What you need to know as a mobile phone expert

Below tutorial will give you full details of how a mobile phone work and best way to understand and troubleshoot a dead mobile device.

I. Introduction to Electronics

Voltage and Current

Voltage:  Voltage is equal to the  work which would have to

 be done, per unit charge, against a static electric field to move the charge between two points. Measured in (Volts) V=IR

              

          

Current: 

A flow of electric charge through a conductive medium. Measured in (Amps)

Current flow

In any circuit current flows from the positive terminal to

the negative terminal or ground.

Taking advantage of current’s tendency to reach ground points and passing it through components is the way we make current do work in electronics.

Components

All electronics circuitry are made to perform certain tasks. To carry our those tasks electronic components are used to build up the circuit.

Used components in a circuit depends on the tasks we need from that circuit.

We have two different classes of components:

1.Passive components

2.Active components

Passive components

Resistors resist the flow of electric current.

Voltage pushing the current through a wire will drop as resistor value increases.

A resistor will drop the current flow wither it was a DC constant signal, or AC wave signal produced by device’s circuitry.

Component 1. Resistor measured in Ohms (Ω)

Component 2. Capacitor measured in Farads (F)

Component 3. Inductor measured in Henry's (H)

Frequency

It’s the number of waves passing a wire within a time period of

one second.

If a voltage varies in time we call that a wave as Illustrated in above figure(4)

Frequency is measured in Hertz (Hz).

If voltage is constant and not varying with time, we call it a DC voltage, which is a direct current

flow of electrons as illustrated Below:

DC Voltage

IC integrated circuits:

IC chips consists of thousands and millions of transistors the are combined together to create a complete circuit to carry out complex functions.

Generally in mobile device we find the following chipsets:

1.PAM: Power Amplifier module

2.Main processor

3.Memory flash

4.Power management IC

5.And other ICs included to perform several additional tasks

Below, i will give you an example of a chipset

II. Power Module in Mobile Device

Power Sequence concept

1. In the above figure (CPU) is representing the power management side (Baseband) of the a mobile device

2. First the basic power voltage coming from battery needs to get to the power IC, which will carry on and switch the   

     main processor of a mobile device.

3. Sleep clock is necessary for the microprocessor to stay partially on even if the device is turned off completely.

                           

         How does a mobile phone Power up?

1. Power button is pressed for a short period of time

    as shown in figure (13), this will connect the power

on signal to ground,  and power on signal  will be

 connected to the CPU.

2. CPU will detect the power ON/OFF signal coming from

   connecting the power switch to ground, and will

   switch on the internal power supplies of the baseband

   to the baseband circuitry and RF (Radio frequency)

   circuit. Figure (14) CPU release power regulators.

NOTE: Do not mix CPU with microprocessor, CPU

            includes the power management IC which is

            the basic  Power supply unit in any mobile device

CPU regulators will supply RF circuit power side,

     and RF circuit will power the crystal oscillator

which will provide a clock signal that will time

     the operations of the Processor IC.

     

 

    The processor IC then sends a signal  indicating the

    flash memory to start downloading the software  to

    and check is being performed if main sections of

    logic circuitry is running fine.

Finally, if all clocks are ok, voltages are supplied,

device will start up and software interface(Phone booting stage) will appear

on the screen.

Power Concept Example:

1. All Mobile Phones no matter the Technology, FDMA, TDMA, GSM and CDMA, plus all the added bells and whistles

       i.e. Camera, FM Radio, MP3 etc all have to do the same thing when they first power up.

2.  The Logic side of the phone needs to go through its power up routine. A mobile phone has no idea what to do until

       the Microprocessor IC (the brain) has accessed the operating instructions (program), which is  held in the Flash IC.

The block diagram above explains the general power sequence for Samsung Phone and can be used for any mobile device:

      Vbat --- Vcore & 32 KHz ---RST_AP---Hold AP --- RF Supply --- 26 MHz ---Firmware upload 

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