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AS1109

Datasheet - Detailed Descr i p ti on

8.5 Error Detection Functions

8.5.1 Open-LED Detection

The AS1109 open-LED detection is based on the comparison between VDS and VTHL. The open LED status is aquired at the rising edge of

OEN and stored internally. While detecting open-LEDs the output port must be turned on. Open LED detection can be started with 1 clock pulse

during error detection mode while the output port is turned on.

Note:

LEDs which are turned off at test time cannot be tested.

8.5.2 Shorted-LED

The AS1109 shorted-LED detection is based on the comparison between VDS and VTHH. The shortened LED status is acquired at the rising

edge of OEN and stored internally. While detecting shorted-LEDs the output port must be turned on. Shorted-LED detection can be started with

2 clock pulses during error detection mode while the output port is turned on.

For valid results, the voltage at OUTN0:OUTN7 must be lower then VTHH under low-current diagnostic mode operating conditions. This can be

achieved by reducing the VLED voltage or by adding additional diodes, resistors or LED’s.

Note:

LEDs which are turned off at test time cannot be tested.

8.5.3 Overtemperature

Thermal protection for the AS1109 is provided by continuously monitoring the device’s core temperature. The overtemperature status is aquired

at the rising edge of OEN and stored internally.

Table 6. Open LED Detection Modes

Output Port State

Effective Output

Point Conditions

Detected Open-LED

Error Status Code

Meaning

On

VDS < VTHL

0

Open Circuit

On

VDS > VTHL

1

Normal

Table 7. Shorted LED Detection Modes

Output Port State

Effective Output

Point Conditions

Detected Shorted-LED

Error Status Code

Meaning

On

VDS > VTHH

0

Short Circuit

On

VDS < VTHH

1

Normal

Table 8. Overtemperature Modes

Output Port State

Effective Output

Point Conditions

Detected Overtemperature

Status Code

Meaning

Don’t Care

Temperature > TOV1

0

Overtemperature Condition

Don’t Care

Temperature < TOV1

1Normal