mk1709 Integrated Device Technology, mk1709 Datasheet - Page 4

• Manufacturer Part Number: mk1709
• Description: Low Emi Clock Generator
• Manufacturer: Integrated Device Technology

External Components
The MK1709 requires a minimum number of external
components for proper operation.
Decoupling Capacitor
A decoupling capacitor of 0.01µF must be connected
between VDD and GND on pins 2 and 3 for the MK1709S,
or pins 1 and 8 for the MK1709AG. Place the capacitor as
close to these pins as possible. For optimum device
performance, the decoupling capacitor should be mounted
on the component side of the PCB. Avoid the use of vias in
the decoupling circuit.
Series Termination Resistor
When the PCB trace between the clock output and the load
is over 1 inch, series termination should be used. To series
terminate a 50Ω trace (a commonly used trace impedance),
place a 33Ω resistor in series with the clock line, as close to
the clock output pin as possible. The nominal impedance of
the clock output is 20Ω.
Select Pin Operation
The S1, S0 select pins are 2-level, meaning they have three
separate states to make the selections shown in the table on
page 2.
PCB layout Recommendations
For optimum device performance and lowest output phase
noise, the following guidelines should be observed.
1) The 0.01µF decoupling capacitor should be mounted on
the component side of the board as close to the VDD pin as
possible. No vias should be used between the decoupling
capacitor and VDD pin. The PCB trace to VDD pin should
be kept as short as possible, as should the PCB trace to the
ground via.
2) Place a 33Ω series termination resistor (if needed) close
to the clock output to minimize EMI.
3) An optimum layout is one with all components on the
same side of the board, minimizing vias through other signal
layers. Other signal traces should be routed away from the
MK1709. This includes signal traces just underneath the
device, or on layers adjacent to the ground plane layer used
by the device.
IDT™ / ICS™ LOW EMI CLOCK GENERATOR
MK1709
LOW EMI CLOCK GENERATOR
4
MK1709
REV H 070506
SSCG