A8516 Просмотр технического описания (PDF) - Allegro MicroSystems
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A8516 Datasheet PDF : 17 Pages
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A8516
LED Backlight Driver for LCD Monitors and Televisions
Typical PWM Operation Waveforms
VBAT = 12 V, Load = 6 strings, 16 LEDs each string, 56 mA per string, Output capacitors = 2 × 2.2 μF ceramic
VOUT
VPWM
C2
VEN
C1
t
Symbol
C1
C2
–*
C4
t
Parameter Units/Division
VEN
VPWM
VOUT
Total ILED
time
10 V
10 V
1V
100 mA
2 ms
*Offset = 46 V
PWM dimming at 200 Hz 10% duty cycle;
Output voltage ripple approximately 0.8 V (out of 50 V)
VOUT
ILED
C4
VPWM
C2 VEN
C1
t
Symbol
C1
C2
–*
C4
t
Parameter Units/Division
VEN
VPWM
VOUT
ILED
time
10 V
10 V
1V
100 mA
50 μs
*Offset = 46 V
PWM dimming at 5 kHz 10% duty cycle
Ratio of LED Current versus PWM Duty Cycle
PWM frequency = 200 Hz
100
Ratio of LED Current versus PWM Frequency
PWM duty cycle = 10%
100
90
80
10
70
60
50
Compensated
pulse width
40
1
Uncompensated
30
pulse width
20
10
0.1
0
0.1
1
10
100
0.1
1
10
PWM Duty Cycle (%)
PWM Frequency (kHz)
To improve the accuracy of PWM dimming at very high frequency and/or very low duty cycle, it is
necessary to compensate the PWM pulse width, as described in Application Information section.
Allegro MicroSystems, Inc.
9
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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