MC13201 Technical Data, Rev. 1.1,

22

Freescale Semiconductor

8.5.1

Single Port Operation

The integrated RF switch allows users to operate in a single port configuration. In Single Port Mode, an

internal RX switch and separate PA are used and pins RFIN_P (PAO_P) and RFIN_M (PAO_M) become

bidirectional and connect both for TX and RX. When receiving, the RX switch is enabled to the internal

LNA and the TX PA is disabled. When transmitting, the RX switch is disabled (isolating the LNA) and a

TX PA is enabled. The optional CT_Bias pin provides a reference or bias voltage which is at VDDA for

transmit and is at ground for receive. This signal can be used to provide the proper bias voltage to a balun

that converts a single-ended antenna to the differential interface required by the transceiver.

Figure 13. Single Port RF Operation with a Balun

Figure 13 shows a single port example with a balun. The CT_Bias is connected to the balun center-tap

providing the proper DC bias voltage to the balun depending on RX or TX.

8.5.2

Dual Port Operation

A second set of pins designated PAO_P and PAO_N allow operation in a dual port configuration. There

are separate paths for transmit and receive with the optional CT_Bias pin providing a signal that indicates

if the radio is in TX or RX Mode which then can be used to drive an external low noise amplifier, power

amplifier, or antenna switch.

In dual port operation, the RFIN_P and RFIN_N are inputs only, the internal RX switch to the LNA is

enabled to receive, and the associated TX PA stays disabled. Pins PAO_P and PAO_N become the

differential output pins and the associated TX PA is enabled for transmit.

Figure 14 shows two dual port configurations. First is a single antenna configuration with an external low

noise amplifier (LNA) for greater range. An external antenna switch is used to multiplex the antenna

between receive and transmit. An LNA is in the receive path to add gain for greater receive sensitivity.

Two external baluns are required to convert the single-ended antenna switch signals to the differential

signals required by the radio. Separate RFIN and PAO signals are provided for connection with the baluns,

and the CT_bias signal is programmed to provide the external switch control. The polarity of the external

switch control is selectable.

Balun

Bypass

RFIN_P (PAO_P)

RFIN_M (PAO_M)

CT_Bia

s

PAO_P

PAO_M

MC13201