【文章內(nèi)容簡介】 AGRAM Complete Current Output Converter High Stability Buried Zener Reference Laser Trimmed to High Accuracy (1/4 LSB Max Error, AD561K, T) Trimmed Output Application Resistors for 0 V to +10 V, 65 V Ranges Fast Settling – 250 ns to 1/2 LSB Guaranteed Monotonicity Over Full Operating Temperature Range TTL/DTL and CMOS Compatible (Positive True Logic) Single Chip Monolithic Construction Available in Chip Form MlLSTD883Compliant Versions Available 【 1】 【 AD561 PRODUCT HIGHLIGHTS】 1. Advanced monolithic processing and laser trimming at the wafer level have made the AD561 the most accurate 10bit converter available, while keeping costs consistent with large volume integrated circuit production. The AD561K and T have 1/4 LSB max relative accuracy and 1/2 LSB max differential nonlinearity. The low TC R2R ladder guarantees that all AD561 units will be monotonic over the entire operating temperature range. 2. Digital system interfacing is simplified by the use of a positive true straight binary code. The digital input voltage threshold is a function of the positive supply level。 connecting VCC to the digital logic supply automatically sets the threshold to the proper level for the logic family being used. Logic sink current requirement is only 25 mA. 3. The high speed current steering switches are designed to settle in less than 250 ns for the worst case digital code transition. This allows construction of successiveapproximation A/D converters in the 3 ms to 5 ms range. 4. The AD561 has an output voltage pliance range from –2 V to +10 V, allowing direct currenttovoltage conversion with just an output resistor, omitting the op amp. The 40 MW open collector output impedance results in negligible errors due to output leakage currents. 5. The AD561 is available in versions pliant with MILSTD883. Refer to the Analog Devices Military Products Databook or current AD561/883B data sheet for detailed specifications. 【 2】【 Analysis and Application of AD561】 THE AD561 OFFERS TRUE 10BIT RESOLUTION OVER FULL TEMPERATURE RANGE Accuracy: Analog Devices defines accuracy as the maximum deviation of the actual, adjusted DAC output (see page 5) from the ideal analog output (a straight line drawn from 0 to FS – lLSB) for any bit bination. The AD561 is laser trimmed to 1/4 LSB (% of FS) maximum error at +25176。C for the K and T versions – 1/2 LSB for the J and S. Monotonicity: A DAC is said to be monotonic if the output either increases or remains constant for increasing digital inputs such that the output will always be a singlevalued function of the input. All versions of the AD561 are monotonic over their full operating temperature range. Differential Nonlinearity: Monotonic behavior requires that the differential nonlinearity error be less than 1 LSB both at +25176。C and over the temperature range of interest. Differential nonlinearity is the measure of the variation in analog value, normalized to full scale, associated with a 1 LSB change in digital input code. For example, for a 10 volt full scale output, a change of 1 LSB in digital input code should result in a mV change in the analog output (1 LSB = 10 V 180。 1/1024 = mV). If in actual use, however, a 1 LSB change in the input code results in a change of only mV (1/4 LSB) in analog output, the differential nonlinearity error would be mV, or 3/4 LSB The AD561K and T have a max differential linearity error of 1/2 LSB. The differential nonlinearity temperature coefficient must also be considered if the device is to remain monotonic over its full operating temperature range. A differential nonlinearity temperature coefficient of ppm/176。