Document Number: 38-07012 Rev. *K Page 3 of 14
Operation
The CY22381 is an upgrade to the existing CY2081. The new
device has a wider frequency range, greater flexibility, improved
performance, and incorporates many features that reduce PLL
sensitivity to external system issues.
The device has three PLLs that allow each output to operate at
an independent frequencies. These three PLLs are completely
programmable.
The CY223811 is the CY22381 with NiPdAu lead finish.
Configurable PLLs
PLL1 generates a frequency that is equal to the reference
divided by an eight-bit divider (Q) and multiplied by an 11-bit
divider in the PLL feedback loop (P). The output of PLL1 is sent
to the crosspoint switch. The frequency of PLL1 can optionally
be changed by using the external CMOS general purpose input.
See the following section on “General-Purpose Input” for more
detail.
PLL2 generates a frequency that is equal to the reference
divided by an eight-bit divider (Q) and multiplied by an 11-bit
divider in the PLL feedback loop (P). The output of PLL2 is sent
to the crosspoint switch.
PLL3 generates a frequency that is equal to the reference
divided by an eight-bit divider (Q) and multiplied by an 11-bit
divider in the PLL feedback loop (P). The output of PLL3 is sent
to the cross-point switch.
General-Purpose Input
The CY22381 features an output control pin (pin 8) that can be
programmed to control one of four features.
When programmed as a frequency select (FS), the input can
select between two arbitrarily programmed frequency settings.
The frequency select can change the following; the frequency of
PLL1, the output divider of CLKB, and the output divider of
CLKA. Any divider change as a result of switching the FS input
is guaranteed to be glitch free.
The general-purpose input can simultaneously control the
Suspend feature, turning off a set of PLLs and outputs
determined during programming.
When programmed as an output enable (OE) the input forces all
outputs to be placed in a three-state condition when LOW.
When programmed as a Shutdown, the input forces a full chip
shutdown mode when LOW.
Crystal Input
The input crystal oscillator is an important feature of this device
because of its flexibility and performance features.
The oscillator inverter has programmable drive strength. This
allows for maximum compatibility with crystals from various
manufacturers, processes, performances, and qualities.
The input load capacitors are placed on-die to reduce external
component cost. These capacitors are true parallel-plate
capacitors for ultra-linear performance. These were chosen to
reduce the frequency shift that occurs when non-linear load
capacitance interacts with load, bias, supply, and temperature
changes. Non-linear (FET gate) crystal load capacitors must not
be used for MPEG, communications, or other applications that
are sensitive to absolute frequency requirements
The value of the load capacitors is determined by six bits in a
programmable register. The load capacitance can be set with a
Pinouts
Figure 1. 8-pin SOIC pinout
1
2
3
4
5
6
7
8
CLKC
GND
XTALIN
XTALOUT
FS/
SUSPEND/OE/SHUTDOWN
V
DD
CLKA
CLKB
Pin Definitions
Name Pin Number Description
CLKC 1 Configurable clock output C
GND 2 Ground
XTALIN 3 Reference crystal input or external reference clock input
XTALOUT 4 Reference crystal feedback (float if XTALIN is driven by external reference clock)
CLKB 5 Configurable clock output B
CLKA 6 Configurable clock output A
V
DD
7 Power supply
FS/SUSPEND
/
OE/SHUTDOWN
8
General Purpose Input. Can be Frequency Control, Suspend mode control, Output Enable, or
full-chip shutdown.
