Electronic Components Datasheet Search |
|
AD7545AUQ Datasheet(PDF) 5 Page - Analog Devices |
|
AD7545AUQ Datasheet(HTML) 5 Page - Analog Devices |
5 / 8 page AD7545A –5– REV. C Figure 5 and Table III illustrate the recommended circuit and code relationship for bipolar operation. The D/A function itself uses offset binary code and inverter U1 on the MSB line con- verts twos complement input code to offset binary code. If ap- propriate, inversion of the MSB may be done in software using an exclusive –OR instruction and the inverter omitted. R3, R4 and R5 must be selected to match within 0.01%, and they should be the same type of resistor (preferably wire-wound or metal foil), so that their temperature coefficients match. Mis- match of R3 value to R4 causes both offset and full-scale error. Mismatch of R5 to R4 and R3 causes full-scale error. Figure 5. Bipolar Operation (Twos Complement Code) Table III. Twos Complement Code Table for Circuit of Figure 5 Data Input Analog Output 0 1 1 1 1 1 1 1 1 1 1 1 +VIN × 2047 2048 0 0 0 0 0 0 0 0 0 0 0 1 +VIN × 1 2048 0 0 0 0 0 0 0 0 0 0 0 0 0 Volts 1 1 1 1 1 1 1 1 1 1 1 1 –VIN × 1 2048 1 0 0 0 0 0 0 0 0 0 0 0 –VIN × 2048 2048 Figure 6 and Table IV show an alternative method of achieving bipolar output. The circuit operates with sign plus magnitude code and has the advantage that it gives 12-bit resolution in each quadrant compared with 11-bit resolution per quadrant for the circuit of Figure 5. The AD7592 is a fully protected CMOS change-over switch with data latches. R4 and R5 should match each other to 0.01% to maintain the accuracy of the D/A con- verter. Mismatch between R4 and R5 introduces a gain error. Refer to Reference 1 (supplemental application material) for additional information on these circuits. Figure 6. 12-Bit Plus Sign Magnitude Converter Table IV. 12-Bit Plus Sign Magnitude Code Table for Circuit of Figure 6 Sign Binary Numbers in Bit DAC Register Analog Output 0 1 1 1 1 1 1 1 1 1 1 1 1 + VIN × 4095 4096 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Volts 1 0 0 0 0 0 0 0 0 0 0 0 0 0 Volts 1 1 1 1 1 1 1 1 1 1 1 1 1 – VIN × 4095 4096 Note: Sign bit of “0” connects R3 to GND. APPLICATIONS HINTS Output Offset: CMOS D/A converters such as Figures 4, 5 and 6 exhibit a code dependent output resistance which, in turn, can cause a code dependent error voltage at the output of the amplifier. The maximum amplitude of this error, which adds to the D/A converter nonlinearity, depends on VOS, where VOS is the amplifier input offset voltage. To maintain specified accuracy with VREF at 10 V, it is recommended that VOS be no greater than 0.25 mV, or (25 × 10–6) (V REF), over the temperature range of operation. Suitable op amps are AD517 and AD711. The AD517 is best suited for fixed reference applications with low band- width requirements: it has extremely low offset (150 µV max for lowest grade) and in most applications will not require an offset trim. The AD711 has a much wider bandwidth and higher slew rate and is recommended for multiplying and other applications requiring fast settling. An offset trim on the AD711 may be necessary in some circuits. General Ground Management: AC or transient voltages between AGND and DGND can cause noise injection into the analog output. The simplest method of ensuring that voltages at AGND and DGND are equal is to tie AGND and DGND together at the AD7545A. In more complex systems where the AGND and DGND intertie is on the backplane, it is recom- mended that two diodes be connected in inverse parallel between the AD7545A AGND and DGND pins (1N914 or equivalent). |
Similar Part No. - AD7545AUQ |
|
Similar Description - AD7545AUQ |
|
|
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 |