cy2xf23 Cypress Semiconductor Corporation., cy2xf23 Datasheet - Page 2

• Manufacturer Part Number: cy2xf23
• Description: High Performance Lvds Oscillator With Frequency Margining - I 2c Control
• Manufacturer: Cypress Semiconductor Corporation.

Functional Description
The CY2XF23 is a phase locked loop (PLL) based high perfor-
mance clock generator. It uses an internal crystal oscillator as a
reference, and outputs one differential LVDS clock. It has an I
Bus serial interface
frequency.
The CY2XF23 comes configured for four different frequencies.
At power on, the four configurations are transparently loaded into
an internal volatile memory which in turn controls the PLL. The
user can switch between the four frequencies through the I
Bus. The user can also configure the CY2XF23 with new output
frequencies by shifting new data into the internal memory.
Frequency margining is a common application for this feature.
One frequency is used for the standard operating mode of the
device, while additional frequencies are available for margin
testing, either during product development or in system
manufacturing test.
Note that all configuration changes made using I
temporary and are lost when power is removed from the device.
At power on, the device returns to its original state.
The configuration for a particular frequency is stored in a 6-byte
block of memory, known as a word. The CY2XF23 has four such
words, labeled Frequency Word 0 through Frequency Word 3.
An additional register byte contains a 2-bit field, which selects
one of the four frequency words. By writing to this Select Byte,
the user can switch back and forth between the four programmed
frequencies. The select byte is always defined to select
Frequency Word 0 at power on.
When changing the output frequency, the frequency transition is
not guaranteed to be smooth. There can be frequency excur-
sions beyond the start frequency and the new frequency.
Glitches and runt pulses are possible, and time must be allowed
for the PLL to re-lock.
If more than four frequencies are needed, the I
used to change any of the four frequency words. When writing
frequency words via I
selected word. Instead, write one of the three unselected words
before changing the select byte to select that new word.
Figure 2
selected.
Figure 2. Frequency Words
Document Number: 001-53145 Rev. *A
Note
16h – 1Bh
1Ch – 21h
10h – 15h
22h – 27h
Register
1. The serial interface is I
Address
40h
to V
DD
, setup time, and output hold time.
shows how the frequency words are arranged and
Select Byte
Frequency Word 0
Frequency Word 1
Frequency Word 2
Frequency Word 3
[1]
2
2
C Bus compliant, with the following exceptions: SDA input leakage current, SDA input capacitance, SDA and SCLK are clamped
, which is used to change the output
C, users should not change the currently
Default = 00
Bits [1:0]
00
01
10
11
Sel
2
Control
C Bus can be
PRELIMINARY
2
C are
PLL
2
2
C
C
Configuration Software
Cypress provides CyberClocks™ Online web-based software
that enables users to create data values for shifting into the
frequency words. This software is required because the
algorithm is too complicated to describe here.
The software is located at www.cyberclocksonline.com.
The user specifies the output frequency. The software then
calculates the bit stream. The bit stream is generic in the sense
that it can be shifted into any of the four Frequency Words. This
process is repeated for all frequencies of interest.
Programming Description
The CY2XF23 is a programmable device. Before being used in
an application, it must be programmed with the output
frequencies and other variables described in a later section. Two
different device types are available, each with its own
programming flow. They are described in the following sections.
Field Programmable CY2XF23F
Field programmable devices are shipped unprogrammed and
must be programmed before being installed on a printed circuit
board (PCB). Customers use CyberClocks Online Software to
specify the device configuration and generate a JEDEC
(extension .jed) programming file. Programming of samples and
prototype quantities is available using a Cypress programmer.
Third party vendors manufacture programmers for small to large
volume applications. Cypress’s value added distribution partners
also provide programming services. Field programmable
devices are designated with an “F” in the part number. They are
intended for quick prototyping and inventory reduction. The
CY2XF23 is one time programmable (OTP).
Factory Configured CY2XF23
For customers wanting ready-to-use devices, the CY2XF23 is
available with no field programming required. All requests are
submitted to the local Cypress Field Application Engineer (FAE)
or sales representative. After the request is processed, the user
receives a new part number, samples, and data sheet with the
programmed values. This part number is used for additional
sample requests and production orders.
CY2XF23
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