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Revision 1.21

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AS1109

Datasheet - Detailed Descr i p ti on

Figure 14. Switching Global Error Mode Timing Diagram

8.3 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.

8.4 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.

Note:

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

If there are multiple AS1109s 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

be applied to the SDI input of the first device of the chain. If one device produces an error this error will show up after n*tP(I/O) + tSW(ERROR) at

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 AS1109, 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

TFLAG = SDO = 1: No over-temperature warning.

TFLAG = SDO = 0: Over-temperature warning.

1

Enabled

Open-LED Detection

OFLAG = SDO = 1: No open-LED error.

OFLAG = SDO = 0: Open-LED error.

2

Enabled

Shorted-LED Detection

SFLAG = SDO = 1: No shorted-LED error.

SFLAG = SDO = 0: Shorted-LED error.

3

Don't Care

Low-Current Diagnostic Mode

4

Don't Care

Shutdown Mode

SDI = 1: Wakeup

SDI = 0: Shutdown

tTESTING

tSU(ERROR)

OFLAG(IN)

SFLAG(IN)

TFLAG(IN)

TFLAG

OFLAG

SFLAG

tSW(ERROR)

SDI

OEN

LD

CLK

SDO

Acquisition of Error

Status

Don’t

Care

Don’t

Care

tGSW(ERROR)

tP(I/O)

tP4

tP(I/O)

tP(I/O)

tSW(ERROR)

tGSW(ERROR)

tGSW(ERROR)

Don’t

Care