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a FEATURES Complete 8-Bit DAC Voltage Output—0 V to 2.56 V Internal Precision Band-Gap Reference Single-Supply Operation: +5 V (؎10%) Full Microprocessor Interface Fast: 1 ␮s Voltage Settling to ؎1/2 LSB Low Power: 75 mW No User Trims Required Guaranteed Monotonic Over Temperature All Errors Specified TMIN to TMAX Small 16-Pin DIP or 20-Pin PLCC Package Low Cost

DACPORT, Low-Cost Complete ␮P-Compatible 8-Bit DAC AD557 FUNCTIONAL BLOCK DIAGRAM



The AD557 DACPORT® is a complete voltage-output 8-bit digital-to-analog converter, including output amplifier, full microprocessor interface and precision voltage reference on a single monolithic chip. No external components or trims are required to interface, with full accuracy, an 8-bit data bus to an analog system.

1. The 8-bit I2L input register and fully microprocessorcompatible control logic allow the AD557 to be directly connected to 8- or 16-bit data buses and operated with standard control signals. The latch may be disabled for direct DAC interfacing.

The low cost and versatility of the AD557 DACPORT are the result of continued development in monolithic bipolar technologies. The complete microprocessor interface and control logic is implemented with integrated injection logic (I2L), an extremely dense and low-power logic structure that is process-compatible with linear bipolar fabrication. The internal precision voltage reference is the patented low-voltage band-gap circuit which permits full-accuracy performance on a single +5 V power supply. Thin-film silicon-chromium resistors provide the stability required for guaranteed monotonic operation over the entire operating temperature range, while laser-wafer trimming of these thin-film resistors permits absolute calibration at the factory to within ± 2.5 LSB; thus, no user-trims for gain or offset are required. A new circuit design provides voltage settling to ± 1/2 LSB for a full-scale step in 800 ns.

2. The laser-trimmed on-chip SiCr thin-film resistors are calibrated for absolute accuracy and linearity at the factory. Therefore, no user trims are necessary for full rated accuracy over the operating temperature range. 3. The inclusion of a precision low-voltage band-gap reference eliminates the need to specify and apply a separate reference source. 4. The AD557 is designed and specified to operate from a single +4.5 V to +5.5 V power supply. 5. Low digital input currents, 100 µA max, minimize bus loading. Input thresholds are TTL/low voltage CMOS compatible. 6. The single-chip, low power I2L design of the AD557 is inherently more reliable than hybrid multichip or conventional single-chip bipolar designs.

The AD557 is available in two package configurations. The AD557JN is packaged in a 16-pin plastic, 0.3"-wide DIP. For surface mount applications, the AD557JP is packaged in a 20-pin JEDEC standard PLCC. Both versions are specified over the operating temperature range of 0°C to +70°C. DACPORT is a registered trademark of Analog Devices, Inc. Covered by U.S. Patent Nos. 3,887,863; 3,685,045; 4,323,795; other patents pending.

REV. A 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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703

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