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Cellphones Major parts functions…April 7, 2008
We are going to discuss here some techniques and steps to repair dead condition in mobile phones
irrespectively of brands..
First of all let us now about the main functions to power on a mobile phone so you can consult our next
lesson…
Key Components and funtions:
· Battery
· Power Switch
· battery terminal
· Power IC
· Oscilator
· Frequency divider
· CPU
· Flash (ROM / EEPROM)
Battery:
A battery is used to provide power supply to our mother board unit so if this battery or on of its funtions fails
the whole mobile phone fails to power on. So battery must be in good condition to make a mobile phone
power on. Some times the third Pin used in battery which is called "BSI" is not working correctly but voltage
can be found in " + " and " - " terminals, in this situation mobile phone cannot turn on.
Mobile phone battery requires only two pins for charging, then why there is a third pin? The question is definitely a curiosity generating one. The third pin called BSI pinperforms very important functions and act as an interface between the Mobile phone and the Battery. When the battery is removed, without switching off the Mobile phone, the BSI circuit is first interrupted which convey the information to the processor to shut down all communications to prevent damage. To communicate with the BSI, the battery pack also has a BSI pin. BSI stands for Battery Status Indicator or Battery System Indicator.
The Mobile phone battery has Lithium Ion chemistry. The Li-ion battery has three components inside. These are Anode, Cathode and Electrolyte. The anode is made up of carbon and cathode is a metal oxide. The Anode is commonly made of Graphite. The metal oxide in the cathode may be Lithium cobalt oxide, lithium iron phosphate or lithium manganese oxide. The electrolyte is lithium salt dissolved in an organic solvent. It is a mixture of organic carbonates like ethylene
carbonate or diethyl carbonate containing lithium ions. The sources of lithium ions are Anion salts like Lithium hexa fluorophosphates( LiPF6), Lithium hexa fluoro arsenate monohydrate(LiAsF6), Lithium perchlorate(LiClO4), Lithium tetrafluoro borate(LiBF4), Lithium triflate(LiCF3SO3) etc. Based on the anion salts used, the voltage, efficiency, life etc of lithium battery varies.
In some Mobile Phone, the battery power connector has three pins and the battery also has three pins. These pins are Positive, Negative and BSI. The BSI pin in the Mobile phone performs important functions. The battery pack has three pin outs. The pins located at the ends are + Bat and – Bat pins to charge the battery from the adapter. Thethird pin is the shorter BSI pin usually present in the middle position. The battery block of the Mobile phone has a BSI resistor for identifying the battery pack placed in the phone.The BSI fixed resistor value indicates the capacity and chemistry of battery. It also tells the phone processor about the temperature and charging voltage and current passing to the mobile phone. The BSI resistor connected to ground and the phone measures theresistance between the BSI and Ground and tells the processor about the type of battery inserted into the phone.
Power Switch:
A power switch is used in a mobile phone to turn on and off mobile phones if it is faulty the whole unit cannot
power on so keep checking its terminals wether they are connected with the power IC of not if not then you
can make a jumpwer and connect it.
Battery terminal:
battery terminals connect battery to mobile phone component unit if its points are dry soldered of
unsoldered or bended then you can change and fix this problem which is alwways in the result of no power
on. so if battery terminals are working correctly you need to proceed further.
Power IC:
A power IC distributes current among all the components actually a power IC works as " voltage regulator"
and " power on funtion" so if a power on funtion is faulty the whole unit will not power on. but there are some
problems with ICs that we cannot check them wether they are working right or not rather we can only
assume that they are faulty if the other functions are correct.
Oscilator:
An oscilator makes low frequency which is called clock frequency. this frequency is used to run digital
components if this frequency is not available digital components fail to work and the result is power on
failure. the out put frequency is used in mobile phone’s CPU and Memory chips and UEM Ic if used.
Frequency divider:
Frequency dividing is a funtion which is used in mobile phones to divide clocke frequency to get accurate
frequency to run digital components so if divider is failed power on fault mat occur. this frequency dividing
funtion is built in radio ICs commonly like hagar IC or Mojoelner in Nokia mobile phones.
CPU
A CPU (central processing unit) is like a brain in mobile phones which controls the major parts of mobile
phones so its funtionality is very necessory in mobile phones while testing in boot process but its
functionality is assosiated with Memory chips used in mobile phone specially Flash chip.
Flash Chip ( EEPROM)
A flash chip holds booting information in it self it has instructions stored in itself for the CPU to control other
components so if flash chip or its software is damaged it mean the set do not power on. in case of damaged
software the phone should be treated in flashing process