SP000012956 データシートの表示（PDF） - Infineon Technologies

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SP000012956

ASK/FSK 868MHz Wireless Transceiver

Infineon Technologies 

2.4

Functional Block Description

TDA5250 D2

Version 1.7

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 +4dBm at

2.1V supply voltage. In low power mode the transmit power is approximately -7dBm at 5V and -

32dBm 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 1st Mixer

The Double Balanced 1st Mixer converts the input frequency (RF) in the range of 868-870 MHz

down to the intermediate frequency (IF) at approximately 290MHz. 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 1157MHz in receive mode providing the above

mentioned IF frequency of 290MHz. 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

290MHz IF signal.

2.4.4 Downconverter 2nd I/Q Mixers

The Low pass filter is followed by 2 mixers (inphase I and quadrature Q) that convert the 289MHz

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

19

2007-02-26

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