Electronic Components Datasheet Search |
|
DAC312 Datasheet(PDF) 11 Page - Analog Devices |
|
DAC312 Datasheet(HTML) 11 Page - Analog Devices |
11 / 14 page DAC312 –11– REV. C ANALOG OUTPUT CURRENTS Both true and complemented output sink currents are provided where IO + IO = IFR. Current appears at the true output when a “1” is applied to each logic input. As the binary count increases, the sink current at pin 18 increases proportionally, in the fash- ion of a “positive logic” D/A converter. When a “0” is applied to any input bit, that current is turned off at pin 18 and turned on at pin 19. A decreasing logic count increases IO as in a negative or inverted logic D/A converter. Both outputs may be used si- multaneously. If one of the outputs is not required it must still be connected to ground or to a point capable of sourcing IFR; do not leave an unused output pin open. Both outputs have an extremely wide voltage compliance en- abling fast direct current-to-voltage conversion through a resis- tor tied to ground or other voltage source. Positive compliance is 25 V above V– and is independent of the positive supply. Negative compliance is +10 V above V–. The dual outputs enable double the usual peak-to-peak load swing when driving loads in quasi-differential fashion. This fea- ture is especially useful in cable driving, CRT deflection and in other balanced applications such as driving center-tapped coils and transformers. POWER SUPPLIES The DAC312 operates over a wide range of power supply volt- ages from a total supply of 20 V to 36 V. When operating with V– supplies of –10 V or less, IREF ≤ 1 mA is recommended. Low reference current operation decreases power consumption and increases negative compliance, reference amplifier negative common-mode range, negative logic input range, and negative logic threshold range; consult the various figures for guidance. For example, operation at –9 V with IREF = 1 mA is not recom- mended because negative output compliance would be reduced to near zero. Operation from lower supplies is possible, however at least 8 V total must be applied to insure turn-on of the inter- nal bias network. Symmetrical supplies are not required, as the DAC312 is quite insensitive to variations in supply voltage. Battery operation is feasible as no ground connection is required; however, an artifi- cial ground may be used to insure logic swings, etc. remain be- tween acceptable limits. TEMPERATURE PERFORMANCE The nonlinearity and monotonicity specifications of the DAC312 are guaranteed to apply over the entire rated operating temperature range. Full-scale output current drift is tight, typi- cally ±10 ppm/°C, with zero-scale output current and drift es- sentially negligible compared to 1/2 LSB. The temperature coefficient of the reference resistor R14 should match and track that of the output resistor for minimum overall full-scale drift. Settling times of the DAC312 decrease approxi- mately 10% at –55 °C; at +125°C an increase of about 15% is typical. SETTLING TIME The DAC312 is capable of extremely fast settling times; typi- cally 250 ns at IREF = 1.0 mA. Judicious circuit design and care- ful board layout must be employed to obtain full performance potential during testing and application. The logic switch design enables propagation delays of only 25 ns for each of the 12 bits. Settling time to within 1/2 LSB of the LSB is therefore 25 ns, with each progressively larger bit taking successively longer. The MSB settles in 250 ns, thus determining the overall settling time of 250 ns. Settling to 10-bit accuracy requires about 90 ns to 130 ns. The output capacitance of the DAC312 including the package is approximately 20 pF; therefore, the output RC time constant dominates settling time if RL > 500 Ω. Settling time and propagation delay are relatively insensitive to logic input amplitude and rise and fall times, due to the high gain of the logic switches. Settling time also remains essentially constant for IREF values down to 0.5 mA, with gradual increases for lower IREF values lies in the ability to attain a given output level with lower load resistors, thus reducing the output RC time constant. Measurement of the settling time requires the ability to accu- rately resolve ±1/2 LSB of current, which is ±500 nA for 4 mA FSR. In order to assure the measurement is of the actual settling time and not the RC time of the output network, the resistive termination on the output of the DAC must be 500 Ω or less. This does, however, place certain limitations on the testing ap- paratus. At IREF values of less than 0.5 mA, it is difficult to pre- vent RC damping of the output and maintain adequate sensitivity. Because the DAC312 has 8 equal current sources for the 3 most significant bits, the major carry occurs at the code change of 000111111111 to 111000000000. The worst case set- tling time occurs at the zero to full-scale transition and it re- quires 9.2 time constants for the DAC output to settle to within ±1/2 LSB (0.0125%) of its final value. The DAC312 switching transients or “glitches” are on the order of 500 mV-ns. This is most evident when switching through the major carry and may be further reduced by adding small capaci- tive loads at the output with a minor sacrifice in transition speeds. Fastest operation can be obtained by using short leads, minimiz- ing output capacitance and load resistor values, and by adequate bypassing at the supply, reference, and VLC terminals. Supplies do not require large electrolytic bypass capacitors as the supply current drain is independent of input logic states; 0.1 µF capaci- tors at the supply pins provide full transient protection. |
Similar Part No. - DAC312_15 |
|
Similar Description - DAC312_15 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |