Electronic Components Datasheet Search |
|
AD7982 Datasheet(PDF) 14 Page - Analog Devices |
|
AD7982 Datasheet(HTML) 14 Page - Analog Devices |
14 / 16 page AD7684 Rev. A | Page 14 of 16 Table 9. Recommended Driver Amplifiers Amplifier Typical Application ADA4841-x Very low noise ADA4941-1 Very low noise, single to differential AD8021 Very low noise and high frequency AD8022 Low noise and high frequency OP184 Low power, low noise, and low frequency AD8605, AD8615 5 V single-supply, low power AD8519 Small, low power, and low frequency AD8031 High frequency and low power VOLTAGE REFERENCE INPUT The AD7684 voltage reference input, REF, has a dynamic input impedance. It should therefore be driven by a low impedance source with efficient decoupling between the REF and GND pins, as explained in more detail in the Layout section. When REF is driven by a very low impedance source (for example, an unbuffered reference voltage such as the low temperature drift ADR43x reference or a reference buffer using the AD8031 or the AD8605), a 10 μF (X5R, 0805 size) ceramic chip capacitor is appropriate for optimum performance. If desired, smaller reference decoupling capacitor values down to 2.2 μF can be used with minimal impact on performance, especially DNL. POWER SUPPLY The AD7684 powers down automatically at the end of each conversion phase and therefore the power scales linearly with the sampling rate, as shown in Figure 24. This makes the part ideal for low sampling rates (even of a few Hz) and low battery powered applications. 0.01 0.1 1 10 100 1000 100 10 1k 10k 100k SAMPLING RATE (SPS) VDD = 5V VDD = 2.7V Figure 24. Operating Current vs. Sampling Rate DIGITAL INTERFACE The AD7684 is compatible with SPI, QSPI, digital hosts, and DSPs (for example, Blackfin® ADSP-BF53x or ADSP-219x). The connection diagram is shown in Figure 25, and the corresponding timing is given in Figure 2. A falling edge on CS initiates a conversion and the data transfer. After the fifth DCLOCK falling edge, DOUT is enabled and forced low. The data bits are then clocked MSB first by subsequent DCLOCK falling edges. The data is valid on both DCLOCK edges. Although the rising edge can be used to capture the data, a digital host also using the DCLOCK falling edge allows a faster reading rate, provided it has an acceptable hold time. CS DCLOCK DOUT DATA IN CLK CONVERT DIGITAL HOST AD7684 Figure 25. Connection Diagram LAYOUT The printed circuit board housing the AD7684 should be designed so that the analog and digital sections are separated and confined to certain areas of the board. The pinout of the AD7684 with all its analog signals on the left side and all its digital signals on the right side eases this task. Avoid running digital lines under the device because these couple noise onto the die, unless a ground plane under the AD7684 is used as a shield. Fast switching signals, such as CS or clocks, should never run near analog signal paths. Crossover of digital and analog signals should be avoided. At least one ground plane should be used. It could be common or split between the digital and analog sections. In such a case, it should be joined underneath the AD7684. The AD7684 voltage reference input REF has a dynamic input impedance and should be decoupled with minimal parasitic inductances. This is done by placing the reference decoupling ceramic capacitor close to, and ideally right up against, the REF and GND pins and by connecting these pins with wide, low impedance traces. Finally, the power supply, VDD, of the AD7684 should be decoupled with a ceramic capacitor, typically 100 nF, and placed close to the AD7684. It should be connected using short and large traces to provide low impedance paths and reduce the effect of glitches on the power supply lines. EVALUATING THE PERFORMANCE OF THE AD7684 Other recommended layouts for the AD7684 are outlined in the evaluation board for the AD7684 (EVAL-AD7684CBZ). The evaluation board package includes a fully assembled and tested evaluation board, documentation, and software for controlling the board from a PC via the EVAL-CONTROL BRD3Z. |
Similar Part No. - AD7982 |
|
Similar Description - AD7982 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |