SI4200-GM Silicon Laboratories Inc, SI4200-GM Datasheet - Page 23

• Manufacturer Part Number: SI4200-GM
• Description: IC TXRX TRI-BAND 32MLP
• Manufacturer: Silicon Laboratories Inc

Specifications of SI4200-GM

• Frequency: 850MHz, 900MHz, 1.8GHz
• 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-VQFN Exposed Pad, 32-HVQFN, 32-SQFN, 32-DHVQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Operating Temperature: -
• Sensitivity: -
• Memory Size: -
• Data Rate - Maximum: -
• Current - Transmitting: -
• Current - Receiving: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

DCXO Overview
The Si4134T integrates the DCXO circuitry required to
generate a precise system reference clock using only
an external crystal resonator. (See Figure 16.) An
internal digitally programmable capacitor array (CDAC)
provides a coarse method of adjusting the reference
frequency in discrete steps. An integrated analog
varactor (CVAR) allows for a fine and continuous
adjustment of the reference frequency by an external
control voltage (XAFC). This control voltage is supplied
by the AFC DAC on the baseband IC. The complete
DCXO solution effectively replaces the TCVCXO
module typically required to provide a 13 or 26 MHz
reference clock for the system. The Si4134T generates
a single-ended 13 or 26 MHz output (XDRV) to drive the
Si4201, and the Si4201 then buffers a 13 or 26 MHz
reference clock (XOUT) to be sent to other system
components such as the baseband. The complete
circuit is shown in the "Typical Triple-Band Application
Schematic" on page 16.
DCXO Tuning
The DCXO uses the CDAC and the CVAR to correct for
both static and dynamic frequency errors, respectively.
To compensate for crystal systematic offset error, the
CDAC ensures a minimum of ±10 ppm frequency
adjustment capability. The CDAC is programmed using
register 28h.
DAC
AFC
XOUT
Figure 16. DCXO System Signal Routing Diagram
Si4201
XIN
Y1
XTAL2
XTAL1
XDRV
XAFC
Rev. 1.2
The
programmed during powerup or after an initial
calibration. Periodic adjustments to compensate for
aging may also be performed over time to ensure
accuracy.
The baseband determines the appropriate frequency
adjustment based on the receipt of the FCCH burst. The
baseband then adjusts the XAFC voltage using the
baseband AFC DAC (12 or 13-bit), which controls the
varactor on the Si4134T.
The baseband AFC DAC can adjust CVAR to correct for
frequency variations caused by temperature drift. The
step size per bit depends on the resolution of the AFC
DAC and its output voltage range.
DCXO Crystal Selection
The tuning range specifications listed in Table 8 on
page 15 for CDAC and CVAR assume that Aero+ is
used with a crystal that conforms to the crystal
parameters listed in the same table. Other crystals may
be used with Aero+ for cost and/or performance
reasons. For example, using a higher sensitivity crystal
extends
compensation range. However, care must be taken
when using a more sensitive crystal because other
system parameters are affected. Contact Silicon
Laboratories' applications support for assistance in
specifying other crystals.
CVAR
CDAC[5:0]
the
CDAC[5:0]
CVAR
register
and
AMP
(register 28)
the
Si4134T
To
PLLs
CDAC
Aero+
frequency
may
be
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