Data Sheet

ADRF5549

Rev. A | Page 13 of 15

THEORY OF OPERATION

The ADRF5549 requires a positive supply voltage applied to

VDD1-ChA, VDD2-ChA, VDD1-ChB, VDD2-ChB, and

SWVDD-ChAB. Use bypassing capacitors on the supply lines

to filter noise and use 300 Ω series resistors on the BP-Chx and

PD-ChAB digital control pins for glitch and overcurrent

protection.

SIGNAL PATH SELECT

When SWCTRL-ChAB is set to high, the ADRF5549 supports

transmit operations. During this operation, when applying an

RF input to ANT-ChA and ANT-ChB, the signal paths connect

from ANT-ChA to TERM-ChA and from ANT-ChB to TERM-

ChB.

When SWCTRL-ChAB is set to low, the ADRF5549 supports

receive operations. During this operation, applying an RF input

at ANT-ChA and ANT-ChB connects ANT-ChA to RxOUT-

ChA and ANT-ChB to RxOUT-ChB.

Receive Operation

The ADRF5549 supports high gain mode, low gain mode,

power-down high isolation mode, and power-down low

isolation mode during receive operations (see Table 6).

When PD-ChAB is set to low, the LNA powers up and the user

can select high gain mode or low gain mode. To select high gain

mode, set BP-ChA or BP-ChB to low. To select low gain mode,

set BP-ChA or BP-ChB to high.

When PD-ChAB is set to high, the ADRF5549 enters power-

down mode. To select power-down high isolation mode, set

BP-ChA or BP-ChB to low. To select power-down low isolation

mode, set BP-ChA or BP-ChB to high.

BIASING SEQUENCE

To power-up the ADRF5549, perform the following steps:

1. Connect GND to ground.

2. Power up VDD1-ChA, VDD2-ChA, VDD1-ChB, VDD2-

ChB, and SWVDD-ChAB.

3. Power up SWCTRL-ChAB.

4. Power up PD-ChAB.

5. Power up BP-ChA and BP-ChB.

6. Apply an RF input signal to ANT-ChA and ANT-ChB.

To power-down the device, perform these steps in the reverse

order.

Table 5. Truth Table: Signal Path

SWCTRL-ChAB

Transmit Operation

Receive Operation

Low

Off

On

High

On

Off

1

See the signal path descriptions in Table 6.

Table 6. Truth Table: Receive Operation, SWCTRL-CHAB=Low

Operation and Mode

PD-ChAB

BP-ChA or BP-ChB

Signal Path

Receive Operation

ANT-ChA to RxOUT-ChA or ANT-ChB to RxOUT-ChB

High Gain Mode

Low

Low

Low Gain Mode

Low

High

Power-Down High Isolation Mode

High

Low

Power-Down Low Isolation Mode

High

High