FEATURES FUNCTIONAL BLOCK DIAGRAMS AD7817 OVERTEMP REG TEMP SENSOR REF 2.5V VIN1 VIN2 B A>B OTI A CHARGE REDISTRIBUTION DAC DATA OUT CONTROL LOGIC REG CONTROL MUX VIN3 SAMPLING CAPACITOR VIN4 AGND DGND DOUT DIN SCLK RD/WR VBALANCE CLOCK BUSY CS CONVST Figure 1. AD7817 Functional Block Diagram VDD AD7818 OVERTEMP REG TEMP SENSOR REF 2.5V APPLICATIONS Data acquisition systems with ambient temperature monitoring Industrial process control Automotive Battery charging applications VDD REFIN 01316-001 10-bit ADC with 9 µs conversion time 1 AD7818 and 4 AD7817 single-ended analog input channels On-chip temperature sensor Resolution of 0.25°C ±2°C error from −40°C to +85°C −55°C to +125°C operating range Wide operating supply range: 2.7 V to 5.5 V Inherent track-and-hold functionality On-chip reference (2.5 V ± 1%) Overtemperature indicator Automatic power-down at the end of a conversion Low power operation 4 µW at a throughput rate of 10 SPS 40 µW at a throughput rate of 1 kSPS 400 µW at a throughput rate of 10 kSPS Flexible serial interface VIN1 B A>B OTI A CHARGE REDISTRIBUTION DAC DATA OUT DIN/OUT MUX SAMPLING CAPACITOR VBALANCE AGND CONTROL LOGIC CONTROL REG CLOCK GENERATOR SCLK RD/WR CONVST 01316-002 Data Sheet Dual, Low Power CMOS, Analog Front End with DSP Microcomputer AD7817/AD7818 Figure 2. AD7818 Functional Block Diagram GENERAL DESCRIPTION The AD7817/AD7818 are 10-bit, single- and 4-channel analog-todigital converters (ADCs) with an 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 digital-to-analog converter (DAC), an on-chip temperature sensor with an accuracy of ±2°C, an on-chip clock oscillator, inherent track-and-hold functionality, and an on-chip reference (2.5 V). The on-chip temperature sensor of the AD7817/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 the Temperature Measurement section. The AD7817/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, and National Semiconductors MICROWIRE protocols. For more Rev. D information, refer to the AD7817 Serial Interface section and the AD7818 Serial Interface Mode section. The AD7817 is available in a narrow body, 0.15 inch, 16-lead SOIC and a 16-lead TSSOP, and the AD7818 comes in an 8-lead SOIC and an 8-lead 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 AD7817 and AD7818 to achieve superior power performance at slower throughput rates, that is, 40 µW at 1 kSPS throughput rate. Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 ©2012 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com AD7817/AD7818 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Converter Details ....................................................................... 12 Applications ....................................................................................... 1 Typical Connection Diagram ................................................... 12 Functional Block Diagrams ............................................................. 1 Analog Inputs.............................................................................. 12 General Description ......................................................................... 1 On-Chip Reference .................................................................... 13 Product Highlights ........................................................................... 1 ADC Transfer Function ............................................................. 13 Revision History ............................................................................... 2 Temperature Measurement ....................................................... 14 Specifications..................................................................................... 3 Temperature Measurement Error Due to Reference Error... 14 Timing Characteristics ................................................................ 6 Self-Heating Considerations ..................................................... 14 Absolute Maximum Ratings ............................................................ 7 Operating Modes ........................................................................ 15 ESD Caution .................................................................................. 7 Power vs. Throughput................................................................ 17 Pin Configurations and Function Descriptions ........................... 8 AD7817 Serial Interface ............................................................. 17 Terminology .................................................................................... 10 AD7818 Serial Interface Mode ................................................. 18 Control Byte .................................................................................... 11 Outline Dimensions ....................................................................... 19 Circuit Information .................................................................... 12 Ordering Guide .......................................................................... 20 REVISION HISTORY 10/12—Rev. C to Rev. D Deleted AD7816.................................................................. Universal Changes to Format ............................................................. Universal Deleted Figure 15; Renumbered Sequentially............................. 14 Updated Outline Dimensions ....................................................... 19 Changes to Ordering Guide .......................................................... 20 9/04—Rev. B to Rev. C Changes to Ordering Guide .............................................................6 Changes to Operating Modes Section and Figure 16 ................ 13 Changes to Figure 17...................................................................... 14 Changes to AD7817 Serial Interface, Read Operation Section and Figure 20................................................................................... 15 Changes to Figure 21...................................................................... 16 Rev. D | Page 2 of 20 Data Sheet AD7817/AD7818 SPECIFICATIONS VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted. The AD7817 temperature sensor is specified with an external 2.5 V reference, and the AD7818 temperature sensor is specified with an on-chip reference. For VDD = 2.7 V, TA = 85°C maximum and temperature sensor measurement error = ±3°C. Table 1. Parameter DYNAMIC PERFORMANCE (AD7817 ONLY) A Version 1 B Version1 S Version1 Unit Signal-to-(Noise + Distortion) Ratio 2 Total Harmonic Distortion2 Peak Harmonic or Spurious Noise2 Intermodulation Distortion2 Second-Order Terms Third-Order Terms Channel-to-Channel Isolation2 DC ACCURACY (AD7817 ONLY) Resolution Minimum Resolution for Which No Missing Codes are Guaranteed Relative Accuracy2 Differential Nonlinearity2 Gain Error2 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 10 10 10 Bits ±1 ±1 ±2 ±10 ±1/2 ±2 ±1/2 ±1 ±1 ±2 ±10 ±1/2 ±2 ±1/2 ±1 ±1 ±2 +20/−10 ±1/2 ±2 ±1/2 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 Gain Error Match2 Offset Error2 Offset Error Match TEMPERATURE SENSOR (AD7817 ONLY) Measurement Error Ambient Temperature 25°C TMIN to TMAX Measurement Error Ambient Temperature 25°C TMIN to TMAX Temperature Resolution REFERENCE INPUT (AD7817 ONLY) 3, 4 REFIN Input Voltage Range3 Input Impedance Input Capacitance ON-CHIP REFERENCE (AD7817 ONLY) 5 Temperature Coefficient3 CONVERSION RATE (AD7817 ONLY) Track-and-Hold Acquisition Time4 Conversion Time Temperature Sensor Channel 1 to Channel 4 Test Conditions/Comments Sample rate = 100 kSPS, any channel, fIN = 20 kHz −75 dB typical −75 dB typical 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 Rev. D | Page 3 of 20 Source Impedance < 10 Ω AD7817/AD7818 Parameter POWER REQUIREMENTS (AD7817 ONLY) 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 DYNAMIC PERFORMANCE (AD7818 ONLY) 6 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)6 Resolution Minimum Resolution for Which No Missing Codes are Guaranteed Relative Accuracy2 Differential Nonlinearity2 Gain Error2 Offset Error2 TEMPERATURE SENSOR (AD7818 ONLY)6 Measurement Error Ambient Temperature 25°C TMIN to TMAX Measurement Error Ambient Temperature 25°C TMIN to TMAX Temperature Resolution ON-CHIP REFERENCE (AD7818 ONLY)5 Temperature Coefficient3 CONVERSION RATE (AD7818 ONLY)6 Track-and-Hold Acquisition Time4 Conversion Time Temperature Sensor Channel 1 Data Sheet A Version 1 B Version1 S Version1 Unit Test Conditions/Comments 5.5 2.7 5.5 2.7 5.5 2.7 V max V min For specified performance 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 57 –65 –67 dB min dB max dB typ –67 –67 –80 dB typ dB typ dB typ 10 10 Bits Bits ±1 ±1 ±10 ±4 LSB max LSB max LSB max LSB max ±2 ±3 °C max °C max ±2 ±3 1/4 °C max °C max °C/LSB 30 ppm/°C typ 400 ns max 27 9 µs max µs max Logic inputs = 0 V or VDD 1.6 mA typical 2.5 V external reference connected 5.5 µA typical 2 µA typical VDD = 3 V See the Power vs. Throughput section for description of power dissipation in auto power-down mode Typically 6 µW Sample rate = 100 kSPS, any channel, fIN = 20 kHz −75 dB typical −75 dB typical fa = 19.9 kHz, fb = 20.1 kHz fIN = 20 kHz Any channel External reference VREF = 2.5 V On-chip reference Nominal 2.5 V Rev. D | Page 4 of 20 Source impedance < 10 Ω Data Sheet Parameter POWER REQUIREMENTS (AD7818 ONLY)6 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 ANALOG INPUTS (AD7817/AD7818) 7 Input Voltage Range Input Leakage Input Capacitance LOGIC INPUTS (AD7817/AD7818)4 Input High Voltage, VINH Input Low Voltage, VINL Input High Voltage, VINH Input Low Voltage, VINL Input Current, IIN Input Capacitance, CIN LOGIC OUTPUTS (AD7817/AD7818)4 Output High Voltage, VOH AD7817/AD7818 A Version 1 B Version1 S Version1 Unit Test Conditions/Comments 5.5 2.7 V max V min For specified performance 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 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 Output Low Voltage, VOL High Impedance Leakage Current High Impedance Capacitance 1 Logic inputs = 0 V or VDD 1.3 mA typical 2.5 V external reference connected 6 µA typ 2 µA typ VDD = 3 V See the Power vs Throughput section for description of power dissipation in auto power-down mode Typically 6 µW 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% The B Version and the S Version only apply to the AD7817. The A Version applies to the AD7817 or the AD7818 (as stated in specification). See Terminology. 3 The accuracy of the temperature sensor is affected by reference tolerance. The relationship between the two is explained in the Temperature Measurement Error Due to Reference Error section. 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 These specifications are typical for AD7818 at temperatures above 85°C and with VDD greater than 3.6 V. 7 This refers to the input current when the part is not converting. Primarily due to the reverse leakage current in the ESD protection diodes. 2 Rev. D | Page 5 of 20 AD7817/AD7818 Data Sheet TIMING CHARACTERISTICS VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V. All specifications TMIN to TMAX, unless otherwise noted. Sample tested during initial release and after any redesign or process changes that may affect the parameters. 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. See Figure 17, Figure 18, Figure 21, and Figure 22. Table 2. Parameter tPOWER-UP t1a t1b t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 1 t131 t14a1, 2 t14b1, 2 t15 t16 t17 2 Unit 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 Test Conditions/Comments Power-up time from rising edge of CONVST Conversion time Channel 1 to Channel 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) These figures are measured with the load circuit of Figure 3. They are defined as the time required for DOUT to cross 0.8 V or 2.4 V for VDD = 5 V ± 10% and 0.4 V or 2 V for VDD = 3 V ± 10%, as shown in Table 1. 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 the external bus loading capacitances. 200µA TO OUTPUT PIN IOL 1.6V CL 50pF 200µA IOL 01316-003 1 A Version/B Version 2 9 27 20 50 0 0 10 10 40 40 0 0 20 20 30 30 150 40 400 Figure 3. Load Circuit for Access Time and Bus Relinquish Time Rev. D | Page 6 of 20 Data Sheet AD7817/AD7818 ABSOLUTE MAXIMUM RATINGS TA = 25°C unless otherwise noted. Table 3. Parameter VDD to AGND VDD to DGND Analog Input Voltage to AGND VIN1 to VIN4 Reference Input Voltage to AGND1 Digital Input Voltage to DGND Digital Output Voltage to DGND Storage Temperature Range Junction Temperature 16-Lead 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) 8-Lead 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 + 0.3V –0.3 V to VDD + 0.3 V –0.3 V to VDD + 0.3 V −65°C to +150°C 150°C 450 mW 120°C/W 260°C 215°C 220°C 450 mW 100°C/W 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. 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 (that is, 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 VDD pin. Connect the diode as shown in this figure. Rev. D | Page 7 of 20 AD7817/AD7818 Data Sheet CONVST 1 16 RD/WR 2 15 SCLK 14 DIN BUSY OTI 3 AD7817 CS 4 TOP VIEW (Not to Scale) 13 DOUT AGND 5 12 DGND REFIN 6 11 VDD VIN1 7 10 VIN4 VIN2 8 9 VIN3 01316-004 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS Figure 4. AD7817 Pin Configuration Table 4. AD7817 Pin Function Descriptions Pin No. 1 Mnemonic CONVST 2 BUSY 3 OTI 4 CS 5 6 AGND REFIN 7 to 10 11 12 13 VIN1 to VIN4 14 15 DIN SCLK 16 RD/WR VDD DGND DOUT Description 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 track-and-hold in hold mode. Track-and-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 powers down. See the Operating Modes section. 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, that is, 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-and-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 on-chip reference, tie the REFIN pin to AGND. If an external reference is connected to the AD7817, the internal reference shuts down. Analog Input Channels. The AD7817 has four analog input channels. The input channels are single-ended 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 the 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. Set the RD/WR logic high for a read operation and logic low for a write operation. Rev. D | Page 8 of 20 Data Sheet AD7817/AD7818 OTI 2 8 AD7818 RD/WR SCLK TOP VIEW GND 3 (Not to Scale) 6 DIN/OUT VIN 4 7 5 VDD 01316-005 CONVST 1 Figure 5. AD7818 Pin Configuration Table 5. AD7818 Pin Function Descriptions Pin No. 1 Mnemonic CONVST 2 OTI 3 4 GND VIN 5 6 7 VDD DIN/OUT SCLK 8 RD/WR Description Logic Input Signal. The convert start signal initiates a 10-bit analog-to-digital conversion on the falling edge of this signal. The falling edge of this signal places track-and-hold in hold mode. Track-and-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 AD7818 powers down. See the Operating Modes section. 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, that is, 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 the Control Byte section. Positive Supply Voltage, 2.7 V to 5.5 V. Logic Input and Output. Serial data is clocked in and out of the AD7818 at this pin. Clock Input for the Serial Port. The serial clock is used to clock data into and out of the 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 AD7818 whether the next data transfer operation is a read or a write. Set the RD/WR logic high for a read operation and logic low for a write. Rev. D | Page 9 of 20 AD7817/AD7818 Data Sheet TERMINOLOGY Signal-to-(Noise + Distortion) Ratio 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) = (6.02N + 1.76) dB Thus, for a 10-bit converter, this is 62 dB. Total Harmonic Distortion (THD) THD is the ratio of the rms sum of harmonics to the fundamental. For the AD7817/AD7818, it is defined as: THD (dB ) = 20 log V2 2 + V3 2 + V4 2 + V5 2 + V6 2 V1 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 full-scale 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. 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. 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. where: V1 is the rms amplitude of the fundamental. V2, V3, V4, V5, and V6 are the rms amplitudes of the second through the sixth harmonics. 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; however, for parts where the harmonics are buried in the noise floor, it is a noise peak. Intermodulation Distortion With inputs consisting of sine waves at two frequencies, fa and fb, any active device with nonlinearities creates 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). The AD7817/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 Gain Error Match This is the difference in gain error between any two channels. Offset Error This is the deviation of the first code transition (0000 . . . 000) to (0000 . . . 001) from the ideal, that is, AGND + 1 LSB. Offset Error Match This is the difference in offset error between any two channels. Track-and-Hold Acquisition Time The track-and-hold acquisition time is the time required for the output of the track-and-hold amplifier to reach its final value, within ±1/2 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 VIN input of the AD7817 or the AD7818. It means that the user must wait for the duration of the trackand-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. Rev. D | Page 10 of 20 Data Sheet AD7817/AD7818 CONTROL BYTE Overtemperature Register The AD7817/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 AD7817/AD7818 is transferred to one of the two on-chip registers as follows. If any of the five MSBs of the control byte are logic one, the entire eight bits of the control byte are transferred to the overtemperature register (see Figure 6). 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 than the contents of the overtemperature register (OTR), 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 7). However, the usable temperature range of the temperature sensor is −55°C to +125°C. Figure 7 shows the OTR and how to set TALARM (the temperature at which the OTI goes low). 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 6). 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 000 address. Table 6 shows the channel 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 must be approximately midscale. After power-up, the default channel selection is DB2 = DB1 = DB0 = 0 (temperature sensor). OTR (Dec) = TALARM (°C) + 103°C 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, OTI goes 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. Table 6. Channel Selection DB0 0 1 0 1 0 1 Channel Selection Temperature sensor Channel 1 Channel 2 Channel 3 Channel 4 Internal reference (1.23 V) Device All All AD7817 AD7817 AD7817 All DB2 DB1 DB0 ADDRESS REGISTER IF ANY BIT DB7 TO DB3 ARE LOGIC 0 THEN DB2 TO DB0 ARE WRITTEN TO THE ADDRESS REGISTER MSB DB7 LSB 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 6. Address and Overtemperature Register Selection OVERTEMPERATURE REGISTER MSB LSB 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 + 103°C TALARM RESOLUTION = 18/LSB Figure 7. The Overtemperature Register (OTR) Rev. D | Page 11 of 20 01316-011 DB1 0 0 1 1 0 1 01316-012 DB2 0 0 0 0 1 1 AD7817/AD7818 Data Sheet CIRCUIT INFORMATION TYPICAL CONNECTION DIAGRAM The AD7817/AD7818 are single- and four-channel, 9 µs conversion time, 10-bit ADCs with an on-chip temperature sensor, reference, and serial interface logic functions on a single chip. The ADC section consists of a conventional, successive approximation converter based around a capacitor DAC. The AD7817/AD7818 are capable of running on a 2.7 V to 5.5 V power supply, and they 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 AD7817/AD7818 require a 2.5 V reference, which can be provided from their internal reference or from an external reference source. The on-chip reference is selected by connecting the REFIN pin to analog ground. Figure 8 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 the AD7817 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, connect a 10 µF capacitor between REFIN and AGND. For applications where power consumption is a concern, use the automatic power-down at the end of a conversion to improve power performance. See the Power vs. Throughput section. 10µF 3-WIRE SERIAL INTERFACE 0.1µF VDD CONVERTER DETAILS 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. The on-chip reference is not available, however, 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 Temperature Measurement Error Due to Reference Error section. Tie all unused analog inputs to a voltage within the nominal analog input range to avoid noise pickup. For minimum power consumption, tie the unused analog inputs to AGND. 0V TO 2.5V INPUT SCLK RD/WR DOUT DIN AD7817 AGND DGND CONVST BUSY OTI REFIN AD780/ REF-192 CS 10µF EXTERNAL REFERENCE 01316-013 OPTIONAL EXTERNAL REFERENCE Figure 8. Typical Connection Diagram ANALOG INPUTS Analog Input Figure 9 shows an equivalent circuit of the analog input structure of the AD7817/AD7818. The two diodes, D1 and D2, provide ESD protection for the analog inputs. Take care to ensure that the analog input signal never exceeds the supply rails by more than 200 mV. This causes 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 C2 capacitor in Figure 9 is typically about 4 pF and can mostly be attributed to pin capacitance. The R1 resistor is a lumped component made up of the on resistance of a multiplexer and a switch. This resistor is typically about 1 kΩ. The C1 capacitor is the ADC sampling capacitor and has a capacitance of 3 pF. VDD D1 AIN C2 4pF R1 1kΩ C1 3pF VBALANCE D2 CONVERT PHASE—SWITCH OPEN TRACK PHASE—SWITCH CLOSED Figure 9. Equivalent Analog Input Circuit Rev. D | Page 12 of 20 01316-014 Conversion is initiated by pulsing the CONVST input. The conversion clock for the part is internally generated; therefore, an external clock is not required, except when reading from and writing to the serial port. The on-chip, track-and-hold goes from track mode 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. A microcontroller can use this signal to determine when the result of the conversion should be read. The track-and-hold acquisition time of the AD7817/AD7818 is 400 ns. AIN1 AIN2 AIN3 AIN4 MICROCONVERTER/ MICROPROCESSOR SUPPLY 2.7V TO 5.5V Data Sheet AD7817/AD7818 DC Acquisition Time ON-CHIP REFERENCE 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. The AD7817/AD7818 have an on-chip, 1.2 V band gap reference that is gained up to give an output of 2.5 V. By connecting the REFIN pin to analog ground, the on-chip reference is selected. This selection causes SW1 to open and the reference amplifier to power up during a conversion (see Figure 11). Therefore, the on-chip reference is not available externally. An external 2.5 V reference can be connected to the REFIN pin, which has the effect of shutting down the on-chip reference circuitry and reducing IDD by approximately 0.25 mA. Figure 10 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. EXTERNAL REFERENCE DETECT REFIN 1.2V R2 R1 1kΩ SW1 C1 3pF 1.2V 01316-015 VIN 26kΩ 2.5V BUFFER Figure 10. Equivalent Sampling Circuit TCHARGE = 7.6 × (R2 + 1 kΩ) × 3 pF 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. 24kΩ 01316-016 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 Figure 11. On-Chip Reference ADC TRANSFER FUNCTION The output coding of the AD7817/AD7818 is straight binary. The designed code transitions occur at successive integer LSB values (that is, 1 LSB, 2 LSBs, and so on). The LSB size is = 2.5 V/1024 = 2.44 mV. The ideal transfer characteristic is shown in Figure 12. 111...111 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 cause the THD to degrade at high throughput rates. ADC CODE 111...110 111...000 1LSB = 2.5/1024 2.44mV 011...111 000...010 000...000 1LSB 0V +2.5V × 1LSB ANALOG INPUT Figure 12. ADC Transfer Function Rev. D | Page 13 of 20 01316-017 000...001 AD7817/AD7818 Data Sheet TEMPERATURE MEASUREMENT The on-chip temperature sensor can be accessed via multiplexer Channel 0, that is, 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 13. The result of the 10-bit conversion on Channel 0 can be converted to degrees centigrade by the following: TAMB = −103°C + (ADC Code/4) 192Dec ADC CODE 912Dec Figure 13. Temperature Sensor Transfer Characteristics 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. SELF-HEATING CONSIDERATIONS The AD7817/AD7818 have an analog-to-digital conversion function capable of a throughput rate of 100 kSPS. At this throughput rate, the AD7817/AD7818 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 rises as a result of this power dissipation. Figure 14 to Figure 16 show the selfheating effect in a 16-lead SOIC. Figure 14 and Figure 15 show the self-heating effect on a two-layer and four-layer PCB. The plots were generated by assembling a heater (resistor) and temperature sensor (diode) in the package being evaluated. In Figure 14, 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 15 where the heater is switched off after 2 sec. Figure 16 shows the relative effects of self-heating in air, fluid, and thermal contact with a large heat sink. 0.50 Table 7 shows some ADC codes for various temperatures. 0.40 Table 7. Temperature Sensor Output 0.35 Temperature −55°C −25°C 0°C +25°C +55°C +125°C TEMPERATURE (°C) ADC Code 00 1100 0000 01 0011 1000 01 1001 1100 10 0000 0000 10 0111 1000 11 1001 0000 2-LAYER PCB 0.45 0.30 0.25 0.20 4-LAYER PCB 0.15 0.10 0.05 0 TEMPERATURE MEASUREMENT ERROR DUE TO REFERENCE ERROR –0.05 0 The AD7817/AD7818 are trimmed using a precision 2.5 V reference to give the transfer function previously described. 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. 10 20 30 40 50 60 TIME (Seconds) 01316-019 –55°C 01316-018 TEMPERATURE +125°C As can be seen from the expression, a reference error produces 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 is 2.2 LSBs (+0.5°C) and 16 LSBs (+4°C) at +125°C. Figure 14. Self-Heating Effect 2-Layer and 4-Layer PCB with the Heater (6 mW) Turned Off After 30 sec 0.25 0.20 TEMPERATURE (°C) CODE (DEC) = ([113.3285 × K × T]/[q × VREF] − 0.6646) × 1024 So, for example, to calculate the ADC code at 25°C, CODE = ([113.3285 × 298 × 1.38 × 10−23]/[1.6 × 10−19 × 2.5] − 0.6646) × 1024 0.15 0.10 2-LAYER PCB 4-LAYER PCB 0.05 0 –0.05 = 511.5 (200 Hex) 0 1 2 3 TIME (Seconds) 4 5 01316-020 where: K = Boltzmann’s Constant, 1.38 × 10−23 q = charge on an electron, 1.6 × 10−19 T = temperature (K) Figure 15. Self-Heating Effect 2-Layer and 4-Layer PCB with the Heater Switched Off After 2 sec Rev. D | Page 14 of 20 Data Sheet AD7817/AD7818 Figure 16 represents 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 in 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. 0.8 0.7 TEMPERATURE (°C) 0.6 AIR 0.5 OPERATING MODES The AD7817/AD7818 have two possible modes of operation depending on the state of the CONVST pulse at the end of a conversion. Mode 1 In this mode of operation, the CONVST pulse is brought high before the end of a conversion, that is, before BUSY goes low (see Figure 17). When operating in this mode, do not initiate a new conversion until 100 ns after the end of a serial read operation. This quiet time is to allow the track-and-hold to accurately acquire the input signal after a serial read. Mode 2 0.4 In this mode of operation, AD7817/AD7818 automatically power down at the end of a conversion (see Figure 18). The CONVST is brought low to initiate a conversion and is left logic low until after the end of the conversion. At this point, that is, when BUSY goes low, the devices power down. FLUID 0.3 0.2 HEAT SINK 0.1 –0.1 0 2 4 6 8 10 TIME (Seconds) 12 14 16 01316-021 0 Figure 16. Self-Heating Effect in Air, Fluid, and Thermal Contact with a Heat Sink 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 AD7817/AD7818 only to carry out a conversion (see the Power vs. Throughput section). In Figure 18, the CS line is applicable to the AD7817 only. Rev. D | Page 15 of 20 AD7817/AD7818 Data Sheet t1 t2 CONVST t3 BUSY t17 CS t15 t16 OTI RD/WR SCLK DB7 – DB0 DB7(DB9) – DB0 DOUT 01316-023 DIN Figure 17. Mode 1 Operation tPOWER-UP t1 CONVST t3 BUSY CS t15 OTI t16 RD/WR SCLK DB7 – DB0 DOUT DB7(DB9) – DB0 Figure 18. Mode 2 Operation Rev. D | Page 16 of 20 01316-024 DIN Data Sheet AD7817/AD7818 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 the Operating Modes section). POWER (mW) 1 tPOWER-UP tCONVERT 2µs 8µs CONVST 0.1 tCYCLE 100µs @ 10kSPS 0.01 Figure 19. Automatic Power-Down 0 Figure 19 shows how the automatic power-down is implemented to achieve the optimum power performance from the AD7817 and AD7818. The devices operate in Mode 2, and the duration of CONVST pulse is set 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. 10 20 30 40 50 60 70 THROUGHPUT (kHz) 80 01316-026 01316-025 BUSY Figure 20. Power vs. Throughput Rate AD7817 SERIAL INTERFACE The serial interface on the AD7817 is a 5-wire interface that has 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 AD7817 operates in 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 RD/WR line is set logic high (see Figure 21). 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. For example, if the AD7817 operates in 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 typically dissipate 4.8 mW 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 typical. 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. CS t4 t10 RD/WR t8 t5 SCLK 1 2 3 t11 7 8 1 2 3 9 10 t9 t6 t7 DB7 DB6 DB5 CONTROL BYTE DOUT DB1 DB0 t14b t13 t12 DB9 DB8 Figure 21. AD7817 Serial Interface Timing Diagram Rev. D | Page 17 of 20 t14a DB7 DB1 DB0 01316-027 DIN AD7817/AD7818 Data Sheet Read Operation AD7818 SERIAL INTERFACE MODE Figure 21 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. During a read operation, 10 bits of data are transferred. However, a choice is available to only clock 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 data is read back, it is erased. A conversion must be done again; otherwise, no data is read back. The serial interface on the AD7818 is a 3-wire interface that has read and write capabilities. Data is read from the output register and the control byte is written to the AD7818 via the DIN/DOUT line. The AD7818 operates in 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 AD7818. When data is being written to the AD7818, the RD/WR line is set logic low, and when data is being read from the AD7818 the line is set logic high (see Figure 22). The serial interface on AD7818 is designed to allow the AD7818 to interface with 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 22 shows the timing diagram for a serial read from the 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/DOUT 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, a choice is available to only clock 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/DOUT pin becomes a logic input on the falling edge of RD/WR. Write Operation Figure 21 also shows the 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, 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, that is, RD/WR, SCLK, and DIN/DOUT (see Figure 8). Write Operation A control byte write operation to the AD7818 is also shown in Figure 22. The RD/WR input goes low to indicate to the part that a serial write is about to occur. The 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 AD7818 the RD/WR pin must be brought logic high and low again. RD/WR SCLK t8 1 2 3 t6 t11 7 8 t9 t12 t7 DIN/OUT DB7 DB6 DB5 DB1 1 DB0 2 3 9 10 t13 DB9 DB8 CONTROL BYTE Figure 22. AD7818 Serial Interface Timing Diagram Rev. D | Page 18 of 20 t14a DB7 DB1 DB0 01316-028 t5 Data Sheet AD7817/AD7818 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 8 4.00 (0.1574) 3.80 (0.1497) 5 1 6.20 (0.2441) 5.80 (0.2284) 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 0.50 (0.0196) 0.25 (0.0099) 1.75 (0.0688) 1.35 (0.0532) 8° 0° 0.51 (0.0201) 0.31 (0.0122) COPLANARITY 0.10 SEATING PLANE 45° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 012407-A COMPLIANT TO JEDEC STANDARDS MS-012-AA 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 23. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 10.00 (0.3937) 9.80 (0.3858) 4.00 (0.1575) 3.80 (0.1496) 9 16 1 8 6.20 (0.2441) 5.80 (0.2283) 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.50 (0.0197) 0.25 (0.0098) 1.75 (0.0689) 1.35 (0.0531) 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 24. 16-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-16) Dimensions shown in millimeters and (inches) 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15° MAX 1.10 MAX 0.40 0.25 6° 0° 0.23 0.09 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 25.8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters Rev. D | Page 19 of 20 0.80 0.55 0.40 10-07-2009-B 0.15 0.05 COPLANARITY 0.10 AD7817/AD7818 Data Sheet 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 8° 0° 0.75 0.60 0.45 COMPLIANT TO JEDEC STANDARDS MO-153-AB Figure 26. 16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16) Dimensions shown in millimeters ORDERING GUIDE Model 1 AD7817ARZ AD7817ARZ-REEL AD7817ARZ-REEL7 AD7817ARU AD7817ARU-REEL AD7817ARU-REEL7 AD7817ARUZ AD7817ARUZ-REEL AD7817ARUZ-REEL7 AD7817BRZ AD7817BRZ-REEL AD7817BRZ-REEL7 AD7817BRU AD7817BRU-REEL7 AD7817BRUZ AD7817BRUZ-REEL AD7817BRUZ-REEL7 AD7817SR AD7817SR-REEL AD7817SR-REEL7 AD7818ARZ AD7818ARZ-REEL7 AD7818ARM AD7818ARM-REEL AD7818ARM-REEL7 AD7818ARMZ AD7818ARMZ-REEL AD7818ARMZ-REEL7 1 Temperature Range −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 −40°C to +85°C −40°C to +85°C −40°C to +85°C Temperature Error at 25°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 ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C ±2°C Z = RoHS Compliant Part. ©2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D01316-0-10/12(D) Rev. D | Page 20 of 20 Package Description 16-Lead SOIC_N 16-Lead SOIC_N 16-Lead SOIC_N 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead SOIC_N 16-Lead SOIC_N 16-Lead SOIC_N 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead SOIC_N 16-Lead SOIC_N 16-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP Package Option R-16 R-16 R-16 RU-16 RU-16 RU-16 RU-16 RU-16 RU-16 R-16 R-16 R-16 RU-16 RU-16 RU-16 RU-16 RU-16 R-16 R-16 R-16 R-8 R-8 RM-8 RM-8 RM-8 RM-8 RM-8 RM-8 Branding C3A C3A C3A T1P T1P T1P