A8514KLPTR-T データシートの表示（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
As an example, a system that delivers a full LED current of
80 mA per LED would deliver 60 mA of current per LED when
an APWM signal is applied with a duty cycle of 25% (figures
16 and 17).
Although the order in which APWM and the PWM signal are
enabled does not matter, when enabling the A8514 into low cur-
rent output while PWM and APWM dimming, the APWM signal
should be enable before or at the same time as the PWM signal.
This sequence will prevent the light output intensity from chang-
ing during power up of the IC.
Figure 18 shows the sequencing of the APWM and PWM signal
during power-up to prevent inadvertent light intensity changes.
The full intensity light output with no APWM or PWM dimming
is 80 mA per channel.
ILED
C1
ILED
C1
C2
APWM
C2
APWM
PWM/EN
C3
t
Figure 16. Diagram showing the transition of LED current from 60 mA
to 80 mA, when a 25% duty cycle signal is removed from the APWM pin.
PWM = 1; shows ILED (ch1, 50 mA/div.), APWM (ch2, 10 V/div.), and
PWM/EN (ch3, 5 V/div.), time = 500 μs/div.
PWM/EN
C3
t
Figure 17. Diagram showing the transition of LED current from 80 mA
to 60 mA, when a 25% duty cycle signal is applied to the APWM pin;
PWM = 1; shows ILED (ch1, 50 mA/div.), APWM (ch2, 10 V/div.), and
PWM/EN (ch3, 5 V/div.), time = 500 μs/div.
APWM
C1
ILED
C2
PWM/EN
C3
VOUT
C4
t
Figure 18. Diagram showing power-up sequencing LED current of 5 mA
per channel with a 10% duty cycle PWM signal and a 95% duty cycle
APWM signal; shows APWM (ch1, 5 V/div.), ILED (ch2, 50 mA/div.),
PWM/EN (ch3, 5 V/div.), and VOUT (ch4, 10 V/div.), time = 500 μs/div.
C1
IOUT
C2
APWM
C3
PWM/EN
t
Figure 19. Transition of output current level when a 50% duty cycle signal
is applied to the APWM pin, in conjunction with a 50% duty cycle PWM
dimming being applied to the PWM pin; shows IOUT (ch1, 50 mA/div.),
APWM (ch2, 10 V/div.), and PWM/EN (ch3, 5 V/div.), time = 500 μs/div.
Allegro MicroSystems, Inc.
17
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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