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AD5543BRZ Datenblatt(PDF) 9 Page - Analog Devices |
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AD5543BRZ Datenblatt(HTML) 9 Page - Analog Devices |
9 / 20 page Data Sheet AD5543/AD5553 Rev. F | Page 9 of 20 CIRCUIT OPERATION The AD5543/AD5553 contain 16-/14-bit current output, DACs, serial input registers, and DAC registers. Both converters use a 3-wire serial data interface. DAC SECTION The DAC architecture uses a current steering R-2R ladder design. Figure 18 shows the typical equivalent DAC structure. The DAC contains a matching feedback resistor for use with an external op amp (see Figure 19). With RFB and IOUT terminals connected to the op amp output and inverting node, respectively, a precision voltage output is achieved as VOUT = −VREF × D/65,536 (AD5543) (1) VOUT = −VREF × D/16,384 (AD5553) (2) Note that the output voltage polarity is the opposite of the VREF polarity for dc reference voltages. These DACs are designed to operate with either negative or positive reference voltages. The VDD power pin is only used by the internal logic to drive the on and off states of the DAC switches. VREF VDD RFB IOUT R R R GND 2R 2R 2R S1 S2 DIGITAL INTERFACE CONNECTIONS OMITTED FOR CLARITY; SWITCHES S1 AND S2 ARE CLOSED, VDD MUST BE POWERED. 5kΩ R Figure 18. Equivalent R-2R DAC Circuit Note that a matching switch is used in series with the internal 5 kΩ feedback resistor. If users attempt to measure RFB, power must be applied to VDD to achieve continuity. RFB IOUT1 GND SCLK SDIN VREF VREF R1 SYNC AD5543/ AD5553 VDD VDD AGND C1 A1 R2 VOUT = 0 TO –VREF µCONTROLLER NOTES 1. R1 AND R2 USED ONLY IF GAIN ADJUSTMENT IS REQUIRED. 2. C1 PHASE COMPENSATION (4pF TO 6pF) MAY BE REQUIRED IF A1 IS A HIGH SPEED AMPLIFIER. Figure 19. Voltage Output Configuration These DACs are also designed to accommodate ac reference input signals. The AD5543 accommodates input reference voltages in the range of −12 V to +12 V. The reference voltage inputs exhibit a constant nominal input resistance value of 5 kΩ ± 30%. The DAC output (IOUT) is code dependent, producing various resistances and capacitances. External amplifier choice should take into account the variation in impedance generated by the AD5543 on the inverting input node of the amplifier. The feedback resistance, in parallel with the DAC ladder resistance, dominates output voltage noise. To maintain good analog performance, power supply bypassing of 0.01 µF to 0.1 µF ceramic or chip capacitors, in parallel with a 1 µF tantalum capacitor, is recommended. Due to degradation of PSRR in frequency, users must avoid using switching power supplies. |
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Ähnliche Beschreibung - AD5543BRZ |
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