UniClock CY22U1

Document Number: 001-50320 Rev. *E

Page 4 of 15

Multiple VDD Power Supply Option

The device has programmable power supply options. The

operating supply voltages are 2.5 V, 3.0 V, or 3.3 V for CY22U1S

and 1.8 V for CY22U1L.

Power Management Feature

The UniClock CY22U1 offers PD# (active LOW) and OE (active

HIGH) functions. When the power down mode is selected

(PD# = 0), the oscillator and PLL are placed in a low supply

current standby mode and the output is tristated and weakly

pulled LOW. The oscillator and PLL circuits must relock when the

part exits the power down mode. If the output is disabled

(OE = 0), the output is tristated and weakly pulled LOW. In this

mode, the oscillator and PLL circuits continue to operate, which

enables a rapid return to normal operation when the output is

enabled.

I

n addition, the PD# or OE mode can be programmed to occur

asynchronously or synchronously with respect to the output

signal. When the asynchronous setting is used, entering power

down or disabling the output occurs immediately (enabling logic

delays), regardless of the position in the clock cycle. Similarly,

exiting power down or enabling the output occurs immediately

with no guarantee of full output clock pulses. However, when the

synchronous setting is used, the part waits for a falling edge at

the output before entering power down or disabling the output.

This prevents output glitches. The first output pulse is

guaranteed to be a full clock pulse when enabling outputs with a

synchronous OE pin. The first output pulse is not guaranteed to

be a full clock when exiting power down in synchronous or

asynchronous mode.

Output Frequency Tuning

The UniClock CY22U1 contains an on-chip oscillator with a built

in programmable capacitor array for fine tuning of the output

frequency. The capacitive load seen by the crystal is adjusted by

programming the memory bits. This feature can compensate for

crystal variations or provide a more accurate synthesized

frequency. Figure 2 shows the crystal oscillator tuning circuit

block diagram.

Crystal Oscillator Tuning Circuit

Figure 2. Crystal Oscillator Tuning Block Diagram

Table 1. Crystal Oscillator Tuning Capacitor Values

Cap

Value [1]

Unit

5.000

pF

2.500

pF

1.250

pF

0.625

pF

0.313

pF

0.156

pF

0.078

pF

0.039

pF

X7

-R

X6

X5

X4

X3

X2

X1

X7

X6

X5

X4

X3

X2

X1

X0

X0

Note

1. The capacitor values are nominal.