ADGM1304JCPZ-R2 datasheet(31/34 Pages) AD

31 / 34 page

Data Sheet

ADGM1304

Rev. G | Page 31 of 34

Figure 61 shows the hot switching condition when the switch is

turned off with 10 mA passing through the switch during

switching.

GATE

RF1

RFC

SWITCH IS ON

10mA

GATE

RF1

RFC

SWITCHING FROM ON TO OFF

10mA

NOTES

1. THE PRESENCE OF THE APPLIED SIGNAL DURING

SWITCHING CYCLE DAMAGES THE SWITCH CONTACTS.

DAMAGE AREA

SEE NOTE 1.

Figure 61. Hot Switching Condition When Turning the Switch from On to Off State

FLOATING NODE

The ADGM1304 has no internal impedance to ground, and

charges can develop on the switch terminals, leading to unreliable

switch behavior. To mitigate this behavior, provide a discharge

path to all switch nodes. Figure 62 to Figure 65 show examples

of cases to avoid where floating nodes can occur when using the

switch. Conditions to avoid include the following:

•

Leaving the RFx pins open circuit (see Figure 62).

•

Connecting a series capacitor directly to the switch (see

Figure 63).

•

Connecting the RFx pin of two switches together directly

or connecting the RFC pin to the RFx pin (see Figure 64

and Figure 65).

RFx

RFC

FLOATING

OPEN CIRCUIT

Figure 62. RFx Pins Left Open Circuit

RFx

RFC

FLOATING

Figure 63. Series Capacitor Directly Connected to MEMS Switch

RFx

RFC

FLOATING

RFx

RFC

Figure 64. RFx Pins of Two MEMS Switches Directly Connected

RFx

RFC

FLOATING

RFC

RFx

Figure 65. RFC Connected to RFx

Provide a discharge path to the switch nodes to avoid floating

nodes. In a typical application, a 50 Ω termination connected to

the switch provides this path. Driving switch nodes with a

device of adequate impedance (<10 MΩ) provides a discharge

path. If there is no discharge path in the application circuit, add

a 10 MΩ shunt resistor or inductor on the source RFx pin of

the MEMS switch to provide the discharge path. Note that the

shunt resistors introduce leakage. Figure 66 shows an example

of a configuration providing a discharge path.

RFx

RFC

Figure 66. Switch Configuration Providing a Discharge Path

Figure 67 and Figure 68 illustrate typical cascaded switch use cases

and the corresponding schemes to mitigate floating node risks.

RFC

ADGM1304

RF1

RF2

RF3

RF4

RF1

RF2

RF3

RF4

RFC

Figure 67. Two ADGM1304 Devices Connected in Path Selection

Configuration with 10 MΩ Shunt Resistors to Mitigate Floating Nodes

ADGM1304

RF1

RF2

RF3

RF4

RFC

RF1

RF2

RF3

RF4

RFC

RF1

RF2

RF3

RF4

RFC

Figure 68. Three ADGM1304 Devices Connected in Fanout Configuration

with 10 MΩ Shunt Resistors to Mitigate Floating Nodes

Avoid connecting shunt capacitors directly to the switch. A capa-

citor can store a charge and potentially lead to hot switching

events when the switch opens or closes if there are no alternative

discharge paths. These events affect the cycle lifetime of the switch.

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