Receiver

The receiver is a triple conversion receiver consisting of two ASICs CRFU2a (N402) and PLUSSA (N401). CRFU2a contains LNA bias circuitry with an external transistor which provides step gain depending on the incoming RF level and the first and second mixers. PLUSSA contains the third mixer. All filtering is external. The received RF signal from the antenna is fed via the duplex filter (3 pole bandpass filter Z401) to the LNA. Biasing and the AGC step circuitry are integrated into CRFU2a but the...

Sleep Mode

In the sleep mode all the regulators except the baseband VBB and the SIM card VSIM regulators are off. Sleep mode is activated by the MAD after MCU and DSP clocks have been switched off. The voltage regulators for the RF section are switched off and the VCXO power control, VCXOPwr is set low. In this state only the 32 kHz sleep clock oscillator in CCONT is running. The flash memory power down input is connected to the VCXO power control, so that the flash is deep powered down during sleep mode....

Battery connector

The BSI contact on the battery connector is used to detect when the battery is to be removed to be able to shut down the operations of the SIM card before the power is lost if the battery is removed with power on. The BSI contact in the battery pack should be shorter than the supply power contacts to give enough time for the SIM shut down. A vibra alerting device is used for giving silent signal to the user of an incoming call. The device is not placed in the phone but it will be added to a...

Digital control

The baseband functions are controlled by the MAD asic, which consists of a MCU, a system ASIC and a DSP. The DCS PCN specific asic is named as MAD2. There are separate controller asics in TDMA and JDC named as MAD1 and MAD3. All the MAD asics contain the same core processors and similar building blocks, but differ from each other in system specific functions, pinout and package types. MAD2 contains following building blocks - ARM RISC processor with both 16-bit instruction set (THUMB mode) and...

Power

Pressing the power key, that is monitored by the MAD, which starts the power down procedure. 2. If the battery voltage is dropped below the operation limit, either by not charging it or by removing the battery. 3. Letting the CCONT watchdog expire, which switches off all CCONT regulators and the phone is powered down. 4. Setting the real time clock to power off the phone by a timer. The RTC generates an interrupt signal, when the alarm is gone off. The RTC interrupt signal is connected to the...

Power up

Pressing the power key, that generates a PWRONX interrupt signal from the power key to the CCONT, which starts the power up procedure. 2. Connecting a charger to the phone. The CCONT recognizes the charger from the VCHAR voltage and starts the power up procedure. Before battery voltage voltage rises over 3.0 V Charging Logic gives an initial charge (with limited current) to the battery. After battery voltage reaches that voltage limit the power up procedure is as described in the previous...

Real time clock

Requirements for a real time clock implementation are a basic clock hours and minutes , a calender and a timer with alarm and power on off -function and miscellaneous calls. The RTC will contain only the time base and the alarm timer but all other functions e.g. calendar will be implemented with the MCU software. The RTC needs a power backup to keep the clock running when the phone battery is disconnected. The backup power is supplied from a rechargable polyacene battery that can keep the clock...

Frequency Synthesizers

A 13 MHz VCTCXO module is used as a stable reference for both the RF and BB circuitry. Temperature variations in the VCTCXO module are controlled by an AFC voltage which is generated by a 11 bit D A converter in COB-BA_GJ. The output of the VCTCXO module feeds both the UHF PLL and the VHF PLL both of which are located in PLUSSA and the BB circuitry for A D conversion. The BB uses this information for frequency compensation algorithms. The UHF synthesizers contains a 64 65 dual modulus...