AS1113 Ver la hoja de datos (PDF) - austriamicrosystems AG

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AS1113

50mA, 16-Channel LED Driver with Diagnostics

austriamicrosystems AG 

AS1113

Data Sheet - Detailed Description

Detailed Shorted-LED Error Report

The detailed shorted-LED error report can be read out immediately after global error mode has been run (see Global

Error Mode on page 11). SDI must be 1 for the first device.

Figure 15. Detailed Shorted-LED Error Report Timing Diagram

OEN

LD

CLK

Global Flag Readout

Detailed Error Report Readout

tTESTING

tSU(ERROR)

tGSW(ERROR)

tGSW(ERROR)

tH(L)

tP4

SDI

tGSW(ERROR)

tSW(ERROR)

DBit15 DBit14 DBit13 DBit12 DBitn DBit2 DBit1 DBit0

New Data Input

SDO

TTFFLLAAGG OFLAG

SFLAG

tP4

For detailed timing information see Timing Diagrams on page 9.

SBit15 SBit14 SBit13 SBit12 SBitn SBit2 SBit1 SBit0

Shorted-LED Error Report Output

tP1

Don’t

Care

Don’t

Care

Detailed Shorted-LED Error Report Example

Consider a case where three AS1113s are cascaded in one chain. A 1 indicates a LED is on, a 0 indicates a LED is off,

and an X indicates a shorted LED. This test is used on-the-fly.

IC1:[11111XX111111111] IC2:[1111111111111111] IC3:[X100011111111111]

IC1 has two shorted LEDs which are switched on, IC3 has one shorted LED switched off due to input. 3*16 clock

cycles are needed to write the entire error code out. The detailed error report would look like this:

Input Data: 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

LED Status: 1 1 1 1 1 X X 1 1 1 1 1 1 1 1 1

Failure Code: 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1

1111111111111111

1111111111111111

1111111111111111

0100011111111111

X1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

1111111111111111

Showing IC1 as the device with two shorted LEDs at position 6 and 7, and IC3 with one shorted LED at position 1. The

shorted LED at position 1 of IC3 cannot be detected, since LEDs turned off at test time are not tested and will show a

logic "1" at the detailed error report. To test all LEDs this test should be run with an all 1s test pattern. For a test with an

all on test pattern, low-current diagnostic mode should be entered first to reduce on-screen flickering.

Note: In an actual report there are no spaces in the output. LEDs turned off during test time cannot be tested and will

show a logic 1 in the detailed error report.

Low-Current Diagnostic Mode

To run the open- or shorted-LED test, a test pattern must be used that will turn on each LED to be tested. This test pat-

tern will cause a short flicker on the screen while the test is being performed. The low-current diagnostic mode can be

initiated prior to running a detailed error report to reduce this on-screen flickering.

Note: Normally, displays using such a diagnostic mode require additional cables, resistors, and other components to

reduce the current. The AS1113 has this current-reduction capability built-in, thereby minimizing the number of

external components required.

Low-current diagnostic mode can be initiated via 3 clock pulses during error-detection mode. After the falling edge of

LD, a test pattern displaying all 1s can be written to the shift register which will be used for the next error-detection test.

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