CY22388 CYPRESS [Cypress Semiconductor], CY22388 Datasheet - Page 2

• Manufacturer Part Number: CY22388
• Description: Universal Programmable Clock Generator (UPCG)
• Manufacturer: CYPRESS [Cypress Semiconductor]

Document #: 001-07704 Rev. **
General Description
The CY22800 is a multi-function clock generator that supports
various applications in consumer and communications
markets. The device uses the Cypress proprietary PLL along
with Spread Spectrum and VCXO technology to make it one of
the most versatile clock synthesizer in the market place. The
CY22800 is a field-programmable synthesizer that can be
programmed using an easy-to-use programmer dongle,
CY36800, with one of many predefined configuration files for
fast sample generation of prototype builds. The CY22800 is a
reprogrammable device that can be programmed up to five
thousand times. The latest configurations available for this
device are summarized in Table 1.
Spread Spectrum Clock Generation (SSCG)
The CY22800 is capable of generating Spread Spectrum
Clocks (SSCG) for the purpose of reducing EMI found in
today’s high-speed digital electronic systems.
The device uses proprietary Spread Spectrum Clock (SSC)
technology to synthesize and modulate the frequency of the
input clock. By modulating the frequency of the clock, the
measured EMI at the fundamental and harmonic frequencies
is greatly reduced. This reduction in radiated energy can
significantly reduce the cost of complying with regulatory
agency (EMC) requirements and improve time-to-market
without degrading system performance.
The CY22800 uses a preprogrammed configuration of
memory arrays to synthesize output frequency and offers eight
different spread percentages (refer to Table 1 – Code numbers
-015 to -022), and an additional option to turn the spread on
and off.
For the above-mentioned configurations, the modulation
frequency varies with the reference frequency as follows:
f
mod
=
1000
f
ref
VCXO
One of the key components of the CY22800 device is the
VCXO. The VCXO is used to “pull” the reference crystal higher
or lower in order to lock the system frequency to an external
source. This is ideal for applications where the output
frequency needs to track along with an external reference
frequency that is constantly shifting.
A special pullable crystal must be used in order to have
adequate VCXO pull range. Pullable Crystal specifications are
included in this data sheet.
VCXO Profile
Figure 1 shows an example of what a VCXO profile looks like.
The analog voltage input is on the X-axis and the PPM range
is on the Y-axis. An increase in the VCXO input voltage results
in a corresponding increase in the output frequency. This has
the effect of moving the PPM from a negative to positive offset.
Figure 1. VCXO Profile
-100
-150
-200
200
150
100
-50
50
0
0
0.5
1
VCXO input [V]
1.5
2
2.5
CY22800
3
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