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Revision 1.18

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AS1109

Data Sheet - D e t a i l e d D e s c r i p t i o n

Figure 14. Switching Global Error Mode Timing Diagram

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

encountered.

Note: For a valid result SDI must be 1 for the first device.

Table 5. Global Error Mode Selections

Clock

Pulses

Output Port

Error-Detection Mode

Global Error Flag/Shutdown Condition

0

Don't Care

Over-Temperature

Detection

1

Enabled

Open-LED Detection

2

Enabled

Shorted-LED Detection

3

Don't Care

Low-Current Diagnostic

Mode

4

Don't Care

Shutdown Mode

SDI = 1: Wakeup

SDI = 0: Shutdown

SDI

OEN

LD

CLK

SDO

Acquisition of

Error Status

Don’t

Care

Don’t

Care

Don’t

Care