Single- and 4-Channel, 9 s, 10-Bit ADCs with On-Chip Temperature Sensor AD7816/AD7817/AD7818 FEATURES 10-Bit ADC with 9 s Conversion Time One (AD7818) and Four (AD7817) Single-Ended Analog Input Channels The AD7816 Is a Temperature Measurement Only Device On-Chip Temperature Sensor Resolution of 0.25ⴗC ⴞ2ⴗC Error from –40ⴗC to +85ⴗC –55ⴗC to +125ⴗC Operating Range Wide Operating Supply Range 2.7 V to 5.5 V Inherent Track-and-Hold Functionality On-Chip Reference (2.5 V ⴞ 1%) Overtemperature Indicator Automatic Power-Down at the End of a Conversion Low Power Operation 4 W at a Throughput Rate of 10 SPS 40 W at a Throughput Rate of 1 kSPS 400 W at a Throughput Rate of 10 kSPS Flexible Serial Interface APPLICATIONS Ambient Temperature Monitoring (AD7816) Thermostat and Fan Control High Speed Microprocessor Temperature Measurement and Control Data Acquisition Systems with Ambient Temperature Monitoring (AD7817 and AD7818) Industrial Process Control Automotive Battery Charging Applications GENERAL DESCRIPTION The AD7818 and AD7817 are 10-bit, single- and 4-channel A/D converters with on-chip temperature sensor that can operate from a single 2.7 V to 5.5 V power supply. Each part contains a 9 µs successive-approximation converter based around a capacitor DAC, an on-chip temperature sensor with an accuracy of ⫾2°C, an on-chip clock oscillator, inherent track-andhold functionality and an on-chip reference (2.5 V). The AD7816 is a temperature monitoring only device in a SOIC/ MSOP package. The on-chip temperature sensor of the AD7817 and AD7818 can be accessed via 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 with a resolution of ⫾0.25°C. See Temperature Measurement section of this data sheet. FUNCTIONAL BLOCK DIAGRAM VDD REFIN AD7817 OVERTEMP REG TEMP SENSOR VIN3 VIN4 A>B OTI A REF 2.5V VIN1 VIN2 B MUX SAMPLING CAPACITOR CHARGE REDISTRIBUTION DAC CONTROL LOGIC DATA OUT CONTROL REG DOUT DIN SCLK RD/WR CLOCK VBALANCE AGND DGND BUSY CS CONVST The AD7816, AD7817, and AD7818 have a flexible serial interface that allows easy interfacing to most microcontrollers. The interface is compatible with the Intel 8051, Motorola SPI® and QSPI™ protocols and National Semiconductors MICROWIRE™ protocol. For more information refer to the Serial Interface section of this data sheet. The AD7817 is available in a narrow body 0.15" 16-lead small outline IC (SOIC), in a 16-lead, thin shrink small outline package (TSSOP), while the AD7816/AD7818 come in an 8-lead small outline IC (SOIC) and an 8-lead microsmall outline IC (MSOP). PRODUCT HIGHLIGHTS 1. The devices have an on-chip temperature sensor that allows an accurate measurement of the ambient temperature to be made. The measurable temperature range is –55°C to +125°C. 2. 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 overtemperature register. The overtemperature indicator pin goes logic low when a predetermined temperature is exceeded. 3. The automatic power-down feature enables the AD7816, AD7817, and AD7818 to achieve superior power performance at slower throughput rates, e.g., 40 µW at 1 kSPS throughput rate. REV. C 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. 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. 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AD7816/AD7817/AD7818 AD7817–SPECIFICATIONS1 (V Parameter DD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V unless otherwise noted) A Version *B Version *S Version Unit DYNAMIC PERFORMANCE Signal to (Noise + Distortion) Ratio2 Total Harmonic Distortion2 Peak Harmonic or Spurious Noise2 Intermodulation Distortion2 Second Order Terms Third Order Terms Channel-to-Channel Isolation2 DC ACCURACY Resolution Minimum Resolution for Which No Missing Codes are Guaranteed Relative Accuracy2 Differential Nonlinearity2 Gain Error2 Gain Error Match2 Offset Error2 Offset Error Match TEMPERATURE SENSOR1 Measurement Error Ambient Temperature 25°C TMIN to TMAX Measurement Error Ambient Temperature 25°C TMIN to TMAX Temperature Resolution REFERENCE INPUT3, 4 REFIN Input Voltage Range3 Input Impedance Input Capacitance ON-CHIP REFERENCE5 Temperature Coefficient3 CONVERSION RATE Track/Hold Acquisition Time4 Conversion Time Temperature Sensor Channels 1 to 4 POWER REQUIREMENTS VDD IDD Normal Operation Using External Reference Power-Down (VDD = 5 V) Power-Down (VDD = 3 V) Auto Power-Down Mode 10 SPS Throughput Rate 1 kSPS Throughput Rate 10 kSPS Throughput Rate Power-Down Test Conditions/Comments Sample Rate = 100 kSPS, Any Channel, fIN = 20 kHz 58 –65 –65 58 –65 –65 58 –65 –65 dB min dB max dB max –67 –67 –80 –67 –67 –80 –67 –67 –80 dB typ dB typ dB typ 10 10 10 Bits 10 ⫾1 ⫾1 ⫾2 ⫾10 ⫾1/2 ⫾2 ⫾1/2 10 ⫾1 ⫾1 ⫾2 ⫾10 ⫾1/2 ⫾2 ⫾1/2 10 ⫾1 ⫾1 ⫾2 +20/–10 ⫾1/2 ⫾2 ⫾1/2 Bits LSB max LSB max LSB max LSB max LSB max LSB max LSB max ⫾2 ⫾3 ⫾1 ⫾2 ⫾2 ⫾3 °C max °C max ⫾2.25 ⫾3 1/4 ⫾2.25 ⫾3 1/4 ⫾2.25 ⫾6 1/4 °C max °C max °C/LSB 2.625 2.375 40 10 2.625 2.375 40 10 2.625 2.375 40 10 V max V min kΩ min pF max 80 80 150 ppm/°C typ 400 400 400 ns max 27 9 27 9 27 9 µs max µs max 5.5 2.7 5.5 2.7 5.5 2.7 V max V min 2 1.75 10 4 2 1.75 10 4 2 1.75 12.5 4.5 mA max mA max µA max µA max 6.4 48.8 434 12 6.4 48.8 434 12 6.4 48.8 434 13.5 µW typ µW typ µW typ µW max –75 dB typ –75 dB typ fa =19.9 kHz, fb = 20.1 kHz fIN = 20 kHz Any Channel External Reference Internal Reference External Reference VREF = 2.5 V On-Chip Reference 2.5 V + 5% 2.5 V – 5% Nominal 2.5 V –2– Source Impedance < 10 Ω For Specified Performance Logic Inputs = 0 V or VDD 1.6 mA typ 2.5 V External Reference Connected 5.5 µA typ 2 µA typ VDD = 3 V See Power vs. Throughput Section for Description of Power Dissipation in Auto Power-Down Mode Typically 6 µW REV. C AD7816/AD7817/AD7818 = 2.7 V to 5.5 V, GND = 0 V, REF AD7816/AD78186–SPECIFICATIONS1 (Votherwise noted) DD Parameter A Version Unit DYNAMIC PERFORMANCE (AD7818 Only) Signal to (Noise + Distortion) Ratio2 Total Harmonic Distortion2 Peak Harmonic or Spurious Noise2 Intermodulation Distortion2 Second Order Terms Third Order Terms Channel-to-Channel Isolation2 DC ACCURACY (AD7818 Only) Resolution Minimum Resolution for Which No Missing Codes are Guaranteed Relative Accuracy2 Differential Nonlinearity2 Gain Error2 Offset Error2 TEMPERATURE SENSOR1 Measurement Error Ambient Temperature 25°C TMIN to TMAX Measurement Error Ambient Temperature 25°C TMIN to TMAX Temperature Resolution REFERENCE INPUT3, 4 (AD7816 Only) REFIN Input Voltage Range3 Input Impedance Input Capacitance ON-CHIP REFERENCE5 Temperature Coefficient3 CONVERSION RATE Track/Hold Acquisition Time4 Conversion Time Temperature Sensor Channel 1 POWER REQUIREMENTS VDD IDD Normal Operation Using External Reference Power-Down (VDD = 5 V) Power-Down (VDD = 3 V) Auto Power-Down Mode 10 SPS Throughput Rate 1 kSPS Throughput Rate 10 kSPS Throughput Rate Power-Down REV. C IN = 2.5 V unless Test Conditions/Comments Sample Rate = 100 kSPS, Any Channel, fIN = 20 kHz 57 –65 –67 dB min dB max dB typ –67 –67 –80 dB typ dB typ dB typ 10 Bits 10 ⫾1 ⫾1 ⫾10 ⫾4 Bits LSB max LSB max LSB max LSB max ⫾2 ⫾3 °C max °C max ⫾2 ⫾3 1/4 °C max °C max °C/LSB 2.625 2.375 50 10 V max V min kΩ min pF max 30 ppm/°C typ 400 ns max Source Impedance < 10 Ω 27 9 µs max µs max (AD7818 Only) 5.5 2.7 V max V min 2 1.75 10.75 4.5 mA max mA max µA max µA max 6.4 48.8 434 13.5 µW typ µW typ µW typ µW max –75 dB typ –75 dB typ fa = 19.9 kHz, fb = 20.1 kHz fIN = 20 kHz Any Channel External Reference VREF = 2.5 V On-Chip Reference 2.5 V + 5% 2.5 V – 5% Nominal 2.5 V –3– For Specified Performance Logic Inputs = 0 V or VDD 1.3 mA typ 2.5 V External Reference Connected 6 µA typ 2 µA typ VDD = 3 V See Power vs. Throughput Section for Description of Power Dissipation in Auto Power-Down Mode Typically 6 µW AD7816/AD7817/AD7818–SPECIFICATIONS Parameter A Version *B Version *S Version Unit VREF 0 ⫾1 10 VREF 0 ⫾1 10 VREF 0 ⫾1 10 V max V min µA min pF max 2.4 0.8 2 0.4 ⫾3 10 2.4 0.8 2 0.4 ⫾3 10 2.4 0.8 2 0.4 ⫾3 10 V min V max V min V max µA max pF max 4 2.4 4 2.4 4 2.4 V min V min 0.4 0.2 ⫾1 15 0.4 0.2 ⫾1 15 0.4 0.2 ⫾1 15 V max V max µA max pF max Test Conditions/Comments 7 ANALOG INPUTS Input Voltage Range (AD7817 and AD7818) Input Leakage Input Capacitance LOGIC INPUTS4 Input High Voltage, VINH Input Low Voltage, VINL Input High Voltage, VINH Input Low Voltage, VINL Input Current, IIN Input Capacitance, CIN LOGIC OUTPUTS4 Output High Voltage, VOH Output Low Voltage, VOL High Impedance Leakage Current High Impedance Capacitance VDD = 5 V ⫾ 10% VDD = 5 V ⫾ 10% VDD = 3 V ⫾ 10% VDD = 3 V ⫾ 10% Typically 10 nA, VIN = 0 V to VDD ISOURCE = 200 µA VDD = 5 V ⫾ 10% VDD = 3 V ⫾ 10% ISINK = 200 µA VDD = 5 V ⫾ 10% VDD = 3 V ⫾ 10% NOTES *B and S Versions apply to AD7817 only. For operating temperature ranges, see Ordering Guide. 1 AD7816 and AD7817 temperature sensors specified with external 2.5 V reference, AD7818 specified with on-chip reference. All other specifications with external and on-chip reference (2.5 V). For V DD = 2.7 V, TA = 85°C max and temperature sensor measurement error = ⫾3°C. 2 See Terminology. 3 The accuracy of the temperature sensor is affected by reference tolerance. The relationship between the two is explained in the section titled Temperature Measurement Error Due to Reference Error. 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 external reference is applied. 6 All specifications are typical for AD7818 at temperatures above 85°C and with VDD greater than 3.6 V. 7 Refers to the input current when the part is not converting. Primarily due to reverse leakage current in the ESD protection diodes. Specifications subject to change without notice. REFIN AD7816 OVERTEMP REG TEMP SENSOR VDD VDD B A>B AD7818 OTI TEMP SENSOR A REF 2.5V CHARGE REDISTRIBUTION DAC DATA OUT DIN/OUT MUX SAMPLING CAPACITOR CONTROL LOGIC CLOCK VBALANCE AGND CONTROL REG VIN1 REF 2.5V RD/WR AGND Figure 1. AD7816 Functional Block Diagram A CHARGE REDISTRIBUTION DAC DATA OUT DIN/OUT VBALANCE CONVST OTI A>B B MUX SAMPLING CAPACITOR SCLK OVERTEMP REG CONTROL LOGIC CONTROL REG SCLK RD/WR CLOCK GENERATOR CONVST Figure 2. AD7818 Functional Block Diagram –4– REV. C AD7816/AD7817/AD7818 TIMING CHARACTERISTICS1, 2 (VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V. All specifications TMIN to TMAX unless otherwise noted) Parameter A, B Versions Unit Test Conditions/Comments tPOWER-UP t1a t1b t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t123 t133 t14a3, 4 t14b3, 4 t15 t16 t17 2 9 27 20 50 0 0 10 10 40 40 0 0 20 20 30 30 150 40 400 µs max µs max µs max ns min ns max ns min ns min ns min ns min ns min ns min ns min ns min ns max ns max ns max ns max ns max ns min ns min Power-Up Time from Rising Edge of CONVST Conversion Time Channels 1 to 4 Conversion Time Temperature Sensor CONVST Pulse Width CONVST Falling Edge to BUSY Rising Edge CS Falling Edge to RD/WR Falling Edge Setup Time RD/WR Falling Edge to SCLK Falling Edge Setup DIN Setup Time before SCLK Rising Edge DIN Hold Time after SCLK Rising Edge SCLK Low Pulse Width SCLK High Pulse Width CS Falling Edge to RD/WR Rising Edge Setup Time RD/WR Rising Edge to SCLK Falling Edge Setup Time DOUT Access Time after RD/WR Rising Edge DOUT Access Time after SCLK Falling Edge DOUT Bus Relinquish Time after Falling Edge of RD/WR DOUT Bus Relinquish Time after Rising Edge of CS BUSY Falling Edge to OTI Falling Edge RD/WR Rising Edge to OTI Rising Edge SCLK Rising Edge to CONVST Falling Edge (Acquisition Time of T/H) NOTES 1 Sample tested during initial release and after any redesign or process change that may affect this parameter. All input signals are measured with tr = tf = 1 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V. 2 See Figures 16, 17, 20 and 21. 3 These figures are measured with the load circuit of Figure 3. They are defined as the time required for D OUT to cross 0.8 V or 2.4 V for V DD = 5 V ⫾ 10% and 0.4 V or 2 V for VDD = 3 V ⫾ 10%, as quoted on the specifications page of this data sheet. 4 These times are derived from the measured time taken by the data outputs to change 0.5 V when loaded with the circuit of Figure 3. The measured number is then extrapolated back to remove the effects of charging or discharging the 50 pF capacitor. This means that the times quoted in the timing characteristics are the true bus relinquish times of the part and as such are independent of external bus loading capacitances. Specifications subject to change without notice. 200A TO OUTPUT PIN IOL 1.6V CL 50pF 200A IOL Figure 3. Load Circuit for Access Time and Bus Relinquish Time REV. C –5– AD7816/AD7817/AD7818 ABSOLUTE MAXIMUM RATINGS 1 µSOIC Package, Power Dissipation . . . . . . . . . . . . . . 450 mW θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 206°C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C (TA = 25°C unless otherwise noted) VDD to AGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V VDD to DGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V Analog Input Voltage to AGND VIN1 to VIN4 . . . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V Reference Input Voltage to AGND2 . . . –0.3 V to VDD + 0.3 V Digital Input Voltage to DGND . . . . . . –0.3 V to VDD + 0.3 V Digital Output Voltage to DGND . . . . . –0.3 V to VDD + 0.3 V Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150°C TSSOP, Power Dissipation . . . . . . . . . . . . . . . . . . . . 450 mW θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 120°C/W Lead Temperature, Soldering . . . . . . . . . . . . . . . . . . 260°C Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C 16-Lead SOIC Package, Power Dissipation . . . . . . . . 450 mW θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 100°C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C 8-Lead SOIC Package, Power Dissipation . . . . . . . . . . 450 mW θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 157°C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C NOTES 1 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 listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2 If the Reference Input Voltage is likely to exceed V DD by more than 0.3 V (e.g., during power-up) and the reference is capable of supplying 30 mA or more, it is recommended to use a clamping diode between the REF IN pin and VDD pin. The diagram below shows how the diode should be connected. VDD REFIN BAT81 AD7816/AD7817 –6– REV. C AD7816/AD7817/AD7818 ORDERING GUIDE Model AD7816AR AD7816AR-REEL AD7816AR-REEL7 AD7816ARM AD7816ARM-REEL AD7816ARM-REEL7 AD7816ACHIPS AD7817AR AD7817AR-REEL AD7817AR-REEL7 AD7817ARZ* AD7817ARU AD7817ARU-REEL AD7817ARU-REEL7 AD7817BR AD7817BR-REEL AD7817BR-REEL7 AD7817BRZ* AD7817BRZ-REEL* AD7817BRZ-REEL7* AD7817BRU AD7817BRU-REEL AD7817BRU-REEL7 AD7817SR AD7817SR-REEL AD7817SR-REEL7 AD7818AR AD7818AR-REEL AD7818AR-REEL7 AD7818ARM AD7818ARM-REEL AD7818ARM-REEL7 EVAL-AD7816/ AD7817/AD7818EB Temperature Range Temperature Error @ +25°C Package Description Package Options Branding –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 R-8 R-8 R-8 RM-8 RM-8 RM-8 C4A C4A C4A –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 –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 –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 –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 –40°C to +85°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 ± 1°C ± 1°C ± 1°C ± 2°C ± 2°C ± 2°C ± 2°C ± 2°C ± 2°C ± 2°C ± 2°C ± 2°C 8-Lead Narrow Body (SOIC) 8-Lead Narrow Body (SOIC) 8-Lead Narrow Body (SOIC) 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP Die 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead (TSSOP) 16-Lead (TSSOP) 16-Lead (TSSOP) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead (TSSOP) 16-Lead (TSSOP) 16-Lead (TSSOP) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 16-Lead Narrow Body (SOIC) 8-Lead Narrow Body (SOIC) 8-Lead Narrow Body (SOIC) 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP Evaluation Board R-16 R-16 R-16 R-16 RU-16 RU-16 RU-16 R-16 R-16 R-16 R-16 R-16 R-16 RU-16 RU-16 RU-16 R-16 R-16 R-16 R-16 R-8 R-8 RM-8 RM-8 RM-8 C3A C3A C3A *Z = Pb free part CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7816/AD7817/AD7818 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. REV. C –7– WARNING! ESD SENSITIVE DEVICE AD7816/AD7817/AD7818 AD7817 PIN FUNCTION DESCRIPTIONS Pin Mnemonic Description 1 CONVST 2 BUSY 3 OTI 4 CS 5 6 AGND REFIN 7–10 VIN1 to VIN4 11 12 13 VDD DGND DOUT 14 15 DIN SCLK 16 RD/WR Logic Input Signal. The convert start signal. A 10-bit analog-to-digital conversion is initiated on the falling edge of this signal. The falling edge of this signal places the track/hold in hold mode. The track/ hold goes into track mode again at the end of the conversion. The state of the CONVST signal is checked at the end of a conversion. If it is logic low, the AD7817 will power-down—see Operating Mode section of the data sheet. Logic Output. The busy signal is logic high during a temperature or voltage A/D conversion. The signal can be used to interrupt a microcontroller when a conversion has finished. Logic Output. The Overtemperature Indicator (OTI) is set logic low if the result of a conversion on Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Overtemperature Register (OTR). The signal is reset at the end of a serial read operation, i.e., a rising RD/WR edge when CS is low. Logic Input Signal. The chip select signal is used to enable the serial port of the AD7817. This is necessary if the AD7817 is sharing the serial bus with more than one device. Analog Ground. Ground reference for track/hold, comparator and capacitor DAC. Analog Input. An external 2.5 V reference can be connected to the AD7817 at this pin. To enable the onchip reference the REFIN pin should be tied to AGND. If an external reference is connected to the AD7817, the internal reference will shut down. Analog Input Channels. The AD7817 has four analog input channels. The input channels are singleended with respect to AGND (analog ground). The input channels can convert voltage signals in the range 0 V to VREF. A channel is selected by writing to the Address Register of the AD7817—see Control Byte section. Positive Supply Voltage, 2.7 V to 5.5 V. Digital Ground. Ground reference for digital circuitry. Logic Output With a High Impedance State. Data is clocked out of the AD7817 serial port at this pin. This output goes into a high impedance state on the falling edge of RD/WR or on the rising edge of the CS signal, whichever occurs first. Logic Input. Data is clocked into the AD7817 at this pin. Clock Input for the Serial Port. The serial clock is used to clock data into and out of the AD7817. Data is clocked out on the falling edge and clocked in on the rising edge. Logic Input Signal. The read/write signal is used to indicate to the AD7817 whether the data transfer operation is a read or a write. The RD/WR should be set logic high for a read operation and logic low for a write operation. PIN CONFIGURATION SOIC/TSSOP CONVST 1 16 RD/WR 15 SCLK BUSY 2 OTI 3 CS 4 14 DIN AD7817 13 DOUT TOP VIEW AGND 5 (Not to Scale) 12 DGND REFIN 6 11 VDD VIN1 7 10 VIN4 VIN2 8 9 VIN3 –8– REV. C AD7816/AD7817/AD7818 AD7816 AND AD7818 PIN FUNCTION DESCRIPTIONS Pin Mnemonic Description 1 CONVST 2 OTI 3 4 (AD7818) GND VIN 4 (AD7816) REFIN 5 6 7 VDD DIN/OUT SCLK 8 RD/WR Logic Input Signal. The convert start signal initiates a 10-bit analog-to-digital conversion on the falling edge of the this signal. The falling edge of this signal places the track/hold in hold mode. The track/hold goes into track mode again at the end of the conversion. The state of the CONVST signal is checked at the end of a conversion. If it is logic low, the AD7816 and AD7818 will power down—see Operating Mode section of the data sheet. Logic Output. The Overtemperature Indicator (OTI) is set logic low if the result of a conversion on Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Overtemperature Register (OTR). The signal is reset at the end of a serial read operation, i.e., a rising RD/WR edge. Analog and Digital Ground. Analog Input Channel. The input channel is single-ended with respect to GND. The input channel can convert voltage signals in the range 0 V to 2.5 V. The input channel is selected by writing to the Address Register of the AD7818—see Control Byte section. Reference Input. An external 2.5 V reference can be connected to the AD7816 at this pin. To enable the on-chip reference the REFIN pin should be tied to AGND. If an external reference is connected to the AD7816, the internal reference will shut down. Positive supply voltage, 2.7 V to 5.5 V. Logic Input and Output. Serial data is clocked in and out of the AD7816/AD7818 at this pin. Clock Input for the Serial Port. The serial clock is used to clock data into and out of the AD7816/AD7818. Data is clocked out on the falling edge and clocked in on the rising edge. Logic Input. The read/write signal is used to indicate to the AD7816 and AD7818 whether the next data transfer operation is a read or a write. The RD/WR should be set logic high for a read operation and logic low for a write. PIN CONFIGURATIONS Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the rms sum of harmonics to the fundamental. For the AD7891 it is defined as: SOIC/MSOP (AD7816) CONVST 1 8 RD/WR THD (dB) = 20 log AD7816 7 SCLK OTI 2 TOP VIEW GND 3 (Not to Scale) 6 DIN/OUT REFIN 4 Peak Harmonic or Spurious Noise Peak harmonic or spurious noise is defined as the ratio of the rms value of the next largest component in the ADC output spectrum (up to fS/2 and excluding dc) to the rms value of the fundamental. Normally, the value of this specification is determined by the largest harmonic in the spectrum, but for parts where the harmonics are buried in the noise floor, it will be a noise peak. 8 RD/WR AD7818 7 SCLK TOP VIEW GND 3 (Not to Scale) 6 DIN/OUT OTI 2 VIN 4 5 VDD Intermodulation Distortion TERMINOLOGY Signal-to-(Noise + Distortion) Ratio With inputs consisting of sine waves at two frequencies, fa and fb, any active device with nonlinearities will create distortion products at sum and difference frequencies of mfa ⫾ nfb where m, n = 0, 1, 2, 3, etc. Intermodulation terms are those for which neither m nor n are equal to zero. For example, the second order terms include (fa + fb) and (fa – fb), while the third order terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb). This is the measured ratio of signal-to-(noise + distortion) at the output of the A/D converter. The signal is the rms amplitude of the fundamental. Noise is the rms sum of all nonfundamental signals up to half the sampling frequency (fS/2), excluding dc. The ratio is dependent upon the number of quantization levels in the digitization process; the more levels, the smaller the quantization noise. The theoretical signal-to-(noise + distortion) ratio for an ideal N-bit converter with a sine wave input is given by: Signal-to-(Noise + Distortion) = (6.02 N + 1.76) dB Thus for a 10-bit converter, this is 62 dB. REV. C V1 where V1 is the rms amplitude of the fundamental and V2, V3, V4, V5, and V6 are the rms amplitudes of the second through the sixth harmonics. 5 VDD SOIC/MSOP (AD7818) CONVST 1 V22 +V32 +V42 +V52 +V62 –9– AD7816/AD7817/AD7818 The AD7816, AD7817, and AD7818 are tested using the CCIF standard where two input frequencies near the top end of the input bandwidth are used. In this case, the second and third order terms are of different significance. The second order terms are usually distanced in frequency from the original sine waves while the third order terms are usually at a frequency close to the input frequencies. As a result, the second and third order terms are specified separately. The calculation of the intermodulation distortion is as per the THD specification where it is the ratio of the rms sum of the individual distortion products to the rms amplitude of the fundamental expressed in dBs. Channel-to-Channel Isolation Channel-to-channel isolation is a measure of the level of crosstalk between channels. It is measured by applying a fullscale 20 kHz sine wave signal to one input channel and determining how much that signal is attenuated in each of the other channels. The figure given is the worst case across all four channels. Address Register If the five MSBs of the control byte are logic zero, the three LSBs of the control byte are transferred to the Address Register—see Figure 4. The Address Register is a 3-bit-wide register used to select the analog input channel on which to carry out a conversion. It is also used to select the temperature sensor, which has the address 000. Table I shows the selection. The Internal Reference selection connects the input of the ADC to a band gap reference. When this selection is made and a conversion is initiated, the ADC output should be approximately midscale. After power-up the default channel selection is DB2 = DB1 = DB0 = 0 (Temperature Sensor). Table I. Channel Selection Relative Accuracy Relative accuracy or endpoint nonlinearity is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. DB2 DB1 DB0 Channel Selection Device 0 0 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 All AD7817/AD7818 AD7817 AD7817 AD7817 All Temperature Sensor Channel 1 Channel 2 Channel 3 Channel 4 Internal Ref (1.23 V) Overtemperature Register 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, i.e., AGND + 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, i.e., 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. If any of the five MSBs of the control byte are logic one, then the entire eight bits of the control byte are transferred to the Overtemperature Register—see Figure 4. At the end of a temperature conversion a digital comparison is carried out between the 8 MSBs of the temperature conversion result (10 bits) and the contents of the Overtemperature Register (8 bits). If the result of the temperature conversion is greater that the contents of the Overtemperature Register (OTR), then the Overtemperature Indicator (OTI) goes logic low. The resolution of the OTR is 1°C. The lowest temperature that can be written to the OTR is – 95°C and the highest is +152°C—see Figure 5. However, the usable temperature range of the temperature sensor is –55°C to +125°C. Figure 5 shows the OTR and how to set TALARM (the temperature at which the OTI goes low). OTR (Dec) = TALARM (°C) + 103°C Track/Hold Acquisition Time Track/hold acquisition time is the time required for the output of the track/hold amplifier to reach its final value, within ⫾1/2 LSB, after the end of conversion (the point at which the track/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 VIN input of the AD7817 or AD7818. It means that the user must wait for the duration of the track/hold acquisition time after the end of conversion or after a channel change/ step input change to VIN before starting another conversion, to ensure that the part operates to specification. For example, to set TALARM to 50°C, OTR = 50 + 103 = 153 Dec or 10011001 Bin. If the result of a temperature conversion exceeds 50°C then OTI will go logic low. The OTI logic output is reset high at the end of a serial read operation or if a new temperature measurement is lower than TALARM. The default power on TALARM is 50°C. DB2 DB1 DB0 ADDRESS REGISTER IF DB7 TO DB3 ARE LOGIC 0 THEN DB2 TO DB0 ARE WRITTEN TO THE ADDRESS REGISTER CONTROL BYTE LSB MSB The AD7816, AD7817, and AD7818 contain two on-chip registers, the Address Register and the Overtemperature Register. These registers can be accessed by carrying out an 8-bit serial write operation to the devices. The 8-bit word or control byte written to the AD7816, AD7817, and AD7818 is transferred to one of the two on-chip registers as follows. DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 CONTROL BYTE DB0 OVERTEMPERATURE REGISTER (OTR) IF ANY BIT DB7 TO DB3 IS SET TO A LOGIC 1 THEN THE FULL 8 BITS OF THE CONTROL WORD ARE WRITTEN TO THE OVERTEMPERATURE REGISTER DB7 DB6 DB5 DB4 DB3 DB2 DB1 Figure 4. Address and Overtemperature Register Selection –10– REV. C AD7816/AD7817/AD7818 OVERTEMPERATURE REGISTER LSB MSB DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 1 0 1 0 1 0 1 1 1 0 1 0 1 0 1 MINIMUM TEMPERATURE = –95 C MAXIMUM TEMPERATURE = +152 C OVERTEMPERATURE REGISTER (DEC) = TALARM + 103ⴗC TALARM RESOLUTION = 1ⴗ/ LSB Figure 5. The Overtemperature Register (OTR) CIRCUIT INFORMATION TYPICAL CONNECTION DIAGRAM The AD7817 and AD7818 are single- and four-channel, 9 µs conversion time, 10-bit A/D converters with on-chip temperature sensor, reference, and serial interface logic functions on a single chip. The AD7816 has no analog input channel and is intended for temperature measurement only. The A/D converter section consists of a conventional successive-approximation converter based around a capacitor DAC. The AD7816, AD7817, and AD7818 are capable of running on a 2.7 V to 5.5 V power supply and the AD7817 and AD7818 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 –55°C to +125°C. The part requires a 2.5 V reference, which can be provided from the part’s own internal reference or from an external reference source. The on-chip reference is selected by connecting the REFIN pin to analog ground. Figure 6 shows a typical connection diagram for the AD7817. The AGND and DGND are connected together at the device for good noise suppression. The BUSY line is used to interrupt the microcontroller at the end of the conversion process and the serial interface is implemented using three wires—see Serial Interface section for more details. An external 2.5 V reference can be connected at the REFIN pin. If an external reference is used, a 10 µF capacitor should be connected between REFIN and AGND. 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 Power vs. Throughput section of this data sheet. SUPPLY 2.7V TO 5.5V 0V TO 2.5V INPUT Conversion is initiated by pulsing the CONVST input. The conversion clock for the part is internally generated so no external clock is required except when reading from and writing to the serial port. The on-chip track/hold goes from track-to-hold mode and the conversion sequence is started on the falling edge of the CONVST signal. At this point the BUSY signal goes high and low again 9 µs or 27 µs later (depending on whether an analog input or the temperature sensor is selected) to indicate the end of the conversion process. This signal can be used by a microcontroller to determine when the result of the conversion should be read. The track/hold acquisition time of the AD7817 and AD7818 is 400 ns. 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 27 µs to complete. Temperature measurement is explained in the Temperature Measurement section of this data sheet. The on-chip reference is not available to the user, but REFIN can be overdriven by an external reference source (2.5 V only). The effect of reference tolerances on temperature measurements is discussed in the section titled Temperature Measurement Error Due to Reference Error. REV. C 3-WIRE SERIAL INTERFACE 0.1F VDD CONVERTER DETAILS 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 AGND. 10F SCLK RD/WR DOUT AIN1 AIN2 AIN3 AIN4 DIN C/P AD7817 AGND DGND CONVST BUSY OTI REFIN OPTIONAL EXTERNAL REFERENCE AD780/ REF-192 CS 10F EXTERNAL REFERENCE Figure 6. Typical Connection Diagram ANALOG INPUTS Analog Input Figure 7 shows an equivalent circuit of the analog input structure of the AD7817 and AD7818. 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. This will cause these diodes to become 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. The capacitor C2 in Figure 7 is typically about 4 pF and can mostly be attributed to pin capacitance. The 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. The capacitor C1 is the ADC sampling capacitor and has a capacitance of 3 pF. –11– AD7816/AD7817/AD7818 VDD D1 R1 1k⍀ C1 3pF 1.2V AIN VBALANCE C2 4pF EXTERNAL REFERENCE DETECT REFIN SW1 D2 1.2V CONVERT PHASE - SWITCH OPEN TRACK PHASE - SWITCH CLOSED 26k⍀ BUFFER 2.5V Figure 7. Equivalent Analog Input Circuit 24k⍀ DC Acquisition Time The ADC starts a new acquisition phase at the end of a conversion and ends on the falling edge of the CONVST signal. At the end of a conversion a settling time is associated with the sampling circuit. This settling time lasts approximately 100 ns. The analog signal on VIN + is also being acquired during this settling time. Therefore, the minimum acquisition time needed is approximately 100 ns. Figure 9. On-Chip Reference ADC TRANSFER FUNCTION The output coding of the AD7816, AD7817, and AD7818 is straight binary. The designed code transitions occur at successive integer LSB values (i.e., 1 LSB, 2 LSBs, etc.). The LSB size is = 2.5 V/1024 = 2.44 mV. The ideal transfer characteristic is shown in Figure 10 below. Figure 8 shows the equivalent charging circuit for the sampling capacitor when the ADC is in its acquisition phase. R2 represents the source impedance of a buffer amplifier or resistive network, R1 is an internal multiplexer resistance and C1 is the sampling capacitor. VIN R1 1k⍀ ADC CODE R2 111...111 111...110 C1 3pF Figure 8. Equivalent Sampling Circuit 111...000 1LSB=2.5/1024 2.44mV 011...111 000...010 000...001 During the acquisition phase the sampling capacitor must be charged to within a 1/2 LSB of its final value. The time it takes to charge the sampling capacitor (TCHARGE) is given by the following formula: 000...000 1LSB 0V +2.5V•1LSB ANALOG INPUT Figure 10. ADC Transfer Function TCHARGE = 7.6 × (R2 + 1 kΩ) × 3 pF AC Acquisition Time In ac applications it is recommended to always buffer analog input signals. The source impedance of the drive circuitry must be kept as low as possible to minimize the acquisition time of the ADC. Large values of source impedance will cause the THD to degrade at high throughput rates. TEMPERATURE MEASUREMENT The on-chip temperature sensor can be accessed via multiplexer Channel 0, i.e., by writing 0 0 0 to the channel address register. The temperature is also the power on default selection. The transfer characteristic of the temperature sensor is shown in Figure 11 below. The result of the 10-bit conversion on Channel 0 can be converted to degrees centigrade by using the following equation. ON-CHIP REFERENCE The AD7816, AD7817, and AD7818 have an on-chip 1.2 V band gap reference that is gained up to give an output of 2.5 V. The on-chip reference is selected by connecting the REFIN pin to analog ground. This causes SW1 (see Figure 9) to open and the reference amplifier to power up during a conversion. Therefore, the on-chip reference is not available externally. 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 and reducing IDD by about 0.25 mA. –12– TAMB = –103°C + (ADC Code/4) 125°C TEMPERATURE For small values of source impedance, the settling time associated with the sampling circuit (100 ns) is, in effect, the acquisition time of the ADC. For example, with a source impedance (R2) of 10 Ω the charge time for the sampling capacitor is approximately 23 ns. The charge time becomes significant for source impedances of 1 kΩ and greater. –55°C 192Dec ADC CODE 912Dec Figure 11. Temperature Sensor Transfer Characteristic REV. C AD7816/AD7817/AD7818 and temperature sensor (diode) in the package being evaluated. In Figure 12, the heater (6 mW) is turned off after 30 sec. The PCB has little influence on the self-heating over the first few seconds after the heater is turned on. This can be more clearly seen in Figure 13 where the heater is switched off after 2 seconds. Figure 14 shows the relative effects of self-heating in air, fluid and in thermal contact with a large heat sink. For example, if the result of a conversion on Channel 0 was 1000000000 (512 Dec), the ambient temperature is equal to –103°C + (512/4) = +25°C. Table II below shows some ADC codes for various temperatures. Table II. Temperature Sensor Output ADC Code Temperature 00 1100 0000 01 0011 1000 01 1001 1100 10 0000 0000 10 0111 1000 11 1001 0000 –55°C –25°C 0°C +25°C +55°C +125°C These diagrams represent the worst-case effects of self-heating. The heater delivered 6 mW to the interior of the package in all cases. This power level is equivalent to the ADC continuously converting at 100 kSPS. The effects of the self-heating can be reduced at lower ADC throughput rates by operating on Mode 2 (see Operating Modes section). When operating in this mode, the on-chip power dissipation reduces dramatically and, as a consequence, the self-heating effects. TEMPERATURE MEASUREMENT ERROR DUE TO REFERENCE ERROR 0.50 2-LAYER PCB 0.45 CODE (Dec) = ([113.3285 × K × T]/[q × VREF] – 0.6646) × 1024 where: 0.40 0.35 TEMPERATURE – ⴗC The AD7816, AD7817, and AD7818 are trimmed using a precision 2.5 V reference to give the transfer function described previously. To show the effect of the reference tolerance on a temperature reading, the temperature sensor transfer function can be rewritten as a function of the reference voltage and the temperature. 0.30 0.25 0.20 4-LAYER PCB 0.15 0.10 0.05 K = Boltzmann’s Constant, 1.38 × 10–23 q = Charge on an electron, 1.6 × 10–19 T = Temperature (K) 0.00 –0.05 0 10 20 30 40 TIME – secs So, for example, to calculate the ADC code at 25°C 60 Figure 12. Self-Heating Effect Two-Layer and Four-Layer PCB CODE = ([113.3285 × 298 × 1.38 × 10–23]/[1.6 × 10–19 × 2.5] – 0.6646) × 1024 = 511.5 (200 Hex) 0.25 As can be seen from the expression, a reference error will produce a gain error. This means that the temperature measurement error due to reference error will be greater at higher temperatures. For example, with a reference error of –1%, the measurement error at –55°C would be 2.2 LSBs (0.5°C) and 16 LSBs (4°C) at 125°C. The AD7817 and AD7818 have an analog-to-digital conversion function capable of a throughput rate of 100 kSPS. At this throughput rate the AD7817 and AD7818 will consume between 4 mW and 6.5 mW of power. Because a thermal impedance is associated with the IC package, the temperature of the die will rise as a result of this power dissipation. The graphs below show the self-heating effect in a 16-lead SOIC package. Figures 12 and 13 show the self-heating effect on a two-layer and four-layer PCB. The plots were generated by assembling a heater (resistor) –13– TEMPERATURE – ⴗC 0.20 SELF-HEATING CONSIDERATIONS REV. C 50 0.15 0.10 2-LAYER PCB 4-LAYER PCB 0.05 0.00 –0.05 0 1 2 3 TIME – secs 4 5 Figure 13. Self-Heating Effect Two-Layer and Four-Layer PCB AD7816/AD7817/AD7818 0.8 OPERATING MODES The AD7816, AD7817, and AD7818 have two possible modes of operation depending on the state of the CONVST pulse at the end of a conversion. 0.7 TEMPERATURE – ⴗC 0.6 AIR 0.5 Mode 1 In this mode of operation the CONVST pulse is brought high before the end of a conversion, i.e., before the BUSY goes low (see Figure 16). When operating in this mode a new conversion should not be initiated until 100 ns after the end of a serial read operation. This quiet time is to allow the track/hold to accurately acquire the input signal after a serial read. 0.4 FLUID 0.3 0.2 HEAT SINK 0.1 0.0 –0.01 0 2 4 6 8 10 TIME – secs 12 14 Mode 2 16 Figure 14. Self-Heating Effect in Air, Fluid, and in Thermal Contact with a Heat Sink 0.25 0.20 FLUID TEMPERATURE – ⴗC AIR 0.15 HEATSINK When the AD7816, AD7817, and AD7818 are operated in Mode 2 (see Figure 17), they automatically power down at the end of a conversion. The CONVST is brought low to initiate a conversion and is left logic low until after the end of the conversion. At this point, i.e., when BUSY goes low, the devices will powerdown. The devices are powered up again on the rising edge of the CONVST signal. Superior power performance can be achieved in this mode of operation by powering up the AD7816, AD7817, and AD7818 only to carry out a conversion (see Power vs. Throughput section). In Figure 17 the CS line is applicable to the AD7817 only. 0.10 0.05 0.00 –0.05 0.0 0.5 1.0 TIME – secs 1.5 2.0 Figure 15. Self-Heating Effect in Air, Fluid, and in Thermal Contact with a Heat Sink t1 t2 CONVST t3 BUSY t17 CS t15 t16 OTI RD/ WR SCLK DIN DB7 – DB0 DB7(DB9) – DB0 DOUT Figure 16. Mode 1 Operation –14– REV. C AD7816/AD7817/AD7818 t POWER-UP t1 CONVST t3 BUSY CS t15 OTI t16 RD/ WR SCLK DIN DB7 – DB0 DB7(DB9) – DB0 DOUT Figure 17. Mode 2 Operation POWER VS. THROUGHPUT 10 Superior power performance can be achieved by using the Automatic Power-Down (Mode 2) at the end of a conversion (see Operating Modes section of this data sheet). POWER – mW 1 t POWER-UP t CONVERT 2s 8s CONVST 0.1 BUSY t CYCLE 100s @ 10kSPS 0.01 0 Figure 18. Automatic Power-Down Figure 18 shows how the Automatic Power-Down is implemented to achieve the optimum power performance from the AD7816, AD7817, and AD7818. The devices are operated in Mode 2 and the duration of CONVST pulse is set to be equal to the power-up time (2 µs). As the throughput rate of the device is reduced the device remains in its power-down state longer, and the average power consumption over time drops accordingly. For example, if the AD7817 is operated in a continuous sampling mode with a throughput rate of 10 kSPS, the power consumption is calculated as follows. The power dissipation during normal operation is 4.8 mW, VDD = 3 V. If the power up time is 2 µs and the conversion time is 9 µs, the AD7817 can be said to dissipate 4.8 mW typically for 11 µs (worst case) during each conversion cycle. If the throughput rate is 10 kSPS, the cycle time is 100 µs and the power dissipated while powered up during each cycle is (11/100) × (4.8 mW) = 528 µW typ. Power dissipated while powered down during each cycle is (89/100) × (3 V × 2 µA) = 5.34 µW typ. Overall power dissipated is 528 µW + 5.34 µW = 533 µW. REV. C 10 20 30 40 50 THROUGHPUT – kHz 60 70 80 Figure 19. Power vs. Throughput Rate AD7817 SERIAL INTERFACE The serial interface on the AD7817 is a 5-wire interface with read and write capabilities, with data being read from the output register via the DOUT line and data being written to the control register via the DIN line. The part operates in a slave mode and requires an externally applied serial clock to the SCLK input to access data from the data register or write to the control byte. The RD/WR line is used to determine whether data is being written to or read from the AD7817. When data is being written to the AD7817, the RD/WR line is set logic low and when data is being read from the part the line is set logic high (see Figure 20). The serial interface on the AD7817 is designed to allow the part to be interfaced to systems that provide a serial clock that is synchronized to the serial data, such as the 80C51, 87C51, 68HC11, 68HC05, and PIC16Cxx microcontrollers. –15– AD7816/AD7817/AD7818 CS t4 t10 RD/WR t5 SCLK t11 t8 1 2 3 7 t6 8 1 2 3 9 10 t9 t7 DIN DB7 DB6 DB5 DB1 DB0 t12 CONTROL BYTE t14b t13 DOUT DB9 DB8 t14a DB7 DB1 DB0 Figure 20. AD7817 Serial Interface Timing Diagram Read Operation Figure 20 shows the timing diagram for a serial read from the AD7817. CS is brought low to enable the serial interface and RD/ WR is set logic high to indicate that the data transfer is a serial read from the AD7817. The rising edge of RD/WR clocks out the first data bit (DB9), subsequent bits are clocked out on the falling edge of SCLK (except for the first falling SCLK edge) and are valid on the rising edge. 10 bits of data are transferred during a read operation. However, the user has the choice of clocking only eight bits if the full 10 bits of the conversion result are not required. The serial data can be accessed in a number of bytes if 10 bits of data are being read. However, RD/WR must remain high for the duration of the data transfer operation. Before starting a new data read operation the RD/WR signal must be brought low and high again. At the end of the read operation, the DOUT line enters a high impedance state on the rising edge of the CS or the falling edge of RD/WR, whichever occurs first. The readback process is a destructive process in that once the data is read back it is erased. A conversion must be done again; otherwise no data will be read back. Write Operation Figure 20 also shows a control byte write operation to the AD7817. The RD/WR input goes low to indicate to the part that a serial write is about to occur. The AD7817 control byte is loaded on the rising edge of the first eight clock cycles of the serial clock with data on all subsequent clock cycles being ignored. To carry out a second successive write operation, the RD/WR signal must be brought high and low again. Simplifying the Serial Interface To minimize the number of interconnect lines to the AD7817, the user can connect the CS line to DGND. This is possible if the AD7817 is not sharing the serial bus with another device. It is also possible to tie the DIN and DOUT lines together. This arrangement is compatible with the 8051 microcontroller. The 68HC11, 68HC05, and PIC16Cxx can be configured to operate with a single serial data line. In this way the number of lines required to operate the serial interface can be reduced to three, i.e., RD/WR, SCLK, and DIN/OUT (see Figure 6). AD7816 AND AD7818 SERIAL INTERFACE MODE The serial interface on the AD7816 and AD7818 is a 3-wire interface with read and write capabilities. Data is read from the output register and the control byte is written to the AD7816 and AD7818 via the DIN/OUT line. The part operates in a slave mode and requires an externally applied serial clock to the SCLK input to access data from the data register or write the control byte. The RD/WR line is used to determine whether data is being written to or read from the AD7816 and AD7818. When data is being written to the devices the RD/WR line is set logic low and when data is being read from the part the line is set logic high (see Figure 21). The serial interface on the AD7816 and AD7818 are designed to allow the part to be interfaced to systems that provide a serial clock that is synchronized to the serial data, such as the 80C51, 87C51, 68HC11, 68HC05, and PIC16Cxx microcontrollers. Read Operation Figure 21 shows the timing diagram for a serial read from the AD7816 and AD7818. The RD/WR is set logic high to indicate that the data transfer is a serial read from the devices. When RD/WR is logic high the DIN/OUT pin becomes a logic output and the first data bit (DB9) appears on the pin. Subsequent bits are clocked out on the falling edge of SCLK, starting with the second SCLK falling edge after RD/WR goes high and are valid on the rising edge of SCLK. Ten bits of data are transferred during a read operation. However the user has the choice of clocking only eight bits if the full 10 bits of the conversion result are not required. The serial data can be accessed in a number of bytes if 10 bits of data are being read; however, RD/WR must remain high for the duration of the data transfer operation. To carry out a successive read operation the RD/WR pin must be brought logic low and high again. At the end of the read operation, the DIN/OUT pin becomes a logic input on the falling edge of RD/WR. Write Operation A control byte write operation to the AD7816 and AD7818 is also shown in Figure 21. The RD/WR input goes low to indicate to the part that a serial write is about to occur. The AD7816 and AD7818 control bytes are loaded on the rising edge of the first eight clock cycles of the serial clock with data on all subsequent clock cycles being ignored. To carry out a successive write to the AD7816 or AD7818 the RD/WR pin must be brought logic high and low again. –16– REV. C AD7816/AD7817/AD7818 RD/WR t5 1 SCLK t11 t8 2 3 7 t6 8 t9 DB7 DB1 DB5 DB6 2 t12 t7 DIN/D OUT 1 3 9 10 t14a t13 DB0 DB9 DB8 DB7 DB1 DB0 CONTROL BYTE Figure 21. AD7816/AD7818 Serial Interface Timing Diagram OUTLINE DIMENSIONS 8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8) 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters Dimensions shown in millimeters and (inches) 3.00 BSC 5.00 (0.1968) 4.80 (0.1890) 8 4.00 (0.1574) 3.80 (0.1497) 8 5 1 4 5 4.90 BSC 3.00 BSC 6.20 (0.2440) 5.80 (0.2284) 1 4 PIN 1 1.27 (0.0500) BSC 1.75 (0.0688) 1.35 (0.0532) 0.25 (0.0098) 0.10 (0.0040) COPLANARITY SEATING 0.10 PLANE 0.51 (0.0201) 0.31 (0.0122) 0.50 (0.0196) ⴛ 45ⴗ 0.25 (0.0099) 0.65 BSC 1.10 MAX 0.15 0.00 8ⴗ 0.25 (0.0098) 0ⴗ 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067) 0.38 0.22 COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MS-012AA 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 0.23 0.08 8ⴗ 0ⴗ 0.80 0.60 0.40 SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-187AA 16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16) 16-Lead Standard Small Outline Package [SOIC] Narrow Body (R-16) Dimensions shown in millimeters Dimensions shown in millimeters and (inches) 5.10 5.00 4.90 10.00 (0.3937) 9.80 (0.3858) 4.00 (0.1575) 3.80 (0.1496) 16 9 1 8 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 16 6.20 (0.2441) 5.80 (0.2283) 1.75 (0.0689) 1.35 (0.0531) 9 4.50 4.40 4.30 0.50 (0.0197) ⴛ 45ⴗ 0.25 (0.0098) 6.40 BSC 1 8 PIN 1 8ⴗ 0.51 (0.0201) SEATING 0.25 (0.0098) 0ⴗ 1.27 (0.0500) PLANE 0.31 (0.0122) 0.40 (0.0157) 0.17 (0.0067) 1.20 MAX 0.15 0.05 COMPLIANT TO JEDEC STANDARDS MS-012AC 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 0.20 0.09 0.65 BSC 0.30 0.19 COPLANARITY 0.10 SEATING PLANE 8ⴗ 0ⴗ COMPLIANT TO JEDEC STANDARDS MO-153AB REV. C –17– 0.75 0.60 0.45 AD7816/AD7817/AD7818 Revision History Location Page 9/04—Data Sheet changed from REV. B to REV. C. Updated ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Changes to Operating Modes section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Changes to Figure 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Changes to Figure 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Changes to AD7817 Serial Interface, Read Operation section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Changes to Figure 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Changes to Figure 21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 –18– REV. C –19– –20– C01316–0–9/04(C)