SND SC6820 Plaform Maintain Guide Version: 1.0.0 Date: 2012-10-15
SND SC6820 Plaform Maintain Guide
Version: 1.0.0
Date: 2012-10-15
Chapter 1. Mobile theory instruction
一.1 Hardware Instruction
SC6820 reference platform hardware circuit comprising: baseband chip, the radio frequency section, the
memory section, the display part, audio part, power source part, the peripheral device (Wifi, BT, the GPS),
etc.. For details, refer to Figure 1-1 shows the SC6820 platform reference hardware overall block diagram of
the mobile phone.
1
Hardware overall block diagram of Figure 1 1 SC6820
一.1.1 Major components introduction
一、BB chip introduction
二、SC6820 GSM/GPRS/EDGE Multimedia baseband chip for developers to design high-performance GSM / GPRS /
EDGE Android smartphone to provide a cost-effective solution. Integrating rich multimedia capabilities in the
new generation of smart phones, and its peripheral circuit design is simple and flexible according to customer
demand for a variety of functions and applications currently popular.
三、RF chip introduction
SR1018 Is a support for quad-band GSM / GPRS / EDGE terminal RF transceiver, which uses CMOS
technology, an area of 4 × 5 mm2, it can be convenient with Spreadtrum's SC6820 Baseband chip can be
used with a variety of power amplifier (PA) and the antenna switch.
key signal requirements
26M clock signal
Figure 1 1 BB 26 M the clock MCLKI clock requirements
Form 1 1 BB 26 M clock parameters
32K clock signal
32K clock requirement:32.768K;+/-20ppm;12.5pf/9pf
Sensor clock singal
Sensor The clock requires reference to the following figure, note the parameters.
图 1-1 Sensor 输入时钟 图 1-2 Sensor 输出时钟
SIM card signal
一. The order of the SIM card:1. RST 2. VCC 3. I/O 4.CLK
二. SIM Voltage requirements: 3V+/-10%
三. SIM CLK Signal requirements: high level between 3.15 and VCC +0.3 V low minimum
between -0.3 ~ 0.7V; rise time is not more than 50ns clock cycle and not more than 9%; duty
cycle at 40~ 60%; clock frequency 3.25M.
四. SIM IO Signal requirements: a high level between 3.8 and VCC +0.3 V low minimum -
0.3 ~ 0.4V of; rise time is less than 1us; fall time, tens of ns.
T Card Signal
Figure 1 4 T card write operation timing
Figure 1 5 T card read operation timing
Audio signals
一.Handset, Speaker, headphone no obvious 217Hz RF noise, compare the picture below
Figure 16 217Hz noise 17 no obvious 217Hz noise
一.Headset, Speaker no obvious murmur.
一.2 Software Download
一.2.1 Download workflow
SC6820 chip power boot from ROM, after first detection U1TXD/NBOOT, state judge NBOOT pin, if U1TXD for low
into USB download mode; If U1TXD high, and then detect the button, USB download mode specific the keys
(KEYIN0 KEYOUT0 combination) press enter; if there is no specific button is pressed, the UART0 and UART1
polling receive, if any of 80ms withina UART port (UART0 and UART1) received from the download tool 3 0x7E into
the UART download mode, 80ms within two UART port (UART0 and UART1) did not receive 3 0X 7E, enter the
NAND BOOT modenormal boot. Detailedprocess, you can referto Figure
Figure 1 9 SC6820 BOOT way
一.2.2 The 1.2.2 boot process description
1、 Spreadtrum Android platform boot interrupt two kinds:
2、 The boot key press PBINT low (ground), boot interrupt.
3、 The charger into the generate Charge interrupt.
4、 alarm interrupt.
In addition, Spreadtrum platform, the power-on self-test function, the phone automatically boot
mode is turned on automatically boot on power. Auto-boot mode can be modified by modifying
the of NV parameters or phone to enter the engineering mode.
Attention:
The Spreadtrum SC6820 platforms have the power-on self-test function, so normal phone,
power-on, the phone will be about 120mA current, when the self-test end, shut down! The current
restored to the shutdown current.
一.3 Power Management
SC6820 integrates two DCDC, 25 adjustable LDO, the power demand to meet the the SC6820 chip internal and external devices, which greatly reduces the cost of a mobile phone peripheral. Power input and power output of each interface separation, increase the flexibility of the external power supply selection and device selection, and convenient power consumption debug.
一.3.1 internal LDO description
SC6820 power management is shown in Figure 1-10. The SC6820 chip built PMU functions, baseband
chip and peripheral circuits provide power management supply SC6820 phone can choose to configure an external
DC / DC power supply device.
图 1-10 SC6820 内部 LDO 示意图
一.3.2 Charge Management
SC6820 platform support charger and USB charging two charging, the charging process, the pre-charge, constant
current charge, constant voltage charge in three stages.
一.4 Clock Design
一.4.1 Real-time clock design
图 1-11 RTC 时钟电路
一.4.2 System Clock Description
SC6820
MCLKI GPI2
WIFI/BT
CLK_REQUEST
XTAL_IN
SR1018GPS
CLK_IN
图 1-12 26M 时钟框图
Chapter 2. Maintain Guide
一.5 can not download
The download process, you can refer to the instructions of the previous chapters.
Can not download most of the problems arise because the IO interface on the PCB or the BB chip Weld even welding
caused, carefully check the PCB welding is a very important step. Exclude welding problems, if the problem persists,
step-by-step analysis of the circuit. Detailed reference to the following flowchart.
Figure 21 can not download the repair process
一.6 Can not power on
The handset open process can be found in the previous chapter。Can not power on mostly cause by PCB fake weld ,even weld,it will lead to chipset out of work .If power supply correctly still can not open phone,it must by 26M or 32.768K clock out of working
Referring specifically to the following process chart。
Chart 2-2 can not working repair processes
Figure 2 3:32 K failure analysis process
Figure 2-4 26 M failure analysis process
一.7 Power Failed supply
Power failed supply mostly cause by IO port connect not good, normally is PCBA have IO port fake weld or even weld.\
Charging cable connector pin loose also can lead to connect not good, try to change cable.
。Referring specifically to the following process chart。
Figure 2-5: Charging schematic (SC6820 same)
Chart 2-6 will not charge maintenance processes
一.8 LCD displayed not correctl
LCD displayed not correctly because EMI filter Fake Weld, even welding;or LCD module FPC destroy, connect port destroy,。Please refer to the repair process
Figure 2- 7 LCD reference circuit diagram (SC6820 data line 24, rarely use resistance TP)
Chart 2 -8 LCD display abnormal repair process
一.9 Touch panel not working
SC6820 chipset use capacitance touch panel,by exterior touch panel control IC ,control panel inspection function.Touch panel not working cause by assembly not good,TP destroy,TP port not working or touch control IC welding not good
Specific overhaul process see chart 2-9;
Capacitive touch screen control schematic
Figure 29 touch screen repair processes
一.10 LCD backlight not light
Smart handset disply require high brightness,in order to improve backlight brightness need use 8---12 LED or more LED lens, meanwhile to keep all lens brightness the same need use Series backlight circuit, Basic principles as shown below, specific repair processes see chart 2-10
LCD backlight driver circuit
Chart 2-10 backlight not light repair process chart
一.11 SIM card not identify
Not identify SIM card mostly cause by card seat weld not good or destroyed,sometime might by the Shunt capacitance of the signal line even tin, Short circuit etc. Specific maintenance processes reference chart 2-12;
Chart 2 -11 Sim card circuit (SC6820 principle is the same)
Chart 2 -12 SIM card repair process
一.12 T- Flash not identify
T card not identify mostly cause by T card seat welding not good or flip touch not closely;
Figure 2 -13 T -card circuit
Figure 2-14 T-card repair process
Camera not workingCamera not working
一.13 Camera not working
Camera not working mostly cause by touch not good,e.g.. insert not correctly,insert not fastness,the
port weld not good. Specific maintenance processes reference chart。
Figure 2 15 Camera circuit diagram
Chart 2 16 Camera abnormal repair process (Figure Sensor which represents the Camera)
一.14 Side key invalidation
SC6820 support 8×8 keyboard matrix , but smart handset side key more less,so power switch
special treatment,one side connect PBINT PIN OF SC6820,another side grounding.the key most use
FPC weld way,so key invalidation most cause by FPC destroy or weld not good, but sometime by BB
welding not good or PCB problem.
Chart 218 keyboard failure repair process
一.15 MIC silence
MIC selence normal by MIC destroy or MIC access parts fake weld,even weld or weld not good then parts destroy.If the volume lower than normal ,it cause by MIC polarity weld on contrary side.our model most MIC
are in the sub-PCBA connect with the motherboard circuit connection by FPC,so touch not fastness can lead to silence.
Specific maintenance process parameters see The test chart is 2-20;
Chart 2 19 Mic schematics
Chart 2 20 Mic to uplink silent maintenance process
一.16 Receiver silence
chart 2-21 receiver circuit diagram
Chart 2-22 receiver silence repair process
一.17 Speaker silence
Chart 2-23 Speaker circuit diagram
Chart 2 -24 Speaker silent repair process
一.18 Earphone abnormity
Earphone can not identify and silence, mostly cause by earphone port connect not good or the relative part welding not
good. A few is cause by relative circuit part destroy,or BB chipset welding not good.
Specific maintenance processes reference chart 2-26;
chart 2-25 earphone circuit diagram
Chart 2-26 headphones silent maintenance process
一.19 Vibrator not working
马达 Vibrator not shaking normal cause by vibrator destroy, the vibrator control line directly connect with BB chipset.
If get rid of by welding, try update software ensure still not working,try remove welding again to change BB chipset.
一.20 Flash len not shining
Flash len most use FPC welding with PCBA, the len not shine most cause by FPC destroy or weld not good.
If not, it might by relative parts weld not good or destroy,
The specific repair process reference chart to 2-28;
Chart 2-27 camera flash drive circuit
Chart 2-28 flash light maintenance processes
一.21 The ambient light sensor is invalid
Our model light sensor use FPC connect with PCBA,light sensor invalid need check the seal
around
Chipset whether good enough not to light leakage.
If not,it might be FPC destroy or connect not good.
Specific maintenance processes reference chart 2-29;
Chart 2-29 light sensor invalid maintenance processes
一.22 Signal weakness, WLAN invalid
The handset signal weakness,WLAN invalid most cause by the port problem which antenna
connect with PCBA,RF line port loose,some metal parts grounding problem.
Calibration the PCBA comprehensive measurement to inspect the Conduction properties whether OK, If OK,
focuson check the port of connect PCBA with RF line. Whether welding not good or destroy
The specific maintenence processes reference chart 2-30
Chart 2-30 signal, network maintenance process
一.23 the peripheral equipment problem
SC6820 have lots of peripheral ports to add various function device.e.g. Wifi、BT、GPS、ATV、FM
etc.
To repair these device,usually be divided into two categories:
1 .the device failed start,usually cause by the device chip or peripheral parts weld not good.
After get rid of weld problem, Refer to the following chart 2-31 for maintenance;
Chart 2-31 peripherals can not open
2. the performence badness e.g. Wifi speed too slow or can not connect,BT distance short,GPS not
locate,ATV
And FM search problem, it most by relative antenna connect not good,RF access weld not good or
destroy.
Specific maintenance methods refer to chart 2-32
Chart 2-32 peripherals short distance, poor performance maintenance process
一.24 RF maintenance problem guide
When usual use handset have not signal and dial problem, should try PCBA calibration
comprehensive measurement first to ensure RF performance indicators whether OK.
In that course it mitht appear AFC、APC、AGC not good will lead to testing fail situation ,as following
Separate to introduce maintenance method::
一.24.1 AFC Fail
Adverse Reference Chart 2-33 steps for maintenance, such as replacing the devices still can use the shows
calibration AFC FailOscilloscope, spectrum analyzers and other instruments combined with Mobile Tester tool to
measure the RF control signal and the node RF signal accurately locate further maintenance;
图表 2-33 AFC Fail 维修参考
一.24.2 APC Fail
Adverse Reference Chart 2-34 steps for maintenance, such as replacing the devices still can use the shows
calibration APC Fail
Oscilloscope, spectrum analyzers and other instruments combined with Mobile Tester tool to measure the RF
control signal and the node RF signal accurately locate further maintenance;
图表 2-34 APC Fail
一.24.3 AGC Fail
Overwhelming majority of adverse receiver AGC Fail reasons pathway components poor welding lead, need to
focus on examination of SAW and its matching circuit, the specific 维 修 步 骤 可 参 考 图 表 2-35 ;
图表 2-35 AGC Fail 维修步骤
一.24.4 MobileTester tool instruction
MobileTester tool is a common platform Spreadtrum its function is very powerful debugging tools, this is
mainly a brief description of the RF in the repair process can
Use this tool to quickly determine the positioning of the tool allows non-signaling mode phone is in force
transmitting and receiving our by state
Current and output power when the phone information to locate the problem.
The AFC repair, MobileTester reference set as follows:1. 打开 MobileTester 工具 ;
1. Serial port settings and select CAL MODE, test status to enter the mobile phone powerClick on the "Active". Click "Set Band" select EGSM900 band3. Set: the Channel 61, PCL: 5, the CDAC value is set to 55, CAFC is set to 7000, the point of the TX ON;4. Read instrument frequency error5. Adjust the the CDAC values (45-63), keep CAFC value unchanged, Frequence Error absolute value less than 450HZKeep CDAC constant adjustment CAFC value measurement frequency error, calculate the frequency error with the CAFC value changes in the slope of the CAFC the slope of between 4-10 Hz / bit, the AFC calibration Pass Note: CDAC and CAFC value adjustment should be first off the transmitter to set
The APC maintenance, MobileTester reference set as follows:1 open MobileTester tools;
Serial port settings and select CAL MODE, test status to enter the mobile phone powerClick on the "Active". Choose to test the band EGSM / DCS Click "Set Band"Setting: Channel 61/698, Pcl: 5/0 Power Factor value is set to 32767;Read instrument power
Chapter 2 Maintain Skill
Any repair, the first step to use a multimeter measurement Vbat Vchg on to whether there is a short circuit. Avoid greater damage on power.Overhaul circuit, based on simple to complex, from the majority of cases to the principle of the few cases, such as the current situation, you should begin to start the external interface and external LDO last doubts BB chip replacement of the BB chip is the most tedious; still large current the probability of the situation, BB chip power input pin is shorted to ground is greater than the the RF PA chip power shorted probability, so maintenance is necessary to first analyze the BB chip troubleshoot RF PA chip. And so on other problems.
Patch parts, such as Camera, LCD, Speaker, Vibrator, Mic, etc., if the visual interface or circuit Weld, and even
welding phenomenon, tested replacement parts can easily be identified.
Not able to solve the problem of maintenance in accordance with conventional methods to measure the voltage or
waveform to accurately locate the problem, instead of blindly replacement devices, otherwise easily lead to
confusion maintenance.