AD9632 datasheet(17/20 Pages) AD

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AD9631/AD9632

REV. A

–17–

–V

OUT

1000pF

0.1

µF

1000pF

0.1

µF

–V

OPTIONAL

–V

OUT

Inverting Configuration

Noninverting Configuration

Supply Bypassing

Figure 65. Inverting and Noninverting Configurations for

Evaluation Boards

Table I.

AD9631A

AD9632A

Gain

Component

–1

+10

+100

–1

+10

+100

274

Ω

140

Ω

274

Ω

2 k

Ω

2 k

Ω

274

Ω

274

Ω

2 k

Ω

2 k

Ω

274

Ω

274

Ω

221

Ω

20.5

Ω

274

Ω

274

Ω

221

Ω

20.5

Ω

RO (Nominal)

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

100

Ω

100

Ω

49.9

Ω

49.9

Ω

100

Ω

130

Ω

100

Ω

100

Ω

100

Ω

100

Ω

100

Ω

100

Ω

100

Ω

RT (Nominal)

61.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

61.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

Small Signal

BW (MHz)

320

1.3

250

Layout Considerations

The specified high speed performance of the AD9631 and

AD9632 requires careful attention to board layout and compo-

nent selection. Proper RF design techniques and low pass para-

sitic component selection are mandatory.

The PCB should have a ground plane covering all unused por-

tions of the component side of the board to provide a low im-

pedance path. The ground plane should be removed from the

area near the input pins to reduce stray capacitance.

Chip capacitors should be used for the supply bypassing (see

Figure 64). One end should be connected to the ground plane

and the other within 1/8 inch of each power pin. An additional

large (0.47

µF–10 µF) tantalum electrolytic capacitor should be

connected in parallel, though not necessarily so close, to supply

current for fast, large signal changes at the output.

The feedback resistor should be located close to the inverting

input pin in order to keep the stray capacitance at this node to a

minimum. Capacitance variations of less than 1 pF at the in-

verting input will significantly affect high speed performance.

Stripline design techniques should be used for long signal traces

(greater than about 1 inch). These should be designed with a

characteristic impedance of 50

Ω or 75 Ω and be properly termi-

nated at each end.

Evaluation Board

An evaluation board for both the AD9631 and AD9632 is avail-

able that has been carefully laid out and tested to demonstrate

that the specified high speed performance of the device can be

realized. For ordering information, please refer to the Ordering

Guide.

The layout of the evaluation board can be used as shown or

serve as a guide for a board layout.

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