ServiceManualV1.1 Newgen Telecom GSM Engineering
Copyright ©NEWGEN TELECOM Co. Ltd. Page 11
internal charging circuit, and coin battery for “real time clock (simply, RTC) as shown in Fig.6.
2-4-5-1. Earpiece/Melody Speaker/ Headset Interface;
Earpiece, or receiver speaker, is providing voice signal that a phone user wants to hear during a call, while
melody speaker is used only for melody sound playing (64 poly phonic sound). The reason why employed
separate speaker is that a phone user usually listens voice signal in normal phone operating position, making
the phone close to the listener’s ear after flip open, while melody playing is performed under flip closed
condition to show off to a friend or other people. Headset is recently used as a means of hands free device, or
for privacy during a call, and Z400 is providing required interface for dedicated headset device that has 4-
pole plug design (for detailed operation, refer to HW troubleshooting guide, where you also can see a photo
of headset)
2-4-5-2. Power Management IC (or, simply PMIC; U201) ;
Though this block is not clearly seen in the Fig.6, PMIC takes charge of very important role, which is
generating various DC voltages for each functional block. Some of them may need to be turned ON/OFF
according to the predetermined timing sequence (please note that GSM is TDD system in its operation).
Z400 is utilizing 6 different DC supplies from PMIC block, and refer to “power distribution chart” for
detailed information. You will probably understand later that the knowledge on these supply lines will be
very helpful for troubleshooting purposes because many cases of problems are closely related to DC supply
failure.
2-4-5-3. Internal Charger;
Analog BB IC has a circuitry for charging a battery, which is called “internal charger”, with the help of travel
charger (or, simply TC). Actually, TC is not a charger but a constant DC voltage supplier and internal
charger circuitry is playing a role of charging a battery. This circuit is composed of “pass Transistor” (p-
channel MOSFET), and current sensing resistor, and control block that is integrated onto the IC internally.
It controls the gate bias voltage of the pass TR with the help of SW, and adjusts charging voltage and current
according to different battery type. Detailed structure of the charging circuitry will be covered in “HW
troubleshooting guide” later.
2-4-5-4. Real Time Clock (or, simply RTC);
RTC is a functional block that manages time and date information as is with a time watch or time clock to a
phone user, and it operates independently from other blocks with independent DC supply called “coin
battery”, and can operate even without battery for a given time. The 32.769 KHz crystal(X301) at base band
processor IC (U301) is mainly employed as reference signal source to count time. For detailed information,
refer to “HW troubleshooting guide”.
2-4-6. Base and Processor IC (CX805-32; U301);
Base band processor IC acts as brain for a human, it commands, controls, monitors, and performs signal
processing whole radio and it’s beyond the scope of this manual to cover detailed operation of the processor
