FEATURES Complete A/D Converter with Reference and Clock Fast Successive Approximation Conversion: s No Missing Codes Over Temperature +125C: AD570S Digital Multiplexing: Three-State Outputs 18-Pin Ceramic DIP Low Cost Monolithic Construction
The an 8-bit successive approximation A/D converter consisting of a DAC, voltage reference, clock, comparator, successive approximation register and output buffers--all fabricated on a single chip. No external components are required to perform a full accuracy 8-bit conversion in 25 µs. The AD570 incorporates the most advanced integrated circuit design and processing technology available today. I2L (integrated injection logic) processing in the fabrication of the SAR function along with laser trimming of the high stability SiCr thin-film resistor ladder network at the wafer stage (LWT) and a temperature compensated, subsurface Zener reference insures full 8-bit accuracy at low cost. Operating on supplies +5 V and 15 V, the AD570 accepts analog inputs +10 V unipolar 5 V bipolar, externally selectable. As the BLANK and CONVERT input is driven low, the three-state outputs go into the high impedance state and a conversion commences. Upon completion of the conversion, the DATA READY line goes low and the data appears at the output. Pulling the BLANK and CONVERT input high three states the outputs and readies the device for the next conversion. The AD570 executes a true 8-bit conversion with no missing codes in approximately 25 µs. The AD570 is available in two version; the AD570J is specified for the to +70°C temperature range, the AD570S for to +125°C. Both guarantee full 8-bit accuracy and no missing codes over their respective temperature ranges.
1. The is a complete 8-bit A/D converter. No external components are required to perform a conversion. Full-scale calibration accuracy 0.8% (2 LSB of 8 bits) is achieved without external trims. 2. The is a single chip device employing the most advanced IC processing techniques. Thus, the user has at his disposal a truly precision component with the reliability and low cost inherent in monolithic construction, 3. The AD570 accepts either unipolar V) or bipolar +5 V) analog inputs by grounding or opening a single pin. 4. The device offers true 8-bit accuracy and exhibits no missing codes over its entire operating temperature range. 5. Operation is guaranteed with 15 V and +5 V supplies. The device will also operate with 12 V supply. 6. The AD570S is also available processed to MIL-STD-883C, Class B. The military data sheet for the AD570SD/883B is included in the Analog Devices Military Products Databook.
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Model RESOLUTION1 RELATIVE ACCURACY TMIN to TMAX FULL-SCALE CALIBRATION UNIPOLAR OFFSET BIPOLAR OFFSET DIFFERENTIAL NONLINEAIRTY TMIN to TMAX TEMPERATURE RANGE TEMPERATURE COEFFICIENTS Unipolar Offset Bipolar Offset Full-Scale Calibration POWER SUPPLY REJECTION TTL Positive Supply +5.5 V Negative Supply 13.5 V ANALOG INPUT IMPEDANCE ANALOG INPUT RANGES Unipolar Bipolar OUTPUT CODING Unipolar Bipolar LOGIC OUTPUT Output Sink Current (VOUT 0.4 V max, TMIN to TMAX) Output Source Current (VOUT 2.4 V max, TMIN to TMAX) Output Leakage LOGIC INPUTS Input Current Logic "1" Logic "0" CONVERSION TIME POWER SUPPLY V+ V OPERATING CURRENT V+ V PACKAGE OPTION2 Ceramic DIP (D-18) Min AD570J Typ Max 8 1/2
Positive True Binary Positive True Offset Binary
NOTES 1 The is a selected version of the AD571 10-bit A-to-D converter. Only TTL logic inputs should be connected to Pins 1 and 18 (or no connection made) or damage may result. 2 For details on grade package offerings for SD-grade in accorance with MIL-STD-883, refer to Analog Devices' Military Products databook or current /883 data sheet. Specifications subject to change without notice. Specifications shown in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min and max specifications are guaranteed, although only those shown in boldface are tested on all production units.
V+ to Digital Common. V to Digital Common. 16.5 V Analog Common to Digital Common. 1 V Analog Input to Analog Common. 15 V Control Inputs. to V+ Digital Outputs (Blank Mode). to V+ Power Dissipation. 800 mW
signal, an input current will be generated which exactly matches the DAC output with all bits on. (The input resistor is trimmed slightly low to facilitate user trimming, as discussed on the next page.)
The is a complete 8-bit A/D converter which requires no external components to provide the complete successiveapproximation analog-to-digital conversion function. A block diagram of the AD570 is shown on last page. Upon receipt of the CONVERT command, the internal 8-bit current output DAC is sequenced by the I2L successive-approximation register (SAR) from its most-significant bit (MSB) to least-significant bit (LSB) to provide an output current which accurately balances the input signal current through the 5 k input resistor. The comparator determines whether the addition of each successively-weighted bit current causes the DAC current sum to be greater or less than the input current; if the sum is less the bit is left on, if more, the bit is turned off. After testing all the bits, the SAR contains a 8-bit binary code which accurately represents the input signal to within ± 1/2 LSB (0.20%). Upon completion of the sequence, the DATA READY signal goes low, and the bit output lines become active high or low depending on the code in the SAR. When the BLANK and CONVERT line is brought high, the output buffers again go "open", and the SAR is prepared for another conversion cycle. The temperature compensated buried Zener reference provides the primary voltage reference to the DAC and guarantees excellent stability with both time and temperature. The bipolar offset input controls a switch which allows the positive bipolar offset current (exactly equal to the value of the MSB less 1/2 LSB)
The AD570 is designed and specified for optimum performance using +5 V and 15 V supply. The supply current drawn by the device is a function of the operating mode (BLANK or CONVERT), as given on the specification page. The supply currents change only moderately over temperature as shown in Figure 2, and do not change significantly with changes in V from 10.8 volts to 16 volts.
The AD570 contains all the active components required to perform a complete A/D conversion. Thus, for most situations, all that is necessary is to connect the power supply (+5 V and 15 V), the analog input, and the conversion start signal. But, there are some features and special connections which should be considered for achieving optimum performance. The functional pinout is shown in Figure 3.
V ANALOG COMMON ANALOG IN 0.151 THE AD570 IS ALSO AVAILABLE IN A LASER-TRIMMED PASSIVATED CHIP FORM. CONSULT CHIP CATALOG FOR APPLICATION PARTICULARS. FIGURE 3 SHOWS THE CHIP METALLIZATION LAYOUT AND BONDING PADS.
to be injected into the summing node of the comparator to offset the DAC output. Thus the nominal +10 V unipolar input range becomes +5 V range. The 5 k thinfilm input resistor is trimmed so that with a full-scale input REV. A 3