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NB2780A
Low Power, Reduced EMI
Clock Synthesizer
The NB2780A is a versatile spread spectrum frequency modulator
designed specifically for a wide range of clock frequencies. The
NB2780A reduces ElectroMagnetic Interference (EMI) at the clock
source, allowing system wide reduction of EMI of all clock dependent
signals. The NB2780A allows significant system cost savings by
reducing the number of circuit board layers, ferrite beads and
shielding that are traditionally required to pass EMI regulations.
The NB2780A uses the most efficient and optimized modulation
profile approved by the FCC and is implemented by using a
proprietary all digital method.
The NB2780A modulates the output of a single PLL in order to
“spread” the bandwidth of a synthesized clock, and more importantly,
decreases the peak amplitudes of its harmonics. This results in
significantly lower system EMI compared to the typical narrow band
signal produced by oscillators and most frequency generators.
Lowering EMI by increasing a signal’s bandwidth is called ‘spread
spectrum clock generation’.
The NB2780A is targeted towards all portable devices with very
low power requirements like MP3 players and digital still cameras.
Features
• Generates an EMI Optimized Clocking Signal at the Output
• Integrated Loop Filter Components
• Operates with a 3.3 V / 2.5 V Supply
• Operating Current less than 5.0 mA
• Low Power CMOS Design
• Input Frequency Range: 30 MHz to 50 MHz for Both Voltages
• Generates a 1X Low EMI Spread Spectrum clock of the Input
Frequency
• Frequency Deviation "0.75% (TYP) @ 46 MHz
• Available in TSOP−6 Package (TSOT−23−6)
• Pb−Free Package is Available
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MARKING
DIAGRAM*
6
1
TSOP−6
(TSOT−23−6)
SN SUFFIX
CASE 318G
E07AYWG
G
1
E07 = Specific Device Code
A = Assembly Location
Y = Year
W = Work Week
G = Pb−Free Package
(Note: Microdot may be in either location)
*For additional marking information, refer to
Application Note AND8002/D.
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 7 of this data sheet.
© Semiconductor Components Industries, LLC, 2005
December, 2006 − Rev. 3
1
Publication Order Number:
NB2780A/D
XIN/CLKIN
XOUT
Crystal
Oscillator
NB2780A
PD
Frequency
Divider
Feedback
Divider
Modulation
Phase
Detector
Loop
Filter
VDD
PLL
VCO
Output
Divider
ModOUT
Table 1. KEY SPECIFICATIONS
Description
Supply Voltages
Frequency Range
Cycle−to−Cycle Jitter
Output Duty Cycle
Modulation Rate Equation
Frequency Deviation
Figure 1. Block Diagram
VSS
Specification
VDD = 3.3 V / 2.5 V
30 MHz < CLKIN < 50 MHz
200 ps (maximum)
45/55% (worst case)
FIN/1280
"0.75% (TYP) @ 46 MHz
PD 1
XOUT 2
XIN/CLKIN 3
NB2780A
6 VSS
5 ModOUT
4 VDD
Figure 2. Pin Configuration
Table 2. PIN DESCRIPTION
Pin #
1
2
3
4
5
6
Pin Name
PD
XOUT
XIN/CLKIN
VDD
ModOUT
VSS
Type
I
O
I
P
O
P
Description
Powerdown control pin. Pull low to enable Powerdown mode. Connect to VDD if not used.
Crystal connection. If using an external reference, this pin must be left unconnected.
Crystal connection or external reference frequency input. This pin has dual functions. It can be
connected either to an external crystal or an external reference clock
Power supply for the entire chip.
Spread spectrum clock output.
Ground connection.
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