 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ADC12L063 Datasheet(PDF) 20 Page - National Semiconductor (TI) |
|
|
||||||||||||||||||||||||||||||
ADC12L063 Datasheet(HTML) 20 Page - National Semiconductor (TI) |
|
|
20 / 22 page  Applications Information (Continued) 4.0 POWER SUPPLY CONSIDERATIONS The power supply pins should be bypassed with a 10 µF capacitor and with a 0.1 µF ceramic chip capacitor within a centimeter of each power pin. Leadless chip capacitors are preferred because they have low series inductance. As is the case with all high-speed converters, the ADC12L063 is sensitive to power supply noise. Accordingly, the noise on the analog supply pin should be kept below 100 mV P-P. No pin should ever have a voltage on it that is in excess of the supply voltages, not even on a transient basis. Be espe- cially careful of this during turn on and turn off of power. The V DR pin provides power for the output drivers and may be operated from a supply in the range of 2.5V to V D (nominal 3.3V). This can simplify interfacing to 3V devices and systems. DO NOT operate the V DR pin at a voltage higher than V D. 5.0 LAYOUT AND GROUNDING Proper grounding and proper routing of all signals are es- sential to ensure accurate conversion. Maintaining separate analog and digital areas of the board, with the ADC12L063 between these areas, is required to achieve specified per- formance. The ground return for the data outputs (DR GND) carries the ground current for the output drivers. The output current can exhibit high transients that could add noise to the conversion process. To prevent this from happening, the DR GND pins should NOT be connected to system ground in close prox- imity to any of the ADC12L063’s other ground pins. Capacitive coupling between the typically noisy digital cir- cuitry and the sensitive analog circuitry can lead to poor performance. The solution is to keep the analog circuitry separated from the digital circuitry, and to keep the clock line as short as possible. Digital circuits create substantial supply and ground current transients. The logic noise thus generated could have sig- nificant impact upon system noise performance. The best logic family to use in systems with A/D converters is one which employs non-saturating transistor designs, or has low noise characteristics, such as the 74LS, 74HC(T) and 74AC(T)Q families. The worst noise generators are logic families that draw the largest supply current transients dur- ing clock or signal edges, like the 74F and the 74AC(T) families. The effects of the noise generated from the ADC output switching can be minimized through the use of 47 Ω to 56Ω resistors in series with each data output line. Locate these resistors as close to the ADC output pins as possible. Since digital switching transients are composed largely of high frequency components, total ground plane copper weight will have little effect upon the logic-generated noise. This is because of the skin effect. Total surface area is more important than is total ground plane volume. Generally, analog and digital lines should cross each other at 90˚ to avoid crosstalk. To maximize accuracy in high speed, high resolution systems, however, avoid crossing analog and digital lines altogether. It is important to keep clock lines as short as possible and isolated from ALL other lines, including other digital lines. Even the generally accepted 90˚ crossing should be avoided with the clock line as even a little coupling can cause problems at high frequencies. This is because other lines can introduce jitter into the clock line, which can lead to degradation of SNR. Also, the high speed clock can introduce noise into the analog chain. Best performance at high frequencies and at high resolution is obtained with a straight signal path. That is, the signal path through all components should form a straight line wherever possible. Be especially careful with the layout of inductors. Mutual inductance can change the characteristics of the circuit in 20026316 FIGURE 7. Example of a Suitable Layout www.national.com 20 |
Similar Part No. - ADC12L063 |
|
Similar Description - ADC12L063 |
|
|
|
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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
