A8509 View Datasheet(PDF) - Allegro MicroSystems
Part Name
Description
MFG CO.
A8509
Allegro MicroSystems
'A8509' PDF : 28 Pages View PDF
A8509
Wide Input Voltage Range, High Efficiency
4-Channel Fault Tolerant LED Driver
Table 1. Fault Modes
Fault Name
Type
Primary switch current
protection (pulse-by- Auto-restart
pulse current limit)
Secondary switch
current limit
Latched
LEDx pin short to GND
protection
Auto-restart
LEDx pin open
Auto-restart
LED short protection Auto-restart
FSET pin short
protection
Auto-restart
ISET pin short
protection
Auto-restart
Overvoltage protection Auto-restart
Output undervoltage
protection
Overtemperature
protection
Auto-restart
Auto-restart
VIN UVLO
Auto-restart
Active
Always
Always
Startup
Normal
operation
Always
Always
Always
Always
Always
Always
Always
Fault
Flag
Set
No
Yes
Yes
No
No
No
No
No
Yes
Yes
No
Description
Boost
Sink
driver
This fault condition is triggered by the pulse-by-pulse current limit
when the SENSP pin voltage exceeds VSENSEP .
Off for
a single On
cycle
When the current through the boost switch exceeds the secondary
current limit (VSENSESEC) the IC immediately shuts down the LED
drivers and the boost. To re-enable the A8509 the EN pin must be
Off
Off
toggled.
This fault prevents the IC from starting-up if any of the LEDx pins are
shorted. The IC stops soft start from starting while any of the LEDx
pins are determined to be shorted. After the short is removed, soft
Off
Off
start is allowed to start.
When an LEDx pin is open the device will determine which LEDx
pin is open by increasing the output voltage until OVP is reached.
Any LED string below regulation will be turned off. The device then
goes back to normal operation by reducing the output voltage to the
appropriate voltage level.
Off for
open
On pins. On
for all
others
Off for
This fault occurs when the LED pin voltage exceeds VLEDSC . When
shorted
the LED short protection is detected, the LED string that is above the On pins. On
threshold will be removed from operation.
for all
others
This fault occurs when the FSET pin current goes above 150% of the
On in
maximum current. The boost stops switching, and the IC disables
the LED sinks until the fault is removed. When the fault is removed
Off
soft
start
the IC tries to restart with soft start.
current
This fault occurs when the ISET pin current goes above 150% of the
maximum current. The boost stops switching and the IC disables the
LED sinks until the fault is removed. When the fault is removed the
Off
Off
IC tries to regulate to the preset LED current.
The fault occurs when the OVP pin voltage exceeds the VOVP(th)
Stop
threshold. The A8509 immediately stops switching to try to reduce
the output voltage. If the output voltage decreases then the A8509
during
OVP
On
restarts switching to regulate the output voltage.
event
This fault occurs when the OVP pin senses less than 100 mV on the
pin. The IC disables the external P-FET switch, if one is used.
Off
Off
The fault occurs when the die temperature exceeds the
overtemperature threshold, typically 165°C.
Off
Off
This fault occurs when VIN drops below VUVLO(th)(max), 8.5 V. This
fault resets all latched faults.
Off
Off
Allegro MicroSystems, Inc.
18
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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