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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 Band selection........................................................................................... 4
1.2 Demodulation............................................................................................ 5
1.3 Audio Codec.............................................................................................. 6
1.3.1 Voice Downlink Patch..................................................................................................7
1.4 Earpiece Receiver ...................................................................................... 7
1.5 Headset .................................................................................................... 7
1.6 Speaker Phone .......................................................................................... 7
1.7 Data Download Receive Path ...................................................................... 8

2 Transmit .................................................................................................. 8
2.1 Audio (Voice uplink Patch).......................................................................... 9
2.2 Data Download Transmit Path .................................................................... 9
2.3 Stereo Audio Path...................................................................................... 9
2.4 Modulation................................................................................................................... 10
2.5 RF TX PA ............................................................................................... 12
2.6 TX PA Power Control in SKY77318 .......................................................... 13

3 Triton-Lite Monitoring ADC ....................................................................14

4 Baseband Serial Port (BSP) ....................................................................15

5 Microcontroller Serial Port (USP) ...........................................................15

6 General purposes I/O (GPIO).................................................................15

7 TFT LCD Display......................................................................................17
7.1 Display Backlights ...................................................................................................... 18
7.2 Image Processor ...................................................................................... 18
7.3 Camera Module ........................................................................................ 19

8 32kHz RTC ..............................................................................................19

9 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 VAPC
PA_EN BS1
W215 PIN 5 PIN 2 PIN 20
TP201 TP202
of T201 of T201 of U201
Standby Low x Low Low x
RX EGSM900 Low Low Low Low Low
RX DCS1800 Low Low Low Low High
TX GSM900 High High High High Low
TX DCS1800 High High High High High


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 Aufz