AS1109
Data Sheet - Detailed Description
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 possi-
ble 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.
Error Detection Functions
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.
Table 6. Open LED Detection Modes
Effective Output
Point Conditions
Detected Open-LED
Error Status Code
Output Port State
Meaning
On
On
VDS < VTHL
VDS > VTHL
0
1
Open Circuit
Normal
Shorted-LED
The AS1109 shorted-LED detection is based on the comparison between VDS and VTHH. The shortened LED status is
aquired 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.
Table 7. Shorted LED Detection Modes
Effective Output
Point Conditions
Detected Shorted-LED
Error Status Code
Output Port State
Meaning
On
On
VDS > VTHH
VDS < VTHH
0
1
Short Circuit
Normal
Overtemperature
Thermal protection for the AS1109 is provided by continuously monitoring the device’s core temperature. The overtem-
perature status is aquired at the rising edge of OEN and stored internally.
Table 8. Overtemperature Modes
Effective Output
Point Conditions
Detected Overtemperature
Status Code
Output Port State
Meaning
Overtemperature
Condition
Don’t Care
Don’t Care
Temperature > TOV1
Temperature < TOV1
0
1
Normal
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