SI4205-BM Silicon Laboratories Inc, SI4205-BM Datasheet - Page 18

• Manufacturer Part Number: SI4205-BM
• Description: IC TXRX TRI-BAND 32LGA
• Manufacturer: Silicon Laboratories Inc

Specifications of SI4205-BM

• Frequency: 850MHz, 900MHz, 1.8GHz, 1.9GHz
• Modulation Or Protocol: GSM
• Applications: Cellular, GSM Cellular Radio
• Voltage - Supply: 2.7 V ~ 3.3 V
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Package / Case: 32-LGA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Operating Temperature: -
• Sensitivity: -
• Memory Size: -
• Data Rate - Maximum: -
• Current - Transmitting: -
• Current - Receiving: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

Aero I
Transmitter
The transmit (TX) section consists of an I/Q baseband
upconverter, an offset phase-locked loop (OPLL) and
two output buffers that can drive external power
amplifiers (PA), one for the GSM 850 (824 to 849 MHz)
and E-GSM 900 (880 to 915 MHz) bands and one for
the DCS 1800 (1710 to 1785 MHz) and PCS 1900
(1850 to 1910 MHz) bands. The OPLL requires no
external duplexer to attenuate transmitter noise or
spurious signals in the receive band, saving both cost
and power. Additionally, the output of the transmit VCO
(TXVCO) is a constant-envelope signal that reduces the
problem of spectral spreading caused by non-linearity in
the PA.
A quadrature mixer upconverts the differential in-phase
(TXIP, TXIN) and quadrature (TXQP, TXQN) signals
with the IFLO to generate a SSB IF signal that is filtered
and used as the reference input to the OPLL. The IFLO
frequency is generated between 766 and 896 MHz and
internally divided by 2 to generate the quadrature LO
signals for the quadrature modulator, resulting in an IF
between 383 and 448 MHz. For the E-GSM 900 band,
two different IFLO frequencies are required for spur
management.
programmed per channel in the E-GSM 900 band. The
IFLO frequencies are defined in Table 7 on page 13.
The OPLL consists of a feedback mixer, a phase
detector, a loop filter, and a fully integrated TXVCO. The
TXVCO is centered between the DCS 1800 and
PCS 1900 bands, and its output is divided by 2 for the
GSM 850 and E-GSM 900 bands. The RFLO frequency
is generated between 1272 and 1483 MHz. To allow a
single VCO to be used for the RFLO, high-side injection
is used for the GSM 850 and E-GSM 900 bands, and
18
DCS/PCS
GSM
PA
PA
Therefore,
RFOG
RFOD
REG
the
TXBAND[1:0]
IF
Figure 10. Transmitter Block Diagram
1, 2
N
PLL
RF2
PDRB
[15:0]
REG
must
PLL
RF
Rev. 1.0
be
low-side injection is used for the DCS 1800 and
PCS 1900 bands. The I and Q signals are automatically
swapped when switching bands. Therefore, there is no
need for the customer to externally swap the I and Q
signals. However, for additional layout flexibility, the
SWAP bit in register 03h can be used to manually
exchange the I and Q signals.
Low-pass filters before the OPLL phase detector reduce
the harmonic content of the quadrature modulator and
feedback mixer outputs. The cutoff frequency of the
filters is programmable with the FIF[3:0] bits in register
04h, and should be set to the recommended settings
detailed in the register description.
DET
FIF[3:0]
N
IF
[15:0]
PDIB
PLL
IF
2
BBG[1:0]
SWAP
Si4205
TXIP
TXIN
TXQP
TXQN
Q
I