Friday, 24 June 2011

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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 card and 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.
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