Datenblatt-Suchmaschine für elektronische Bauteile |
|
AD585 Datenblatt(PDF) 6 Page - Analog Devices |
|
AD585 Datenblatt(HTML) 6 Page - Analog Devices |
6 / 6 page AD585 REV. A –6– LOGIC INPUT The sample-and-hold logic control was designed for versatile logic interfacing. The HOLD and HOLD inputs may be used with both low and high level CMOS, TTL and ECL logic sys- tems. Logic threshold programmability was achieved by using a differential amplifier as the input stage for the digital inputs. A predictable logic threshold may be programmed by referencing either HOLD or HOLD to the appropriate threshold voltage. For example, if the internal 1.4 V reference is applied to HOLD an input signal to HOLD between +1.8 V and +VS will place the AD585 in the hold mode. The AD585 will go into the sample mode for this case when the input is between –VS and +1.0 V. The range of references which may be applied is from (–VS +4 V) to (+VS –3 V). OPTIONAL CAPACITOR SELECTION If an additional capacitor is going to be used in conjunction with the internal 100 pF capacitor it must have a low dielectric absorption. Dielectric absorption is just that; it is the charge absorbed into the dielectric that is not immediately added to or removed from the capacitor when rapidly charged or discharged. The capacitor with dielectric absorption is modeled in Figure 14. Figure 14. Capacitor Model with Dielectric Absorption If the capacitor is charged slowly, CDA will eventually charge to the same value as C. But unfortunately, good dielectrics have very high resistances, so while CDA may be small, RX is large and the time constant RX CDA typically runs into the millisecond range. In fast charge, fast-discharge situations the effect of di- electric absorption resembles “memory”. In a data acquisition system where many channels with widely varying data are being sampled the effect is to have an ever changing offset which ap- pears as a very nonlinear sample-to-hold offset since the differ- ence between the voltage being measured and the voltage previ- ously measured determines the fraction by which the dielectric absorption figure is multiplied. It is impossible to readily correct for this error source. The only solution is to use a capacitor with dielectric absorption less than the maximum tolerable error. Capacitor types such as polystyrene, polypropy- lene or Teflon are recommended. GROUNDING Many data-acquisition components have two or more ground pins which are not connected together within the device. These “grounds” are usually referred to as the Logic Power Return Analog Common (Analog Power Return), and Analog Signal Ground. These grounds must be tied together at one point, usually at the system power-supply ground. Ideally, a single solid ground would be desirable. However, since current flows through the ground wires and etch stripes of the circuit cards, and since these paths have resistance and inductance, hundreds of millivolts can be generated between the system ground point and the ground pin of the AD585. Separate ground returns should be provided to minimize the current flow in the path from sensitive points to the system ground point. In this way supply currents and logic-gate return currents are not summed into the same return path as analog signals where they would cause measurement errors. Figure 15. Basic Grounding Practice OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 14-Pin Cerdip (Q-14) 20-Terminal LCC (E-20A) 20-Terminal PLCC (P-20A) |
Ähnliche Teilenummer - AD585 |
|
Ähnliche Beschreibung - AD585 |
|
|
Link URL |
Privatsphäre und Datenschutz |
ALLDATASHEETDE.COM |
War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller 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 |