Regulators - Nokia N72 Service Manual

RM-180
Nokia Customer Care System Module
• loop filter
• VCO (Voltage Controlled Oscillator)
• balun
The VCO frequencies are locked by PLLs into a reference oscillator, VCTCXO (Voltage Controlled Temperature
Compensated Crystal Oscillator).
The PLLs are located in RF ASICs and controlled via RFBus.
Reference oscillators
A 38.4MHz VCTCXO is used as a reference oscillator for the frequency synthesizers.

Regulators

RF ASICs contain integrated regulators to supply regulated voltages for their internal circuitry and other RF
parts. Rx VCO supply is got via a switch from an RF ASIC VR1 regulator. VCO can be switched on and off by
controlling the switch via RFBus.
Supply voltage for the VCTCXO is provided by a BB mixed mode ASIC. The same supply is used for reference
clock input buffers, output buffers and for the digital control blocks of both RF ASICs.
Other supplies, like 4.7 V supply for PLL charge pumps and bias reference (VREFRF01) are also provided by
the BB mixed mode ASIC.
Figure 113 RF supply connections from the BB mixed mode ASIC
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