature sensor is affected by reference tolerance. Rev. I | Page 5 of 24 AD7416/AD7417/AD7418 AD7416 SPECIFICATIONS VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted. Table 2. Parameter TEMPERATURE SENSOR AND ADC Accuracy Min Resolution Temperature Conversion Time Update Rate, tR OTI Delay Supply Current Unit Test Conditions/Comments ±2.0 °C ±3.0 °C TA = −25°C to + 100°C (VDD = 3 V minimum) 1 TA = −40°C to + 125°C (VDD = 3 V minimum)1 40 400 1 × tR 350 0.2 80 75 VDD × 0.7 −0.3 +0.005 −0.005 20 6 × tR 1.0 600 1.5 Bits μs μs ms mA μA μA °C °C VDD + 0.5 VDD × 0.3 +1.0 −1.0 V V μA μA pF 0.4 1 250 0.8 V μA ns V Depends on fault queue setting I2C active I2C inactive Shutdown mode VIN = 5 V VIN = 0 V All digital inputs 2.5 50 0 μs ns ns IOL = 3 mA VOH = 5 V CL = 400 pF, IO = 3 mA IOUT = 4 mA AD7416/AD7417/AD7418 See Figure 4 See Figure 4 See Figure 4 50 ns See Figure 4 ns ns See Figure 4 See Figure 4 50 300 For VDD = 2.7 V to 3 V, TA maximum = 85°C and temperature sensor measurement error = ±3°C maximum. Sample tested during initial release and after any redesign or process change that may affect this parameter. t1 SCL t4 t2 t5 SDA DATA IN t3 SDA DATA OUT t6 Figure 4. Diagram for Serial Bus Timing Rev. I | Page 6 of 24 01126-004 2 Max 10 TOTI Default Temperature THYST Default Temperature DIGITAL INPUTS Input High Voltage, VIH Input Low Voltage, VIL Input High Current, IIH Input Low Current, IIL Input Capacitance, CIN DIGITAL OUTPUTS Output Low Voltage, VOL Output High Current Output Fall Time, tf OS Output Low Voltage, VOL AC ELECTRICAL CHARACTERISTICS 2 Serial Clock Period, t1 Data In Setup Time to SCL High, t2 Data Out Stable after SCL Low, t3 SDA Low Setup Time to SCL Low (Start Condition), t4 SDA High Hold Time after SCL High (Stop Condition), t5 SDA and SCL Fall Time, t6 1 Typ AD7416/AD7417/AD7418 ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. 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. Parameter VDD to AGND VDD to DGND Analog Input Voltage to AGND AIN1 to AIN4 Reference Input Voltage to AGND1 Digital Input Voltage to DGND Digital Output Voltage to DGND Operating Temperature Range A Version B Version Storage Temperature Range Junction Temperature TSSOP, Power Dissipation θJA Thermal Impedance Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) 16-Lead SOIC Package, Power Dissipation θJA Thermal Impedance Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) 8-Lead SOIC Package, Power Dissipation θJA Thermal Impedance Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) MSOP Package, Power Dissipation θJA Thermal Impedance Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) 1 Rating −0.3 V to +7 V −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 + 0.3 V REFIN VDD BAT81 AD7417 −40°C to +125°C −40°C to +85°C −65°C to +150°C 150°C 450 mW 120°C/W 260°C 215°C 220°C 450 mW 100°C/W 01126-025 Table 3. Figure 5. Diode Connection ESD CAUTION 215°C 220°C 450 mW 157°C/W 215°C 220°C 450 mW 206°C/W 215°C 220°C If the reference input voltage is likely to exceed VDD by more than 0.3 V (for example, during power-up) and the reference is capable of supplying 30 mA or more, it is recommended to use a clamping diode between the REFIN pin and the VDD pin. Figure 5 shows how the diode should be connected. Rev. I | Page 7 of 24 AD7416/AD7417/AD7418 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS NC 1 16 NC SDA 2 SCL 3 AD7417 14 VDD 13 A0 TOP VIEW REFIN 5 (Not to Scale) 12 A1 GND 6 11 A2 AIN1 7 10 AIN4 AIN2 8 9 AIN3 NC = NO CONNECT 01126-005 OTI 4 15 CONVST Figure 6. AD7417 Pin Configuration (SOIC/TSSOP) Table 4. AD7417 Pin Function Descriptions Pin No. 1, 16 2 3 4 Mnemonic NC SDA SCL OTI 5 REFIN 6 7 to 10 GND AIN1 to AIN4 11 12 13 14 15 A2 A1 A0 VDD CONVST Description No Connection. Do not connect anything to this pin. Digital I/O. Serial bus bidirectional data. Push-pull output. Digital Input. Serial bus clock. This pin is a logic output. The overtemperature indicator (OTI) is set if the result of a conversion on Channel 0 (temperature sensor) is greater than an 8-bit word in the TOTI setpoint register. The signal is reset at the end of a serial read operation. Open-drain output. Reference Input. An external 2.5 V reference can be connected to the AD7417 at this pin. To enable the on-chip reference, the REFIN pin should be tied to GND. If an external reference is connected to the AD7417, the internal reference shuts down. Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry. Analog Input Channels. The AD7417 has four analog input channels. The input channels are single-ended with respect to GND. The input channels can convert voltage signals in the range of 0 V to VREF. A channel is selected by writing to the configuration register of the AD7417. Digital Input. This is the highest programmable bit of the serial bus address. Digital Input. This is the middle programmable bit of the serial bus address. Digital Input. This is the lowest programmable bit of the serial bus address. Positive Supply Voltage, 2.7 V to 5.5 V. Logic Input Signal. Convert start signal. The rising edge of this signal fully powers up the part. The power-up time for the part is 4 μs. If the CONVST pulse is greater than 4 μs, the falling edge of CONVST places the track-and-hold mode into hold mode and initiates a conversion. If the pulse is less than 4 μs, an internal timer ensures that the track-and-hold does not go into hold, and conversion is not initiated until the power-up time has elapsed. The track-and-hold goes into track mode again at the end of conversion (see the Operating Modes section). Rev. I | Page 8 of 24 8 VDD SDA 1 7 A0 SCL 2 6 A1 TOP VIEW GND 4 (Not to Scale) 5 A2 OTI 3 SCL 2 OTI 3 AD7416 AD7418 TOP VIEW GND 4 (Not to Scale) 01126-006 SDA 1 Figure 7. AD7416 Pin Configuration (SOIC/MSOP) 8 CONVST 7 VDD 6 REFIN 5 AIN 01126-007 AD7416/AD7417/AD7418 Figure 8. AD7418 Pin Configuration (SOIC/MSOP) Table 5. AD7416 Pin Function Descriptions Pin No. 1 2 3 Mnemonic SDA SCL OTI 4 5 6 7 8 GND A2 A1 A0 VDD Description Digital I/O. Serial bus bidirectional data. Push-pull output. Digital Input. Serial bus clock. This pin is a logic output. The OTI is set if the result of a conversion on Channel 0 (temperature sensor) is greater than an 8-bit word in the TOTI setpoint register. The signal is reset at the end of a serial read operation. Open-drain output. Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry. Digital Input. This is the highest programmable bit of the serial bus address. Digital Input. This is the middle programmable bit of the serial bus address. Digital Input. This is the lowest programmable bit of the serial bus address. Positive Supply Voltage, 2.7 V to 5.5 V. Table 6. AD7418 Pin Function Descriptions Pin No. 1 2 3 Mnemonic SDA SCL OTI 4 5 GND AIN 6 REFIN 7 8 CONVST VDD Description Digital I/O. Serial bus bidirectional data. Push-pull output. Digital Input. Serial bus clock. This is a logic output. The OTI is set if the result of a conversion on Channel 0 (temperature sensor) is greater than an 8-bit word in the TOTI setpoint register. The signal is reset at the end of a serial read operation. Open-drain output. Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry. Analog Input Channel. The input channel is single-ended with respect to GND. The input channel can convert voltage signals in the range of 0 V to VREF. The analog input channel is selected by writing to the configuration register of the AD7418 and choosing Channel 4. Reference Input. An external 2.5 V reference can be connected to the AD7418 at this pin. To enable the on-chip reference, the REFIN pin should be tied to GND. If an external reference is connected to the AD7418, the internal reference shuts down. Positive Supply Voltage, 2.7 V to 5.5 V. Logic Input Signal. Convert start signal. The rising edge of this signal fully powers up the part. The power-up time for the part is 4 μs. If the CONVST pulse is greater than 4 μs, the falling edge of CONVST places the track-and-hold mode into hold mode and initiates a conversion. If the pulse is less than 4 μs, an internal timer ensures that the track-and-hold does not go into hold, and conversion is not initiated until the power-up time has elapsed. The track-and-hold goes into track mode again at the end of conversion (see the Operating Modes section). Rev. I | Page 9 of 24 AD7416/AD7417/AD7418 TERMINOLOGY Relative Accuracy Relative accuracy or endpoint nonlinearity is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. Differential Nonlinearity This is the difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC. Offset Error This is the deviation of the first code transition (0000…000) to (0000…001) from the ideal, that is, GND + 1 LSB. Offset Error Match This is the difference in offset error between any two channels. Gain Error This is the deviation of the last code transition (1111…110) to (1111…111) from the ideal, that is, VREF − 1 LSB, after the offset error has been adjusted out. Gain Error Match This is the difference in gain error between any two channels. Track-and-Hold Acquisition Time Track-and-hold acquisition time is the time required for the output of the track-and-hold amplifier to reach its final value, within ±½ LSB, after the end of conversion (the point at which the track-and-hold returns to track mode). It also applies to situations where a change in the selected input channel takes place or where there is a step input change on the input voltage applied to the selected AIN input of the AD7417 or AD7418. It means that the user must wait for the duration of the track-andhold acquisition time after the end of conversion, or after a channel change or step input change to AIN before starting another conversion, to ensure that the part operates to specification. Rev. I | Page 10 of 24 AD7416/AD7417/AD7418 THEORY OF OPERATION SUPPLY 2.7V TO 5.5V + A temperature measurement is made by selecting the Channel 0 of the on-chip mux and carrying out a conversion on this channel. A conversion on Channel 0 takes 30 μs to complete. Temperature measurement is explained in the Temperature Measurement section. AIN4 TYPICAL CONNECTION DIAGRAM Figure 9 shows a typical connection diagram for the AD7417. Using the A0, A1, and A2 pins allows the user to select from up to eight AD7417 devices on the same serial bus, if desired. An external 2.5 V reference can be connected at the REFIN pin. If an VDD SCL SDA CONVST OTI AD7417 GND REFIN OPTIONAL EXTERNAL REFERENCE AD780/ REF192 MICROCONTROLLER/ MICROPROCESSOR A0 A1 A2 10µF FOR EXTERNAL REFERENCE Figure 9. Typical AD7417 Connection Diagram ANALOG INPUTS Figure 10 shows an equivalent circuit of the analog input structure of the AD7417 and AD7418. The two diodes, D1 and D2, provide ESD protection for the analog inputs. Care must be taken to ensure that the analog input signal never exceeds the supply rails by more than 200 mV to prevent these diodes from becoming forward-biased and start conducting current into the substrate. The maximum current these diodes can conduct without causing irreversible damage to the part is 20 mA. Capacitor C2 in Figure 10 is typically about 4 pF and can primarily be attributed to pin capacitance. Resistor R1 is a lumped component made up of the on resistance of a multiplexer and a switch. This resistor is typically about 1 kΩ. Capacitor C1 is the ADC sampling capacitor and has a capacitance of 3 pF. VDD D1 R1 1kΩ C1 3pF VBALANCE AIN C2 4pF The on-chip reference is not available to the user, but REFIN can be overdriven by an external reference source (2.5 V only). All unused analog inputs should be tied to a voltage within the nominal analog input range to avoid noise pickup. For minimum power consumption, the unused analog inputs should be tied to GND. 2-WIRE SERIAL INTERFACE 0.1µF AIN1 AIN2 AIN3 0V TO 2.5V INPUT CONVERTER DETAILS Conversion is initiated on the AD7417/AD7418 by pulsing the CONVST input. The conversion clock for the part is internally generated so that no external clock is required except when reading from and writing to the serial port. The on-chip trackand-hold goes from track mode to hold mode, and the conversion sequence is started on the falling edge of the CONVST signal. A conversion is also initiated in the automatic conversion mode every time a read or write operation to the AD7416/AD7417/ AD7418 takes place. In this case, the internal clock oscillator (which runs the automatic conversion sequence) is restarted at the end of the read or write operation. The track-and-hold goes into hold mode approximately 3 μs after the read or write operation is complete, and a conversion is then initiated. The result of the conversion is available either 15 μs or 30 μs later, depending on whether an analog input channel or the temperature sensor is selected. The track-and-hold acquisition time of the AD7417/AD7418 is 400 ns. + 10µF 01126-008 The AD7417 and AD7418 are single-channel and four-channel, 15 μs conversion time, 10-bit ADCs with on-chip temperature sensor, reference, and serial interface logic functions on a single chip. The AD7416 has no analog input channel and is intended for temperature measurement only. The ADC section consists of a conventional successive approximation converter based around a capacitor DAC. The AD7416, AD7417, and AD7418 are capable of running on a 2.7 V to 5.5 V power supply, and the AD7417 and AD7418 accept an analog input range of 0 V to +VREF. The on-chip temperature sensor allows an accurate measurement of the ambient device temperature to be made. The working measurement range of the temperature sensor is −40°C to +125°C. The parts require a 2.5 V reference that can be provided from the part’s own internal reference or from an external reference source. external reference is used, a 10 μF capacitor should be connected between REFIN and GND. SDA and SCL form the 2-wire I2C compatible interface. For applications where power consumption is of concern, the automatic power-down at the end of a conversion should be used to improve power performance (see the Operating Modes section.) D2 CONVERT PHASE: SWITCH OPEN TRACK PHASE: SWITCH CLOSED 01126-009 CIRCUIT INFORMATION Figure 10. Equivalent Analog Input Circuit ON-CHIP REFERENCE The AD7417/AD7418 have an on-chip 1.2 V band gap reference that is amplified by a switched capacitor amplifier to give an output of 2.5 V. The amplifier is only powered up at the start of the conversion phase and is powered down at the end of the conversion. The on-chip reference is selected by connecting the REFIN pin to analog ground, which causes SW1 (see Figure 11) to open and the reference amplifier to power up during a conversion. Therefore, the on-chip reference is not available externally. Rev. I | Page 11 of 24 AD7416/AD7417/AD7418 The temperature resolution of the ADC is 0.25°C, which corresponds to 1 LSB of the ADC. The ADC can theoretically measure a temperature span of 255°C; the guaranteed temperature range is −40°C to +125°C. The result of the conversion is stored in the temperature value register (0x00) as a 16-bit word. The 10 MSBs of this word store the temperature measurement (see Table 9 and Table 10). An external 2.5 V reference can be connected to the REFIN pin. This has the effect of shutting down the on-chip reference circuitry. REFIN EXTERNAL REFERENCE DETECT 1.2V The temperature conversion formulas using the 10 MSBs of the temperature value register are SW1 1.2V 2.5V BUFFER 01126-010 24kΩ Figure 11. On-Chip Reference TEMPERATURE MEASUREMENT A common method of measuring temperature is to exploit the negative temperature coefficient of a diode, or the base-emitter voltage of a transistor, operated at a constant current. Unfortunately, this technique requires calibration to null out the effect of the absolute value of VBE, which varies from device to device. Positive Temperature = ADC Code/4 (1) Negative Temperature = (ADC Code − 512)/4 (2) The MSB is removed from ADC Code in Equation 2. INTERNAL REGISTER STRUCTURE The AD7417/AD7418 have seven internal registers, as shown in Figure 13. Six of these are data registers and one is an address pointer register. The AD7416 has five internal registers (the ADC and Config2 registers are not applicable to the AD7416). TEMPERATURE VALUE REGISTER (READ-ONLY ADDRESS 0x00) CONFIGURATION REGISTER (READ/WRITE ADDRESS 0x01) The technique used in the AD7416/AD7417/AD7418 is to measure the current change in VBE when the device is operated at two different currents. This is given by THYST SETPOINT REGISTER (READ/WRITE ADDRESS 0x02) ADDRESS POINTER REGISTER (SELCTS DATA REGISTER FOR READ/WRITE) ΔVBE = KT / q ×1n(N ) where: K is Boltzmann’s constant. q is the charge on the electron (1.6 × 10−19 Coulombs). T is the absolute temperature in Kelvins. N is the ratio of the two currents. TOTI SETPOINT REGISTER (READ/WRITE ADDRESS 0x03) ADDRESS ADC VALUE REGISTER (READ-ONLY ADDRESS 0x04) I DATA CONFIG2 REGISTER (READ/WRITE ADDRESS 0x05) VDD N×I SDA SCL SERIAL BUS INTERFACE 01126-012 26kΩ Figure 13. AD7417/AD7418 Register Structure VOUT+ Address Pointer Register TO ADC SENSING TRANSISTOR SENSING TRANSISTOR 01126-011 VOUT– Figure 12. Temperature Measurement Technique Figure 12 shows the method the AD7416/AD7417/AD7418 use to measure the device temperature. To measure ΔVBE, the sensor (substrate transistor) is switched between operating currents of I and N × I. The resulting waveform is passed through a chopper-stabilized amplifier that performs the functions of amplification and rectification of the waveform to produce a dc voltage proportional to ΔVBE. This voltage is measured by the ADC to give a temperature output in 10-bit twos complement form. The address pointer register is an 8-bit register that stores an address that points to one of the six data registers. The first data byte of every serial write operation to the AD7416/AD7417/ AD7418 is the address of one of the data registers, which is stored in the address pointer register, and selects the data register to which subsequent data bytes are written. Only the three LSBs of the address pointer register are used to select a data register. Table 7. Address Pointer Register P71 0 1 P61 0 P51 0 P3 to P7 must be set to 0. Rev. I | Page 12 of 24 P41 0 P31 0 P2 P1 P0 Register select AD7416/AD7417/AD7418 The AD7416 contains a temperature-only channel; the AD7417 has four analog input channels and a temperature channel; and the AD7418 has two channels, a temperature channel, and an analog input channel. The temperature channel address for all parts is the same, Channel 0. The address for the analog input channel on the AD7418 is Channel 4. Table 12 outlines the channel selection on the parts, and Table 13 shows the fault queue settings. D1 and D2 are explained in the OTI Output section. Table 8. Register Addresses P2 0 0 0 0 1 1 P1 0 0 1 1 0 0 P0 0 1 0 1 0 1 Registers Temperature value Configuration register THYST setpoint TOTI setpoint ADC value (AD7417/AD7418 only) Config2 (AD7417/AD7418 only) Temperature Value Register (Address 0x00) The temperature value register is a 16-bit, read-only register whose 10 MSBs store the temperature reading from the ADC in 10-bit twos complement format. Bit D5 to Bit D0 are unused. Table 9. Temperature Value Register D15 MSB D14 B8 D13 B7 D12 B6 D11 B5 D10 B4 D9 B3 D8 B2 D7 B1 D6 LSB The temperature data format is shown in Table 10. This shows the full theoretical range of the ADC from −128°C to +127°C, but in practice, the temperature measurement range is limited to the operating temperature range of the device. Table 10. Temperature Data Format Temperature −128°C −125°C −100°C −75°C −50°C −25°C −10°C −0.25°C 0°C +0.25°C +10°C +25°C +50°C +75°C +100°C +125°C +127°C Digital Output 10 0000 0000 10 0000 1100 10 0111 0000 10 1101 0100 11 0011 1000 11 1001 1100 11 1101 1000 11 1111 1111 00 0000 0000 00 0000 0001 00 0010 1000 00 0110 0100 00 1100 1000 01 0010 1100 01 1001 0000 01 1111 0100 01 1111 1100 D2 OTI polarity D1 Cmp/Int Channel Selection Temperature sensor (all parts), Channel 0 AIN1 (AD7417 only), Channel 1 AIN2 (AD7417 only), Channel 2 AIN3 (AD7417 only), Channel 3 AIN4 (AD7417) and AIN (AD7418), Channel 4 Table 13. Fault Queue Settings D4 0 0 1 1 D3 0 1 0 1 Number of Faults 1 (power-up default) 2 4 6 TOTI Setpoint Register (Address 0x03) The TOTI setpoint register is a 16-bit, read/write register whose nine MSBs store the TOTI setpoint in twos complement format equivalent to the nine MSBs of the temperature value register. Bit 6 to Bit 0 are unused. Table 14. THYST Setpoint and TOTI Setpoint Registers D15 MSB D14 B7 D13 B6 D12 B5 D11 B4 D10 B3 D9 B2 D8 B1 D7 LSB ADC Value Register (Address 0x04) Table 11. Configuration Register D4 D3 Fault queue D5 0 1 0 1 0 The THYST setpoint register is a 16-bit, read/write register whose nine MSBs store the THYST setpoint in twos complement format equivalent to the nine MSBs of the temperature value register. Bit D6 to Bit D0 are unused. The configuration register is an 8-bit, read/write register that is used to set the operating modes of the AD7416/AD7417/AD7418. Bit D7 to Bit D5 control the channel selection as outlined in Table 12. Bits[D7:D5] should always be set to 000 for the AD7416. Bit D4 and Bit D3 are used to set the length of the fault queue. D2 sets the sense of the OTI output. D1 selects the comparator or interrupt mode of operation, and D0 = 1 selects the shutdown mode (default: D0 = 0). D6 D5 Channel selection D6 0 0 1 1 0 THYST Setpoint Register (Address 0x02) Configuration Register (Address 0x01) D7 Table 12. Channel Selection D7 0 0 0 0 1 D0 Shutdown The ADC value register is a 16-bit, read-only register whose 10 MSBs store the value produced by the ADC in binary format. Bit D5 to Bit D0 are unused. Table 15 shows the ADC value register with 10 MSBs containing the ADC conversion request. Table 15. ADC Value Register D15 MSB D14 B8 D13 B7 D12 B6 D11 B5 D10 B4 D9 B3 D8 B2 D7 B1 D6 LSB ADC Transfer Function The designed code transitions occur at successive integer LSB values (that is, 1 LSB, 2 LSB, and so on). The LSB size = VREF/1024. The ideal transfer function characteristic for the AD7417 and AD7418 ADC is shown in Figure 14. Rev. I | Page 13 of 24 AD7416/AD7417/AD7418 ADC CODE 111...111 111...110 111...000 1LSB – VREF/1024 011...111 000...010 000...001 0V 1/2LSB 01126-013 000...000 +VREF – 1LSB ANALOG INPUT 2. Figure 14. Ideal Transfer Function Characteristic for the AD7417/AD7418 Config2 Register (Address 0x05) A second configuration register is included in the AD7417/ AD7418 for the functionality of the CONVST pin. It is an 8-bit register with Bit D5 to Bit D0 being left at 0. Bit D7 determines whether the AD7417/AD7418 should be operated in its default mode (D7 = 0), performing conversions every 355 μs or in its CONVST pin mode (D7 = 1), where conversions start only when the CONVST pin is used. Bit 6 contains the Test 1 bit. When this bit is 0, the I2C filters are enabled (default). Setting this bit to 1 disables the filters. 3. Table 16. Config2 Register D7 Conversion mode D6 Test 1 D5 0 D4 0 D3 0 D2 0 D1 0 D0 0 SERIAL BUS INTERFACE Control of the AD7416/AD7417/AD7418 is carried out via the I2C compatible serial bus. The AD7416/AD7417/AD7418 are connected to this bus as a slave device, under the control of a master device, for example, the processor. Serial Bus Address As with all I2C compatible devices, the AD7416/AD7417/AD7418 have a 7-bit serial address. The four MSBs of this address for the AD7416 are set to 1001; the AD7417 are set to 0101, and the three LSBs can be set by the user by connecting the A2 to A0 pins to either VDD or GND. By giving them different addresses, up to eight AD7416/AD7417 devices can be connected to a single serial bus, or the addresses can be set to avoid conflicts with other devices on the bus. The four MSBs of this address for the AD7418 are set to 0101, and the three LSBs are all set to 0. Any number of bytes of data can be transferred over the serial bus in one operation, but it is not possible to mix read and write in one operation because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation. Writing to the AD7416/AD7417/AD7418 Depending on the register being written to, there are three different writes for the AD7416/AD7417/AD7418. • • If a serial communication occurs during a conversion operation, the conversion stops and restarts after the communication. The serial bus protocol operates as follows: 1. direction of the data transfer, that is, whether data is written to or read from the slave device. The peripheral whose address corresponds to the transmitted address responds by pulling the data line low during the low period before the ninth clock pulse, known as the acknowledge bit. All other devices on the bus now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is a 0, then the master writes to the slave device. If the R/W bit is a 1, then the master reads from the slave device. Data is sent over the serial bus in sequences of nine clock pulses, eight bits of data followed by an acknowledge bit from the receiver of data. Transitions on the data line must occur during the low period of the clock signal and remain stable during the high period, because a low-to-high transition when the clock is high may be interpreted as a stop signal. When all data bytes have been read or written, stop conditions are established. In write mode, the master pulls the data line high during the 10th clock pulse to assert a stop condition. In read mode, the master device pulls the data line high during the low period before the ninth clock pulse. This is known as no acknowledge. The master then takes the data line low during the low period before the 10th clock pulse, then high during the 10th clock pulse to assert a stop condition. 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. All slave peripherals connected to the serial bus respond to the 7-bit address (MSB first) plus an R/W bit, which determines the Rev. I | Page 14 of 24 Writing to the address pointer register for a subsequent read. To read data from a particular register, the address pointer register must contain the address of that register. If it does not, the correct address must be written to the address pointer register by performing a single-byte write operation, as shown in Figure 15. The write operation consists of the serial bus address followed by the address pointer byte. No data is written to any of the data registers. Writing a single byte of data to the configuration register, the Config2 register, or to the TOTI setpoint or THYST setpoint registers. The configuration register is an 8-bit register, so only one byte of data can be written to it. If only 8-bit temperature comparisons are required, the temperature LSB can be ignored in TOTI and THYST, and only eight bits need to be written to the TOTI setpoint and THYST setpoint registers. Writing a single byte of data to one of these registers consists of the serial bus address, the data register address written to the address pointer register, followed by the data byte AD7416/AD7417/AD7418 1 THYST setpoint registers. This consists of the serial bus address, the register address written to the address pointer register, followed by two data bytes written to the selected data register. This is illustrated in Figure 17. 9 1 9 SCL 1 0 0 1 A2 A1 A0 R/W START BY MASTER P7 P6 P5 P4 P3 P2 P1 P0 ACK. BY AD741x 1 ACK. BY AD741x 1 FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE STOP BY MASTER 01126-014 SDA 1AD741x = AD7416/AD7417/AD7418. Figure 15. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation 1 9 1 9 SCL SDA 1 0 0 1 A2 A1 A0 P7 R/W START BY MASTER P6 P5 P4 P3 P2 P1 P0 ACK. BY AD741x 1 ACK. BY AD741x 1 FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE 1 9 SCL (CONTINUED) SDA (CONTINUED) D7 D6 D5 D4 D3 D2 D1 STOP BY MASTER D0 01126-015 ACK. BY AD741x 1 FRAME 3 DATA BYTE 1AD741x = AD7416/AD7417/AD7418. Figure 16. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register 1 9 1 9 SCL SDA 1 0 0 1 A2 A1 A0 R/W START BY MASTER P7 P6 P5 P4 P3 P2 P1 P0 ACK. BY AD741x 1 ACK. BY AD741x 1 FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE 1 9 1 9 SCL (CONTINUED) SDA (CONTINUED) D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 ACK. BY STOP BY AD741x 1 MASTER FRAME 3 MOST SIGNIFICANT DATA BYTE D0 STOP BY ACK. BY 1 MASTER AD741x FRAME 4 LEAST SIGNIFICANT DATA BYTE 1AD741x = AD7416/AD7417/AD7418. Figure 17. Writing to the Address Pointer Register Followed by Two Bytes of Data to the TOTI Setpoint or THYST Setpoint Register Rev. I | Page 15 of 24 01126-016 • written to the selected data register. This is illustrated in Figure 16. Writing two bytes of data to the TOTI setpoint or THYST setpoint register. If 9-bit resolution is required for the temperature setpoints, two bytes of data must be written to the TOTI setpoint and AD7416/AD7417/AD7418 Reading Data From the AD7416/AD7417/AD7418 Note that when reading back from the AD7416/AD7417/ AD7418, no more than three bytes of data must be read back. A stop command must be inserted at the end of the read communication. If a stop command is not inserted by the master and the AD7416/AD7417/AD7418 receive more SCL cycles than the maximum needed for three bytes of data, then the I2C interface on the AD7416/AD7417/AD7418 pulls the SDA line low and prevents it from going high again. To recover the AD7416/AD7417/AD7418 interface, the part must be powered off and on again. Reference the AN-686 Application Note, Implementing an I2C® Reset at www.analog.com for more information on I2C interfaces. Reading data from the AD7416/AD7417/AD7418 is a singlebyte or 2-byte operation. Reading back the contents of the configuration register is a single-byte read operation, as shown in Figure 18, with the register address previously having been set by a single-byte write operation to the address pointer register. Reading data from the temperature value register, the TOTI setpoint or THYST setpoint register is a 2-byte operation, as shown in Figure 19. It is also possible to read the most significant bit of a 9-bit or 10-bit register in this manner. 1 9 1 9 SCL 1 0 0 1 A2 A1 A0 R/W START BY MASTER D7 D6 D5 D4 D3 D2 D1 D0 NO ACK. BY STOP BY MASTER MASTER ACK. BY AD741x 1 FRAME 2 SINGLE DATA BYTE FROM AD741x 1 FRAME 1 SERIAL BUS ADDRESS BYTE 1AD741x = AD7416/AD7417/AD7418. Figure 18. Reading a Single Byte of Data from the Configuration Register 1 9 1 9 SCL SDA 1 0 0 1 A2 A1 A0 START BY MASTER R/W D15 D14 D13 D12 D11 D10 D9 D8 ACK. BY MASTER ACK. BY AD741x 1 FRAME 2 MOST SIGNIFICANT BYTE FROM AD741x 1 FRAME 1 SERIAL BUS ADDRESS BYTE 1 9 SDA (CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0 FRAME 3 LEAST SIGNIFICANT DATA BYTE FROM AD741x 1 1AD741x = AD7416/AD7417/AD7418. Figure 19. Reading Two Bytes of Data from the TOTI Setpoint or THYST Setpoint Register Rev. I | Page 16 of 24 STOP BY NO ACK. BY MASTER MASTER 01126-018 SCL (CONTINUED) 01126-017 SDA AD7416/AD7417/AD7418 OTI OUTPUT FAULT QUEUE The OTI output has two operating modes that are selected by Bit D1 of the configuration register. In the comparator mode, (D1 = 0), the OTI output becomes active when the temperature exceeds TOTI and remains active until the temperature falls below THYST. This mode allows the AD7416/AD7417/AD7418 to be used as a thermostat, for example, to control the operation of a cooling fan. To avoid false triggering of the AD7416/AD7417/AD7418 in noisy environments, a fault queue counter is provided that can be programmed by Bit D3 and Bit D4 of the configuration register (see Table 11) to count 1, 2, 4, or 6 fault events before OTI becomes active. To trigger OTI, the faults must occur consecutively. For example, if the fault queue is set to 4, then four consecutive temperature measurements greater than TOTI (or less than THYST) must occur. Any reading that breaks the sequence resets the fault queue counter, so if there are three readings greater than TOTI followed by a reading less than TOTI, the fault queue counter is reset without triggering OTI. TOTI THYST OTI OUTPUT COMPARATOR MODE POWER-ON DEFAULTS The AD7416/AD7417/AD7418 always power up with the following defaults: OTI OUTPUT INTERRUPT MODE OUTPUT; OTHERWISE, THE OTI OUTPUT REMAINS ACTIVE INDEFINITELY, ONCE TRIGGERED. 01126-019 READ1 READ1 READ1 READ1 READ1 READ1 READ1 1IN INTERRUPT MODE, A READ OPERATION OR SHUTDOWN RESETS THE OTI Figure 20. Operation of OTI Output (Shown Active Low) The open-drain configuration of OTI allows the OTI outputs of several AD7416/AD7417/AD7418 devices to be wire-AND’ed together when in active low mode. The OTI output is used to indicate that an out-of-limit temperature excursion has occurred. OTI is an open-drain output that can be programmed to be active low by setting Bit D2 of the configuration register to 0 or active high by setting Bit D2 of the configuration register to 1. In the interrupt mode (D1 = 1), the OTI output becomes active when the temperature exceeds TOTI and remains active even if the temperature falls below THYST, until it is reset by a read operation. Once OTI becomes active by the temperature exceeding TOTI, and resets, it remains inactive even if the temperature remains, or subsequently rises again, above TOTI. It does not become active again until the temperature falls below THYST. It then remains active until reset by a read operation. Once OTI becomes active by the temperature falling below THYST and then resets, it remains inactive even if the temperature remains, or subsequently falls again, below THYST. OTI is also reset when the AD7416/AD7417/AD7418 are placed in shutdown mode by setting Bit D0 of the configuration register to 1. The OTI output requires an external pull-up resistor. This can be connected to a voltage different from VDD (for example, to allow interfacing between 5 V and 3.3 V systems) provided that the maximum voltage rating of the OTI output is not exceeded. The value of the pull-up resistor depends on the application but should be as large as possible to avoid excessive sink currents at the OTI output, which can heat the chip and affect the temperature reading. The maximum value of the pull-up resistor that meets the output high current specification of the OTI output is 30 kΩ, but higher values can be used if a lower output current is required. For most applications, a value of 10 kΩ is suitable. • • • • • Address pointer pointing to temperature value register comparator mode TOTI = 80°C THYST = 75°C OTI active low Fault queue = 1 These default settings allow the AD7416/AD7417/AD7418 to be used as a standalone thermostat without any connection to a serial bus. OPERATING MODES The AD7416/AD7417/AD7418 have two possible modes of operation depending on the value of D0 in the configuration register. Mode 1 Normal operation of the AD7416/AD7417/AD7418 occurs when D0 = 0. In this active mode, a conversion takes place every 400 μs. After the conversion has taken place, the part partially powers down, consuming typically 350 μA of the current until the next conversion occurs. Two situations can arise in this mode on the request of a temperature read. If a read occurs during a conversion, the conversion aborts and a new one starts on the stop/repeat start condition. The temperature value that is read is that of the previous completed conversion. The next conversion typically occurs 400 μs after the new conversion has begun. If a read is called between conversions, a conversion is initiated on the stop/repeat start condition. After this conversion, the part returns to performing a conversion every 400 μs. With VDD = 3 V for each 400 μs cycle, the AD7416/AD7417/ AD7418 spend 40 μs (or 10% of the time) in conversion mode. The part spends 360 μs (or 90% of time) in partial power-down mode. Thus, the average power dissipated by the AD7416/ AD7417/AD7418 is 3 mW × 0.1 + 1 mW × 0.9 = 1.2 mW Rev. I | Page 17 of 24 AD7416/AD7417/AD7418 Mode 2 CONVST Pin Mode For applications where temperature measurements are required at a slower rate, for example, every second, power consumption of the part can be reduced by writing to the part to go to a full power-down between reads. The current consumption in full power-down is typically 0.2 μA and full power-down is initiated when D0 = 1 in the configuration register. When a measurement is required, a write operation can be performed to power up the part. The part then performs a conversion and is returned to power-down. The temperature value can be read in full powerdown because the I2C bus is continuously active. Conversions are initiated only by using the CONVST pin. In this method of operation, CONVST is normally low. Thus, the average power dissipation is 3 mW × 0.004 + 60 nW × 0.9996 = 1.2 μW The CONVST pin should not be pulsed when reading from or writing to the port. Figure 21 shows the recommended minimum times for the CONVST pulse when the temperature channel is selected. Figure 22 shows the minimum times an analog input channel is selected. The fastest throughput rate at which the AD7416/AD7417/ AD7418 can be operated is 2.5 kHz (that is, a read every 400 μs conversion period). Because TOTI and THYST are 2-byte reads, the read time with the I2C operating at 100 kbps would be 270 μs. If temperature reads are called too often, reads will overlap with conversions, aborting them continuously, which results in invalid readings. 100ns CONVST 40µs 01126-023 The power dissipation in this mode depends on the rate at which reads take place. Taking the requirements for a temperature measurement every 100 ms as an example, the optimum power dissipation is achieved by placing the part in full power-down, waking it up every 100 ms, letting it operate for 400 μs and putting it into full power-down again. In this case, the average power consumption is calculated as follows. The part spends 40 μs (or 0.04% of time) converting with 3 mW dissipation and a 99.96 ms (99.96% of time) in full shutdown with 60 nW dissipation. The rising edge of CONVST starts the power-up time. This power-up time is 4 μs. If the CONVST high time is longer than 4 μs, a conversion is initiated on the falling edge of CONVST and the track-and-hold also enters its hold mode at this time. If the CONVST high time is less than 4 μs, an internal timer, initiated by the rising edge of CONVST, holds off the trackand-hold and the initiation of conversion until the timer times out (4 μs after the rising edge of CONVST, which corresponds with the power-up time). The CONVST input remains low at the end of conversion, thus causing the part to enter its powerdown mode. In this method of operation, CONVST is normally low with a high going pulse controlling the power-up, and the conversion starts. Figure 21. CONVST When Temperature Channel Selected CONVST START MODE 100ns CONVST 15µs Figure 22. CONVST When VIN Channel Selected Rev. I | Page 18 of 24 01126-024 The AD7417/AD7418 have an extra mode, set by writing to the MSB of the Config2 register. AD7416/AD7417/AD7418 APPLICATIONS INFORMATION SUPPLY DECOUPLING FAN CONTROLLER The AD7416/AD7417/AD7418 should be decoupled with a 0.1 μF ceramic capacitor between VDD and GND. This is particularly important if the part is mounted remote from the power supply. Figure 23 shows a simple fan controller that switches on a cooling fan when the temperature exceeds 80°C and switches it off again when the temperature falls below 75°C. The AD7416 can be used as a standalone device in this application or with a serial bus interface if different trip temperatures are required. If the AD7416 is used with a bus interface, the sense of OTI can be set to active high, Q1 and R1 can be omitted, and OTI can be connected directly to the gate of Q2, with R2 as the pull-up resistor. POWER-ON RESET To ensure proper power-on reset, make sure that the supply voltage on the VDD pin is at 0 V. Refer to the AN-588 Application Note, AD7416/AD7417/AD7418 Power-On Reset Circuit at www.analog.com for more information. A failed power-on reset can prevent the default values from being loaded into the AD7416/ AD7417/AD7418 registers. If the correct values are not loaded into the registers, then the device cannot start operating. The output from the temperature value and ADC value registers will be a constant value. 12V VDD 3V TO 5.5V R1 10kΩ 8 To restart the device operation, the registers have to be loaded with their default values via the I2C bus. Therefore, in the event of an inadequate power-on reset and for all three devices, the following registers should be loaded with their default values: Q1 2N3904 OR SIMILAR 01126-020 3 4 Configuration register—default value = 0x00 Config2 register—default value = 0x00 THYST setpoint register—default value = 0x4B00 TOTI setpoint register—default value = 0x5500 Figure 23. AD7416 Used as a Fan Controller THERMOSTAT MOUNTING THE AD7416/AD7417/AD7418 The AD7416/AD7417/AD7418 can be used for surface or air temperature sensing applications. If the device is cemented to a surface with thermally conductive adhesive, the die temperature is within about 0.2°C of the surface temperature, due to the low power consumption of the device. Take care to insulate the back and leads of the device from the air if the ambient air temperature is different from the surface temperature being measured. Figure 24 shows the AD7416 used as a thermostat. The heater switches on when the temperature falls below THYST and switches off again when the temperature rises above TOTI. For this application and for comparator mode, program the OTI output active low. The GND pin provides the best thermal path to the die, so the temperature of the die is close to that of the printed circuit ground track. Take care to ensure that this is in close thermal contact with the surface being measured. As with any IC, the AD7416/AD7417/AD7418 and its associated wiring and circuits must be kept free from moisture to prevent leakage and corrosion, particularly in cold conditions where condensation is more likely to occur. Water resistant varnishes and conformal coatings can be used for protection. The small size of the AD7416 package allows it to be mounted inside sealed metal probes that provide a safe environment for the device. Rev. I | Page 19 of 24 VDD 3V TO 5.5V HEATER R1 10kΩ 8 AD7416 3 RELAY D1 1N4001 RLA1 Q1 2N3904 OR SIMILAR HEATER SUPLY 01126-021 • • • • AD7416 Q2 LOGIC LEVEL MOSFET RATED TO SUIT FAN CURRENT R2 10kΩ 4 Figure 24. AD7416 Used as a Thermostat AD7416/AD7417/AD7418 line. This arrangement means that each device must be read to determine which one has generated the interrupt, and if a unique interrupt is required for each device, the OTI outputs can be connected separately to the I/O chip. SYSTEM WITH MULTIPLE AD7416 DEVICES The three LSBs of the AD7416 serial address can be set by the user, allowing eight different addresses from 1001000 to 1001111. Figure 25 shows a system in which eight AD7416 devices are connected to a single serial bus, with their OTI outputs wire-AND’ed together to form a common interrupt R1 10kΩ 4 5 4 6 1 5 4 7 2 6 1 5 8 3 7 2 6 1 5 4 4 8 3 7 2 6 1 5 8 4 Figure 25. Multiple Connection of AD7416 Devices to a Single Serial Bus Rev. I | Page 20 of 24 3 7 2 6 1 5 4 AD7416 1 2 8 3 AD7416 5 6 7 AD7416 1 2 8 3 AD7416 6 7 3 2 1 01126-022 4 2 8 3 AD7416 5 7 AD7416 6 8 3 AD7416 7 AD7416 8 PROCESSOR SUPER I/O CHIP VDD 3V TO 5.5V AD7416/AD7417/AD7418 OUTLINE DIMENSIONS 10.00 (0.3937) 9.80 (0.3858) 4.00 (0.1575) 3.80 (0.1496) 9 16 1 8 1.27 (0.0500) BSC 0.50 (0.0197) 0.25 (0.0098) 1.75 (0.0689) 1.35 (0.0531) 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 6.20 (0.2441) 5.80 (0.2283) SEATING PLANE 0.51 (0.0201) 0.31 (0.0122) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-012-AC 060606-A CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 26. 16-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-16) Dimensions shown in millimeters and (inches) 5.00 (0.1968) 4.80 (0.1890) 1 5 6.20 (0.2441) 5.80 (0.2284) 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) 0.50 (0.0196) 0.25 (0.0099) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-012-A A CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 27. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) Rev. I | Page 21 of 24 012407-A 8 4.00 (0.1574) 3.80 (0.1497) AD7416/AD7417/AD7418 5.10 5.00 4.90 16 9 4.50 4.40 4.30 6.40 BSC 1 8 PIN 1 1.20 MAX 0.15 0.05 0.20 0.09 0.30 0.19 0.65 BSC COPLANARITY 0.10 SEATING PLANE 0.75 0.60 0.45 8° 0° COMPLIANT TO JEDEC STANDARDS MO-153-AB Figure 28. 16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16) Dimensions shown in millimeters 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5 5.15 4.90 4.65 4 PIN 1 0.65 BSC 0.95 0.85 0.75 1.10 MAX 0.15 0.00 0.38 0.22 COPLANARITY 0.10 0.23 0.08 8° 0° SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 29. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters Rev. I | Page 22 of 24 0.80 0.60 0.40 AD7416/AD7417/AD7418 ORDERING GUIDE Model 1 AD7416AR AD7416AR-REEL AD7416AR-REEL7 AD7416ARZ AD7416ARZ-REEL AD7416ARZ-REEL7 AD7416ARM AD7416ARM-REEL AD7416ARM-REEL7 AD7416ARMZ AD7416ARMZ-REEL AD7416ARMZ-REEL7 AD7417-WAFER AD7417AR AD7417AR-REEL AD7417AR-REEL7 AD7417ARZ AD7417ARZ-REEL AD7417ARZ-REEL7 AD7417ARU AD7417ARU-REEL AD7417ARU-REEL7 AD7417ARUZ AD7417ARUZ-REEL AD7417ARUZ-REEL7 AD7417BR AD7417BR-REEL AD7417BR-REEL7 AD7417BRZ AD7417BRZ-REEL AD7417BRZ-REEL7 AD7418ACHIPS AD7418ARZ AD7418ARZ-REEL AD7418ARZ-REEL7 AD7418ARM AD7418ARM-REEL AD7418ARM-REEL7 AD7418ARMZ AD7418ARMZ-REEL AD7418ARMZ-REEL7 EVAL-AD7416/7/8EBZ 1 Temperature Range −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C Temperature Error ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±1°C ±1°C ±1°C ±1°C ±1°C ±1°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C Package Description 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) Bare Die Wafer 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Thin Shrink Small Outline Package (TSSOP) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) 16-Lead Standard Small Outline Package (SOIC_N) Die 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) 8-Lead Mini Small Outline Package (MSOP) Evaluation Board Z = RoHS Compliant Part. Rev. I | Page 23 of 24 Branding C6A C6A C6A C6A# C6A# C6A# Package Option R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 RM-8 RM-8 R-16 R-16 R-16 R-16 R-16 R-16 RU-16 RU-16 RU-16 RU-16 RU-16 RU-16 R-16 R-16 R-16 R-16 R-16 R-16 C7A C7A C7A T0G T0G T0G R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 RM-8 RM-8 AD7416/AD7417/AD7418 NOTES I2C refers to a communications protocol originally developed by Philips Semiconductors (Now NXP Semiconductors). ©1998–2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D01126-0-11/10(I) Rev. I | Page 24 of 24