Electronic Components Datasheet Search |
|
CY22801KFXI Datasheet(PDF) 4 Page - Cypress Semiconductor |
|
CY22801KFXI Datasheet(HTML) 4 Page - Cypress Semiconductor |
4 / 23 page CY22801 Document #: 001-15571 Rev. *E Page 4 of 23 External Reference Crystal/Clock Input CY22801 can accept external reference clock input as well as crystal input. External reference clock input frequency range is from 1MHz to 133 MHz. The input crystal oscillator of the CY22801 is an important feature because of the flexibility it provides in selecting a crystal as a reference clock source. The oscillator inverter has programmable gain, enabling maximum compatibility with a reference crystal, based on manufacturer, process, performance, and quality. Input load capacitors are placed on the CY22801 die to reduce external component cost. These capacitors are true parallel-plate capacitors, designed to reduce the frequency shift that occurs when non-linear load capacitance is affected by load, bias, supply, and temperature changes. The value of the input load capacitors is determined by eight bits in a programmable register. Total load capacitance is determined by the formula: CapLoad = (CL – CBRD – CCHIP)/0.09375 pF In CyClocksRT, enter the crystal capacitance (CL). The value of CapLoad is determined automatically and programmed into the CY22801. Output Clock Frequencies The CY22801 is a very flexible clock generator with up to three individual outputs, generated from an integrated PLL. See Figure 2 for details. The output of the PLL runs at high frequency and is divided down to generate the output clocks. Two programmable dividers are available for this purpose. Therefore, although the output clocks may have different frequencies, they must be related, based on the PLL frequency. It is also possible to direct the reference clock input to any of the outputs, thereby bypassing the PLL. Lastly, the reference clock may be passed through either divider. Figure 2. Basic PLL Block Diagram VCXO One of the key components of the CY22801 device is the VCXO. The VCXO is used to ‘pull’ the reference crystal higher or lower to lock the system frequency to an external source. This is ideal for applications where the output frequency needs to track along with an external reference frequency that is constantly shifting. A special pullable crystal must be used to have adequate VCXO pull range. Pullable crystal specifications are included in this datasheet. VCXO is not compatible with Spread spectrum and Serial Interface. VCXO Profile Figure 3 shows an example of a VCXO profile. The analog voltage input is on the X-axis and the PPM range is on the Y-axis. An increase in the VCXO input voltage results in a corresponding increase in the output frequency. This moves the PPM from a negative to positive offset. Figure 3. VCXO Profile Spread Spectrum Clock Generation (SSCG) Spread spectrum clock generation (SSCG) in CY22801 helps to reduce EMI found in today’s high-speed digital electronic systems. The device uses the proprietary spread spectrum clock (SSC) technology to synthesize and modulate the frequency of the input clock. By modulating the frequency of the clock, the measured EMI at the fundamental and harmonic frequencies is greatly reduced. This reduction in radiated energy can significantly reduce the cost of complying with the regulatory agency electromagnetic compatibility (EMC) requirements and improve time to market without degrading system performance. Programmed spread spectrum modulation will appear same on all three clock outputs as they come from same PLL even if operating at different frequencies. Spread spectrum is not compatible with VCXO feature. CLKC Crosspoint Switch Matrix REF (XIN/CLKIN) /P PFD VCO /Q CLKB CLKA Post Divider 1N Post Divider 2N -200 -150 -100 -50 0 50 100 150 200 00.5 11.5 22.5 33.5 VCXO input [V] [+] Feedback |
Similar Part No. - CY22801KFXI |
|
Similar Description - CY22801KFXI |
|
|
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 |