W215_W218_Circuit_Description.pdf

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W215/W218
Level 3
Circuit Description
25 April 2007
V1.0
W215/W218 Level 3 C
Index
1
Receive .................................................................................................... 4
1.1
1.
2
1.
3
1.
4
1.
5
1.
6
1.
7
2
Band selection........................................................................................... 4
Demodulation............................................................................................ 5
Audio Codec.............................................................................................. 6
Earpiece Receiver ...................................................................................... 7
Headset .................................................................................................... 7
Speaker Phone .......................................................................................... 7
Data Download Receive Path ...................................................................... 8
1.3.1 Voice Downlink Patch..................................................................................................7
Transmit ..................................................................................................
8
2.1
2.2
2.3
2.4
2.5
2.6
3
4
5
6
7
Audio (Voice uplink Patch)..........................................................................
9
Data Download Transmit Path ....................................................................
9
Stereo Audio Path......................................................................................
9
Modulation
...................................................................................................................
10
RF TX PA
...............................................................................................
12
TX PA Power Control in SKY77318
..........................................................
13
Triton-Lite Monitoring ADC ....................................................................14
Baseband Serial Port (BSP) ....................................................................15
Microcontroller Serial Port (USP) ...........................................................15
General purposes I/O (GPIO).................................................................15
TFT LCD Display......................................................................................17
7.1
Display Backlights
......................................................................................................
18
7.2 Image Processor ...................................................................................... 18
7.3 Camera Module ........................................................................................ 19
8
9
32kHz RTC ..............................................................................................19
SIM Card Circuit .....................................................................................19
9.1
SIM Card Supply Voltage Generation ......................................................... 20
10 Keypad................................................................................................... 20
10.1 Keypad Matrix ......................................................................................... 21
11 Vibrator circuit .......................................................................................21
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W215/W218 Level 3 C
12 Memory ..................................................................................................21
13 Power .....................................................................................................22
13.1 Low-Dropout Voltage Regulators...............................................................
22
13.2 Power Down Methods ..............................................................................
23
14 Sleep Module ..........................................................................................23
14.1 Sleep Up Sequence..................................................................................
24
14.2 Sleep off Sequence ..................................................................................
24
15 Power Tree .............................................................................................25
16 Charging Circuit and External Power .....................................................25
16.1 Battery Support .......................................................................................
25
16.2 Charger Support......................................................................................
25
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W215/W218 Level 3 C
1 Receive
1.1
Band selection
The radio frequency signal is received from internal PIFA-type antenna. Received
GSM RF signal enters to PCB through the RF switch
JP201.
At this moment the T/R switch
SW201
is switched to RX mode to let the signal input to next stage. Then the signal goes
into SAW filter,
BF201 and BF202
, which reject out-band signal and transfer the signal
from single-end to balanced. And the matching circuits between T/R switch and SAW
filter reduce the unwanted RF signal reflection and provide a flat frequency response in the
operation band. Finally the received signal will fed into Locosto Plus
U101
DRP core
through a balanced MLCC matching network. The following table describes the control
voltages of T/R switch and PA:
SW_LO_TX SW_HI_TX
W215
Standby
RX EGSM900
RX DCS1800
TX GSM900
TX DCS1800
PIN 5
of T201
Low
Low
Low
High
High
PIN 2
of T201
x
Low
Low
High
High
PA_EN
TP201
Low
Low
Low
High
High
VAPC
PIN 20
TP202
of U201
Low
Low
Low
High
High
x
Low
High
Low
High
BS1
The RF signal is received by internal antenna or by RF plug, and the signal is passing
through the RF switch JP201 and then fed into T/R switch. The low band (GSM900) RX
received signal is transmitted from
SW201
(Pin
11)
and input to low-band SAW filter
BF201,
while the high band (DCS1800) RX received signal from
SW201
(Pin
1)
and then
input to high-band SAW filter
BF202.
The last stage of RX on PCB is Locosto
U101
(Loocsto-Plus), and the DRP process will make the signal into binary data.
Figure 1: Locosto TX/RX Paths Description
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W215/W218 Level 3 C
1.2
Locosto RX Mode
Formatiert:
Nummerierung
und Aufzählungszeichen
Figure 2: Locosto RX Signal Process
As described in Figure 2, when the RF signal is input to Locosto, it will be amplified by
a differential LNA in advance, in order to obtain a better NF in the last receiving stage.
And then it will be turned into discrete IF signal by a high-speed mixer. After passing
through a filter and an A/D converter, the discrete signal will become digital signal and
then input to Locosto core to do DSP process. The detail RX signal route is depicted as
below:
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