Market status of SD card
No one doubts that SD Card is one of the most popular memory cards in the world. SD Card standard started in 2000, and has expanded its applications into digital still camera, mobile phone and PC peripherals. According to iSuppli 2011 market trend forecast, SD card, as a removable media to carry files, is not only for information, but also audio and videos with its big capacity and low prices.
In 2012, 32 to 64 GB SD cards are coming to market, and some 8GB SD card’s price is less than USD 10 at this time (2012, June). Less than USD 10 is a magic number to spread in the consumer market. That is, the capacity of 8GB SD card is over DVD (4.8GB) and good enough to record and play DVD movies in one card.
Constantly SD card technology updates & the accompanying demand for certification
SD card is constantly expanded its specification with version up for bigger capacity as SDXC and increase BUS-speed by UHS-I (DDR) and UHS-II (LVDS) in the latest update of Ver.4.10 of SD card physical layer specifications both for Card and Host. Because of this update, there are several important test items needed testing to comply with the specifications. With the launch of various SD card specifications; for example, there are more and more different speed rating SD cards in the market, such as Class 2, Class 4 and Class 6. However, could the actual R/W speed truly reflect the lower limit of specification? Technical updates means that some test items must carry through the actual validation to ensure the compliance with specifications. Therefore, we would like to introduce an extremely important test program as so-called “Power supply current test for SD host products.” The following we will make a brief description for the purpose and methods of this test.
What is power supply current test for SD host product?
The purpose of the test is to ensure the Host power supply capability for new cards. SD Hosts, such as smart phone, mobile phone, digital camera and USB-readers, are requested to supply 200mA as minimum. After Ver.4.1o Spec was released, Host can supply more than 500mA to operate with SDXC, UHS-I, UHS-II coming or Wi-Fi IO cards. To ensure such power supply capability, SDA defines test methods as Fig-2 by using Electric Load.
Test results as minimum requirements for SD Host
Fig-3 (bellow) is test result on Host power supply. The vertical axis is output voltage of Host and the horizontal is Icc (Card Loading). In Fig-3, regular voltage of Host output is 3.3 V; however, when the card loading is increased (imitate more power consumption by card operation), Host system shall maintain the voltage more than 2.7 V until 200mA. If the I-V characteristic can assure this condition as green line in Fig-3, it means that Host system has enough power supply as 200mA.
In some case; however, Host output voltage decreases under 3.3V and drop voltage under 2.7V before 200mA Loading (red Line in Fig-3). In other words, this Host does not conform to the minimum power supply requirements. According to our observation on some products in the markets, we found some mobile host, mobile phone, digital camera and USB reader have insufficient power supply while operating with heavy loads (telephoning, zooming, access multi-devices).
For future SD card Products: strict test requirements to meet higher power consumption
Fig-4 (below) shows the UHS-I card dynamic current measured. According to this measurement result, UHS-I memory card could cost up to nearly 400mA power supply. Obviously, Host system shall provide at least more than 200mA to 400mA power supply capability to maintain the proper operation of the UHS-I card.Thus, if Host system has to work on UHS-I or some high power cards like Wi-Fi SD card, it must have more power supply confirming with such Host power supply tests.
What Allion can do? Comprehensive tests to approve product quality
This Host power supply capability test method was proposed by Allion and adopted by SDA as an official test method. As an important core member of SDA, Allion is authorized as “Designated Lab” and contributes its technical discussion and marketing events as well. Allion can support both Host and card developer by our long time experience and know-how on the storage device tests for card and mobile Host device testing. For further information, please contact service@allion.com.