Rainbow Electronics DS1080L User Manual

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.

Applications

Automotive

Cable Modems

Cell Phones

Computer Peripherals

Copiers

Infotainment

PCs

Printers

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

♦ -40°C to +125°C Temperature Operation

♦ Small 8-Lead µSOP Package

DS1080L

Spread-Spectrum Crystal Multiplier

______________________________________________ Maxim Integrated Products 1

SSO

PDNSMSEL

1

2

87X2

V

CC

GND

CMSEL

X1

µSOP

TOP VIEW

3

4

6

5

DS1080L

Pin Configuration

Rev 0; 11/05

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

+Denotes lead-free package.

Ordering Information

PART TEMP RANGE PIN-PACKAGE

DS1080L+

8 µSOP

-40°C to +125°C

DS1080L

Spread-Spectrum Crystal Multiplier

2 _____________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

RECOMMENDED OPERATING CONDITIONS

(TA= -40°C to +125°C)

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.

Voltage on VCCRelative to GND.........................-0.5V to +3.63V

Voltage on Any Lead Relative

to GND ...............-0.5V to (V

CC

+ 0.5V), not to exceed +3.63V

Operating Temperature Range .........................-40°C to +125°C

Storage Temperature Range .............................-55°C to +125°C

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

0.7 x
V

CC

VCC +

0.3

V

Input Logic 0 V

IL

GND -

0.3

0.3 x
V

CC

V

Input Logic Float I

IF

0v < VIN < V

CC

(Note 2) ±1 µA

Input Leakage I

IL

0V < VIN < V

CC

(Note 3) ±80 µA

SSO < 67MHz 15

67MHz ≤ SSO < 101MHz 10

SSO Load C

SSO

101MHz ≤ SSO < 134MHz 7

pF

Crystal or Clock Input
Frequency

f

IN

16.0 33.4 MHz

Crystal ESR X

ESR

90 Ω

Clock Input Duty Cycle F

INDC

40 60 %

Crystal Parallel Load
Capacitance

C

L

(Note 4) 18 pF

DC ELECTRICAL CHARACTERISTICS

(VCC= +3.0V to +3.6V, TA= -40°C to +125°C.)

PARAMETER

CONDITIONS MIN TYP MAX

UNITS

Supply Current I

CC1

C

SSO

= 15pF, SSO = 16MHz 13 mA

Power-Down Current I

CCQ

PDN = GND, all input pins floating 200 µA

Output Leakage (SSO) I

OZ

PDN = GND -1 +1 µA

Low-Level Output Voltage
(SSO)

V

OL

IOL = 4mA 0.4 V

High-Level Output Voltage
(SSO)

V

OH

IOH = -4mA 2.4 V

Input Capacitance (X1/X2) C

IN

(Note 5) 5 pF

SYMBOL

DS1080L

Spread-Spectrum Crystal Multiplier

_____________________________________________________________________ 3

AC ELECTRICAL CHARACTERISTICS

(VCC= +3.0 to +3.6V, TA= -40°C to +125°C.)

PARAMETER

CONDITIONS MIN TYP MAX

UNITS

SSO Duty Cycle

Measured at VCC / 2 40 60 %

Rise Time t

R

(Note 6) 1.6 ns

Fall Time t

F

(Note 6) 1.6 ns

Peak Cycle-to-Cycle Jitter t

J

f

SSO

= 16MHz, TA = -40 to +85°C,

10,000 cycles (Note 5)

75 ps

16MHz 20

Power-Up Time t

POR

PDN pin (Note 7)

33.4MHz 11

ms

Power-Down Time t

PDN

PDN pin (Notes 8 and 9) 100 ns

Dither Rate

fIN /

Note 1: All voltages referenced to ground.
Note 2: Maximum source/sink current applied to input to be considered a float.
Note 3: Applicable to pins CMSEL, SMSEL, and

PDN.

Note 4: See information about C

L1

and CL2in the Applications Information section at the end of the data sheet.

Note 5: Not production tested.
Note 6: For 7pF load.
Note 7: Time between PDN deasserted to output active.
Note 8: Time between PDN asserted to output high impedance.
Note 9: Guaranteed by design.

SYMBOL

SSODC

f

DITHER

1024

DS1080L

Spread-Spectrum Crystal Multiplier

4 _____________________________________________________________________

Typical Operating Characteristics

(VCC= 3.3V, TA = +25°C, unless otherwise noted.)

SUPPLY CURRENT vs. SUPPLY VOLTAGE

DS1080L toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

3.35 3.45 3.55 3.653.253.05 3.15

2

4

6

8

10

12

0

2.95

AT 16MHz

CMSEL = 4x AT 16MHz

CMSEL = 2x AT 16MHz

CMSEL = 1x AT 16MHz

SUPPLY CURRENT vs. TEMPERATURE

DS1080L toc02

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

11010 60

2

4

6

8

10

12

0

-40

AT 16MHz

CMSEL = 2x AT 16MHz

CMSEL = 4x AT 16MHz

CMSEL = 1x AT 16MHz

SUPPLY CURRENT vs. FREQUENCY

DS1080L toc03

FREQUENCY (MHz)

SUPPLY CURRENT (mA)

3121 26

2

4

6

8

12

10

16

14

0

16

AT 16MHz

CMSEL = 2x AT 16MHz

CMSEL = 4x AT 16MHz

CMSEL = 1x AT 16MHz

PDN SUPPLY CURRENT vs. TEMPERATURE

DS1080L toc04

TEMPERATURE (°C)

PDN SUPPLY CURRENT (mA)

11010 60

0.05

0.10

0.15

0.20

0.25

0

-40

AT 16MHz

CMSEL = 1x AT 16MHz

CMSEL = 4x AT 16MHz

CMSEL = 2x AT 16MHz

DUTY CYCLE vs. TEMPERATURE

DS1080L toc05

TEMPERATURE (°C)

DUTY CYCLE (%)

11010 60

44

42

48

52

56

46

50

54

58

60

40

-40

AT 16MHz

DUTY CYCLE vs. SUPPLY VOLTAGE

DS1080L toc06

SUPPLY VOLTAGE (V)

DUTY CYCLE (%)

3.55 3.653.15 3.35 3.453.05 3.25

44

42

48

52

56

46

50

54

58

60

40

2.95

AT 16MHz

OUTPUT DURING

POWER UP AND POWER DOWN

DS1080L toc07

SSO AND PDN

TIME (µs)

POWER
DOWN

t

PDN

t

POR

POWER
UP

DS1080L

Spread-Spectrum Crystal Multiplier

_____________________________________________________________________ 5

CRYSTAL

OSCILLATOR

1x/2x/4x CLOCK MULTIPLYING
PLL WITH SPREAD SPECTRUM

CONFIGURATION DECODE

AND CONTROL

V

CC

V

CC

GND

NOTE: SEE INFORMATION ABOUT CL1 AND CL2 IN THE APPLICATIONS INFORMATION SECTION AT THE END OF THE DATA SHEET.

PDN

SSO

CMSEL

SMSEL

X1

X2

16MHz

TO

33.4MHz

f

SSO

= 16MHz

TO

134MHz

C

L1

C

L2

f

IN

f

SSO

DS1080L

Block Diagram

Pin Description

PIN NAME FUNCTION

1X1

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.

2 GND Signal Ground

3

Clock Multiplier Select. Tri-level digital input.
0 = 1x
Float = 2x
1 = 4x

4

Spread-Spectrum Magnitude Select. Tri-level digital input.
0 = ±0.5%
Float = ±1.0%
1 = ±1.5%

5 PDN

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

6 SSO

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.

7VCCSupply Voltage

8X2

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.

CMSEL

SMSEL

DS1080L

Spread-Spectrum Crystal Multiplier

6 _____________________________________________________________________

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 (f

DITHER

).

+1.5%

+1.0%

+0.5%

-0.5%

f

0

-1.0%

-1.5%

DITHER CYCLE RATE = f

DITHER

= fIN / 1024

f

SSO

t

Figure 1. Spread-Spectrum Frequency Modulation

DS1080L

Spread-Spectrum Crystal Multiplier

_____________________________________________________________________ 7

Applications Information

Crystal Selection

The DS1080L requires a parallel resonating crystal
operating in the fundamental mode, with an ESR of less
than 90Ω. The crystal should be placed very close to
the device to minimize excessive loading due to para­sitic capacitances.

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 CL1and CL2are selected based
on the crystal specifications (from the data sheet of the
crystal used). The crystal parallel load capacitance is
calculated as follows:

For the DS1080L use C

L1

= CL2= CLX.

In this case, the equation then reduces to:

where CL1= CL2= C

LX.

Equation 2 is used to calculate the values of CL1and
CL2based on values on CLand CINnoted 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

0.001µF and 0.1µF. Use a high-quality, ceramic, sur­face-mount capacitor, and mount it as close as possi­ble to the VCCand GND pins of the IC to minimize lead
inductance.

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.

C

C

C

L

LX

IN

Equation

=+

2

2

C

CxC

CC

C

L

LL

LL

IN

Equation

=

+

12

12

1

DS1080L

X2

NOTE: IN THE ABOVE CONFIGURATION WITH PDN CONNECTED TO V

CC

, SMSEL CONNECTED TO GND
AND CMSEL FLOATING, THE DEVICE IS IN NORMAL OPERATION WITH 2x CLOCK MULTIPLICATION, AND
SPREAD-SPECTRUM MAGNITUDE OF ±0.5%.

f

SSO

V

CC

V

CC

V

CC

SSO

PDN

X1

CRYSTAL

C

L1

C

L2

DECOUPLING
CAPACITOR

GND

CMSEL

SMSEL

8

7

6

5

1

2

3

4

Typical Operating Circuit

DS1080L

Spread-Spectrum Crystal Multiplier

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.

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