MAX19792ETX+【PDF 20/23 页】ATTENUATR 46DB 50OHM 4GHZ 36TQFN

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Maxim Integrated

MAX19792

500MHz to 4000MHz Dual Analog Voltage Variable

Attenuator with On-Chip 10-Bit SPI-Controlled DAC

Table 7. Typical Application Circuit

Component Values

Layout Considerations

A properly designed PCB is an essential part of any RF/

microwave circuit. Keep RF signal lines as short as pos-

sible to reduce losses, radiation, and inductance. For best

performance, route the ground-pin traces directly to the

exposed pad underneath the package. This pad MUST

be connected to the ground plane of the board by using

multiple vias under the device to provide the best RF and

thermal conduction path. Solder the exposed pad on the

bottom of the device package to a PCB. Pins 4 and 31

for the MAX19792 have no internal connection. These two

pins are in place to support the MAX19794 part in the fam-

ily. The MAX19794 requires an additional bypass capaci-

tor on each of these pins for proper operation. If desired

to have a common layout to support the MAX19794, then

include these capacitors in the common layout. Refer to

the MAX19794 data sheet for details.

Power-Supply Bypassing

Proper voltage-supply bypassing is essential for high-

frequency circuit stability. Bypass each V

pin with

capacitors placed as close as possible to the device.

Place the smallest capacitor closest to the device. See

the Typical Application Circuit and Table 7 for details.

Exposed Pad RF and

Thermal Considerations

The exposed pad (EP) of the devices 36-pin TQFN pack-

age provides a low thermal-resistance path to the die. It

is important that the PCB on which the IC is mounted be

designed to conduct heat from this contact.

In addition, provide the EP with a low-inductance RF

ground path for the device. The EP must be soldered to

a ground plane on the PCB, either directly or through an

array of plated via holes. Soldering the pad to ground is

also critical for efficient heat transfer. Use a solid ground

plane wherever possible.

*Add two additional 10I series resistors between V

s lead-

ing to C5 and C6, unless a V

power plane is used.

DESIGNATION QTY

DESCRIPTION

C1, C2, C4

22pF Q5%, 50V C0G ceramic

capacitors (0402)

22pF Q5%, 50V C0G ceramic

capacitors (0402)

Not installed for two attenuators

in cascade.

C5C9

1000pF Q5%, 50V C0G ceramic

capacitors (0402)

C12

120pF Q5%, 50V C0G ceramic

capacitor (0402)

Provides some external noise

filtering along with R3.

C13

Not installed, 4.7pF capacitor

could be used to reduce any

potential rise time glitching when

the comparator changes state.

R1, R2

10I Q5% resistors* (0402)

200I Q5% resistor (0402)

Use this resistor to provide some

lowpass noise filtering when used

with C12. The value of R3 slows

down the response time. R3 also

provides protection for the device

in case V

CTRL

is applied without

present.

Maxim MAX19792

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