ADGM1304JCPZ-R2 datasheet(28/34 Pages) AD

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ADGM1304

Data Sheet

Rev. G | Page 28 of 34

APPLICATIONS INFORMATION

POWER SUPPLY RAILS

It is recommended that a 0.1 µF decoupling capacitor be added

to the power supply port of the ADGM1304.

The ADGM1304 can operate with unipolar supplies between

3.0 V and 3.6 V.

The device is fully specified at a 3.3 V analog supply voltage.

POWER SUPPLY RECOMMENDATIONS

Analog Devices has a wide range of power management

products to meet the requirements of most high performance

signal chains.

An example of a unipolar power solution for the ADGM1304 is

shown in Figure 55. The ADP7142 is a low dropout linear

regulator that operates from 2.7 V to 40 V and is ideal for

regulation of high performance analog and mixed-signal

circuits operating from 39 V down to 1.2 V rails. The ADP7142

has 11 µV rms output noise independent of the output voltage.

The ADP7142 can be used to power the supply rail for the

ADGM1304, a microcontroller, and/or other devices in the

signal chain.

ADP7142

LDO

ADGM1304

3.3V

INPUT

Figure 55. Unipolar Power Solution

If low noise performance at the power supply is required, the

ADP7142 can be replaced by the LT1962 or the LT3045-1.

Table 7. Recommended Power Management Devices

Product

Description

ADP7142

40 V, 200 mA, low noise, CMOS LDO linear regulator

LT1962

300 mA, low noise, micropower, LDO regulator

LT3045-1

20 V, 500 mA, ultralow noise, ultrahigh PSRR linear

regulator with VIOC control

SWITCHABLE RF ATTENUATOR

It is common to see RF attenuator networks used in RF instru-

mentation equipment such as vector network analyzers, spectrum

analyzers, and signal generators. Routing RF signals through an

attenuator enables the equipment to accept higher power

signals and increase the dynamic range of the instrument. In RF

attenuation applications like the vector network analyzers,

spectrum analyzers, and signal generators, maintaining the

bandwidth of the signal after it passes through the network is

critical. Any degradation of the signal reduces the performance

of the equipment. Therefore, the RF characteristics of the

switches used for routing are integral to the quality of an

attenuator network.

The ADGM1304 MEMS switch is suited for use as a switchable

RF attenuator due to its low flat insertion loss, very wide RF band-

width, and high reliability. The ADGM1304, as an SP4T switch,

also provides added flexibility. Figure 56 shows an example atten-

uation network configuration using two ADGM1304 switches

and three different attenuators. The fourth channel of the switches

is used as a nonattenuated route.

15dB

10dB

I/O

ADGM1304

5dB

I/O

ADGM1304

Figure 56. Switching RF Attenuators Using ADGM1304 MEMS Switches

RECONFIGURABLE RF FILTER

A reconfigurable RF filter is advantageous in many RF front-

end applications. A reconfigurable RF filter provides more

saved space. As space becomes more constrained in applications,

it is useful to have the option of using an economical

reconfigurable RF filter instead of individual frequency

dependent filters.

The ADGM1304 has low flat insertion loss, very wide RF band-

width, low parasitic, low capacitance, and high linearity, and as

such, is needed to turn on the lump components (capacitor and

inductor). As such, the MEMS switch is suited for

reconfigurable filter application.

In applications such as wireless communications or mobile radios,

the number of bands and modes constantly increases. A recon-

figurable RF filter allows more bands and modes to be covered

using the same components.

Figure 57 shows an example of a reconfigurable band-pass

filter. The topology shown is of a generalized two section,

inductively coupled, single-ended band-pass filter that is

nominally centered on 400 MHz (ultrahigh frequency (UHF)

band). The MEMS switches are positioned in series with each

of the shunt inductors.

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