Model
MASS 2
Version
V_1.0
Prepared by
H/W
Date
22/01/2008
Subject Technical
Manual Page
54/59
The MT6120 uses a digital calibration technique to reduce the PLL settling time once the RF synthesizer is
programmed through a 3-wire serial interface, the calibration loop is activated. The main function of the calibration
loop is to preset the RF VCO to the vicinity of the desired frequency quickly and correctly, thus aiding the PLL to
settle faster. On the other hand, since a large portion of initial frequency error is dealt with by the integrated
calibration loop, the overall locking time can be drastically reduced, irrespective of the desired frequency.
5.
Voltage Control Crystal Oscillator(VCXO)
VCXO consists of an amplifier, a buffer, and a programmable capacitor array. The VCXO provides the MT6120
with a selectable reference frequency of either 13MHz or 26MHz. When VCXOFRQ pin is high, Output Frequency
is 26Mhz. When VCXOFRQ pin is low, Output Frequency is 13Mhz.
VCXOFRQ is high in MEGA2. The Amplifier is designed to be in series resonance with a standard 26Mhz crystal.
The Crystal is connected from the Input pin XAL of Amplifier to ground through a series load capacitance. The
buffer provides a typical 600mVpp voltage swing. As an alternative, the reference frequency can be provided by
an external 26Mhz VCTCXO module. When Pin VCXOCXR is tied to the VCCVCXO supply, the XTAL pin will
accept an external signal. Furthermore, the VCXO control pin can be tied to VCCVCXO to prevent the current
leakage during the sleep mode operation.
6.
Regulator
The MT6120 internal regulators provide low noise, stable, temperature and process independent supply voltages to
critical blocks in the transceiver. An internal P-channel MOSFET pass transistor is used to achieve a low dropout
voltage of less than 150mV in all regulators.
II. RF3166
Summary of Contents for MASS2
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