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24 Threads found on edaboard.com: Pll And Cap And
Inductor do have huge areas! In pll or PA, inductor occupied most of areas. Bur i am not sure if pmoscap is acceptable in performance, i know MIM caps are commonly used in RF design.
I am designing a pll with a LC-VCO. The frequency control of the VCO is done through drain-source connected n-moscap. The output of the loop filter is going to the moscap drain-source and the gate of the moscap is going to the VCO. When the loop is running the oscillation frequency of the (...)
Hi, I want to design a pll in hspice,how do i get the values for design i mean cap and res values ?? Please help
This requirement is actually similar to the Type II phase comparator in the old CD4046B pll except it goes high when one leads the other and low when it lags then becomes tri-state floating when in sync. The output pulse width is thus a current pulse that can be integrated with a cap load to measure the phase error (...)
I have built an FM transmitter circuit using the RDA5820. (It is one of those all in one FM stereo transmitter chips). Anyway, it has a problem with what I think is the pll unlocking after a few minutes of transmitting. It makes a loud popping noise and the carrier is shifting on the analyzer. I am pretty sure there is nothing wrong with (...)
Hi everyone, In fractional N plls the divider value is dithered by a sigma delta modulator. I need to know is this sigma delta modulator is clocked by reference clock or the divider output? and Why? Also, if we had higher frequency clocks can they be used instead? Thanks in advance
An internal charge pump with a cap is equivalent to an external integrator with a reference voltage equal to no phase error. When the phase error is a pulse controlled current source going into capacitive load , they call it a charge pump or essentially an integrator. This is an essential part of the pll to reduce steady state phase error (...)
Hi~:razz: I've designed a pll with the 3rd passive RC Loop filter. But, after layout, the size of RC filter was so big and same area with the integrated inductor. So, instead I thought the active loop filter. and I have question. Is the active filter helpful for reducing layout (...)
Thanks for the answer. This instance measures the periods of VCO output in response to rise cross events and writes the periods into a file. After a transient analysis, a plugin searches this instance and the file and calculates the phase noise power spectrum density (PSD) from (...)
Hi, every one : Could any one tell me how to set the cap value of Cp2 and Cn ? and my ohter question is :why the Vctrl is refer to VCC , but not to gnd ? For my pmos vt is greater than nmos's , this maybe result in small dynamic range for vctrl . The ckt is in the below file
I am wondering how much Kvco is adequate in my vco design. How is it related to other important specifications of the vco such as phase noise, loop stability? My second questions is for the traditional cross coupled LC vco, what is the vco gain formula in terms of tank L and C value and transistor parasitic (...)
Hello, I need to use the 4046 pll, and i don't know how to choose RC values that are optimum to minimize jitter&noise of the VCO? In general, should I use a high C value, thus charging/discharging the cap with higher current, or use a lower C ? Because I need a narrow VCO domain, offset should be used so the VCO (...)
Hi Chmhero, In the e-book "CMOS pll Synthesizers: Analysis and Design" chapter 5, you can find the solution for large N pll.
There are many topics about PIP(MIM)cap vs. mos cap. you can search it in this forum. For pll, I know you can use both of them to reduce die area, because they use different layers.
Hello friends I designed a pll+VCO circuit at 160MHZ with LMX2316 and minicircuit VCOs and 25MHZ crystal osc as ref. Output is stable (Fcom=20KHZ,loop filter BW = 1KHZ),but as shown below have spurs at output near 160MHz carrier.Please guide me to remove the spurs.
That is very simple! It is the rectified coupling of the varactor cap to the pll loop filter cap. I assume that you using a differential tank circuit with a differential varactor. Because the varactor is nonlinear and the tank voltage have second order harmonics on the single ended voltage you see the second (...)
Hi RF IC = pll, Mixer, PA, LNA, OSC, .. RF signaling blocks while Analog IC means : Opamp , OTA, BandGap, Switched cap, Regualtors, Filters, A2D....and all other non-RF signaling blocks
Instead of pulling capacitor values out of thin air, with rules of thumb that may or may not apply, why don't you actually calculate the loop filter values (Resistor and capacitor) that actually mean something? Loop filter component values can be calculated from the desired loop filter (...)
yes, 1. check deadzone. 2. check mismatch and leakage of source/sink. 3. are u sure it's locked? loop isn't unstable? 4. I think pll need this small phase different keep it in "locking".
Simple passive RC filter has been used for pll LPF design for many years,which suffering mismatch and large area problems. Why we can not use Switched cap filter for loop filter? What's the advantage and disadvantage?