preliminary datasheet low cost 24 to 36 mhz 3.3 volt vcxo ics3727xp idt? / ics? low cost 24 to 36 mhz 3.3 volt vcxo 1 ics3727xp rev a 102004 description the ics3727xp combines the functions of a vcxo (voltage controlled crys tal oscillator) and pll (phase-locked loop) frequency doubler onto a single chip. it is designed primarily for data and clock recovery applications within end products such as set-top box receivers. the ics3727xp exhibits a moderate vcxo gain of 200 ppm/v typical, when used with a high quality external pullable quartz crystal. the frequency of the on-chip vcxo is adjusted by an external control voltage input into pin vin. because vin is a high impedance input, it can be driven directly from an pwm rc integrator circuit. frequency output increases with vin voltage input. the usable range of vin is 0 to 3.3 v. features ? ics3727xp offers 24 to 36 mhz output frequency range (output frequency = 2x crystal frequency) and improved power supply noise rejection ? uses an inexpensive 12 to 18 mhz external crystal ? ideal for dv codec applications using 27 mhz external pullable crystal with extended pull range to generate locked 27 mhz clock transport video clock ? on-chip vcxo with guaranteed pull range of 200 ppm minimum ? vcxo input tuning voltage 0 to 3.3 v ? packaged in 8-pin soic (150 mil wide) block diagram 24-36 mhz (2x crystal frequency) x1 x2 voltage controlled crystal oscillator pll frequency doubler vin 12-18 mhz pullable crystal
ics3727xp low cost 24 to 36 mhz 3.3 volt vcxo vcxo idt? / ics? low cost 24 to 36 mhz 3.3 volt vcxo 2 ics3727xp rev a 102004 pin assignment pin descriptions x1 vdd vin gnd gnd nc clk x2 1 2 3 4 8 7 6 5 ics3727xp 8-pin (150 mil) soic pin number pin name pin type pin description 1 xi input crystal connection ? connect to the external pullable crystal. 2 vdd power connect to +3.3 v (0.01uf decoupling capacitor recommended). 3 vin input voltage input to vcxo ? 0 to 3.3 v analog input which controls the oscillation frequency of the vcxo. 4 gnd power connect to ground. 5 clk output clock output. 6 nc ? no internal connection (may connect to ground or vdd). 7 gnd power connect to ground. 8 x2 input crystal connection ? connect to the external pullable crystal.
ics3727xp low cost 24 to 36 mhz 3.3 volt vcxo vcxo idt? / ics? low cost 24 to 36 mhz 3.3 volt vcxo 3 ics3727xp rev a 102004 external component selection the ics3727xp requires a minimum number of external components for proper operation. decoupling capacitor a decoupling capacitor of 0.01f must be connected between vdd (pin 2) and gnd (pin 4), as close to these pins as possible. for optimum device performance, the decoupling capacitor should be mounted on the component side of the pcb. avoid the use of vias in the decoupling circuit. series termination resistor when the pcb trace between the clock output (clk, pin 5) and the load is over 1 inch, series termination should be used. to series terminate a 50 ? trace (a commonly used trace impedance) place a 33 ? resistor in series with the clock line, as close to the clock output pin as possible. the nominal impedance of the clock output is 20 ? . quartz crystal the ics3727xp vcxo function consists of the external crystal and the integrated vcxo oscillator circuit. to assure the best system performance (frequency pull range) and reliability, a crystal device with the recommended parameters (shown below) must be used, and the layout guidelines discussed in the following section shown must be followed. the frequency of oscillation of a quartz crystal is determined by its ?cut? and by the load capacitors connected to it. the ics3727xp incorporates on-chip variable load capacitors that ?pull? (change) the frequency of the crystal. the crystal specified for use with the ics3727xp is designed to have zero frequency error when the total of on-chip + stray capacitance is 14 pf. recommended crystal parameters: initial accuracy at 25 c 20 ppm temperature stability 30 ppm aging 20 ppm load capacitance 14 pf shunt capacitance, c0 7 pf max c0/c1 ratio 250 max equivalent series resistance 35 ? max the external crystal must be connected as close to the chip as possible and should be on the same side of the pcb as the ics3727xp. there should be no via?s between the crystal pins and the x1 and x2 device pins. there should be no signal traces underneath or close to the crystal. crystal tuning load capacitors the crystal traces should include pads for small fixed capacitors, one between x1 and ground, and another between x2 and ground. stuffing of these capacitors on the pcb is optional. the need for these capacitors is determined at system prototype evaluation, and is influenced by the particular crystal used (manufacture and frequency) and by pcb layout. the typical required capacitor value is 1 to 4 pf. to determine the need for and value of the crystal adjustment capacitors, you will need a pc board of your final layout, a frequency counter capable of about 1 ppm resolution and accuracy, two power supplies, and some samples of the crystals which you plan to use in production, along with measured initial accuracy for each crystal at the specified crystal load capacitance, cl. to determine the value of the crystal capacitors: 1. connect vdd of the ics3727xp to 3.3 v. connect pin 3 of the ics3727xp to the second power supply. adjust the voltage on pin 3 to 0v. measure and record the frequency of the clk output. 2. adjust the voltage on pin 3 to 3.3 v. measure and record the frequency of the same output. to calculate the centering error: where: f target = nominal crystal frequency error xtal =actual initial accuracy (in ppm) of the crystal being measured error 10 6 x f 3.0v f tet arg ? () f 0v f tet arg ? () + f tet arg ------------------------------------------------------------------------------ error xta l ? =
ics3727xp low cost 24 to 36 mhz 3.3 volt vcxo vcxo idt? / ics? low cost 24 to 36 mhz 3.3 volt vcxo 4 ics3727xp rev a 102004 if the centering error is less than 25 ppm, no adjustment is needed. if the centering error is more than 25ppm negative, the pc board has excessive stray capacitance and a new pcb layout should be considered to reduce stray capacitance. (alternately, the crystal may be re-specified to a higher load capacitance. contact idt for details.) if the centering error is more than 25 ppm positive, add identical fixed centering capacitors from each crystal pin to ground. the value for each of these caps (in pf) is given by: external capacitor = 2 x (centering error)/(trim sensitivity) trim sensitivity is a parame ter which can be supplied by your crystal vendor. if you do not know the value, assume it is 30 ppm/pf. after any changes, repeat the measurement to verify that the remaining error is acceptably low (typically less than 25 ppm). absolute maximum ratings stresses above the ratings listed below can cause pe rmanent damage to the ics3727xp. these ratings, which are standard values for ics commercially rated parts, are stress ratings only. functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods can affect product reliability. electrical parameters are guaranteed only over the recommended operating temperature range. recommended operation conditions item rating supply voltage, vdd 7 v all inputs and outputs -0.5 v to vdd+0.5 v ambient operating temperature 0 to +70 c storage temperature -65 to +150 c soldering temperature 260 c parameter min. typ. max. units ambient operating temperature 0 +70 c power supply voltage (measured in respect to gnd) +3.15 +3.45 v reference crystal parameters refer to page 3
ics3727xp low cost 24 to 36 mhz 3.3 volt vcxo vcxo idt? / ics? low cost 24 to 36 mhz 3.3 volt vcxo 5 ics3727xp rev a 102004 dc electrical characteristics vdd=3.3 v 5% , ambient temperature 0 to +70 c, unless stated otherwise ac electrical characteristics vdd = 3.3 v 5% , ambient temperature 0 to +70 c, unless stated otherwise note 1: external crystal device must conform with pullable crystal specifications listed on page 3. parameter symbol conditions min. typ. max. units operating voltage vdd 3.15 3.45 v output high voltage v oh i oh = -12 ma 2.4 v output low voltage v ol i ol = 12 ma 0.4 v output high voltage (cmos level) v oh i oh = -4 ma vdd-0.4 v operating supply current idd output = 27 mhz, no load 10 ma short circuit current i os 50 ma vin, vcxo control voltage v ia 03.3v parameter symbol conditions min. typ. max. units output frequency f o vcxo crystal frequency = 1/2 output 24 36 mhz crystal pullability f p 0v< vin < 3.3 v, note 1 + 200 ppm vcxo gain vin = vdd/2 + 1 v, note 1 200 ppm/v output rise time t or 0.8 to 2.0 v, c l =15 pf 1.5 ns output fall time t of 2.0 to 0.8 v, c l =15 pf 1.5 ns output clock duty cycle t d measured at 1.4 v, c l =15 pf 40 50 60 % maximum output jitter, short term t j c l =15 pf 100 ps
ics3727xp low cost 24 to 36 mhz 3.3 volt vcxo vcxo idt? / ics? low cost 24 to 36 mhz 3.3 volt vcxo 6 ics3727xp rev a 102004 package outline and package dimensions (8-pin soic, 150 mil. narrow body) package dimensions are kept current with jedec publication no. 95 ordering information while the information presented herein has been checked for both accuracy and reliability, integrated device technology (idt) assumes no responsibility for either its use or for the infringem ent of any patents or other rights of third parties, which wou ld result from its use. no other circuits, patents, or licenses are implied. this product is intended for use in normal commercial applications. any other applications such as those requiring ex tended temperature range, high re liability, or other extraordina ry environmental requirements are not recomm ended without additional processing by idt. idt reserves the right to change any circuitry or specifications without notice. idt does not authorize or warrant any idt product for use in life support devices o r critical medical instruments. part / order number marking shipping packaging package temperature 3727xpm 3727xpm tubes 8-pin soic 0 to +70 c 3727XPMT 3727xpm tape and reel 8-pin soic 0 to +70 c d eh c h x 45 0 b e q a pin 1 index area millimeters inches symbol min max min max a 1.35 1.75 0.0532 0.0688 a1 1.10 0.25 0.0040 0.0098 b 0.33 0.51 0.013 0.020 c 0.19 0.25 0.0075 0.0098 d 4.80 5.00 .1890 .1968 e 3.80 4.00 0.1497 0.1574 e 1.27 basic 0.050 basic h 5.80 6.20 0.2284 0.2440 h 0.25 0.50 0.010 0.020 l 0.40 1.27 0.016 0.050 a0 8 0 8
ics3727xp low cost 24 to 36 mhz 3.3 volt vcxo vcxo idt? / ics? low cost 24 to 36 mhz 3.3 volt vcxo 7 ics3727xp rev a 102004 revision history rev. originator date description of change a p.griffith 10/20/04 new device/datasheet.
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