tda5251f1 Infineon Technologies Corporation, tda5251f1 Datasheet - Page 18

• Manufacturer Part Number: tda5251f1
• Description: Ask/fsk 315mhz Wireless Transceiver
• Manufacturer: Infineon Technologies Corporation

Confidential
2.4
2.4.1
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 +12dBm at 5V and -
34dBm 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
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
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
2.4.3
The Double Balanced 1
the intermediate frequency (IF) at approximately 105MHz. 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 420MHz in receive mode providing the above
mentioned IF frequency of 105MHz. The mixer is followed by a low pass filter with a corner
frequency of approximately 175MHz in order to prevent RF and LO signals from appearing in the
105MHz IF signal.
2.4.4
The Low pass filter is followed by 2 mixers (inphase I and quadrature Q) that convert the 105MHz
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.
Preliminary Specification
Bit
Bit
D0
D4
Functional Block Description
Power Amplifier (PA)
Low Noise Amplifier (LNA)
Downconverter 1
Downconverter 2
LNA_GAIN
Sub Address 00H: CONFIG
Sub Address 00H: CONFIG
Function
PA_PWR
Function
st
Mixer converts the input frequency (RF) in the range of 315MHz down to
st
nd
0= low TX Power, 1= high TX Power
Mixer
I/Q Mixers
0= low Gain, 1= high Gain
18
Description
Description
Functional Description
Default
Default
TDA5251 F1
Version 1.0
1
1
2003-02-18