BGA430 datasheet(7/24 Pages) INFINEON

7 / 24 page

AN 074 Rev E

7 / 24

19-November-2002

Applications Note No. 074

Silicon Discretes

reverse isolation. Note that all of these results

are taken in a 50 ohm system, and that results in

a 75 ohm system will differ slightly.

Circuit Design Issues Relevant to BGA430:

1) proper device grounding !!

2) proper bypassing of the VCC pin !

The BGA430 is an extremely high gain device

(>30 dB @ 1 GHz) contained within a single

SMT package. As a result, casual or sloppy

PCB layout techniques which add undesired

parasitic inductance between BGA430 ground

leads and PCB ground plane will add enough

feedback to adversely alter the BGA430’s gain

and return loss.

In cases of extremely poor

grounding, sufficient feedback will be present to

enable either gain “peaking” or even an

oscillation. In addition, the VCC pin (Pin 1) needs

to be bypassed with a capacitor that, with its

self-inductance

taken

into

account,

approximates a short-circuit in the 1 to 2 GHz

range. Generally a 0603 or 0402 case-size chip

capacitor in the range of 15 – 22 pF is sufficient.

A photo of a bare I.F. Amp PC board is shown in

Figure 10, with a close-in view of the BGA430

mounting area. Note that seven (7) ground vias

are provided for the BGA430 ground pins,

including three ground vias located immediately

underneath the device. Note the two ground

holes provided for the bypass capacitor C2

(22pF) on the BGA430 VCC pin, and the close

proximity of C2 to the VCC pin.

To summarize:

• The user must avoid any additional parasitic

ground inductance between BGA430 ground

pins and PCB ground plane.

A sufficient

number of ground vias need to be provided

and these vias should be placed as close to

the BGA430 as possible.

• BGA430 VCC pin (Pin 1) must be bypassed

carefully, and the bypass capacitor used

must have its “cold” side well-grounded.

If these two suggestions are carefully followed, a

low-cost, single device solution may be used for

some I.F. amplifier designs, requiring only 3

external elements.

Figure 10. BGA430 Mounting Position on PC

Board.

Compare unpopulated (above) to

populated (below) PCB images.

Note

locations and number of ground vias near

BGA430 MMIC. Pin 1 (VCC) is pad at lower left.

It needs to be pointed out that the BGA430 is

designed to operate at a nominal supply voltage

of +5 volts, with a current draw of approximately

23mA. However, if a higher output compression

point is desired, the BGA430 may be safely run

up to 6.5 volts, and maximum safe current is

35mA. If an adjustable output voltage regulator

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