Learning how do Removable Memory Card (MMC ) works on mobile phones circuit
In this tutorials we are going to tackle out how dos the memory card circuit works on mobile phones. As in my previous post I talked about memory card pin-outs and types of memory cards used on cellular phones.
So this gonna be a continuation for that previous post.
Okay, the block diagram below shows how the removable memory card or MMC card connection to other corresponding components. Since the memory card has two signal function operations, the SD mode and SPI mode, the SD mode indicates that all pins of the memory card ether SD card , miniSD cardand microSD card has a connections while in SPI mode some of the pins are not connected. See the block diagram below.
So this gonna be a continuation for that previous post.
Okay, the block diagram below shows how the removable memory card or MMC card connection to other corresponding components. Since the memory card has two signal function operations, the SD mode and SPI mode, the SD mode indicates that all pins of the memory card ether SD card , miniSD cardand microSD card has a connections while in SPI mode some of the pins are not connected. See the block diagram below.
SD Mode memory card connection block diagram
SPI Mode memory card connection block diagram
In mobile phones ESD and EMI filtering were so very important, the connection between the memory card across to the application processor is being filtered or protected by any means of ESD and EMI interruption.
The power supply voltage and its groundings is also present to make the memory card operational or works.
The MMC circuit components assembly in mobile phones
This picture below show an example on how the MMC circuit components being assembled on cell phones PCB boards.
How can we identify which and what kind of cell phones used SD mode and SPI mode? Do we really need to know about this?
The best easy way to identify which one has SD or SPI designed, is by figuring it out on the schematic diagram, and it is so important to know about this for easy troubleshooting and repair memory card related problem issues.
Have a look of these following schematic diagrams below and configure out the differences between SD mode and SPI mode circuit connection.
1. Memory Card with SD mode connection schematic diagram
2. Memory Card with SPI mode connection schematic diagram
Identifying EMI filters used in mobile phones
Now, the key reasons in this discussion is also by identifying certain types of ESD-EMI filters being used on every mobile phones designs. Since EMI-ESD filters are most commonly get damaged when it comes to memory card failure problem.
In SD mode circuit connection we notice that it's used an EMI filter with large number of internal filter lines while in SPI mode only a few internal filter lines.
See below for particular EMI filters most commonly used in mobile phones MMC circuit
a. SD mode this EMI filter is commonly used
b. SPI mode this EMI filter is commonly used
and the following too.
SD MMC EMI filter
miniSD EMI filter
As you'll notice there are few types of EMI filters, if you became so familiar with this EMI filter chips you can gain a very big advantage on fixing and repairing memory card problems related issues.
So the next thing we are going to tackle next is how to troubleshoot, fix and repair memory card problems and failures on mobile (cellular) phones.
Understanding Mobile Phones Removable Memory Card Pinouts - For Memory Card Problems and Failure Repair
By learning how does the removable memory card works on mobile phone devices. We can easily configure on how to repair if something went wrong when the memory card related problems such as memory card can't be read, memory card not detected and many other related memory card errors on mobile phones occurred.
But first, we must also understand about removable memory cards and how it is being constructed.
In mobile phones there are three types of removable memory card being used the first was the SDcard which is so big in size used on some old model cell phones and then comes the MiniSD and the latest is the microSD card which the smaller one and commonly used in most latest designs.
But first, we must also understand about removable memory cards and how it is being constructed.
In mobile phones there are three types of removable memory card being used the first was the SDcard which is so big in size used on some old model cell phones and then comes the MiniSD and the latest is the microSD card which the smaller one and commonly used in most latest designs.
Secure Digital is what SD means, it is a flash based removable memory card. The card format may also be used other device functions in addition to data storage.
The SD card size dimensions are: 24mm wide x 32mm long. The standard width is 2.1mm, while the Thin SD Memory Card has a width 1.4mm.
| Pin | Pin Name | SD Signal Function SD Mode | SPI Signal Function SPI Mode |
| 1 | DAT3/CS | Data Line 3 | Chip Select/Slave Select [SS] |
| 2 | CMD/DI | Command Line | Master Out/Slave In [MOSI] |
| 3 | VSS1 | Ground | Ground |
| 4 | Vdd | Voltage Supply [2.7v or 3.6v] | Voltage Supply [2.7v or 3.6v] |
| 5 | Clock | Clock | Clock [SCK] |
| 6 | Vss2 | Ground | Ground |
| 7 | DAT0/D0 | Data Line 0 | Master In Slave Out [MISO] |
| 8 | DAT1/IRQ | Data Line 1 | Unused or IRQ |
| 9 | DAT2/NC | Data Line 2 | Unused |
MiniSD Card is a type of Removable NAND flash memory card format.
miniSD cards have memory capacities ranging from 256MB to 4GB. However, some of the capacity may be used for formatting and other functions, and not available for data storage. A miniSD card will fit in an SD card slot with a miniSD Adapter, miniSD Adaptes makes miniSD memory cards compatible with all SD-based devices.
There are 3 speed grades: Class 2, 2MB/s, Class 4, 4MB/s and class 6 card, 6MB/s.
The MiniSD Card measures 20mm x 21.5mm and 1.4mm thick.
| Pin # | Pin Name | SD Signal Function SD Mode | SPI Signal Function SPI Mode |
| 1 | CD/DAT3 | Chip Detect/Data Line 3 | Chip Select |
| 2 | CMD | Command Line | Data In [DI] |
| 3 | VSS1 | Ground | Ground |
| 4 | Vdd | Voltage Supply [2.7v or 3.6v] | Voltage Supply [2.7v or 3.6v] |
| 5 | Clock | Clock | Clock [SCK] |
| 6 | Vss2 | Ground | Ground |
| 7 | DAT0 | Data Line 0 | Data Out [DO] |
| 8 | DAT1 | Data Line 1 | Unused |
| 9 | DAT2 | Data Line 2 | Unused |
| 10 | NC | For future use | For future use |
| 11 | NC | For future use | For future use |
microSD Card is also a type of Removable NAND-type small flash memory card format, and has a dimensions of 11mm x 15mm and 1mm thick. MicroSD is short hand for Micro-Secure Digital [Transflash].
| Pin # | Pin Name | Signal Function |
| 1 | DAT2 | Data Bit 2 |
| 2 | CD/DAT3 | Card Detect / Data Bit 3 |
| 3 | CMD | Command Line |
| 4 | Vdd | Supply Voltage 2.7v / 3.6v |
| 5 | CLK | Clock |
| 6 | Vss | Ground |
| 7 | DAT0 | Data Bit 0 |
| 8 | DAT1 | Data Bit 1 |
| Pin # | Pin Name | Signal Function |
| 1 | NC | No Connect |
| 2 | /CS | Chip Select |
| 3 | DI | Master Out/Slave In (MOSI) |
| 4 | Vdd | Supply Voltage 2.7v / 3.6v |
| 5 | CLK | Clock |
| 6 | Vss | Ground |
| 7 | DO | Master In/Slave Out (MISO) |
| 8 | RSV | Reserved |
Mobile phones manufacturers used SD mode and SPI mode Memory card Signal Function, it only varies according on mobile phones designed. You can easily determine which one is SD mode or SPI mode designed. Just figure out the MMC slot socket then count the corresponding pins on it. In SD mode all pins has a connections while in SPI mode some of the pins are reserved and not in used or have no connection in the circuit.
In continuation of this post by learning how the Removable Memory Card Circuit works on mobile phones, and How to troubleshoot and repair memory card problem issues, we can configure which particular mobile phone used the SD mode and SPI Mode signal functions.
Understanding WLAN and GPS Circuit on Smart Phones
Additional features such as Bluetooth, WLAN and GPS on Smart phones become more popular in the market. As a techie you also need to figure out how this circuit works in order for you to catch up a new evolving designed on mobile phones.
These additional features is packed into an IC component module in a circuit, and this kind of
of circuit are associated with a master clock which typically a external clock crystal oscillator.
With the master clock the data transmitted or received is modulated to a proper certain frequency.
Here's how simply tells us how the circuit works on smart phones.
The WLAN circuit
Wireless Local Area Network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network.
A typical block diagram below shows bluetooth wlan circuit, this block diagram will tell us how the clock oscillator feeds desired frequency to the WLAN module. The Wlan is associated is with the bluetooth transceiver circuitto send receive the data from the Wlan module to register it to the application processor.
In this diagram shows that the WLAN module also needs the RF clock to make it work, this RF clock comes from the RF circuit. In other designed aVoltage Controlled Temperature Compensated Crystal Oscillator(VCTXO) is used as an external clock generator.
These additional features is packed into an IC component module in a circuit, and this kind of
of circuit are associated with a master clock which typically a external clock crystal oscillator.
With the master clock the data transmitted or received is modulated to a proper certain frequency.
Here's how simply tells us how the circuit works on smart phones.
The WLAN circuit
Wireless Local Area Network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network.
A typical block diagram below shows bluetooth wlan circuit, this block diagram will tell us how the clock oscillator feeds desired frequency to the WLAN module. The Wlan is associated is with the bluetooth transceiver circuitto send receive the data from the Wlan module to register it to the application processor.
In this diagram shows that the WLAN module also needs the RF clock to make it work, this RF clock comes from the RF circuit. In other designed aVoltage Controlled Temperature Compensated Crystal Oscillator(VCTXO) is used as an external clock generator.
Typical block diagram of Bluetooth WLAN circuit
The GPS Circuit
The Global Positioning System (GPS) is a space-based global navigation satellite system that provides reliable location and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS satellites.The GPS (global positioning system) circuit comes with a GPS module this is packed into chip, a GPS RX filter, GPS clock crystal oscillator and a GPS antenna.
In this block diagram the GPS module is being feed with different RF clock data signal which also comes from the RF circuit.
Typical block diagram of bluetooth with WLAN and GPS circuit
The components layout of Bluetooth, WLAN and GPS circuit on a PCB board.
This shows an example of the bluetooth circuit associated with WLAN and GPS circuit mounted on PCB board.
You'll figure out that all circuit components such as the ic oscillator,bluetooth chip, wlan chip and gps chip is mounted all together with each corresponding connections. The RF clock is located on the RF circuit section which is comes from the RF chip.
And here's an schematic diagram of WLAN and GPS circuit, for knowing how the circuit components connected with each corresponding components.
This is only a simple explanation how does the circuit works, the main key for this lesson is how to figure out and used this tutorial in troubleshooting and repairing GPS and WLAN problem and failures on a particular mobile phone devices, that we are going to tackle it here and so on...
Understanding about bluetooth circuit in mobile phones, a key to fix bluetooth problem issues
We already know that Bluetooth is an open wireless device technology standard for exchanging data over short distances from fixed and mobile devices(using short wavelength radio transmissions), creating personal area networks (PANs) with high levels of security.The Bluetooth baseband protocol is a combination of circuit and packet switching. Slots can be reserved for synchronous packets. Each packet is transmitted in a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel, which simultaneously supports asynchronous data and synchronous voice.
and that's how it simply works.
Since we are talking about mobile phones here, it is much more really great to know how really bluetooth circuit works on cell phones circuit? Isn't it nice to know, so that we can easily managed how to fix it since it is our main reason in this tutorials by learning how to repair damaged cell phone devices.
In mobile phones Bluetooth problems also occurs when the bluetooth circuit is damaged, Some new cell phone techie find it hard to fix bluetooth for not knowing how the circuit works.
Okay, lets tackle it for a while in just very simple explanation so that all of those without any background in electronics might can catch up too, and then we can use it in our everyday job on GSM field.
Figure the bluetooth circuit block diagram below for it shows how the Bluetooth Circuit works according to each corresponding parts or components that is being connected to it.
and that's how it simply works.
Since we are talking about mobile phones here, it is much more really great to know how really bluetooth circuit works on cell phones circuit? Isn't it nice to know, so that we can easily managed how to fix it since it is our main reason in this tutorials by learning how to repair damaged cell phone devices.
In mobile phones Bluetooth problems also occurs when the bluetooth circuit is damaged, Some new cell phone techie find it hard to fix bluetooth for not knowing how the circuit works.
Okay, lets tackle it for a while in just very simple explanation so that all of those without any background in electronics might can catch up too, and then we can use it in our everyday job on GSM field.
Figure the bluetooth circuit block diagram below for it shows how the Bluetooth Circuit works according to each corresponding parts or components that is being connected to it.
Typical block diagram of a Bluetooth Circuit
The bluetooth transceiver module is packed into chip or IC (integrated circuit), this chip needs a certain power supply to make it work. All the data that has been transmit (send) and receive from the bluetooth antenna and bluetooth RF (radio frequency) transceiver is feeds in for receiving and feeds out when sending to the application processor (cpu IC). There is an RF clock which comes from the RF circuit section is also feeds into it, that certain RF - Radio frequency is also needed by the bluetooth module to make it fully functional.Since all those certain parts on bluetooth circuit were packed only into chips. A way to truly understand how does the circuit connect with each other from each certain components is by reading the circuit schematic diagram to locate this certain components parts on the main PCB board so that we can be able to check, trace and fix when a bluetooh failure happens. here's an example of the bluetooth schematic diagram and figure out how each components connect with other. In this method you can easily identify where that certain parts connected from one another. See here:
And here's an example of the Bluetooth circuit layout of components on a PCB board.
You'll notice that all of the bluetooth components is mounted in one section and near to each other. Some important spots is being labeled for quick troubleshooting guide. Like this picture below, the voltage supply and the RF clock are being labeled for quick check up and test procedures.
For any further deeper questions just post it unto the chat box page.
Understanding how RF circuit Works on Cell Phones
In cell phone repair it is very helpful to understand how the RF circuits works , for this is a big help when
troubleshooting No signal problem issues.
RF stands for radio frequency , this frequency is used to transmit and receive the data signals from a mobile phone.
Here's a brief explanation on how does RF circuit works on mobile phones.
This is for GSM RF circuit only, although the WCDMA circuit and WI-FI circuit have similarity on this but I will try to explain both of it hereafter.
See the block diagram below. Observe how the frequency data signal feeds from a certain parts of an RF circuit design.
A breakdown or failure of each certain part will result to signal loss and the capability to generate, amplify, control , process, send and receive the desired radio frequency during transmission process.
In mobile phones transmission there are two types of operation took place, the receiving operation and the transmitting operation.
In normal mode, RX part is always active in receiving operation the antenna switch is always open its gateway through to the RX circuit, It is always ready to receive and intercepts the radio waves and wait for the desired frequency signal to catch up.
During transmission like making a call or sending a text message the antenna switch will close the gateway of the RX and open the gateway of the TX in order not to interfere the data signal during transmission.
All data that has been receive and before to transmit or send, all this data signals are feeds to the baseband processor.
An explanation of an RF Circuit Parts and what possible problems if a certain part is damaged.
RF Receiver - ( RX radio receiver )
The rf receiver are called RX, this circuit is design to receives, and process the data signals from the airwaves during transmission process. A failure of this circuit will result to unable to receive data signal during transmission.
RF Transmitter - ( TX radio transmitter )
the rf transmitter are called TX which is the one that process, amplify the data signals from a mobile phone .
Once failed to initiate a failure to transmit radio frequency signal, this will result to unable to send data signal during transmission. .
Power amplifier - RF amplifier
The power amplifier is used to amplify, boost up the radio frequency signal before it feeds to the antenna before it thrown over the air waves during transmission. If damaged will result to signal loss, a dropping signal indication on the display.
The Antenna is used to intercepts and thrown the radio radio frequency in the air during transmission
When electricity is "thrown" into the metal of an antenna, the metal reacts to the electricity at an atomic level in the form of a wave.
if damaged or due to a corroded terminal pads, will indicate and show a poor signal or low level frequency signal.
Antenna switch
The antenna switch is used as a gateway that controls and manage the frequency to pass through, it switch the RX frequency signal and TX frequency signal during transmission process. literally the antenna is the signal catcher and likewise the signal thrower. If damaged the gateway to the antenna will be closed and result to network signal indication.
Crystal oscillator
Generates a desired frequency that feeds to the RX and TX circuits. In mobile phones a Voltage controlled Oscillator (VCO) and Voltage Controlled Temperature Compensated Crystal Oscillator (VCTXO) is used in rf circuit.
If damaged the RX and TX will not work and the RF cicuit is at full failure.
SAW filter
Surface Acoustic Wave filter used as an rf synthesizer to purify a desired level of frequency. If damaged result also to no network signal indication.
An example of the RF circuit components layout on a PCB board.
For further questions just post a message on the shout box page.
Mobile Phones Problems and Failure with a damaged flex cable
Almost all equipments with LCD displays utilize flat flexible cable to connect the display to the main circuit board.These flat cable ribbon allows extreme space savings and provides the needed flexible cable connection for devices with movable parts such as LCD displays, clamshell phones, slide cellular phones and other gadgets. Ribbon cable assemblies comes with many forms and varies according to the mobile phones designs.
Clampshell, Fold, Flip, Slide designs of mobile phones used a flat ribbon cables to connect the two separated parts of the phone's assembly.
In most designs like the LCD, camera, earpiece speaker, keypads, ON/OFF power switch and other parts are being connected with flat cable connector from the main PCB board.
Each of those components or parts shared each individual lines paths on the ribbon cable assemblies.
Now, if the flex cable is being damaged it will result and varies to the following failures:
If the LCD's line paths is damaged or cut will results
* No LCD Screen Display
* White Screen, some mobile phone users called it white screen of death (WSOD)
*Black Screen, result to LCD's LED back light failure
*Garbled or Distorted Display, Reversed Display
If the ON/OFF power switch line paths is damaged or cut will result to; unable to power up the phone.
If the Camera line paths is damaged or cut, the camera will not work or causes a failure.
And so on if the earpiece line paths is cut off, no audio sound can be recieve or hear,
and also if the keypads line paths being cut or damaged the keypads won't work or results to keypad malfunction.
Clampshell, Fold, Flip, Slide designs of mobile phones used a flat ribbon cables to connect the two separated parts of the phone's assembly.
In most designs like the LCD, camera, earpiece speaker, keypads, ON/OFF power switch and other parts are being connected with flat cable connector from the main PCB board.
Each of those components or parts shared each individual lines paths on the ribbon cable assemblies.
Now, if the flex cable is being damaged it will result and varies to the following failures:
If the LCD's line paths is damaged or cut will results
* No LCD Screen Display
* White Screen, some mobile phone users called it white screen of death (WSOD)
*Black Screen, result to LCD's LED back light failure
*Garbled or Distorted Display, Reversed Display
If the ON/OFF power switch line paths is damaged or cut will result to; unable to power up the phone.
If the Camera line paths is damaged or cut, the camera will not work or causes a failure.
And so on if the earpiece line paths is cut off, no audio sound can be recieve or hear,
and also if the keypads line paths being cut or damaged the keypads won't work or results to keypad malfunction.
In repairing mobile phones this is very helpful on how to easily determine on how or of which spare parts will come to check first before proceeding to other test and check up methods.
All you need to do is to determine or identify the mobile phones assembly of components that correspond with the flex cable connections. In most cases flex cable have highly risk of being easily damaged on clampshell and slide phones.
A damaged Flex cable can be easily determine visually and some others will not, there are flex cables that are shaded and coated with black adhesive.
Repair Tips: Make sure to have as much or more replacement flex cable stock on your shop to a certain mobile phones that are mostly used in your areas, for quick and easy test and check up procedures. All you need to do is just replace the suspected damaged flex with a good and working or a new one.
Can I earn without any having complete tools yet in mobile phone repair?
I just want to post this simple answers here of some new learners that keep asking me, on how to start earning from repair without any having complete repair tools yet at all.
Some beginners might think that fixing a defective phone might as well as too difficult to deal with.
So this is just a quick and simple answer for the above question.
Well, all I can say is that you can start from the scratch, there are so many mobile phone technicians started from nothing and turned into something, I've been also started from scratch, way back 9 years ago, I repaired cell phones before that only an opening tools like T6 screwdriver and a tweezer on my working table.
Mission Repair
In cell phone repair, there are two types of failure to handle with;
The software and the hardware related problem or failure issues.
Its not been a bit easy to determine which type of failure to deal with a faulty mobile phone indication, that is why many expert uses the method of checking its firmware first before considering that the problem lies on the hardware parts.
this method is by way of reading the mobile phones firmware by a way of using flashing or unlocking tools, then in by this method they can read the logs. This logs is firmware that composed of many codes, the logs can help to determine which part or components causes the problem.
Some software problem related failure issues are of such the following indications, but also the failure lies on the hardware parts in mobile phone devices, like hang up on logo only, often restarted, contact service, contact retailer, contact service provider etc, unable to power up, or dead phone due to its firmware interruption and a lot more which can only explained by after check up process.
For a beginners, these are the things you can do repair as a good way to start.
Well, you can do repair by replacing broken LCD's, replacing a broken power ON/OFF switch, you can do repair minor problems such us ringer problem, not charging, mouthpiece microphone, earpiece speaker problems and more problems that is not necessarily needs a deep troubleshooting procedure.
You can do that as well as it doesn't need any software tools to handle with.
All you need is replacement spare parts, a guide on how to dismantle the handset and or a service manuals.
What about flashing and unlocking?
Flashing and unlocking is not hard and too difficult to deal with, it is because when you purchase a flashing or unlocking tools, the sellers or the resellers will provide a support for their product via online. I have a little bit guide on this blog but not too much, due to some blogging restrictions.
The sellers will update and inform you from time to time which and what mobile phone handsets is newly supported and will work with.You can visit thisforum for where they all hanged out.
The techniques in flashing and unlocking is that you have to be familiar with the software tools and also by reading of the logs and codes.
Some beginners might think that fixing a defective phone might as well as too difficult to deal with.
So this is just a quick and simple answer for the above question.
Well, all I can say is that you can start from the scratch, there are so many mobile phone technicians started from nothing and turned into something, I've been also started from scratch, way back 9 years ago, I repaired cell phones before that only an opening tools like T6 screwdriver and a tweezer on my working table.
Mission Repair
In cell phone repair, there are two types of failure to handle with;
The software and the hardware related problem or failure issues.
Its not been a bit easy to determine which type of failure to deal with a faulty mobile phone indication, that is why many expert uses the method of checking its firmware first before considering that the problem lies on the hardware parts.
this method is by way of reading the mobile phones firmware by a way of using flashing or unlocking tools, then in by this method they can read the logs. This logs is firmware that composed of many codes, the logs can help to determine which part or components causes the problem.
Some software problem related failure issues are of such the following indications, but also the failure lies on the hardware parts in mobile phone devices, like hang up on logo only, often restarted, contact service, contact retailer, contact service provider etc, unable to power up, or dead phone due to its firmware interruption and a lot more which can only explained by after check up process.
For a beginners, these are the things you can do repair as a good way to start.
Well, you can do repair by replacing broken LCD's, replacing a broken power ON/OFF switch, you can do repair minor problems such us ringer problem, not charging, mouthpiece microphone, earpiece speaker problems and more problems that is not necessarily needs a deep troubleshooting procedure.
You can do that as well as it doesn't need any software tools to handle with.
All you need is replacement spare parts, a guide on how to dismantle the handset and or a service manuals.
What about flashing and unlocking?
Flashing and unlocking is not hard and too difficult to deal with, it is because when you purchase a flashing or unlocking tools, the sellers or the resellers will provide a support for their product via online. I have a little bit guide on this blog but not too much, due to some blogging restrictions.
The sellers will update and inform you from time to time which and what mobile phone handsets is newly supported and will work with.You can visit thisforum for where they all hanged out.
The techniques in flashing and unlocking is that you have to be familiar with the software tools and also by reading of the logs and codes.
