Motor de Búsqueda de Datasheet de Componentes Electrónicos |
|
ADN2865 Datasheet(PDF) 27 Page - Analog Devices |
|
ADN2865 Datasheet(HTML) 27 Page - Analog Devices |
27 / 33 page Preliminary Technical Data ADN2865 Rev. PrA | Page 27 of 33 Transmission Lines Use of 50 Ω transmission lines is required for all LVDS and CML input and output signals to minimize reflections: PIN, NIN, RXDATAP/N[7:0], RXCLKP/N, SERDATP, SERDATN, SERCLKP, SERCLKN (also REFCLKP, REFCLKN, if a high frequency reference clock is used, such as 155 MHz). It is also necessary for the PIN/NIN input traces to be matched in length, and the parallel bus / CML output traces to be matched in length to avoid skew between the differential traces. All high speed CML outputs, SERDATP,SERDATN,SERCLKP,SERCLKN also require 100 Ω back termination chip resistors connected between the output pin and VCC. These resistors should be placed as close as possible to the output pins. These 100 Ω resistors are in parallel with on-chip 100 Ω termination resistors to create a 50 Ω back termination (see Figure ). The high speed inputs, PIN and NIN, are internally terminated with 50 Ω to an internal reference voltage (see Figure ). A 0.1 μF is recommended between VREF, Pin 36, and GND to provide an ac ground for the inputs. As with any high speed mixed-signal design, take care to keep all high speed digital traces away from sensitive analog nodes. Figure 28. Typical ADN2865 Applications Circuit Figure 29. ADN2865 AC-Coupled Input Configuration Soldering Guidelines for Chip Scale Package The lands on the 56 LFCSP are rectangular. The printed circuit board pad for these should be 0.1 mm longer than the package land length and 0.05 mm wider than the package land width. The land should be centered on the pad. This ensures that the solder joint size is maximized. The bottom of the chip scale package has a central exposed pad. The pad on the printed circuit board should be at least as large as this exposed pad. The user must connect the exposed pad to VEE using plugged vias so that solder does not leak through the vias during reflow. This ensures a solid connection from the exposed pad to VEE. Choosing AC Coupling Capacitors AC coupling capacitors at the input (PIN, NIN) and output (SERDATP,SERDATN) of the ADN2865 must be chosen such that the device works properly over the full range of data rates used in the application. When choosing the capacitors, the time constant formed with the two 50 Ω resistors in the signal path must be considered. When a large number of consecutive identical digits (CIDs) are applied, the capacitor voltage can droop due to baseline wander (see Figure ), causing pattern- dependent jitter (PDJ). The user must determine how much droop is tolerable and choose an ac coupling capacitor based on that amount of droop. The amount of PDJ can then be approximated based on the capacitor selection. The actual capacitor value selection may require some trade-offs between droop and PDJ. Example: Assuming that 2% droop can be tolerated, then the maximum differential droop is 4%. Normalizing to Vpp: Droop = Δ V = 0.04 V = 0.5 Vpp (1 − e–t/τ) ; therefore, τ = 12t where: τ is the RC time constant (C is the ac coupling capacitor, R = 100 Ω seen by C). t is the total discharge time, which is equal to nΤ. n is the number of CIDs. T is the bit period. The capacitor value can then be calculated by combining the equations for τ and t: R nT C / 12 = Once the capacitor value is selected, the PDJ can be approximated as () ( ) 6. 0 / 1 5 . 0 r nT/RC pspp e t PDJ − − = where: PDJpspp is the amount of pattern-dependent jitter allowed; < 0.01 UI p-p typical. tr is the rise time, which is equal to 0.22/BW, where BW ~ 0.7 (bit rate). Note that this expression for tr is accurate only for the inputs. The output rise time for the ADN2865 is ~100 ps regardless of data rate. 50 50 ADN2865 100 100 VCC 100 100 VCC VTERM VTERM 50 Ω 0.1 μ 0.1 μ ADN2865 50Ω CIN CIN 50 50 VCC TIA 0.1uF PIN NIN VREF 3k 2.5V |
Número de pieza similar - ADN2865 |
|
Descripción similar - ADN2865 |
|
|
Enlace URL |
Política de Privacidad |
ALLDATASHEET.ES |
¿ALLDATASHEET es útil para Ud.? [ DONATE ] |
Todo acerca de Alldatasheet | Publicidad | Contáctenos | Política de Privacidad | Intercambio de Enlaces | Lista de Fabricantes 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 |