AD8432ACPZ-R7 datasheet(27/28 Pages) AD

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AD8432

Rev. 0 | Page 27 of 28

POWER SUPPLY

The AD8432 should be powered by a single 5 V supply connected

to the VPOS terminal. Separate supplies can be used for VPS1,

VPS2, and ENB, or they can all be tied to VPOS by shorting

the W3 and W4 headers and the S1 switch. Ferrite beads and

decoupling capacitors are installed for isolation, protection, and

power supply noise reduction.

INPUT TERMINATION

Active input impedance matching can be realized by installing

a feedback resistor (RFB), the value of which is determined by

the gain and source impedance, as described in the Theory of

Operation section. CFB provides the necessary ac coupling

between the input and output when using active termination;

a 0.1 μF capacitor value is recommended. The RFB and CFB network

presents a load to OPL, and an equivalent load at OPH can be

used to balance the differential output.

Input clamping diodes (IND1 and IND2) can be connected to the

inputs, by shorting the connection on the W1 and W2 headers.

The diodes provide overvoltage protection to the input and

enable faster overdrive recovery times, especially at the lowest

gain (12.04 dB).

OUTPUT

The AD8432 evaluation board provides the space to configure

the output loading conditions required by the user, by populating

the given footprints (for example, RL1, RL2, C7, and C8). SMA

connectors are available at the outputs, and space for a transformer

is also available for differential-to-single-ended conversion.

The 4-pin headers, PRB3 and PRB4, are placed close to the AD8432,

and they provide a way for monitoring the differential output or

the single-ended output using a high impedance differential probe.

The two inner pins of the headers are connected to OPL/OPH,

and the two outer pins of the headers are connected to ground.

There are several footprints provided to install ac coupling

capacitors at the outputs (C7 to C14). The AD8432 outputs are

biased internally at 2.5 V. To maintain the dc bias level, use coupling

capacitors between the outputs and the load.

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