www.ams.com/LED-Driver-ICs/AS1109 Revision 1.21 14 - 24
AS1109
Datasheet - Detailed Description
8.6.3 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 10).
Figure 17. Detailed Shorted-LED Error Report Timing Diagram
Detailed Shorted-LED Error Report Example
Consider a case where five AS1109s 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 with a test pattern where all LEDs are on at test time. Additionally, this test should be run after starting low-current
diagnostic mode (see Low-Current Diagnostic Mode on page 14).
IC1:[11111XX1] IC2:[11111111] IC3:[11111111] IC4:[111X1111] IC5:[11111111]
IC2 has two shorted LEDs and IC4 has one shorted LED switched on due to input. 5*8 clock cycles are needed to write the entire error code out.
The detailed error report would look like this:
Showing IC1 as the device with two shorted LEDs at position 6 and 7, and IC4 with one shorted LED at position 4.
Note: In an actual report there are no spaces in the output. LEDs turned off during test time cannot be tested.
8.6.4 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 pattern 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 diagnosis mode require additional cables, resistors, and other components to reduce the current. The
AS1109 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.
On the next falling edge of OEN, current is reduced to I
LC. With the next rising edge of OEN the current will immediately increase to normal
levels and the detailed error report can be read out entering error-detection mode.
Input Data:
11111111 11111111 11111111 11111111 11111111
LED Status:
11111XX1 11111111 11111111 111X1111 11111111
Failure Code:
11111001 11111111 11111111 11101111 11111111
Global Flag Readout Detailed Error Report Readout
SDI
OEN
LD
CLK
SDO
tH(L)
tSU(ERROR)
tP1
tSW(ERROR)
tP4
TFLAG
SFLAG
Acquisition of Error
Status
DBit6 DBit5 DBit4 DBit3 DBit2 DBit1 DBit0
Don’t
Care
Don’t
Care
SBit6 SBit5 SBit4 SBit3 SBit2 SBit1 SBit0SBit7
New Data Input
Shorted-LED Error Report Output
OFLAG
TFLAG
tP4
tTESTING
Global Flag Readout
DBit7
For detailed timing information see Timing Diagrams on page 8.
tGSW(ERROR)
tGSW(ERROR)
tGSW(ERROR)
