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Why does LED need error detection function? |
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In the early phase, the LED driver was without error detection function.
When the super highway's LED display panel occurred short-circuit error data (one or several LED lines didn't light up), it was inconvenient to maintain and might cause the traffic safety problem. For the sake of this reason, the real-time error detection and read back function was made a regulation in highway LED display specification.
While it also requires the real-time error detection and read back function for the LED display panel in remote districts for easy to maintain. Even for the outdoor high quality LED full color display panel, real-time error detection and read back function is increasingly to be valued. MBI5027 is the exclusive LED driver with real-time error detection and read back function in the current market. |
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Does Macroblock's LED driver with error detection provide constant current function? |
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| With Share-I-O™, all LED drivers with error detection are not only for the existing function of MBI5026, but also provides error detection function with legacy IC footprint and no need to add any footprint. |
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What does the error detection function provided by Macroblock apply to? |
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| When LED is short- or open-circuit is resulted from damaged external circuits, such errors can be detected through the error detection function. |
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While LED drivers with error detection are connected in series, when the open-circuit occurred (error state), will the Error Data be shifted to next IC and affect the following image data output accuracy? |
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While LED drivers enter the error detection mode, the detection data input through SDI, and merely two microseconds (2μs) to detect the error, after finishing the detection and the erroneous state will be read from the system controller; then the image data can be shifted into SDI. The read detection data is shifted from each SDO to next SDI, the error status code in the shift register will be shifted out to SDO and thus read by the system controller. Therefore, the error data will not be shifted to the input.
Please refer to Fig.1. error detection Function Diagram.
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What is the characteristic of MBI5027/MBI5169 to perform the real-time error detection and read back function? |
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MBI5027/MBI5169 offers value-added LED short-/open-circuit error detection function. In several public facilities, the availability of the display panel is severely required. At the first moment of the display error, the system has to be alerted and the system administrator may call for a fix.
MBI5027/MBI5169 provides a feature of LED short-/open-circuit error detection function. MBI5027/MBI5169 has a built-in current detection circuitry which detects the individual current of each output port, when some of LED are open-circuit, the erroneous state will be stored and to be read from the system controller.
The error detection could be enabled and disabled by a simple modified sequence of the legacy control signal pins, OE, LED and CLK. Furthermore, MBI5027/MBI5169 exploits Share-I-O™ technique, which utilizes the data path to pass the error code as well as the image data. The error code passes through legacy signal pin SDO to the system controller without extra pins.
MBI5027/MBI5169 could be a drop-in replacement of MBI5026/MBI5168. The printed circuit board originally is also identical. |
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For the high current application, does MBI provide 8-bit LED driver with error detection function? When will it be available to offer? |
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| Yes. 8-bit LED driver with error detection function has same features as 16-bit LED driver. |
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What are the advantages and characteristics of Macroblock's error detection function compared with other brands LED drivers? |
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The other brand of LED Driver with error detection can merely provide "chip-status report" which means the IC only detects the error data occurred by which IC, but it can't show this error data is occurred by which channel of IC. It will be needed to detect each footprint of IC by sending 16 times data (multiple pass scans) to know which of the error happens.
Macroblock's LED driver exclusively provides "real-time individual LED status report" which means it can detect where the Error is occurred by which channel of IC and to make real-time read back. The error code can identify the individual LED error simultaneously, that is, no multiple pass scans are required. |
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Does it need to make any circuit re-layout or changing of the external resistor (Rtrim) when the system which of the original designed for MBI5026 will upgrade to use MBI5027 with error detection function? |
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| MBI5027, stemmed from MBI5026 design, the pitch of pin, package type and external resistor (Rtrim) are fully compatible with MBI5026. Customers only need to replace MBI5026 to MBI5027 to easy upgrade the system. |
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Under what kind of conditions will occur the open-circuit or short-circuit? What is the percentage? |
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| Open-circuit: |
The usual status is because of the LED is broken and the most error state is for open-circuit, the percentage is over 90%.
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| Short-circuit: |
There are two analyses as below.
1. For LED: LED is punctured by transient high voltage and short-circuit will thus happen. This is because no good measures of ESD protection are taken.
2. The display panel circuitry: The states may be caused by operator or unexpected accidents, such as water dropping or an conductive object falling. The percentage is below 10%. |
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Why does LED need current gain adjustment function? |
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A mass LED display panel is pieced up by every small module, the display quality hinges on uniform brightness; however the disproportionate brightness of LED display panel quality is often occurred by the differentia of LED characteristic of every module. Therefore, LED display panel maker needs to add an adjustable resistor to every module for LED gain control, though this way can reach the purpose of current adjustment, but it takes more human labor and cost, the most points are because of bad reliability and inconvenient maintenance. MBI5028 provides 128-steps current gain adjustment function which adopts digital gain code to make current gain control to reach the high quality requisition of LED Display Panel very easily.
MBI5028/MBI5170 provides additional current adjust feature besides the current adjust via a legacy resistor (Rtrim). To compensate the deviation of the LED characteristics, the system controller passes individual current gain code to each MBI5028/MBI5170 and command MBI5028/MBI5170 to tune up or tune down the output current and therefore compensate the LED brightness. The brightness compensation serves the white balance and elevates the image quality. The manual effort to adjust the resistor (Rext) may be automated with the help by an associated image analysis system. Thus, the cost of tuning a quality image is reduced.
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What is the feature of current gain adjustment? |
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1. The LED driver with current gain adjustment has a built-in DAC and thus can provide a digital way to control the output current.
2. The scope of current adjustment code is 128 steps ranging from 1.984x down to 0.5x and thus provides users with a wild flexibility to perform a white balance adjustment.
3. Like error detection series, current gain adjustment series also exploits Share-I-O™ technique and users can upgrade the original system to the one with an Error Adjustment function. In addition, the PCB initially can be still used for common board. |
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If users who previously applied MBI5026 to the system want to upgrade the system to the one with a current adjustment function, does they need to re-layout any circuitry or make substitution of the external resistor (Rtrim)? |
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| MBI5028, stemmed from MBI5026 design, the pitch of pin, package type and external resistor (Rext) are fully compatible with MBI5026. Customers only need to replace MBI5026 with MBI5028 to completely upgrade the system. |
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Traditionally, an external resistor (Rtrim) is always used to adjust the current of each output port; by contrary, MBI5028 adopts a digital way to adjust the current. What is the advantage for MBI5028 to adopt such a way? |
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1. MBI5028 can reach higher current adjustment to 128 steps, and tune down by ain=1.984x~0.5x.
2. It is much easier to use digital gain code to adjust the brightness.
3. Reduce the inconvenience of adjusting the resistors and save cost. |
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While MBI5028 is powered on, what is the default value of its current gain value? |
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| The default value is 1.984. After MBI5028 is powered on, users can enter the current adjustment mode and change the value. |
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