 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
5P49V6913 Datasheet(PDF) 5 Page - Integrated Device Technology |
|
||||||||||||||||||||||||||||||
5P49V6913 Datasheet(HTML) 5 Page - Integrated Device Technology |
|
|
5 / 36 page  NOVEMBER 11, 2016 5 PROGRAMMABLE CLOCK GENERATOR 5P49V6913 DATASHEET Reference Clock Input Pins and Selection The 5P49V6913 supports up to two clock inputs. One input supports a crystal between XIN and XOUT. XIN can also be driven from a single ended reference clock. XIN can accept small amplitude signals like from TCXO or one channel of a differential clock. The second clock input (CLKIN, CLKINB) is a fully differential input that only accepts a reference clock. The differential input accepts differential clocks from all the differential logic types and can also be driven from a single ended clock on one of the input pins. The CLKSEL pin selects the input clock between either XTAL/REF or (CLKIN, CLKINB). Either clock input can be set as the primary clock. The primary clock designation is to establish which is the main reference clock to the PLL. The non-primary clock is designated as the secondary clock in case the primary clock goes absent and a backup is needed. See the previous page for more details about primary versus secondary clock operation. The two external reference clocks can be manually selected using the CLKSEL pin. The SM bits must be set to “0x” for manual switchover which is detailed in Manual Switchover Mode section. Crystal Input (XIN/REF) The crystal used should be a fundamental mode quartz crystal; overtone crystals should not be used. A crystal manufacturer will calibrate its crystals to the nominal frequency with a certain load capacitance value. When the oscillator load capacitance matches the crystal load capacitance, the oscillation frequency will be accurate. When the oscillator load capacitance is lower than the crystal load capacitance, the oscillation frequency will be higher than nominal and vice versa so for an accurate oscillation frequency you need to make sure to match the oscillator load capacitance with the crystal load capacitance. To set the oscillator load capacitance there are two tuning capacitors in the IC, one at XIN and one at XOUT. They can be adjusted independently but commonly the same value is used for both capacitors. The value of each capacitor is composed of a fixed capacitance amount plus a variable capacitance amount set with the XTAL[5:0] register. Adjustment of the crystal tuning capacitors allows for maximum flexibility to accommodate crystals from various manufacturers. The range of tuning capacitor values available are in accordance with the following table. XTAL[5:0] Tuning Capacitor Characteristics The capacitance at each crystal pin inside the chip starts at 9pF with setting 000000b and can be increased up to 25pF with setting 111111b. The step per bit is 0.5pF. You can write the following equation for this capacitance: Ci = 9pF + 0.5pF × XTAL[5:0] The PCB where the IC and the crystal will be assembled adds some stray capacitance to each crystal pin and more capacitance can be added to each crystal pin with additional external capacitors. You can write the following equations for the total capacitance at each crystal pin: CXIN = Ci1 + Cs1 + Ce1 CXOUT = Ci2 + Cs2 + Ce2 Ci1 and Ci2 are the internal, tunable capacitors. Cs1 and Cs2 are stray capacitances at each crystal pin and typical values are between 1pF and 3pF. Ce1 and Ce2 are additional external capacitors that can be added to increase the crystal load capacitance beyond the tuning range of the internal capacitors. However, increasing the load capacitance reduces the oscillator gain so please consult the factory when adding Ce1 and/or Ce2 to avoid crystal startup issues. Ce1 and Ce2 can also be used to adjust for unpredictable stray capacitance in the PCB. The final load capacitance of the crystal: CL = CXIN × CXOUT / (CXIN + CXOUT) For most cases it is recommended to set the value for capacitors the same at each crystal pin: CXIN = CXOUT = Cx → CL = Cx / 2 The complete formula when the capacitance at both crystal pins is the same: CL = (9pF + 0.5pF × XTAL[5:0] + Cs + Ce) / 2 Parameter Bits Step (pF) Min (pF) Max (pF) XTAL 6 0.5 9 25 |
Similar Part No. - 5P49V6913 |
|
Similar Description - 5P49V6913 |
|
|
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
