AD6411AST データシートの表示（PDF） - Analog Devices

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AD6411AST

DECT RF Transceiver

Analog Devices 

AD6411

UHF VCO Tank Circuit

The UHF VCO is probably the most critical part of an AD6411-

based DECT radio. The design shown in Figure 5 uses a

printed inductor, a BBY53 (or equivalent) common-cathode

dual varactor, and a PIN-diode (BAR63-03W or equivalent)

band switch to cover the DECT band. The capacitance added

to the tank circuit by the PIN-diode is needed to switch the VCO

to the DECT receive band. It is switched out of the circuit in the

transmit mode, in which the VCO is directly modulated by

baseband transmit data. With this scheme, no manufacturing

trim is needed to tune the VCO to the DECT band. Tank com-

ponent values will need slight modification to cover the “ex-

tended DECT” frequency bands. The dimensions of tank

inductor L1 will depend on the circuit board material and thick-

ness used. Contact Analog Devices for assistance on UHF tank

inductor layout.

VCCVCO

VCOB

BSW

AD6411

VCO

2k⍀

BAR63-03W

2k⍀ 2pF

2pF

1.2pF

8.2pF

10k⍀

L1

BAR80

8.2pF 20k⍀

20k⍀

10k⍀

LF

6.8k⍀

1nF

10k⍀

330pF

6.8pF

TX

DATA

IN

AD6411

VBAT

10nF

REGULATOR #1

REGULATOR #2

10nF

VBAT

10nF

10pF

1nF

TO PIN 40 (VCOB)

PASS TRANSISTORS: BCW68F OR EQUIVALENT

Figure 6. Voltage Regulator Circuitry

Transmit/Receive Switching

Since the same antenna is used for both transmit and receive, a

switch consisting of PIN diodes and printed transmission lines is

used to disconnect the receive path from the antenna during

transmit periods. A suggested circuit is shown in Figure 7.

Complete details can be found in Siemens Application Note

No. 007.

ANT

FROM PA

BAR63-03W

27nH

47pF

470pF

50⍀

␭/4

TO RX IN

BAR80

Figure 5. UHF VCO Circuit

Power Management

The AD6411 reduces the external components needed for

power management in a DECT radio by integrating voltage

regulators on-chip. The circuit can therefore operate directly

from a 3.0 V to 5.5 V unregulated battery supply.

There are two regulators. The first, VS1 (Pins 20, 21 and 23),

uses an external BCW68F (or similar) PNP pass transistor to

provide a regulated 2.75 V nominal supply voltage to most of

the AD6411 circuitry. The second regulator, VS2 (Pins 41, 44,

and 45), is intended to provide the regulated voltage to the

UHF VCO section and should not be used for other circuitry.

TX/RX

1=TX

0=RX

Figure 7. T/R Switch

–10–

REV. 0

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