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Rev 0; 11/05
Spread-Spectrum Crystal Multiplier
General Description
The DS1080L is a low-jitter, crystal-based clock generator with an integrated phase-locked loop (PLL) to generate spread-spectrum clock outputs from 16MHz to 134MHz. The device is pin-programmable to select the clock multiplier rate as well as the dither magnitude. The DS1080L has a spread-spectrum disable mode and a power-down mode to conserve power.
Features
Generates Spread-Spectrum Clocks from 16MHz to 134MHz Selectable Clock Multiplier Rates of 1x, 2x, and 4x Center Spread-Spectrum Dithering Selectable Spread-Spectrum Modulation Magnitudes of 0.5%, 1.0%, and 1.5% Spread-Spectrum Disable Mode Low Cycle-to-Cycle Jitter Power-Down Mode with High-Impedance Output Low Cost Low Power Consumption 3.0V to 3.6V Single-Supply Operation -40C to +125C Temperature Operation Small 8-Lead SOP Package
DS1080L
Applications
Automotive Cable Modems Cell Phones Computer Peripherals Copiers Infotainment PCs Printers
Pin Configuration
PART DS1080L+
Ordering Information
TEMP RANGE -40C to +125C PIN-PACKAGE 8 SOP
TOP VIEW
X1 GND CMSEL 1 2 8 7 X2 VCC SSO PDN
+Denotes lead-free package.
DS1080L
3 6 5 SMSEL 4
SOP
______________________________________________ Maxim Integrated Products
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Spread-Spectrum Crystal Multiplier DS1080L
ABSOLUTE MAXIMUM RATINGS
Voltage on VCC Relative to GND .........................-0.5V to +3.63V Voltage on Any Lead Relative to GND ...............-0.5V to (VCC + 0.5V), not to exceed +3.63V Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-55C to +125C Soldering Temperature...................See J-STD-020 Specification
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
(TA = -40C to +125C)
PARAMETER Supply Voltage Input Logic 1 Input Logic 0 Input Logic Float Input Leakage SSO Load Crystal or Clock Input Frequency Crystal ESR Clock Input Duty Cycle Crystal Parallel Load Capacitance SYMBOL VCC VIH VIL IIF IIL CSSO 0v < VIN < VCC (Note 2) 0V < VIN < VCC (Note 3) SSO < 67MHz 67MHz SSO < 101MHz 101MHz SSO < 134MHz fIN XESR FINDC CL (Note 4) 40 16.0 (Note 1) CONDITIONS MIN 3.0 0.7 x VCC GND 0.3 TYP MAX 3.6 VCC + 0.3 0.3 x VCC 1 80 15 10 7 33.4 90 60 18 MHz % pF pF UNITS V V V A A
DC ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to +3.6V, TA = -40C to +125C.)
PARAMETER Supply Current Power-Down Current Output Leakage (SSO) Low-Level Output Voltage (SSO) High-Level Output Voltage (SSO) Input Capacitance (X1/X2) SYMBOL ICC1 ICCQ IOZ VOL VOH CIN CONDITIONS CSSO = 15pF, SSO = 16MHz PDN = GND, all input pins floating PDN = GND IOL = 4mA IOH = -4mA (Note 5) 2.4 5 -1 MIN TYP MAX 13 200 +1 0.4 UNITS mA A A V V pF
2
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Spread-Spectrum Crystal Multiplier
AC ELECTRICAL CHARACTERISTICS
(VCC = +3.0 to +3.6V, TA = -40C to +125C.)
PARAMETER SSO Duty Cycle Rise Time Fall Time Peak Cycle-to-Cycle Jitter Power-Up Time Power-Down Time Dither Rate SYMBOL SSODC tR tF tJ tPOR tPDN fDITHER (Note 6) (Note 6) fSSO = 16MHz, TA = -40 to +85C, 10,000 cycles (Note 5) PDN pin (Note 7) PDN pin (Notes 8 and 9) fIN / 1024 16MHz 33.4MHz CONDITIONS Measured at VCC / 2 MIN 40 1.6 1.6 75 20 11 100 TYP MAX 60 UNITS % ns ns ps ms ns
DS1080L
Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Note 8: Note 9:
All voltages referenced to ground. Maximum source/sink current applied to input to be considered a float. Applicable to pins CMSEL, SMSEL, and PDN. See information about CL1 and CL2 in the Applications Information section at the end of the data sheet. Not production tested. For 7pF load. Time between PDN deasserted to output active. Time between PDN asserted to output high impedance. Guaranteed by design.
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Spread-Spectrum Crystal Multiplier DS1080L
Typical Operating Characteristics
(VCC = 3.3V, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
DS1080L toc01
SUPPLY CURRENT vs. TEMPERATURE
DS1080L toc02
SUPPLY CURRENT vs. FREQUENCY
AT 16MHz 14 SUPPLY CURRENT (mA) 12 10 8 6 4 CMSEL = 2x AT 16MHz CMSEL = 1x AT 16MHz CMSEL = 4x AT 16MHz
DS1080L toc03
12 AT 16MHz 10 SUPPLY CURRENT (mA) 8 6 4 2 0 2.95 3.05 3.15 3.25 3.35 3.45 3.55 CMSEL = 4x AT 16MHz CMSEL = 2x AT 16MHz
12 AT 16MHz 10 SUPPLY CURRENT (mA) 8 6 4 2 0 CMSEL = 1x AT 16MHz CMSEL = 2x AT 16MHz CMSEL = 4x AT 16MHz
16
CMSEL = 1x AT 16MHz
2 0 -40 10 60 110 16 21 26 31 TEMPERATURE (C) FREQUENCY (MHz)
3.65
SUPPLY VOLTAGE (V)
PDN SUPPLY CURRENT vs. TEMPERATURE
DS1080L toc04
DUTY CYCLE vs. TEMPERATURE
58 56 DUTY CYCLE (%) 54 52 50 48 46 AT 16MHz
DS1080L toc05
0.25 AT 16MHz PDN SUPPLY CURRENT (mA) 0.20 CMSEL = 4x AT 16MHz
60
0.15
0.10 CMSEL = 1x AT 16MHz 0.05 CMSEL = 2x AT 16MHz
44 42
0 -40 10 60 110 TEMPERATURE (C)
40 -40 10 60 110 TEMPERATURE (C)
DUTY CYCLE vs. SUPPLY VOLTAGE
DS1080L toc06
OUTPUT DURING POWER UP AND POWER DOWN
DS1080L toc07
60 58 56 DUTY CYCLE (%) 54 52 50 48 46 44 42 40 2.95 3.05 3.15 3.25 3.35 3.45 3.55 AT 16MHz
POWER DOWN SSO AND PDN tPDN tPOR
POWER UP
3.65
SUPPLY VOLTAGE (V)
TIME (s)
4
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Spread-Spectrum Crystal Multiplier
Pin Description
PIN 1 2 NAME X1 GND FUNCTION Crystal Drive/Clock Input. A crystal with the proper loading capacitors is connected across X1 and X2. Instead of a crystal, a clock can be applied at the X1 input. Signal Ground Clock Multiplier Select. Tri-level digital input. 0 = 1x Float = 2x 1 = 4x Spread-Spectrum Magnitude Select. Tri-level digital input. 0 = 0.5% Float = 1.0% 1 = 1.5% Power-Down/Spread-Spectrum Disable. Tri-level digital input. 0 = Power-Down/SSO Tri-Stated Float = Power-Up/Spread Spectrum Disabled 1 = Power-Up/Spread Spectrum Enabled Spread-Spectrum Clock Multiplier Output. Outputs a 1x, 2x, or 4x spread-spectrum version of the crystal or clock applied at the X1/X2 pins. Supply Voltage Crystal Drive Output. A crystal with the proper loading capacitors is connected across X1 and X2. If a clock is connected to X1, then X2 should be left open circuit.
DS1080L
3
CMSEL
4
SMSEL
5
PDN
6 7 8
SSO VCC X2
Block Diagram
VCC X1 16MHz TO 33.4MHz CL1 CL2 PDN CMSEL SMSEL CONFIGURATION DECODE AND CONTROL X2 fIN CRYSTAL OSCILLATOR 1x/2x/4x CLOCK MULTIPLYING PLL WITH SPREAD SPECTRUM VCC SSO fSSO fSSO = 16MHz TO 134MHz
GND
DS1080L
NOTE: SEE INFORMATION ABOUT CL1 AND CL2 IN THE APPLICATIONS INFORMATION SECTION AT THE END OF THE DATA SHEET.
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Spread-Spectrum Crystal Multiplier DS1080L
Detailed Description
The DS1080L is a crystal multiplier with center spreadspectrum capability. A 16MHz to 33.4MHz crystal is connected to the X1 and X2 pins. Alternately, a 16MHz to 33.4MHz clock can be applied to X1 in place of the crystal. In such applications, X2 would be left open circuit. Using the CMSEL input, the user selects whether the attached crystal or input clock is multiplied by 1, 2, or 4. The DS1080L is capable of generating spreadspectrum clocks from 16MHz to 134MHz. The PLL can dither the output clock about its center frequency at a user-selectable magnitude. Using the SMSEL input, the user selects the dither magnitude. The PDN input can be used to place the device into a low-power standby mode where the SSO output is tristated. If the PDN pin is floated, the SSO output is active but the spread-spectrum dithering is disabled. The spread-spectrum dither rate is fixed at fIN / 1024 to keep the dither rate above the audio frequency range. On power-up, the output clock (SSO) remains tri-stated until the PLL reaches a stable frequency (f SSO) and dither (fDITHER).
DITHER CYCLE RATE = fDITHER = fIN / 1024 fSSO +1.5% +1.0% +0.5% f0 -0.5% -1.0% -1.5%
t
Figure 1. Spread-Spectrum Frequency Modulation
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Spread-Spectrum Crystal Multiplier
Typical Operating Circuit
CRYSTAL
DS1080L
CL1
CL2
X1 GND CMSEL SMSEL
1 2 3 4
8 7
X2 VCC SSO PDN
VCC DECOUPLING CAPACITOR
DS1080L
6 5
fSSO VCC
NOTE: IN THE ABOVE CONFIGURATION WITH PDN CONNECTED TO VCC, SMSEL CONNECTED TO GND AND CMSEL FLOATING, THE DEVICE IS IN NORMAL OPERATION WITH 2x CLOCK MULTIPLICATION, AND SPREAD-SPECTRUM MAGNITUDE OF 0.5%.
Applications Information
Crystal Selection
The DS1080L requires a parallel resonating crystal operating in the fundamental mode, with an ESR of less than 90. The crystal should be placed very close to the device to minimize excessive loading due to parasitic capacitances.
where CL1 = CL2 = CLX. Equation 2 is used to calculate the values of CL1 and CL2 based on values on CL and CIN noted in the data sheet electrical specifications.
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 0.001F and 0.1F. Use a high-quality, ceramic, surface-mount capacitor, and mount it as close as possible to the VCC and GND pins of the IC to minimize lead inductance.
Oscillator Input
When driving the DS1080L using an external oscillator clock, consider the input (X1) to be high impedance.
Crystal Capacitor Selection
The load capacitors CL1 and CL2 are selected based on the crystal specifications (from the data sheet of the crystal used). The crystal parallel load capacitance is calculated as follows: CL = CL1 x CL2 CIN CL1 + CL2
Equation 1
Layout Considerations
As noted earlier, the crystal should be placed very close to the device to minimize excessive loading due to parasitic capacitances. Care should also be taken to minimize loading on pins that could be floated as a programming option (SMSEL and CMSEL). Coupling on inputs due to clocks should be minimized.
For the DS1080L use CL1 = CL2 = CLX. In this case, the equation then reduces to: CL = CLX + CIN 2
Equation 2
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Spread-Spectrum Crystal Multiplier DS1080L
Chip Technology
TRANSISTOR COUNT: 3951 SUBSTRATE CONNECTED TO GROUND
Package Information
For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.
is a registered trademark of Dallas Semiconductor Corporation.
Heaney

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