Motor de Búsqueda de Datasheet de Componentes Electrónicos |
|
CDCE421RGERG4 Datasheet(PDF) 4 Page - Texas Instruments |
|
CDCE421RGERG4 Datasheet(HTML) 4 Page - Texas Instruments |
4 / 24 page DEVICE SETUP EXAMPLE f xtal + OutputDivider FeedbackDivider fout f xtal + 1 20 622.08 + 31.154 MHz (2) SERIAL INTERFACE AND CONTROL CDCE421 SCAS842B – APRIL 2007 – REVISED JANUARY 2009..................................................................................................................................................... www.ti.com The following example illustrates the procedure to calculate the required AT-cut crystal frequency needed to generate a desired output frequency. Assuming the requirement to generate an output frequency of 622.08 MHz, Table 1 shows that the desired output frequency lies between 583.5 MHz and 680 MHz. REQUIRED INPUT DESIRED OUTPUT CRYSTAL VCO OUTPUT PRESCALER FEEDBACK FREQUENCY (MHz) FREQUENCY (MHz) SELECTION DIVIDER SETTING DIVIDER(1) From To From To 650.0 766.7 32.500 38.333 VCO 2 1 3 20 583.5 650.0 29.174 32.500 VCO 1 1 3 20 510.0 587.5 31.875 36.719 VCO 2 1 4 16 (1) The feedback divider is set automatically with respect to the prescaler setting. So this means that the device must be configured with: VCO = VCO 1 Output divider = 1 Prescaler setting = 3 To determine the correct crystal frequency needed to get 622.08 MHz with these settings, substitute values into Equation 1. The AT-cut frequency should be 31.154 MHz (between 29.174 MHz and 32.500 MHz, as shown in Table 1) . The CDCE421 uses a unique Texas Instruments proprietary interface protocol that can be configured and programmed via a single input pin to the device. The architecture enables only writing to the device from this input pin. Reading the content of a register can be achieved by sending a read command on the input pin and monitoring the output pins (LVDS or LVPECL). In cases where the output pins cannot be used to read the content, the software controlling the interface must account for what is written to the EEPROM and when it is programmed. Monitoring the outputs verifies the programming modes, and cycling power on the device verifies that the EEPROM is holding the proper configuration. The CDCE421 can be configured and programmed via the SDATA input pin. For this purpose, a square-wave programming sequence must be written to the device as described in the following section. During the EEPROM programming phase, the device requires a stable VCC of 3 V to 3.6 V for secure writing of the EEPROM cells. After each Write to WordX, the written data are latched, made effective, and offer look-ahead before the actual data are stored into the EEPROM. The following table summarizes all valid programming commands. SDATA FUNCTION 00 1100 Enter Programming Mode (State 1 → State 2); bits must be sent in the specified order with the specified timing. Otherwise, a time-out occurs. 11 1011 Enter Register Read Back Mode; bits must be sent in the specified order with the specified timing. Otherwise, a time-out occurs. 000 xxxx xxxx Write to Word0 (State 2)(1) (2) (3) 100 xxxx xxxx Write to Word1 (State 2)(1) (2) (3) 010 xxxx xxxx Write to Word2 (State 2)(1) (2) (3) 110 xxxx xxxx Write to Word3 (State 2)(1) (2) (3) (1) Each rising edge causes a bit to be latched. (2) Between the bits, some longer time delays can occur, but this has no effect on the data. (3) A Write to WordX is expected to be 10 bits long. After the 10th bit, the respective word is latched and its effect can be observed as look-ahead function. 4 Submit Documentation Feedback Copyright © 2007–2009, Texas Instruments Incorporated Product Folder Link(s): CDCE421 |
Número de pieza similar - CDCE421RGERG4 |
|
Descripción similar - CDCE421RGERG4 |
|
|
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 |