ICS1574B

6

Figure 4

Power Supplies and Decoupling

The ICS1574B has two VSS pins to reduce the effects of

package inductance. Both pins are connected to the same

potential on the die (the ground bus). BOTH of these pins

should connect to the ground plane of the PCB as close to

the package as is possible.

The ICS1574B has a VDDO pin which is the supply of +5

volt power to the output driver. This pin should be con-

nected to the power plane (or bus) using standard

high-frequency decoupling practice. That is, capacitors

should have low series inductance and be mounted close to

the ICS1574B.

The VDD pin is the power supply pin for the PLL synthe-

sizer circuitry and other lower current digital functions.

We recommend that RC decoupling or zener regulation be

provided for this pin (as shown in the recommended appli-

cation circuitry). This will allow the PLL to “track”

through power supply fluctuations without visible effects.

See Figure 4 for typical external circuitry.