Datasheet

Data Sheet AD9559
Rev. C | Page 19 of 120
Pin No. Mnemonic
Input/
Output Pin Type Description
63 XOB I Differential
input
Complementary System Clock Input. Complementary signal to XOA. XOB contains
internal dc biasing and should be ac-coupled with a 0.1 μF capacitor except when
using a crystal. When a crystal is used, connect the crystal across XOA and XOB.
64 XOA I Differential
input
System Clock Input. XOA contains internal dc biasing and should be ac-coupled
with a 0.01 μF capacitor except when using a crystal. When a crystal is used,
connect the crystal across XOA and XOB. Single-ended 1.8 V CMOS is also an option,
but a spur may be introduced if the duty cycle is not 50%. When using XOA as
a single-ended input, connect a 0.1 μF capacitor from XOB to ground.
70
REFB
I
Differential
input
Reference B Input. This internally biased input is typically ac-coupled; when
configured in this manner, it can accept any differential signal with single-ended
swing up to 3.3 V. If dc-coupled, input can be LVPECL, LVDS, or single-ended CMOS.
71
REFB
I Differential
input
Complementary Reference B Input. Complementary signal to the input provided
on Pin 70.
EP GND O Exposed pad The exposed pad is the ground connection on the chip. It must be soldered to the
analog ground of the PCB to ensure proper functionality and heat dissipation,
noise, and mechanical strength benefits.