A8514KLPTR-T Просмотр технического описания (PDF) - Allegro MicroSystems
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A8514KLPTR-T Datasheet PDF : 35 Pages
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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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