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| EL4585C EL4585C Horizontal Genlock 8 FSC Features 36 MHz general purpose PLL 8 FSC timing (Use the EL4584 for 4 FSC) Compatible with EL4583C Sync Separator VCXO Xtal or LC tank oscillator k 2nS jitter (VCXO) User-controlled PLL capture and lock Compatible with NTSC and PAL TV formats 8 pre-programmed popular TV scan rate clock divisors Single 5V low current operation General Description The EL4585C is a PLL (Phase Lock Loop) sub system designed for video applications but also suitable for general purpose use up to 36 MHz In a video application this device generates a TTL CMOS compatible Pixel Clock (Clk Out) which is a multiple of the TV Horizontal scan rate and phase locked to it The reference signal is a horizontal sync signal TTL CMOS format which can be easily derived from an analog composite video signal with the EL4583 Sync Separator An input signal to ``coast'' is provided for applications where periodic disturbances are present in the reference video timing such as VTR head switching The Lock detector output indicates correct lock The divider ratio is four ratios for NTSC and four similar ratios for the PAL video timing standards by external selection of three control pins These four ratios have been selected for common video applications including 8 FSC 6 FSC 27 MHz (CCIR 601 format) and square picture elements used in some workstation graphics To generate 4 FSC 3 FSC 13 5 MHz (CCIR 601 format) etc use the EL4584 which does not have the additional divide by 2 stage of the EL4585 For applications where these frequencies are inappropriate or for general purpose PLL applications the internal divider can be by passed and an external divider chain used FREQUENCIES and DIVISORS Function Divisor PAL Fosc (MHz) Divisor NTSC Fosc (MHz) 6Fsc 1702 26 602 1364 21 476 CCIR 601 1728 27 0 1716 27 0 Square 1888 29 5 1560 24 546 8Fsc 2270 35 468 1820 28 636 Applications Pixel Clock regeneration Video compression engine (MPEG) clock generator Video Capture or digitization PIP (Picture In Picture) timing generator Text or Graphics overlay timing Ordering Information Part No Temp Range Package Outline MDP0031 MDP0027 EL4585CN b 40 C to a 85 C 16-Pin DIP EL4585CS b 40 C to a 85 C 16-Lead SO For 3Fsc and 4Fsc clock frequency operation see EL4584 datasheet CCIR 601 divisors yield 1440 pixels in the active portion of each line for NTSC and PAL Square pixels format gives 640 pixels for NTSC and 768 pixels for PAL 6Fsc frequencies do not yield integer divisors Divisor does not include d 2 block Demo Board A demo PCB is available for this product Request ``EL4584 5 Demo Board'' Connection Diagram EL4585 SO P-DIP Packages March 1996 Rev C 4585 - 17 Note All information contained in this data sheet has been carefully checked and is believed to be accurate as of the date of publication however this data sheet cannot be a ``controlled document'' Current revisions if any to these specifications are maintained at the factory and are available upon your request We recommend checking the revision level before finalization of your design documentation 4585C 1995 Elantec Inc EL4585C Horizontal Genlock 8 FSC Absolute Maximum Ratings (TA e 25 C) 7V VCC Supply b 65 C to a 150 C Storage Temperature Lead Temperature 260 C b 0 5V to VCC a 0 5V Pin Voltages b 40 C to a 85 C Operating Ambient Temperature Range Operating Junction Temp Power Dissipation Oscillator Frequency 125 C 400mW 36MHz Important Note All parameters having Min Max specifications are guaranteed The Test Level column indicates the specific device testing actually performed during production and Quality inspection Elantec performs most electrical tests using modern high-speed automatic test equipment specifically the LTX77 Series system Unless otherwise noted all tests are pulsed tests therefore TJ e TC e TA Test Level I II III IV V Test Procedure 100% production tested and QA sample tested per QA test plan QCX0002 100% production tested at TA e 25 C and QA sample tested at TA e 25 C TMAX and TMIN per QA test plan QCX0002 QA sample tested per QA test plan QCX0002 Parameter is guaranteed (but not tested) by Design and Characterization Data Parameter is typical value at TA e 25 C for information purposes only DC Electrical Characteristics (VDD e 5V Parameter IDD VIL Input Low Voltage VIH Input High Voltage IIL Input Low Current IIH Input High Current IIL Input Low Current IIH Input High Current VOL Output Low Voltage VOH Output High Voltage VOL Output Low Voltage VOH Output High Voltage VOL Output Low Voltage VOH Output High Voltage IOL Output Low Current IOH Output High Current IOL IOH Current Ratio ILEAK Filter Out Conditions VDD e 5V (Note 1) TA e 25 C unless otherwise noted) Temp 25 C 25 C 25 C 35 b 100 Min Typ 2 Max 4 15 Test Level I I I I Units mA V V nA nA mA mA V V V V V V mA TD is 3 5in mA All inputs except COAST Vin e 1 5V All inputs except COAST Vin e 3 5V COAST pin Vin e 1 5V COAST pin Vin e 3 5V Lock Det IOL e 1 6mA Lock Det IOH eb1 6mA CLK IOL e 3 2mA CLK IOH eb3 2mA OSC Out IOL e 200mA OSC Out IOH eb200mA Filter Out VOUT e 2 5V Filter Out VOUT e 2 5V Filter Out VOUT e 2 5V Coast Mode VDDlVOUTl0V 25 C 25 C 25 C 25 C 25 C 25 C 25 C 25 C 25 C 25 C 25 C 25 C 25 C 25 C 100 b 100 b 60 I I 60 100 04 I I I 24 04 24 04 24 200 300 b 300 b 200 I I I I I I I I 1 05 b 100 10 g1 0 95 100 nA Note 1 All inputs to 0V COAST floating 2 EL4585C Horizontal Genlock 8 FSC AC Electrical Characteristics (VDD e 5V Parameter VCO Gain 20 MHz Conditions Test circuit 1 VDD e 5V (Note 2) VCXO Oscillator LC Oscillator (Typ) Temp 25 C 25 C 25 C 25 C 35 1 10 TA e 25 C unless otherwise noted) Min Typ 15 5 Max Test Level V V V V Units dB dB ns ns H-sync S N Ratio Jitter Jitter Note 2 Noisy video signal input to EL4583C H-sync input to EL4585C Test for positive signal lock Pin Description Pin No 16 1 2 3 4 5 6 7 Pin Name Prog A B C Osc VCO Out VDD (A) Osc VCO In VSS (A) Charge Pump Out Function Digital inputs to select d N value for internal counter See table below for values Output of internal inverter oscillator Connect to external crystal or LC tank VCO circuit Analog positive supply for oscillator PLL circuits Input from external VCO Analog ground for oscillator PLL circuits Connect to loop filter If the H-sync phase is leading or H-sync frequency l CLK d 2N current is pumped into the filter capacitor to increase VCO frequency If H-sync phase is lagging or frequency k CLK d 2N current is pumped out of the filter capacitor to decrease VCO frequency During coast mode or when locked charge pump goes to a high impedance state Divide select input When high the internal divider is enabled and EXT DIV becomes a test pin outputting CLK d 2N When low the internal divider is disabled and EXT DIV is an input from an external d N Tri-state logic input Low(k VCC) e normal mode Hi Z(or High(l VCC) e coast mode Horizontal sync pulse (CMOS level) input Positive supply for digital I O circuits Lock Detect output Low level when PLL is locked Pulses high when out of lock TD is 3 5in External Divide input when DIV SEL is low internal d 2N output when DIV SEL is high Ground for digital I O circuits Buffered output of the VCO to VCC) e fast lock mode 8 Div Select 9 10 11 12 13 14 15 Coast H-sync In VDD (D) Lock Det Ext Div VSS (D) CLK Out Table 5 VCO Divisors Prog A Pin 16 0 0 0 0 1 1 1 1 Prog B Pin 1 0 0 1 1 0 0 1 1 3 Prog C Pin 2 0 1 0 1 0 1 0 1 Div Value N 1702 1728 1888 2270 1364 1716 1560 1820 TD is 3 5in EL4585C Horizontal Genlock 8 FSC Timing Diagrams PLL Locked Condition (Phase Error e 0) 4585 - 2 Out of Lock Condition Ti c 360 TH TH e H-sync period Ti e phase error period iE e 4585 - 3 Typical Performance Curves Test Circuit 1 4585 - 5 4 EL4585C Horizontal Genlock 8 FSC Typical Performance Curves Idd vs Fosc Contd OSC Gain 20 MHz vs Temp 4585 - 6 4585 - 4 Typical Varactor OSC Gain vs Fosc Charge Pump Duty Cycle Vs iE 4585 - 9 4585 - 7 4585 - 8 EL4585 Block Diagram 4585 - 1 5 EL4585C Horizontal Genlock 8 FSC Description Of Operation The horizontal sync signal (CMOS level falling leading edge) is input to H-SYNC input (pin 10) This signal is delayed about 110nS the falling edge of which becomes the reference to which the clock output will be locked (See timing diagrams ) The clock is generated by the signal on pin 5 OSC in There are 2 general types of VCO that can be used with the EL4585C LC and crystal controlled Additionally each type can be either built up using discrete components including a varactor as the frequency controlling element or complete self contained modules can be purchased with everything inside a metal can These modules are very forgiving of PCB layout but cost more than discrete solutions The VCO or VCXO is used to regulate the clock An LC tank resonator has greater ``pull'' than a crystal controlled circuit but will also be more likely to drift over time and thus will generate more jitter The ``pullability'' of the circuit refers to the ability to pull the frequency of oscillation away from its center frequency by modulating the voltage on the control pin of the VCO module or varactor and is a function of the slope and range of the capacitance-voltage curve of the varactor or VCO module used The VCO signal is sent to the CLK out pin divided by two then sent to the divide by N counter The divisor N is determined by the state of pins 1 2 and 16 and is described in table 5 above The divided signal is sent along with the delayed H-sync input to the phase frequency detector which compares the two signals for phase and frequency differences Any phase difference is converted to a current at the charge pump output (pin 7) A VCO with a positive frequency deviation with control voltage must be used Varactors have negative capacitance slope with voltage resulting in positive frequency deviation with increasing control voltage for the oscillators in figures 10 and 11 below 5 volts and it can source or sink a maximum of about 300mA so all frequency control must be accomplished with variable capacitance from the varactor within this range Crystal oscillators are more stable than LC oscillators which translates into lower jitter but LC oscillators can be pulled from their mid-point values further resulting in a greater capture and locking range If the incoming horizontal sync signal is known to be very stable then a crystal oscillator circuit can be used If the H-sync signal experiences frequency variations of greater than about 300ppm an LC oscillator should be considered as crystal oscillators are very difficult to pull this far When Hsync input frequency is greater than CLK frequency d 2N charge pump output (pin 7) sources current into the filter capacitor increasing the voltage across the varactor thus tending to increase VCO frequency Conversely charge pump output pulls current from the filter capacitor when H-sync frequency is less than CLK d 2N forcing the VCO frequency lower Loop Filter The loop filter controls how fast the VCO will respond to a change in phase comparator output stimulus Its components should be chosen so that fast lock can be achieved yet with a minimum of VCO ``hunting'' preferably in one to two oscillations of charge pump output assuming the VCO frequency starts within capture range If the filter is under-damped the VCO will over and under-shoot the desired operating point many times before a stable lock takes place It is possible to under-damp the filter so much that the loop itself oscillates and VCO lock is never achieved If the filter is over-damped the VCO response time will be excessive and many cycles will be required for a lock condition Over-damping is also characterized by an easily unlocked system because the filter can't respond fast enough to perturbations in VCO frequency A severely over damped system will seem to endlessly oscillate like a very large mass at the end of a long pendulum Due to parasitic effects of PCB traces and component variables it will take some trial and error experimentation to determine the best values to use for any given situation Use the component tables as a starting point but be aware that deviations from these values are not out of the ordinary 6 VCO The VCO should be tuned so that its frequency of oscillation is very close to the required clock output frequency when the voltage on the varactor is 2 5 volts VCXO and VCO modules are already tuned to the desired frequency so this step is not necessary if using one of these units The output range of the charge pump output (pin 7) is 0 to EL4585C Horizontal Genlock 8 FSC Description Of Operation External Divide DIV SEL (pin 8) controls the use of the internal divider When high the internal divider is enabled and EXT DIV (pin 13) outputs the CLK out divided by 2N This is the signal to which the horizontal sync input will lock When divide select is low the internal divider output is disabled and external divide becomes an input from an external divider so that a divisor other than one of the 8 pre-programmed internal divisors can be used Contd be regular during this time Once the near lock condition is attained charge pump output should be very close to its lock-on value and placing the device into normal mode should result in a normal lock very quickly Fast lock mode is intended to be used where H-sync becomes irregular until a stable signal is again obtained Coast Mode Coast mode is enabled by pulling COAST (pin 9) high (above Vcc) In coast mode the internal phase detector is disabled and filter out remains in high impedance mode to keep filter out voltage and VCO frequency as constant a possible VCO frequency will drift as charge leaks from the filter capacitor and the voltage changes the VCO operating point Coast mode is intended to be used when noise or signal degradation result in loss of horizontal sync for many cycles The phase detector will not attempt to adjust to the resultant loss of signal so that when horizontal sync returns sync lock can be re-established quickly However if much VCO drift has occurred it may take as long to re-lock as when restarting Normal Mode Normal mode is enabled by pulling COAST (pin 9) low (below Vcc) If H-SYNC and CLK d 2N have any phase or frequency difference an error signal is generated and sent to the charge pump The charge pump will either force current into or out of the filter capacitor in an attempt to modulate the VCO frequency Modulation will continue until the phase and frequency of CLK d 2N exactly match the H-sync input When the phase and frequency match (with some offset in phase that is a function of the VCO characteristics) the error signal goes to zero lock detect no longer pulses high and the charge pump enters a high impedance state The clock is now locked to the H-sync input As long as phase and frequency differences remain small the PLL can adjust the VCO to remain locked and lock detect remains low Lock Detect Lock detect (pin 12) will go low when lock is established Any DC current path from charge pump out will skew EXT DIV relative to HSYNC in tending to offset or add to the 110nS internal delay depending on which way the extra current is flowing This offset is called static phase error and is always present in any PLL system If when the part stabilizes in a locked mode lock detect is not low adding or subtracting from the loop filter series resistor R2 will change this static phase error to allow LDET to go low while in lock The goal is to put the rising edge of EXT DIV in sync with the falling edge of H-SYNC a 110nS (See timing diagrams ) Increasing R2 decreases phase error while decreasing R2 increases phase error (Phase error is positive when EXT DIV lags H-SYNC ) The resistance needed will depend on VCO design or VCXO module selection Fast Lock Mode Fast Lock mode is enabled by either allowing coast to float or pulling it to mid supply (between and Vcc) In this mode lock is achieved much faster than in normal mode but the clock divisor is modified on the fly to achieve this If the phase detector detects an error of enough magnitude the clock is either inhibited or reset to attempt a ``fast lock'' of the signals Forcing the clock to be synchronized to the H-sync input this way allows a lock in approximately 2 H-cycles but the clock spacing will not 7 EL4585C Horizontal Genlock 8 FSC Applications Information Choosing External Components 1 To choose LC VCO components first pick the desired operating frequency For our example we will use 28 636MHz with an H-sync frequency of 15 734kHz 2 Choose a reasonable inductor value (1-5mH works well) We choose 3 3mH 3 Calculate CT needed to produce FOSC FOSC e 1 2q 0LCT 4585 - 10 Typical LC VCO LC VCO Component Values (Approximate) Frequency (MHz) 26 602 27 0 29 5 35 468 21 476 24 546 28 636 L1 (mH) 33 33 27 22 47 39 33 C1 (pF) 22 21 22 16 26 22 17 C2 (pF) 220 220 220 220 220 220 220 CT e 1 1 e e 9 4pF 4q2F2L 4q2(28 636e6)2(3 3e b 6) 2 5V 4 From the varactor data sheet find CV the desired lock voltage CV e 23pF for our SMV1204-12 for example 5 C2 should be about 10CV so we choose C2 e 220pF for our example 6 Calculate C1 Since C1C2CV CT e a (C1CV) a (C2CV) (C1C2) then C1 e C2CTCV (C2Cv) b (C2CT) b (CTCV) Note Use shielded inductors for optimum performance Typical Xtal VCO For our example C1 e 17pF (A trim cap may be used for fine tuning ) Examples for each frequency using the internal divider follow 4585 - 11 8 EL4585C Horizontal Genlock 8 FSC Typical Application Horizontal genlock provides clock for an analog to digital converter digitizing analog video 4585 - 18 Xtal VCO Component Values (Approximate) Frequency (MHz) 26 602 27 0 29 5 35 468 21 476 24 546 28 636 R1 (kX) 300 300 300 300 300 300 300 C1 (pF) 15 15 15 15 15 15 15 C2 (mF) 001 001 001 001 001 001 Colpitts Oscillator 4585 - 12 001 The above oscillators are arranged as Colpitts oscillators and the structure is redrawn here to emphasize the split capacitance used in a Colpitts oscillator It should be noted that this oscillator configuration is just one of literally hundreds possible and the configuration shown here does not necessarily represent the best solution for all applications Crystal manufacturers are very informative sources on the design and use of oscillators in a wide variety of applications and the reader is encouraged to become familiar with them C1 is to adjust the center frequency C2 DC isolates the control from the oscillator and V1 is the primary control device C2 should be much larger than CV so that V1 has maximum modulation capability The frequency of oscillation is given by Fe 1 2q0LCT C1C2CV (C1C2) a (C1CV) a (C2CV) CT e 9 EL4585C Horizontal Genlock 8 FSC Choosing Loop Filter Components The PLL VCO and loop filter can be described as transfer function Cv e F(VC) where VC is the reverse bias control voltage and CV is varactor capacitance Since F(VC) is nonlinear it is probably best to build the VCO and measure KVCO about 2 5V The results of one such measurement are shown below The slope of the curve is determined by linear regression techniques and equals KVCO For our example KVCO e 9 06 Mrad s V FOSC vs VC LC VCO 4585 - 13 Where Kd e phase detector gain in A rad F(s) e loop filter impedance in V A KVCO e VCO gain in rad s V N e Total internal or external divisor (see 3 below) It can be shown that for the loop filter shown below 5 Now we can solve for C3 C4 and R3 C3 e KdKVCO C3 2Ng0n C4 e R3 e N0n2 10 KdKVCO C3 e KdKVCO (4 77e b 5)(9 06e6) e e 0 01mF 2 N0n (1820)(5000)2 C3 e 0 001mF 10 2Ng0n (2)(1820)(1)(5000) e e 42 1kX (4 77e b 5)(9 06e6) KdKVCO 4585 - 14 Where 0n e loop filter bandwidth and g e loop filter damping factor 1 Kd e 300mA 2qrad e 4 77e-5A rad for the EL4585C 2 The loop bandwidth should be about H-sync frequency 20 and the damping ratio should be 1 for optimum performance For our example 0n e 15 734kHz 20 e 787 Hz 5000 rad S 3 N e 910x2 e 1820 from table 1 Ne FVCO 28 636M e e 1820 e 910x2 FHsync 15 73426k 4 KVCO represents how much the VCO frequency changes for each volt applied at the control pin It is assumed (but probably isn't) linear about the lock point (2 5V) Its value depends on the VCO configuration and the varactor C4 e R3 e We choose R3 e 43kX for convenience 6 Notice R2 has little effect on the loop filter design R2 should be large around 100k and can be adjusted to compensate for any static phase error Ti at lock but if made too large will slow loop response If R2 is made smaller Ti (see timing diagrams) increases and if R2 in- 10 EL4585C Horizontal Genlock 8 FSC creases Ti decreases For LDET to be low at lock l Til k 50nS C4 is used mainly to attenuate high frequency noise from the charge pump The effect these components have on time to lock is illustrated below Xtal Loop Filter Components (Approximate) Frequency (MHz) 26 602 27 0 R2 (kX) 100 100 100 100 100 100 100 R3 (MX) 43 43 43 43 43 43 43 C3 (pF) 68 68 68 68 68 68 68 C4 (pF) 68 68 68 68 68 68 68 Lock Time Let T e R3C3 As T increases damping increases but so does lock time Decreasing T decreases damping and speeds up loop response but increases overshoot and thus increases the number of hunting oscillations before lock Critical damping (g e 1) occurs at minimum lock time Because decreased damping also decreases loop stability it is sometimes desirable to design slightly overdamped (g l 1) trading lock time for increased stability Typical Loop Filter 29 5 35 468 21 476 24 546 28 636 PCB Layout Considerations It is highly recommended that power and ground planes be used in layout The oscillator and filter sections constitute a feedback loop and thus care must be taken to avoid any feedback signal influencing the oscillator except at the control input The entire oscillator filter section should be surrounded by copper ground to prevent unwanted influences from nearby signals Use separate paths for analog and digital supplies keeping the analog (oscillator section) as short and free from spurious signals as possible Careful attention must be paid to correct bypassing Keep lead lengths short and place bypass caps as close to the supply pins as possible If laying out a PCB to use discrete components for the VCO section care must be taken to avoid parasitic capacitance at the OSC pins 3 and 5 and FILTER out (pin 7) Remove ground and power plane copper above and below these traces to avoid making a capacitive connection to them It is also recommended to enclose the oscillator section within a shielded cage to reduce external influences on the VCO as they tend to be very sensitive to ``hand waving'' influences the LC variety being more sensitive than crystal controlled oscillators In general the higher the operating frequency the more important these considerations are Self contained VCXO or VCO modules are already mounted in a shielding cage and therefore do not require as much consideration in layout Many crystal manufacturers publish informative literature regarding use and layout of oscillators which should be helpful 4585 - 16 LC Loop Filter Components (Approximate) Frequency (MHz) 26 602 27 0 29 5 35 468 21 476 24 546 28 636 R2 (kX) 100 100 100 100 100 100 100 R3 (kX) 39 39 43 51 30 36 43 C3 (mF) 0 01 0 01 0 01 0 01 0 01 0 01 0 01 C4 (mF) 0 001 0 001 0 001 0 001 0 001 0 001 0 001 11 EL4585C Horizontal Genlock 8 FSC EL4585 4 Demo Board 4585-19 12 EL4585C Horizontal Genlock 8 FSC EL4585 4 Demo Board Contd The VCO and loop filter section of the EL4583 4 5 Demo Board can be implemented in the following configurations (1) VCXO 4585 - 20 (2) XTAL 4585 - 21 (3) LC Tank 4585 - 22 13 BLANK 14 BLANK 15 EL4585C EL4585C Horizontal Genlock 8 FSC Component Sources Inductors Dale Electronics E Highway 50 PO Box 180 Yankton SD 57078-0180 (605) 665-9301 SaRonix 151 Laura Lane Palo Alto CA 94043 (415) 856-6900 Standard Crystal 9940 Baldwin Place El Monte CA 91731 (818) 443-2121 Crystals VCXO VCO Modules Connor-Winfield 2111 Comprehensive Drive Aurora IL 60606 (708) 851-4722 Piezo Systems 100 K Street PO Box 619 Carlisle PA 17013 (717) 249-2151 Reeves-Hoffman 400 West North Street Carlisle PA 17013 (717) 243-5929 Varactors Alpha Industries 20 Sylvan Road Woburn MA 01801 (617) 935-5150 Motorola Semiconductor Products 2100 E Elliot Tempe AZ 85284 (602) 244-6900 Note These sources are provided for information purposes only No endorsement of these companies is implied by this listing General Disclaimer Specifications contained in this data sheet are in effect as of the publication date shown Elantec Inc reserves the right to make changes in the circuitry or specifications contained herein at any time without notice Elantec Inc assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement WARNING Life Support Policy March 1996 Rev C Elantec Inc 1996 Tarob Court Milpitas CA 95035 Telephone (408) 945-1323 (800) 333-6314 Fax (408) 945-9305 European Office 44-71-482-4596 16 Elantec Inc products are not authorized for and should not be used within Life Support Systems without the specific written consent of Elantec Inc Life Support systems are equipment intended to support or sustain life and whose failure to perform when properly used in accordance with instructions provided can be reasonably expected to result in significant personal injury or death Users contemplating application of Elantec Inc products in Life Support Systems are requested to contact Elantec Inc factory headquarters to establish suitable terms conditions for these applications Elantec Inc 's warranty is limited to replacement of defective components and does not cover injury to persons or property or other consequential damages Printed in U S A |
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