UG-422
Evaluation Board User Guide
Rev. 0 | Page 4 of 8
EVALUATION BOARD HARDWARE
POWER SUPPLIES
Power is applied to the board through test pins +V
S
and −V
S
(see Figure 3). The board accommodates single or dual supplies.
For single-supply operation, connect the negative supply to the
ground plane.
It is very important that the power supply pins of the device
under test (DUT) have a broadband decoupling circuitry. The
board layout facilitates this with footprints for a 0603 ceramic
capacitor (C1 and C2) on each supply. Bulk decoupling is
provided by C3 and C4; 10 µF tantalum capacitors are
recommended.
VOCM INPUT
To set the output common-mode voltage of the
AD8476
, an
external voltage can be applied to VOCM via J3 (referenced
to the ground plane of the board) or the VOCM test point. In
ADC driving applications, it is convenient to apply the ADC
dc reference voltage output directly to J3. A 0.1 μF capacitor
(C5) is used in normal applications to provide bypassing for
the dc voltage applied to the VOCM pin.
VOCM can also be left unconnected. The
AD8476
internally
sets the output common-mode to mid-supply.
SMB INPUT/OUTPUT CONNECTORS
The inputs and outputs have through-hole SMB connector
footprints (which are compatible with most SMA connector
footprints) for convenient connection to coaxial cables. The
recommended connector type is Johnson Components™,
Part Number 131-0701-371 (jack) and 131-1801-371 (plug),
or equivalent.
