AS1109_1 AMSCO [austriamicrosystems AG], AS1109_1 Datasheet - Page 12

• Manufacturer Part Number: AS1109_1
• Description: Constant-Current, 8-Bit LED Driver with Diagnostics
• Manufacturer: AMSCO [austriamicrosystems AG]

AS1109
Data Sheet - D e t a i l e d D e s c r i p t i o n
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*t
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 V
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
Shorted-LED
The AS1109 shorted-LED detection is based on the comparison between V
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 V
conditions. This can be achieved by reducing the V
Note: LEDs which are turned off at test time cannot be tested.
Table 7. Shorted LED Detection Modes
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
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Output Port State
Output Port State
Output Port State
Don’t Care
Don’t Care
On
On
On
On
P(I/O)
Temperature > T
Temperature < T
Point Conditions
Point Conditions
Point Conditions
Effective Output
Effective Output
Effective Output
+ t
V
V
V
V
DS
DS
SW(ERROR)
DS
DS
< V
> V
> V
< V
THH
THH
THL
THL
OV1
OV1
at pin SDO of the last device in the chain. This means it is not possi-
LED
Revision 1.18
voltage or by adding additional diodes, resistors or LED’s.
Detected Overtemperature
Detected Shorted-LED
Detected Open-LED
Error Status Code
Error Status Code
THH
Status Code
DS
under low-current diagnostic mode operating
0
1
0
1
DS
0
1
and V
and V
THL
THH
. The open LED status is aquired
. The shortened LED status is
Overtemperature
Open Circuit
Short Circuit
Condition
Meaning
Meaning
Meaning
Normal
Normal
Normal
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