Data Sheet

HMC7992

Rev. 0 | Page 11 of 13

THEORY OF OPERATION

The HMC7992 requires a single positive supply voltage applied

supply line to minimize RF coupling.

The HMC7992 integrates with an internal 2:4 decoder; the four

RF paths are selected via the two digital control voltages applied

to the A and B control inputs. A small value bypassing capacitor

is recommended on these digital signal lines to improve the RF

signal isolation.

The HMC7992 is internally matched to 50 Ω at the RF common

port (RFC) and the RF ports (RF1, RF2, RF3, and RF4); therefore,

no external matching components are required. The RF pins are

dc-coupled and dc blocking capacitors are required on the RF

paths. The design is bidirectional; the RF input signals can apply

at the RFC port or the RF1 to RF4 ports. The inputs and outputs

are interchangeable.

Depending on the logic level applied to the control input pins,

A and B, one RF output port (for example, RF1) is set to on

mode, by which an insertion loss path is provided from the

input to the output. The other RF output ports (for example,

RF2, RF3, and RF4) are then set to off mode, by which the

outputs are isolated from the input. When the RF output ports

(RF1, RF2, RF3, and RF4) are in isolation mode, they are

internally terminated to 50 Ω, and thereby can absorb the

applied RF signal.

The ideal power-up sequence is as follows:

1. Power up GND.

3. Power up the digital control inputs. The relative order of

the logic control inputs is not important. Powering the

forward bias and damage the internal ESD protection

structures.

4. Apply the RF input.

Table 7. Switch Mode Operation

Digital Control Inputs

Signal Mode

A

B

RFC to RFx

Low

Low

RF Port 1 is in on mode, providing a low insertion loss path from the RFC port to the RF1 port. The remaining RF

ports (RF2, RF3, and RF4) are in off mode; they are isolated from the RFC port and internally terminated to a 50 Ω load.

High

Low

RF Port 2 is in on mode, providing a low insertion loss path from the RFC port to the RF2 port. The remaining RF

ports (RF1, RF3, and RF4) are in off mode; they are isolated from the RFC port and internally terminated to a 50 Ω load.

Low

High

RF Port 3 is in on mode, providing a low insertion loss path from the RFC port to the RF3 port. The remaining RF

ports (RF1, RF2, and RF4) are in off mode; they are isolated from the RFC port and internally terminated to a 50 Ω load.

High

High

RF Port 4 is in on mode, providing a low insertion loss path from the RFC port to the RF4 port. The remaining RF

ports (RF1, RF2, and RF3) are in off mode; they are isolated from the RFC port and internally terminated to a 50 Ω load.