Panasonic EB-X400 Service Manual

Also see for EB-X400: Operating instructions Operating instructions

Contents

– 5-17 –■ MicrophoneTo provide improved speech pick-up, noise immunity and reduced echo, a noise-cancelling type microphone is employed.GSM requires that the sending audio frequency response must fit within the mask shown below:■ DTHF SpeakerTo achieve desktop handsfree feature EB-X400 has DTHF speaker mounted on the lower case back. EB-X400 rings somemelody tones using DTHF speaker via Melody IC (U2011). This LSI IC can control ringing volume.5.2.9. POWER MANAGEMENTThe Power supply circuit needs to supply regulated power to the baseband and RF parts, control battery charging and monitorbattery usage. The Power Management Block consists of 5 parts as follows:1) Power Source2) Power On/Off Control3) Power Source Failure detection4) Voltage Regulation5) Battery Charging & MonitoringLithium-ion (Li+) cells are used in the EB-X400 battery pack. These cells have improved gravimetric and volumetric energydensities compared to that of Nickel-Metal Hydride (Ni-MH) cells.EB-X400 uses power amplifiers operating directly from the nominal 3.7 V battery supply.Due to the finite internal resistance of battery cells the voltage available for the power amplifiers, Baseband and RF regulatorsare significantly reduced due to the large current drawn during the transmit burst.SSFR (dB)50-5-10-151,000100log Frequency (Hz)Figure 5.12. GSM Transmit Audio frequency response mask