TUA6041 INFINEON [Infineon Technologies AG], TUA6041 Datasheet - Page 22

• Manufacturer Part Number: TUA6041
• Description: Low Power 3-Band Digital TV / Portable Tuner IC with Digital Alignment
• Manufacturer: INFINEON [Infineon Technologies AG]

3.4
3.4.1
The mixer-oscillator block includes three balanced mixers (one mixer with an unbalanced
high-impedance input and two mixers with a balanced low-impedance input), two 2-pin
asymmetrical oscillators for the LOW and the MID band, one 4-pin symmetrical oscillator
for the HIGH band, a reference voltage, and a band switch.
Filters between tuner input and IC separate the TV frequency signals into three bands.
The band switching in the tuner front-end is done by using three PNP port outputs. In the
selected band, the signal passes through a tuner input stage with a MOSFET amplifier,
a double-tuned bandpass filter and is finally fed to the mixer input of the IC. The
impedance of the mixer at LOW band has high ohmic, while MID or HIGH band has a
low ohmic input. The input signal is mixed there with the signal from the activated on chip
oscillator to the IF frequency.
The IF is filtered by means of an external SAW filter (Surface Acoustic Waves filter) in
between the 2 mixer output pins and the 2 input pins of the following SAW filter driver.
The SAW filter driver has a low output impedance to drive the SAW filter directly.
3.4.2
The RF AGC stage combines a wide band and a narrow band detection. The wide band
detector (WB) detects the input signal directly at the RF input for each band. The narrow
band detector (NB) detects the level of the SAW filter driver output signal. If both
detected levels are below the RF AGC take-over points, a external capacity will be
charged with the source current of 300 nA or 9 µA (release current). If one of the
detected levels is above the RF AGC take-over points, the external capacity will be
discharged with the sink current of 100 µA (attack current). The integrated current
generates an AGC voltage for gain control of the tuners input transistors. The AGC take-
over and the time constant are selectable by the I
"Subaddress 03H, AGC Control and IF Signal Processing Control" on Page
An integrated RF AGC buffer allows to monitor the AGC voltage without any influence
on the tuner gain control. This buffer can be disabled as shown in
"Subaddress 02H, Reference Divider R and Crystal Oscillator Control" on Page 51
3.4.3
Coming out of the SAW filter the IF signal is sent through a VGA (Variable Gain Amplifier)
which will set the differential IF output signal to the desired level (preferably 1 Vpp). The
gain of the VGA is determined by the DC-voltage at pin IFAMPAGC
Data Sheet
Circuit Description
Mixer-Oscillator-block, SAW filter driver
RF AGC
IF AGC amplifier
22
2
C bus as shown in
Functional Description
Revision 3.1, 2006-12-19
LIGHTNING
TUA 6041-2
Table 17
Table 16
53.