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AS1123

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

Figure 13. 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 AS1123.

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

Note:

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

If there are multiple AS1123s in a chain, the error flag will be gated through all devices. To get a valid result at the end of the chain, a logic 1 must

pin SDO of the last device in the chain. This means it is not possible to identify which device in the chain produced the error. Therefore, if a global

error occurs, the detailed error report can be run to identify which AS1123, or LED produced the error.

Note:

When no error has occurred, the detailed error report can be skipped, setting LD and subsequently OEN low.

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

SDI

OEN

LD

CLK

SDO

Don’t

Care

Don’t

Care

Don’t

Care

Acquisition of

Error Status