TRF6903_08 Datasheet, PDF (22/39 Pages) Texas Instruments – SINGLE-CHIP MULTIBAND RF TRANSCEIVER

TRF6903
SINGLEĆCHIP MULTIBAND RF TRANSCEIVER
SWRS022D − MARCH 2004 − REVISED JUNE 2005
power amplifier
The power amplifier has three programmable attenuation states as determined by A<7:6> and B<7:6>: full
power (0-dB attenuation), 10-dB attenuation, and 20-dB attenuation. This adjustment feature allows the user
to fine-tune the device for optimal output power. The power amplifier can be enabled/disabled during transmit
by bit B<3>, PARXED. During receive, the transmit power amplifier is powered down but the VCO and PLL are
still operating. During ASK or OOK operation, the TX_DATA signal turns the power amplifier on and off according
to the transmit data incident at terminal 32.
CH1 S22
↑1 U
1
0.5
2
5
CAL
OFS
0
0.2
0.5
1
2
5 10
CPL
−5
−0.5
FIL
1k
−2
−1
START 300 MHz
STOP 1000 MHz
Figure 10. Typical PA Output Impedance (S22) at Device Terminal PA_OUT
brownout detector
The brownout detector provides an output voltage to indicate a low supply voltage. This may be used to signal
the need to change transmit power to conserve battery life, or for system power down. The brownout detector
threshold is set with the B word. Four different thresholds are available.
serial control interface
The TRF6903 is controlled through a serial interface; there are five 24-bit control words (A, B, C, D, E) which
set the device state. The A and B words are almost identical, and provide configuration settings for two modes,
designated 0 and 1, which are commonly used to configure the transmit and receive states. The transmit and
receive states can then be rapidly selected using MODE (terminal 21). The C word sets the reference dividers,
the power amplifier bias, and contains various reset bits. The E word contains the bit-rate select, data clock
control bits, and the power amplifier bias control registers. The D word is used to trim the external crystal
frequency and tune the demodulator.
The register address is the composite of bits 23, 22, 1, and 0 of the 24 bits written to the serial interface. For
some words, certain bits of the address are don’t cares and are noted as XX. This flexible addressing scheme
allows backward compatibility with the TRF6901, and because of this flexibility, the data length of each register
varies from 15 bits to 22 bits.
Normal (write) operation of the serial interface is to clock in 24 bits through the CLOCK and DATA terminals.
DATA values are clocked into the 24-bit serial interface shift register on the rising edge of CLOCK. The 24-bit
value is decoded and written into the appropriate data register on the rising edge of STROBE.
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