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DAC7802K Fiches technique(PDF) 10 Page - Burr-Brown (TI) |
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DAC7802K Fiches technique(HTML) 10 Page - Burr-Brown (TI) |
10 / 12 page 10 ® DAC7800, 01, 02 If an application requires the D/A to have zero gain error, the circuit shown in Figure 6 may be used. Resistors R2 and R4 induce a positive gain error greater than worst-case initial negative gain error. Trim resistors R1 and R3 provide a variable negative gain error and have sufficient trim range to correct for the worst-case initial positive gain error plus the error produced by R2 and R4. DATA INPUT ANALOG OUTPUT MSB ↓↓ LSB 1111 1111 1111 +VREF (2047/2048) 1000 0000 0001 +VREF (1/2048) 1000 0000 0000 0 Volts 0111 1111 1111 –VREF (1/2048) 0000 0000 0000 –VREF (2048/2048) TABLE III. Bipolar Output Code. FIGURE 5. Bipolar Configuration. R 3 10k 1 C 10pF DAC A DAC B R 10k 5 Ω DAC780X DGND V REF A V DD +5V C D 2 R 6 Ω 20k R 2 Ω 20k R 10k C 10pF V OUT A V OUT B A1 A3 DAC7802 has a single analog common, AGND. A1–A4, OPA602 or 1/2 OPA2107. – + A2 – + A4 5 Ω Ω R 1 Ω 20k R 4 Ω 20k REF B V I OUT B R FB B – + AGND B I OUT A R FB A – + AGND A 1µF + APPLICATIONS 12-BIT PLUS SIGN DACS For a bipolar DAC with 13 bits of resolution, two solutions are possible. As shown in Figure 7, the addition of a precision difference amplifier and a high speed JFET switch provides a 12-bit plus sign voltage-output DAC. When the switch selects the op amp output, the difference amplifier serves as a non-inverting output buffer. If the analog ground side of the switch is selected, the output of the difference amplifier is inverted. Another option, shown in Figure 8, also produces a 12-bit plus sign output without the additional switch and digital control line. DIGITALLY PROGRAMMABLE ACTIVE FILTER DAC780X are shown in Figure 9 in a digitally programmable active filter application. The design is based on the state- variable filter, Burr-Brown UAF42, an active filter topology that offers stable and repeatable filter characteristics. DAC1 and DAC2 can be updated in parallel with a single word to set the center frequency of the filter. DAC 4, which makes use of the uncommitted op amp in UAF42, sets the Q of the filter. DAC3 sets the gain of the filter transfer function without changing the Q of the filter. The reverse is also true. The center frequency is determined by f C = 1/2πRC where R is the ladder resistance of the D/A (typical value, 10k Ω) and C the internal capacitor value (1000pF) of the UAF42. Exter- nal capacitors can be added to lower the center frequency of the filter. But the highest center frequency for this circuit will be about 16kHz because the effective series resistance of the D/A cannot be less than 10k Ω. Note that the ladder resistance of the D/A may vary from device to device. Thus, for best tracking, DAC2 and DAC3 should be in the same package. Some calibration may be necessary from one filter to another. |
Numéro de pièce similaire - DAC7802K |
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Description similaire - DAC7802K |
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