AD7816-7818 Analog Devices, AD7816-7818 Datasheet
AD7816-7818
Related parts for AD7816-7818
AD7816-7818 Summary of contents
Page 1
... CAPACITOR V IN4 AGND The AD7816, AD7817 and AD7818 have a flexible serial inter- face 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" ...
Page 2
... AD7816/AD7817/AD7818 AD7817–SPECIFICATIONS Parameter DYNAMIC PERFORMANCE Signal to (Noise + Distortion) Ratio 2 Total Harmonic Distortion 2 Peak Harmonic or Spurious Noise 2 Intermodulation Distortion Second Order Terms Third Order Terms 2 Channel-to-Channel Isolation DC ACCURACY Resolution Minimum Resolution for Which No Missing Codes Are Guaranteed 10 2 Relative Accuracy ...
Page 3
... Measurement Error Ambient Temperature + MIN MAX Measurement Error Ambient Temperature + MIN MAX Temperature Resolution 3, 4 REFERENCE INPUT (AD7816 Only) 3 REF Input Voltage Range IN Input Impedance Input Capacitance 5 ON-CHIP REFERENCE 3 Temperature Coefficient CONVERSION RATE 4 Track/Hold Acquisition Time Conversion Time ...
Page 4
... High Impedance Capacitance 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 See Terminology ...
Page 5
... RD/WR Rising Edge to OTI Rising Edge ns min SCLK Rising Edge to CONVST Falling Edge (Acquisition Time of T/H) ns min I 200 OUTPUT C PIN L 50pF 200 –5– AD7816/AD7817/AD7818 = +2.5 V. All specifications MIN MAX to cross 0 2.4 V for 10% and 0.4 V OUT DD 1.6V unless ...
Page 6
... 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 feature proprietary ESD protection circuitry, perma- nent 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 ...
Page 7
... A channel is selected by writing to the Address Register of the AD7817—see Control REF PIN CONFIGURATION SOIC/TSSOP CONVST 1 16 RD/ SCLK BUSY AD7817 OUT TOP VIEW AGND 5 12 DGND (Not to Scale) REF IN1 IN4 IN3 IN2 –7– AD7816/AD7817/AD7818 ...
Page 8
... 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 logic low, the AD7816 and AD7818 will power down—see Operating Mode section of the data sheet. ...
Page 9
... 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 ...
Page 10
... The AD7817 and AD7818 are single- and four-channel conversion time, 10-bit A/D converters with on-chip tempera- ture 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 ...
Page 11
... ADC. Large values of source impedance will cause the THD to degrade at high throughput rates. ON-CHIP REFERENCE The AD7816, AD7817 and AD7818 have an on-chip +1.2 V bandgap reference that is gained up to give an output of +2.5 V. The on-chip reference is selected by connecting the REF to analog ground. This causes SW1 (see Figure 9) to open and the reference amplifier to power up during a conversion ...
Page 12
... TEMPERATURE MEASUREMENT ERROR DUE TO REFERENCE ERROR The AD7816, AD7817 and AD7818 are trimmed using a preci- sion +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 ...
Page 13
... At this point, i.e., when BUSY goes low, the devices will power- down. 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, FLUID AD7817 and AD7818 only to carry out a conversion (see Power vs ...
Page 14
... Figure 18 shows how the Automatic Power-Down is imple- mented 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 s). 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 ...
Page 15
... 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 subse- quent clock cycles being ignored ...
Page 16
... AD7816/AD7817/AD7818 RD/ SCLK DB8 DB7 DB6 IN OUT CONTROL BYTE Figure 21. AD7816/AD7818 Serial Interface Timing Diagram 16-Lead Narrow Body (SOIC) (R-16A) 0.3937 (10.00) 0.3859 (9.80 0.1574 (4.00) 0.2440 (6.20) 0.1497 (3.80 0.2284 (5.80) PIN 1 0.0688 (1.75) 0.0098 (0.25) 0.0532 (1.35) 0.0040 (0.10) 0.0500 0.0192 (0.49) SEATING 0.0099 (0.25) (1 ...