A8514KLPTR-T Ver la hoja de datos (PDF) - Allegro MicroSystems

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A8514KLPTR-T

Wide Input Voltage Range, High Efficiency Fault Tolerant LED Driver

Allegro MicroSystems 

A8514

Wide Input Voltage Range, High Efficiency

Fault Tolerant LED Driver

Boost switch overcurrent protection

The boost switch is protected with cycle-by-cycle current limiting

set at a minimum of 3.0 A. There is also a secondary current limit

that is sensed on the boost switch. When detected this current

limit immediately shuts down the A8514. The level of this cur-

rent limit is set above the cycle-by-cycle current limit to protect

the switch from destructive currents when the boost inductor is

shorted. Various boost switch overcurrent conditions are shown in

figures 26 through 28.

C1

SW node

C2

IL

VOUT

PWM/EN

C3

C4

t

Figure 26. Normal operation of the switch node (SW); inductor current

(IL) and output voltage (VOUT) for 9 series LEDs in each of four strings

configuration; shows SW node (ch1, 20 V/div.), inductor current IL (ch2,

1 A/div.), VOUT (ch3, 10 V/div.), and PWM/EN (ch4, 5 V/div.),

time = 2 μs/div.

C1

SW node

IL

VOUT

C2

PWM/EN

C3

C4

t

Figure 27. Cycle-by-cycle current limiting; inductor current (yellow trace, IL),

note reduction in output voltage as compared to normal operation with the

same configuration (figure 26); shows SW node (ch1, 20 V/div.), inductor

current IL (ch2, 1 A/div.), VOUT (ch3, 10 V/div.), and PWM/EN (ch4, 5 V/div.),

time = 2 μs/div.

PWM/EN

C1

FAULT

C2

SW node

C3

IL

C4

t

Figure 28. Secondary boost switch current limit; when this limit is hit, the

A8514 immediately shuts down; shows PWM (ch1, 5 V/div.), VOUT (ch2,

5 V/div.), SW node (ch3, 50 V/div.), and inductor current IL (ch4, 2 A/div.),

time = 100 ns/div.

Allegro MicroSystems, Inc.

21

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

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