CM9112 Datasheet, PDF (15/18 Pages) California Micro Devices Corp – Dual Inputs Dual Outputs High Accurate Fast Charger

PRELIMINARY
CM9112
Application Information (cont’d)
Sleep mode is entered when the Adapter or USB is
removed (or is the wrong voltage). Charging stops and
VSYS is connected to the battery through Q2. In this
mode, the CM9112 draws less than 1µA of current
from the battery.
Typical Smartphone Applications
A Smartphone is a cellular or mobile phone with
special computer-enabled features not previously
associated with telephones, such as advanced data
functions. Most mobile phone includes some amount of
memory uses such as storing a phone directory, and
most can send and receive text messages, but a
smartphone can perform many more functions,
including PDA, an internet browser, a TV receiver, a
multi-pixel camera, or an MP3 player. Compared to
standard cell phones, smartphones usually have
larger, more colorful displays, contain processors that
are more powerful, and typically run operating system
software. These features are all packed into a smaller
box. This sophistication requires more battery power
than a simple cell phone.
Adapter
10u
0.1u
Q1
100
GAD
VAD
1.Innormalbatteryoperation,Q2isturned
on,thebatterysuppliespowertoboththe
RFandBasebandloads.
2. GSM transmitter requires up to 2.0A of
pulse current. In the charging phase, both
the battery and adapter supply current for
the RF load.
VIN
LDO1
LDO2
VSYS
Baseband
Load
33u
VREF ^Q2
0.1u
Charger
CM9112
VOUT
BSEN
RF
Load
GSM Phone
Figure 7. GSM phone application
Smartphones are available in the two leading cell
phone topologies, CDMA and GSM. They each have
unique power demands.
The GSM is a TDMA (Time Division Multiple Access)
system where up to eight users share a transmitting
frequency channel. During transmitting, a GSM phone
can draw up to 2.0A of pulse current from the battery
(588 µs pulse width, at a duty cycle of 1/8).
When charging the cell phone battery and using the
cell phone at the same time, the power amplifier still
needs to draw 2A pulse current, which cannot be met
with an adapter having less than 2A of rated output
current capacity. Most adapters are rated at only 1A. In
order to charge the battery and use the phone at the
same time, the high-power section (mainly the RF
power amplifier), has to be supported by the battery at
all times, even when the adapter is plugged-in. See the
typical configuration in Figure 7.
With a discharged battery, the charger begins in the
Precharge mode, which will only supply 100mA or less
of charging current. In the case of very low battery volt­
age (typically below 3.2V), the cell phone is prohibited
from transmitting and drawing large current from the
battery.
The CM9112, with its integrated 4.2V, 450mA LDO out­
put, can support the low-power section of a cell phone,
such as the system microprocessor, LCD display and
LED backlight for the user interface. In addition, the
CM9112 can supply power to the system for non-trans­
mitting application such as reading and composing
email messages, or synchronizing data transfers
between a cell phone and a PC.
The CDMA phone demands lower peak current during
transmitting, typically 600mA peak. All the system
power can be supplied by LDO1 when configured as
shown in Figure 8.
© 2006 California Micro Devices Corp. All rights reserved.
07/06/06 490 N. McCarthy Blvd., Milpitas, CA 95035-5112 lTel: [phone] lFax: [phone] lwww.cmd.com
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