TDA5252G2 Datasheet, PDF (18/86 Pages) Infineon Technologies AG – ASK/FSK 915MHz Wireless Transceiver

2.4
Functional Block Description
TDA5252 G2
Version 1.1
Functional Description
2.4.1 Power Amplifier (PA)
The power amplifier is operating in C-mode. It can be used in either high or low power mode. In
high-power mode the transmit power is approximately +13dBm into 50 Ohm at 5V and +6dBm at
2.1V supply voltage. In low power mode the transmit power is approximately -3dBm at 5V and
-30dBm at 2.1V supply voltage using the same matching network. The transmit power is controlled
by the D0-bit of the CONFIG register (subaddress 00H) as shown in the following Table 2-2. The
default output power mode is high power mode.
Table 2-2
Bit
D0
Sub Address 00H: CONFIG
Function
Description
PA_PWR
0= low TX Power, 1= high TX Power
Default
1
In case of ASK modulation the power amplifier is turned fully on and off by the transmit baseband
data, i.e. 100% On-Off-Keying.
2.4.2 Low Noise Amplifier (LNA)
The LNA is an on-chip cascode amplifier with a voltage gain of 15 to 20dB and symmetrical inputs.
It is possible to reduce the gain to 0 dB via logic.
Table 2-3
Bit
D4
Sub Address 00H: CONFIG
Function
Description
LNA_GAIN
0= low Gain, 1= high Gain
Default
1
2.4.3 Downconverter 1^st Mixer
The Double Balanced 1^st Mixer converts the input frequency (RF) in the range of 915MHz down to
the intermediate frequency (IF) at approximately 305MHz. The local oscillator frequency is
generated by the PLL synthesizer that is fully implemented on-chip as described in Section 2.4.5.
This local oscillator operates at approximately 1220MHz in receive mode providing the above
mentioned IF frequency of 305MHz. The mixer is followed by a low pass filter with a corner
frequency of approximately 350MHz in order to prevent RF and LO signals from appearing in the
305MHz IF signal.
2.4.4 Downconverter 2^nd I/Q Mixers
The Low pass filter is followed by 2 mixers (inphase I and quadrature Q) that convert the 305MHz
IF signal down to zero-IF. These two mixers are driven by a signal that is generated by dividing the
local oscillator signal by 4, thus equalling the IF frequency.
Data Sheet
18
2007-02-26