a FEATURES Complete 12-Bit A/D Converter with Reference and Clock 8- and 16-Bit Microprocessor Bus Interface Guaranteed Linearity Over Temperature 0؇C to +70؇C – AD574AJ, K, L –55؇C to +125؇C – AD574AS, T, U No Missing Codes Over Temperature 35 s Maximum Conversion Time Buried Zener Reference for Long-Term Stability and Low Gain T.C. 10 ppm/؇C max AD574AL 12.5 ppm/؇C max AD574AU Ceramic DIP, Plastic DIP or PLCC Package Available in Higher Speed, Pinout-Compatible Versions (15 s AD674B, 80 s AD774B; 10 s (with SHA) AD1674) Available in Versions Compliant with MIL-STD-883 and JAN QPL
Complete 12-Bit A/D Converter AD574A* BLOCK DIAGRAM AND PIN CONFIGURATION +5V SUPPLY VLOGIC DATA MODE SELECT 12/8 CHIP SELECT CS BYTE ADDRESS/ SHORT CYCLE AO READ/CONVERT R/C CHIP ENABLE CE +12/+15V SUPPLY VCC +10V REFERENCE REF OUT ANALOG COMMON AC REFERENCE INPUT REF IN -12/-15V SUPPLY VEE BIPOLAR OFFSET BIP OFF 10V SPAN INPUT 10VIN
3 4 5
7 COMP 12 8
IDAC IDAC = 4 x N x IREF
9 10 19.95k
20V SPAN INPUT 14 20VIN
STATUS STS DB11 27 MSB
S T A T E
N I B B L E A
25 DB9 24 DB8
N I B B L E B
O U T P U T B U F F E R S
N I B B L E
22 DB6 21 DB5
DIGITAL DATA OUTPUTS
18 DB2 17 DB1 DB0 16 LSB 15 DIGITAL COMMON DC
The AD574A is a complete 12-bit successive-approximation analog-to-digital converter with 3-state output buffer circuitry for direct interface to an 8- or 16-bit microprocessor bus. A high precision voltage reference and clock are included on-chip, and the circuit guarantees full-rated performance without external circuitry or clock signals.
1. The AD574A interfaces to most 8- or 16-bit microprocessors. Multiple-mode three-state output buffers connect directly to the data bus while the read and convert commands are taken from the control bus. The 12 bits of output data can be read either as one 12-bit word or as two 8-bit bytes (one with 8 data bits, the other with 4 data bits and 4 trailing zeros).
The AD574A design is implemented using Analog Devices’ Bipolar/I2L process, and integrates all analog and digital functions on one chip. Offset, linearity and scaling errors are minimized by active laser-trimming of thin-film resistors at the wafer stage. The voltage reference uses an implanted buried Zener for low noise and low drift. On the digital side, I2L logic is used for the successive-approximation register, control circuitry and 3-state output buffers. The AD574A is available in six different grades. The AD574AJ, K, and L grades are specified for operation over the 0°C to +70°C temperature range. The AD574AS, T, and U are specified for the –55°C to +125°C range. All grades are available in a 28-pin hermetically-sealed ceramic DIP. Also, the J, K, and L grades are available in a 28-pin plastic DIP and PLCC, and the J and K grades are available in ceramic LCC.
2. The precision, laser-trimmed scaling and bipolar offset resistors provide four calibrated ranges: 0 volts to +10 volts and 0 volts to +20 volts unipolar, –5 volts to +5 volts and –10 volts to +10 volts bipolar. Typical bipolar offset and full-scale calibration errors of ± 0.1% can be trimmed to zero with one external component each. 3. The internal buried Zener reference is trimmed to 10.00 volts with 0.2% maximum error and 15 ppm/°C typical T.C. The reference is available externally and can drive up to 1.5 mA beyond the requirements of the reference and bipolar offset resistors. 4. AD674B (15 µs) and AD774B (8 µs) provide higher speed, pin compatibility; AD1674 (10 µs) includes on-chip SampleHold Amplifier (SHA).
The S, T, and U grades in ceramic DIP or LCC are available with optional processing to MIL-STD-883C Class B; the T and U grades are available as JAN QPL. The Analog Devices’ Military Products Databook should be consulted for details on /883B testing of the AD574A. *Protected by U.S. Patent Nos. 3,803,590; 4,213,806; 4,511,413; RE 28,633 .
REV. B 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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
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