sy89533lhztr Micrel Semiconductor, sy89533lhztr Datasheet - Page 8

• Manufacturer Part Number: sy89533lhztr
• Description: Sy89532/33l 3.3v, Precision, 33mhz To 500mhz Programmable Lvpecl And Lvds Bus Clock Synthesizer
• Manufacturer: Micrel Semiconductor

Micrel, Inc.
precision PLL driven by 14MHz to 18MHz series resonant
crystal. For users who wish to supply a TTL or LVPECL clock
input, please use the SY89534L or SY89535L. The PLL
output is sent to three banks of outputs. Each bank has its own
programmable frequency divider, and the design is optimized
to provide very low skew between banks, and very low jitter.
PLL Programming and Operation
IMPORTANT: If the internal VCO will be used, VCO_SEL
must be tied LOW, and ExtVCO pins can be left unconnected.
feedback ratio is selectable via the MSEL divider control (M3:0
pins). If the designer wishes to use the internal VCO, the
VCO_SEL pin must be tied low. The feedback ratio can be
changed without powering the chip down. The PLL output is
fed to three banks of outputs: Bank A, Bank B, and Bank C.
Banks A and C each have two differential LVPECL output
pairs. Bank B has nine differential output pairs. On the
SY89532L, Bank B is LVPECL. On the SY89533L, Bank B is
LVDS.
be reprogrammed on the fly. The FSEL_x0:2 (where x is A,B,
or C) pins control the divider value. The FSEL divider can be
programmed in ratios from 2 to 18, and the outputs of Banks
A,B, and C can be synchronized after programming by pulsing
the OUT_SYNC pin HIGH-LOW-HIGH.
these steps:
1. Refer to the "Suggested Selections for Specific
2. Determine the desired output frequency, such as
3. Choose a crystal frequency between 14MHz and 18MHz.
4. Refer to the "Feedback Divide Select Table" and the
5. Make sure that XTAL (the crystal frequency) multiplied
frequencies to satisfy these requirements.
M9999-010808
[e-mail] or [phone]
FUNCTIONAL DESCRIPTION
Customer Applications" section for common applications,
as well as the formula used to compute the output
frequency.
66MHz.
In this example, we choose 18MHz for the crystal
frequency. This results in an input/output ratio of 66/18.
"Post-Divide Frequency Select Table" to find values for
MSEL and FSEL such that MSEL/FSEL equals the same
66/18 ratio. In this example, values of MSEL=44 and
FSEL=12 work.
by MSEL is between 600MHz and 1000MHz.
At the core of the SY89532/33L clock synthesizer is a
The internal VCO range is 600MHz to 1000MHz, and the
Each bank has a separate frequency divider circuit that can
To determine the correct settings for SY89532/33L follow
The user may need to experiment with different crystal
8
External VCO Operation
pin can be left floating or tied HIGH, and the external VCO
signal is connected to the ExtVCO differential input pair. The
ExtVCO input structure is designed to accept many popular
logic types. See “Input Interface for ExtVCO Pins” section for
interface diagrams. A SONET OC-48 compliant 622.08MHz
clock is a good example of an application requiring an external
VCO. For this application, use a VCXO to supply the
1244.16MHz. to the ExtVCO pins, and set VCO_SEL to HIGH.
To save power and reduce noise, the internal VCO is shut
down when VCO_SEL is HIGH.
ExtVCO Input Interface
differential or single-ended input signal within 300mV above
V
true or complement inputs to ground, but not both. A logic zero
is achieved by connecting the complement input to ground
with the true input floating. For a TTL input, tie a 2.5k resistor
between the complement input and ground. See “Input Interface
for ExtVCO Pins” section, Figures 5a through 5j.
Input Levels
directly to the ExtVCO inputs. Depending on the actual worst
case voltage seen, the minimum input voltage swing varies as
illustrated in the following table:
CC
If the designer wishes to use an external VCO, the VCO_SEL
The flexible ExtVCO inputs are designed to accept any
Do not leave unused ExtVCO inputs floating. Tie either the
LVDS, CML and HSTL differential signals may be connected
Input Voltage Range
and 300mV below ground.
0 to V
0 to 2.4V
CC
+0.3
Figure 1. Simplified Input Structure
Minimum Voltage Swing
100mV
200mV
Precision Edge
SY89532/33L
®