Data Sheet

HMC8038

Rev. A | Page 9 of 11

THEORY OF OPERATION

The HMC8038 requires a single-supply voltage applied to the

line to minimize RF coupling.

The HMC8038 is controlled via two digital control voltages

capacitor is recommended on these digital signal lines to

improve the RF signal isolation.

The HMC8038 is internally matched to 50 Ω at the RF input

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

no external matching components are required. The RFx pins

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

RF lines. The design is bidirectional; the input and outputs are

interchangeable.

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 are not important. Powering the digital

forward bias and damage ESD protection structures.

4. Power up the RF input.

With the EN pin is logic low, the HMC8038 has two operation

modes: on and off. Depending on the logic level applied to the

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

input to the output, as the other RF output port (for example,

RF2) is set to off mode, by which the output is isolated from the

input. When the RF output port (RF1 or RF2) is in isolation

mode, internally terminate it to 50 Ω, and the port absorbs the

applied RF signal.

When the EN pin is logic high, the EN pin sets the HMC8038

switch to off mode. In off mode, both output ports are isolated

from the input, and the RFC port is open reflective.

Table 7. Switch Operation Mode

Digital Control Inputs

Switch Mode

RFC to RF1

RFC to RF2

0

0

Off mode. The RF1 port is isolated from the RFC port and

is internally terminated to a 50 Ω load to absorb the

applied RF signals.

On mode. A low insertion loss path from the RFC

port to the RF2 port.

0

1

On mode. A low insertion loss path from the RFC port to

the RF1 port.

Off mode. The RF2 port is isolated from the RFC port

and is internally terminated to a 50 Ω load to absorb

the applied RF signals.

1

All in off mode. Both the RF1 and RF2 ports are isolated from the RFC port, and the RFC port is reflective.

1

X stands for don’t care.