Applications Information

Precautions must be taken to minimize RF coupling

through the IC.

Shutdown Modes

At power-up, the device initializes in total shutdown

mode. The digital interface is always active. Table 2

describes the various power modes available.

When the PGA is not on (in shutdown, standby, or

receive mode, or when PKWDW is low), the PS input

pins (RPS, FPS1, FPS2) are pulled down to ground. To

minimize RF coupling, the unselected channels are

also pulled down to ground when the circuit is active.

The current source and the 1.87V PSBIAS voltage gen-

erator are turned on only when the device is performing

the transmit power-sense measurement.

Power-Supply Bypassing and

Ground Management

Optimum system performance is obtained with printed

circuit boards that use separate analog and digital

ground planes. Wire-wrap boards are not recommend-

ed. The two ground planes should be connected

together at the low-impedance power-supply source.

DGND. Ferrite beads may also be used to further iso-

late the analog and digital power supplies.

Mobile-Radio Analog Controller

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11

ADCCTRL

RSSI

RPS

FPS1

FPS2

PSBIAS

PSDWDW

BANT

OLD DATA

VALID

Figure 4c. Power-Sense/Best-Antenna Detailed Interface

RxEN,

TxEN

DESCRIPTION

0 0

Total shutdown

0 1

Transmit mode, all DACs enabled

1 0

Receive mode, SDAC and GDAC outputs disabled

1 1

Standby: REF, GDAC, and XDAC enabled. Rest of

IC is shut down.

Table 2. Power Modes

CS

SCLK

DIN

START A2

A1

A0 RxEN

COMMAND BYTE

TxEN SD

LD

D7

D6

D5

D4

D3

D2

D1

D0

CS

SCLK

DIN

START A2

A1

A0 RxEN TxEN SD

LD

DOUT

WRITE

READ

D7

D6

D5

D4

D3

D2

D1

D0

COMMAND BYTE

Figure 4d. Serial-Interface Timing