A8519KETTR-R datasheet(26/35 Pages) ALLEGRO

26 / 35 page

Wide Input Voltage Range, High-Efficiency,

Fault-Tolerant LED Driver

A8519 and

A8519-1

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Table 5: Fault Mode Table

Fault Name

Type

Active

Fault

Flag

Set

Description

Boost

Disconnect

Switch

LED

Sink

Drivers

Primary Switch

Overcurrent

Protection (cycle-

by-cycle current

limit)

Auto-

restart

Always

This fault condition is triggered when the SW current

exceeds the cycle-by-cycle current limit, ISW(LIM).The

present SW on-time is truncated immediately to limit the

current. Next switching cycle starts normally.

Off for

a single

cycle

Secondary Switch

Current Limit

Latched

Always

YES

When current through boost switch exceeds secondary

SW current limit (ISW(LIM2)), the device immediately shuts

down the disconnect switch, LED drivers, and boost.

The Fault flag is set. To re-enable the part, the PWM pin

needs to be pulled low for 32,750 clock cycles.

OFF

Input Disconnect

Current Limit

Latched

Always

YES

The device is immediately shut off if the voltage

across the input sense resistor is above the

VVSENSE(trip) threshold. To re-enable the device, the

PWM pin must be pulled low for 32,750 clock cycles.

OFF

Secondary OVP

Latched

Always

YES

Secondary overvoltage protection is used for open-diode

detection. When diode D1 opens, the SW pin voltage

will increase until VOVP(sec) is reached . This fault latches

the IC. The input disconnect switch is disabled as well

as the LED drivers. To re-enable the part, the PWM pin

needs to be pulled low for 32,750 clock cycles.

OFF

LEDx Pin Short

Protection

Auto-

restart

Startup

This fault prevents the part from starting up if any of

the LED pins are shorted. The part stops soft-start from

starting while any of the LED pins are determined to be

shorted. Once the short is removed, soft-start is allowed

to start.

OFF

LEDx Pin Open

Auto-

restart

Normal

operation

When an LED pin is open, the device will determine

which LED pin is open by increasing the output voltage

until OVP is reached. Any LED string not in regulation

will be turned OFF. The device will then go back to

normal operation by reducing the output voltage to the

appropriate voltage level.

OFF for

open

pins,

for all

others

ISET Short

Protection

Auto-

restart

Always

Fault occurs when the IISET current goes above 150% of

max current. The boost will stop switching and the IC will

disable the LED sinks until the fault is removed. When

the fault is removed, the IC will try to regulate to the

preset LED current.

OFF

FSET Short

Protection

Auto-

restart

Always

YES

Fault occurs when the FSET current goes above 150%

of max current. The boost will stop switching, Disconnect

switch will turn off, and the IC will disable the LED sinks

until the fault is removed. When the fault is removed, the

IC will try to restart with soft-start.

OFF

Overvoltage

Protection

Auto-

restart

Always

Fault occurs when OVP pin exceeds VOVP(th) threshold.

The IC will immediately stop switching to try to reduce

the output voltage. If the output voltage decreases,

then the IC will restart switching to regulate the output

voltage.

STOP

during

OVP event

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