TEA5777 NXP Semiconductors, TEA5777 Datasheet - Page 11

• Manufacturer Part Number: TEA5777
• Manufacturer: NXP Semiconductors

Specifications of TEA5777

• Lead Free Status / Rohs Status: Supplier Unconfirmed

Philips Semiconductors
TEA5777_1
Product data sheet
8.1.1 AM RF amplifier
8.1.2 Tuning AM antenna circuit
8.1.3 AM I/Q mixer
8.1.4 AM VCO
8.1 AM radio part
Bus communication:
The AM input pin AMRFIN has a (selectable) high-impedance input. The input is intended
to be connected to the top of a tuned circuit. The input impedance is determined by the
LNA gain (bit LNA) and the value of the LNA feedback resistor (bit RFB).
For large RF input signals, the RF AGC reduces the input signal level to the AM front end
in order to prevent overloading. The required AM RF AGC time constant is created by
means of an internal current source and the capacitor connected to pin
PILDET/AMRFAGC. During search operation the response time of this RF AGC circuit
can be speeded up via the bus control by bit AGCRF.
The tuning capacitor for the AM antenna circuit has been integrated by means of a
capacitor bank (C-bank) and the tuning frequency can be programmed in discrete steps
via the bus. No external varactor diode is required. In order to match the capacitor bank to
the external AM antenna coil, a provision has been made to electronically align the IC to
the AM antenna. For this bit CALLIGN has to be set to logic 1 and the corresponding bits
C[6:0] have to be programmed. After this alignment bit CALLIGN should be set to logic 0
again to freeze the alignment capacitor value and to enable the control over the main
capacitor bank again.
For more details on the alignment, see
For LW mode an external capacitor needs to be added in parallel to the LW coil.
AM quadrature mixers, in an orthogonal architecture, convert AM RF signals to the
internal f
The fully integrated VCO provides the local oscillator signals for the AM quadrature
mixers. No external components are required.
The internal VCO frequency ranges from 4 MHz to 14 MHz and the proper divider ratio is
chosen by selecting the MW or LW band via the bus control bit MWLW.
Programming of the VCO is done:
•
•
•
•
Bus communication takes place via the I
of the bus mode is done by hardware programming via pin BUSMODE
4-bit ADC level information, 1-bit IF counter and mono or stereo indication (in FM
mode) can be read via the bus. Alternatively, the mono or stereo and the IF in-window
indication can be obtained via silent readout via the bus lines CLOCK and DATA
For MW: f
For LW: f
IF
= 21 kHz. The mixer architecture provides inherent image rejection.
VCO
VCO
= 32
= 8
Rev. 01 — 11 April 2006
(f
(f
RF
RF
Low-power AM/FM stereo radio for handheld applications
f
IF
f
IF
)
)
Section 13.1
2
C-bus or the 3-wire bus protocol. Selection
and the application note.
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
TEA5777
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