Power Management - Panasonic EB-X400 Service Manual

Microphone
To 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:
SSFR (dB)
5
0
-5
-10
-15
100
Figure 5.12. GSM Transmit Audio frequency response mask
DTHF Speaker
To achieve desktop handsfree feature EB-X400 has DTHF speaker mounted on the lower case back. EB-X400 rings some
melody tones using DTHF speaker via Melody IC (U2011). This LSI IC can control ringing volume.

5.2.9. POWER MANAGEMENT

The Power supply circuit needs to supply regulated power to the baseband and RF parts, control battery charging and monitor
battery usage. The Power Management Block consists of 5 parts as follows:
1) Power Source
2) Power On/Off Control
3) Power Source Failure detection
4) Voltage Regulation
5) Battery Charging & Monitoring
Lithium-ion (Li+) cells are used in the EB-X400 battery pack. These cells have improved gravimetric and volumetric energy
densities 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 regulators
are significantly reduced due to the large current drawn during the transmit burst.
1,000
log Frequency (Hz)
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