A8516 データシートの表示（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
Characteristic Performance
Efficiency versus Battery Voltage
for Various LED Configurations
FET = IRFR120N, VIN = 12 V, fSW = 500 kHz
L = 22 μH, Load = W92050C LEDs at 112 mA per string
95
94
93
92
91
90
89
88
87
86
3 strings 18 LEDs per string
85
VOUT ≈ 60 V, POUT ≈ 20.2 W
84
2 strings 18 LEDs per string
VOUT ≈ 60 V, POUT ≈ 13.4 W
83
3 strings 14 LEDs per string
VOUT ≈ 47 V, POUT ≈ 15.8 W
82
2 strings 14 LEDs per string
81
VOUT ≈ 47 V, POUT ≈ 10.5 W
80
10 11 12 13 14 15 16 17 18 19 20 21 22 23
VBAT (V)
Efficiency of the boost converter stage is affected by the selection of
power MOSFET, switching frequency, input/output voltages, and output
power. The external MOSFET used for the above chart is the IRFR120N,
which has a relatively high RDS(on) = 0.21 Ω. This causes higher
conduction loss, especially at lower input voltage.
Efficiency versus Battery Voltage
for Various LED Configurations
FET = FQB17N08L, VIN = 12 V, fSW = 500 kHz
L = 22 μH, Load = W92050C LEDs at 112 mA per string
95
94
93
92
91
90
89
88
87
86
3 strings 18 LEDs per string
85
VOUT ≈ 60 V, POUT ≈ 20.2 W
84
2 strings 18 LEDs per string
VOUT ≈ 60 V, POUT ≈ 13.4 W
83
3 strings 14 LEDs per string
VOUT ≈ 47 V, POUT ≈ 15.8 W
82
2 strings 14 LEDs per string
81
VOUT ≈ 47 V, POUT ≈ 10.5 W
80
10 11 12 13 14 15 16 17 18 19 20 21 22 23
VBAT (V)
The power MOSFET is replaced with FQB17N08L, which has a lower
RDS(on) = 0.115 Ω. This results in less conduction loss at lower input
voltage, however, the switching loss becomes more significant at higher
input voltage.
Switching Frequency versus FSET Resistor Value
fSW (MHz) = 52 / RFSET (kΩ)
1100
1000
900
800
700
600
500
400
300
50 60 70 80 90 100 110 120 130 140 150
RFSET (kΩ)
Allegro MicroSystems, Inc.
7
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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