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参数资料
| 型号： | A8504EECTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 10/19页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR WHT/RGB BCKLGT 26QFN |
| 标准包装： | 1 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 8 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | RGB，白色 LED |
| 频率： | 200kHz ~ 2MHz |
| 电源电压： | 4.2 V ~ 5.5 V |
| 输出电压： | 47V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 26-WFQFN 裸露焊盘 |
| 供应商设备封装： | 26-QFN/MLP-EP（4x4） |
| 包装： | 标准包装 |
| 工作温度： | -40°C ~ 85°C |
| 产品目录页面： | 1141 (CN2011-ZH PDF) |
| 其它名称： | 620-1215-6 |
A8504
WLED/RGB Backlight Driver for Medium Size LCDs
This current is multiplied internally with a gain of 480, and then
mirrored on all enabled LED x pins. This sets the maximum cur-
rent through the LEDs, referred to as “100% current.” The LED
current can be reduced from 100% by on/off control (PWM) with
an external PWM signal on the PWM pin
On/off Control (PWM) with an External PWM Signal on the
PWM Pin. When the PWM pin is pulled high, the A8504 turns on
and all enabled LED x pins sink 100% current. When the PWM
pin is pulled low, the IC shuts down with the LED x pins disabled.
External PWM applied to the PWM pin should be in the range of
100 to 400 Hz for optimal accuracy.
At startup, the output capacitor is discharged and the IC enters
soft start. The boost current is limited to 1 A, and all active LED x
pins sink 1 / 16 of the set 100% current until all of the enabled
LED x pins reach 0.8 V. After the IC comes out of soft start, the
boost current and the LED x pin currents are set to 100% current.
The output capacitor charges to the voltage level required to sup-
ply full LED x current within a few cycles. The startup sequence
is shown in the Soft Start chart in the Performance Characteristics
section. The IC is shut down immediately when PWM goes low.
Device Internal Protection
Overcurrent Protection (OCP). The A8504 has a pulse-by-pulse
current limit of 2 A on the boost switch. This current limit is
independent of duty cycle.
Thermal Shutdown Protection (TSD). The IC shuts down when
junction temperature exceeds 165°C and restarts when the junc-
tion temperature falls by 40°C.
C1
C2
C3
V PWM
V OUT
I OUT
Overvoltage Protection (OVP). The A8504 has overvoltage
protection to protect the IC against output overvoltage. The
overvoltage level can be set, from 30 to 45 V typical, with an
external resistor, ROVP, as shown in figure 5. When the current
though the OVP pin exceeds 49 μ A, the OVP comparator goes
high. When the OVP pin current falls below 44 μ A, OVP is reset.
Calculate the value for R OVP as follows:
Symbol
C1
C2
C3
t
t
Parameter
V PWM
V OUT(ac)
I OUT
time
Units/Division
2.00 V
500 mV
200 mA
5 ms
R OVP = ( V OVP – 30) / 49 μ A ,
where V OVP is the desired typical OVP level in V, and R OVP is
in Ω . For tighter OVP limits, a low–leakage-current Zener diode,
DZ, can be used, instead of ROVP, to set OVP at up to 47 V. For
Figure 3. Output Voltage Ripple During PWM Dimming. V IN = 5 V,
V BAT = 15 V, f SW = 1 MHz, f PWM = 100 Hz, PWM duty cycle = 50%,
8S8P configuration, 40 mA per channel.
V PWM
C1
V OUT
Turn-on Delay
redundancy, DZ can be connected across ROVP to provide addi-
tional protection, if ROVP should open. Select a 17 V low-leak-
age Zener diode for DZ.
V PWM
6 μ s Typical
100% Current Level
Shutdown
(0 μ A)
I OUT
Shutdown
(0 μ A)
C2
I OUT
t
Symbol
Parameter
Units/Division
Figure 4. Timing of turn-on delay and turn-off delay when using the
PWM pin. V IN = 5 V, V BAT = 15 V, f SW = 1 MHz, f PWM = 100 Hz, 8S8P
configuration, 40 mA per channel.
C1
C2
t
V PWM
I OUT
time
2.00 V
200 mA
5 μ s
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1 . 508.853.5000; www.allegromicro.com
9
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| A8508 | 制造商:ROCKWE 功能描述: |
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