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AD6411 Folha de dados(PDF) 10 Page - Analog Devices |
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AD6411 Folha de dados(HTML) 10 Page - Analog Devices |
10 / 11 page AD6411 –10– REV. 0 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. 2pF 20k 20k 8.2pF 8.2pF 10k BAR80 BAR63-03W 2k L1 6.8pF 1nF 6.8k 2k 330pF 10k 10k 1.2pF 2pF VCCVCO VCOB BSW VCO LF AD6411 TX DATA IN 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. REGULATOR #1 REGULATOR #2 10nF 10nF VBAT VBAT 10nF 10pF 1nF PASS TRANSISTORS: BCW68F OR EQUIVALENT TO PIN 40 (VCOB) AD6411 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. FROM PA BAR63-03W ANT 50 27nH 47pF 470pF TX/RX 1=TX 0=RX TO RX IN BAR80 /4 Figure 7. T/R Switch |
Nº de peça semelhante - AD6411 |
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Descrição semelhante - AD6411 |
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