general description the ds1081l is a spread-spectrum clock modulator ic that reduces emi in high clock-frequency-based, digital electronic equipment. using an integrated phase-locked loop (pll), the ds1081l accepts an input clock signal in the range of 20mhz to 134mhz and delivers a spread-spectrum mod- ulated output clock signal. the pll modulates, or dithers, the output clock about the center input frequency at a pin-selectable magnitude and dither rate, allowing direct emi control and optimization. in addition, through an enable pin the dithering can be enabled or disabled for easy comparison of system performance during emi test- ing. this same input pin also allows the ds1081l output to be tri-stated. by dithering the system clock, all the address, data, and timing signals generated from this signal are also dithered so that the measured emi at the fundamental and harmonic frequencies is greatly reduced. this is accomplished without changing clock rise/fall times or adding the space, weight, design time, and cost asso- ciated with mechanical shielding. the ds1081l is provided in an 8-pin tssop package and operates over a full automotive temperature range of -40? to +125?. applications lcd panels for tvs, desktop monitors, and notebook and tablet pcs automotive telematics and infotainment printers features ? modulates a 20mhz to 134mhz clock with center spread-spectrum dithering ? selectable spread-spectrum modulation magnitudes of: 0.5% 1.0% 1.5% 2.0% ? low 75ps cycle-to-cycle jitter ? spread-spectrum disable mode ? pin compatible with alliance/pulsecore semiconductor p2040 series devices ? clock output disable ? low cost ? low power consumption ? 3.3v single voltage supply ? -40c to +125c temperature range ? small 8-pin tssop package ds1081l 20mhz to 134mhz spread-spectrum clock modulator for lcd panels ______________________________________________ maxim integrated products 1 rev 0; 4/07 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. + denotes lead-free package. t denotes tape-and-reel. ordering information part temp range pin-package ds1081le+ -40? to +125? 8 tssop ds1081le+t -40? to +125? 8 tssop block diagram gnd sso pll with center- dithered spread spectrum configuration decode and control smsel1 clkin smsel2 f sso = 20mhz to 134mhz (dithered) v cc v cc f in = 20mhz to 134mhz ds1081l crsel ssen enable logic typical operating circuit appears at end of data sheet. sso gnd 1 2 8 7 crsel smsel1 smsel2 clkin tssop (4.40mm) top view 3 4 6 5 ds1081l v cc ssen pin configuration
absolute maximum ratings recommended operating conditions (t a = -40? to +125?, unless otherwise noted.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. voltage range on v cc relative to gnd .............-0.5v to +3.63v voltage range on any lead relative to gnd ................-0.5v to (v cc + 0.5v), not to exceed +3.63v operating temperature range .........................-40? to +125? storage temperature range .............................-55? to +125? soldering temperature...................see j-std-020 specification parameter symbol conditions min typ max units supply voltage v cc (note 1) 3.0 3.6 v input logic 1 v ih 0.8 x v cc v cc + 0.3 v input logic 0 v il -0.3 0.2 x v cc v input logic float ( ssen , crsel) v float 0v < v in < v cc 1 a sso < 80mhz 15 sso load c l 80mhz sso < 134mhz 7 pf clkin frequency f in 20 134 mhz clkin duty cycle f indc 40 60 % dc electrical characteristics (v cc = +3.0v to +3.6v, t a = -40? to +125?, unless otherwise noted.) parameter symbol conditions min typ max units supply current i cc c l = 7pf f in = 134mhz 15 ma smsel1/smsel2/clkin input leakage i il:1 0v < v in < v cc -1 +1 a crsel/ ssen input leakage i il:2 0v < v in < v cc -100 +100 a output leakage (sso) i oz ssen = float -1 +1 a low-level output voltage (sso) v ol i ol = 4ma 0.4 v high-level output voltage (sso) v oh i oh = -4ma 2.4 v ac electrical characteristics (v cc = +3.0v to +3.6v, t a = -40? to +125?, unless otherwise noted.) parameter symbol conditions min typ max units sso duty cycle f ssodc measured at v cc /2 40 60 % sso rise time t r c l = 7pf 1 ns sso fall time t f c l = 7pf 1 ns peak cycle-to-cycle jitter t j t a = -40c to +85c, 10,000 cycles 75 ps power-up time t por (note 2) 50 ms ds1081l 20mhz to 134mhz spread-spectrum clock modulator for lcd panels 2 _____________________________________________________________________ note 1: all voltages referenced to ground. currents into the ic are positive and out of the ic are negative. note 2: time between power applied to device and stable output.
ds1081l 20mhz to 134mhz spread-spectrum clock modulator for lcd panels _____________________________________________________________________ 3 typical operating characteristics (t a = +25?, unless otherwise noted.) supply current vs. supply voltage ds1081l toc01 supply voltage (v) supply current (ma) 3.5 3.4 3.3 3.2 3.1 2 4 6 8 10 12 14 0 3.0 3.6 clkin = 134mhz clkin = 20mhz clkin = 66mhz supply current vs. temperature ds1081l toc02 temperature ( c) supply current (ma) 120 100 80 60 40 20 -20 0 2 4 6 8 10 12 14 0 -40 clkin = 134mhz clkin = 33mhz clkin = 66mhz 134 supply current vs. frequency ds1081l toc03 frequency (mhz) supply current (ma) 116 96 76 56 36 2 4 6 8 10 12 14 0 20 v cc = 3.6v v cc = 3.0v duty cycle vs. temperature ds1081l toc04 temperature ( c) duty cycle (%) 120 100 60 80 0 20 40 -20 42 44 46 48 50 52 54 56 58 60 40 -40 clkin = 66mhz duty cycle vs. supply voltage ds1081l toc05 supply voltage (v) duty cycle (%) 3.5 3.4 3.3 3.2 3.1 42 44 46 48 50 52 54 56 58 60 40 3.0 3.6 clkin = 66mhz spectrum attenuation vs. frequency at different dither amplitudes ds1081l toc06 frequency (mhz) attenuation (db) f out = 40mhz 2% 1.5% 0.5% 6db 4.5db 3db 1% f out = 40mhz rbw = 120khz center dither
detailed description the ds1081l modulates an input clock to generate a center-dithered spread-spectrum output. a 20mhz to 134mhz clock is applied to the clkin pin. an internal pll dithers the output clock about its center frequency at a user-selectable magnitude. spread-spectrum dither magnitude the ds1081l can generate dither magnitudes up to ?%. the desired magnitude is selected using input pins smsel1 and smsel2 as shown in table 1. spread-spectrum dither rate the output spread-spectrum dither rate is determined by the input frequency to maximize emi reduction and to ensure that the dither rate is always above the audio frequency range. the user must configure crsel, based on table 2, depending on the input frequency (f in ) so that the appropriate dither rate is programmed. ds1081l 20mhz to 134mhz spread-spectrum clock modulator for lcd panels 4 _____________________________________________________________________ pin description pin name function 1 clkin clock input. 20mhz to 134mhz clock input (f in ). spread-spectrum magnitude select inputs. these digital inputs select the desired spread-spectrum magnitude as shown in the table below. smsel2 smsel1 magnitude selected 2 smsel2 0 0 2.0% 0 1 1.5% 1 0 1.0% 3smsel1 1 1 0.5% 4 gnd ground 5 ssen spread-spectrum enable. three-level input to enable/disable spread-spectrum and to tri-state the output. 0 = power-up/spread-spectrum enabled. float = sso tri-stated. 1 = power-up/spread-spectrum disabled (not a bypass mode). 6 sso spread-spectrum clock output. outputs a center-dithered spread-spectrum version of the clock input at clkin. clock range and dither rate select. three-level input that determines the dither rate. see the detailed description section for details. crsel clkin range dither rate 0 66mhz to 134mhz f in /2048 float 33mhz to 80mhz f in /1024 7 crsel 1 20mhz to 38mhz f in /512 8 v cc supply voltage crsel clkin range dither rate 0 66mhz to 134mhz f in /2048 float 33mhz to 80mhz f in /1024 1 20mhz to 38mhz f in /512 table 2. smsel2 smsel1 magnitude 00 2.0% 01 1.5% 10 1.0% 11 0.5% table 1.
ds1081l 20mhz to 134mhz spread-spectrum clock modulator for lcd panels maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 _____________________ 5 2007 maxim integrated products is a registered trademark of maxim integrated products, inc. is a registered trademark of dallas semiconductor corporation. spread-spectrum enable on power-up, the output clock (sso) remains tri-stated until the internal pll reaches a stable frequency. the ssen input can be used to disable the spread-spec- trum modulation and to tri-state the sso output. if the ssen pin is pulled high, the spread-spectrum modula- tion is turned off, but the device still uses the internal pll to generate the clock signal at sso. if the ssen pin is floated, the output will be tri-stated. application information power-supply decoupling to achieve best results, it is highly recommended that a decoupling capacitor is used on the ic power-supply pins. typical values of decoupling capacitors are 0.01? and 0.1?. use a high-quality, ceramic, surface-mount capacitor, and mount it as close as possible to the v cc and gnd pins of the ic to minimize lead inductance. f in + (0.5%, 1.0%, 1.5%, or 2.0% of f in ) f in f in - (0.5%, 1.0%, 1.5%, or 2.0% of f in ) f sso time 1 dither cycle rate dither amount ( 0.5%, 1.0%, 1.5%, or 2.0%) clkin range (mhz) dither rate 66 to 134 f in /2048 33 to 80 f in /1024 20 to 38 f in /512 if ssen = 1 figure 1. ds1081l spread-spectrum frequency modulation clkin smsel1 smsel2 gnd crsel v cc decoupling capacitor v cc sso f in = 20mhz to 134mhz note: in the above configuration with smsel1, smsel2, and ssen connected to gnd as well as crsel connected to v cc and ssen connected to gnd, the device is configured with a spread-spectrum magnitude of 2.0%, and allows a clkin between 20mhz and 38mhz. ds1081l f sso dithered ssen typical operating circuit package information for the latest package outline information, go to www.maxim-ic.com/dallaspackinfo .
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