AS1109
Data Sheet - Detailed Description
Figure 14. Switching Global Error Mode Timing Diagram
tTESTING
OEN
LD
tGSW(ERROR)
tGSW(ERROR)
tSU(ERROR)
tP(I/O)
tP(I/O)
tP(I/O)
tGSW(ERROR)
CLK
SDI
TFLAG(IN)
OFLAG(IN)
SFLAG(IN)
Don’t
Care
Don’t
Care
Don’t
Care
SDO
TFLAG
OFLAG
SFLAG
tP4
tSW(ERROR)
tSW(ERROR)
Acquisition of
Error Status
Error-Detection Mode
Acquisition of the error status occurs at the rising edge of OEN. Error-detection mode is started on the rising edge of
LD when OEN is high. The CLK signal must be low when entering error detection mode. Error detection for open- and
shorted-LEDs can only be performed for LEDs that are switched on during test time. To switch between error-detection
modes clock pulses are needed (see Table 5).
Note: To test all LEDs, a test pattern that turns on all LEDs must be input to the AS1109.
Global Error Mode
Global error mode is entered when error-detection mode is started. Clock pulses during this period are used to select
between temperature, open-LED, and shorted-LED tests, as well as low-current diagnostic mode and shutdown mode
(see Table 5). In global error mode, an error flag (TFLAG, OFLAG, SFLAG) is delivered to pin SDO if any errors are
encountered.
Table 5. Global Error Mode Selections
Clock
Pulses
Output Port Error-Detection Mode
Global Error Flag/Shutdown Condition
TFLAG = SDO = 1: No over-temperature warning.
TFLAG = SDO = 0: Over-temperature warning.
OFLAG = SDO = 1: No open-LED error.
OFLAG = SDO = 0: Open-LED error.
Over-Temperature
Don't Care
0
Detection
1
2
3
4
Enabled
Enabled
Open-LED Detection
SFLAG = SDO = 1: No shorted-LED error.
SFLAG = SDO = 0: Shorted-LED error.
Shorted-LED Detection
Low-Current Diagnostic
Mode
Don't Care
Don't Care
SDI = 1: Wakeup
SDI = 0: Shutdown
Shutdown Mode
Note: For a valid result SDI must be 1 for the first device.
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