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| 型号： | A8512ELPTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 11/18页 |
| 文件大小： | 0K |
| 描述： | IC LED DVR WHT/RGB BKLGT 24TSSOP |
| 标准包装： | 8,000 |
| 拓扑： | 高端，低端，PWM，升压（升压） |
| 输出数： | 6 |
| 内部驱动器： | 无 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | RGB，白色 LED |
| 频率： | 300kHz ~ 1MHz |
| 电源电压： | 8 V ~ 24 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 24-TSSOP 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
A8512
LED Backlight Driver for LCD Monitors and Televisions
Functional Description
Overview The A8512 is a multi-output WLED/RGB control-
ler for backlighting medium-size displays. It has an integrated
gate driver for driving an external N-channel boost MOSFET.
The gate driver voltage is regulated at 7 V, which allows a wide
selection of power MOSFET (in contrast to being limited to
logic-level MOSFETs when using a 5 V gate driver). The boost
controller operates in fixed-frequency current-mode control. The
switching frequency can be set in the range from 300 kHz to
1 MHz, by an external resistor, R FSET , connected between FSET
and ground.
The external MOSFET switch is protected by pulse-by-pulse cur-
rent limiting. The current limit is independent of duty cycle, and
is set using an external sense resistor, R SC .
LED current required:
R ISET = ( 1.235 / I LED ) × 640 . (3)
In steady-state operation, the maximum average LED current that
can be handled by the IC depends on its thermal budget. That
is, maximum power dissipation and acceptable temperature rise.
The thermal budget is affected by various parameters, such as
PCB size, copper plane around IC, LED V f mismatch, selection
of power components (MOSFET, inductor and diode), maximum
board temperature, and so on.
Boost Switching Frequency Setting Connect an external
resistor between the FSET pin and GND, to set boost switching
frequency, f SW . The value of f SW (MHz) is determined by:
The A8512 has six well-matched current sinks that provide regu-
lated current through the LEDs for uniform display brightness.
The boost converter is controlled by monitoring all LEDx pins
simultaneously and continuously.
f SW = 52 / R FSET ,
where f SW is in MHz and R FSET is in k Ω . The typical range of
R FSET is approximately 51 to 174 k Ω , which corresponds to
1 MHz to 300 kHz.
(4)
Multiple A8512 can be connected in parallel, for applications
that require more than six LED strings. One master controller is
in charge of the boost converter stage, while other slave control-
lers act as LED current sinks only. The converter output voltage
will be boosted to a level just sufficient for all LED currents to be
within regulation.
Up to six A8512s (1 master + 5 slaves) can be connected in
parallel, which allows up to 36 LED strings to be powered by just
one boost converter. The maximum number of LEDs within each
string is limited only by the voltage ratings of the external power
components (MOSFET, diode, and capacitors).
LED Current Setting The maximum LED current can be set, at
up to 130 mA/channel, through the ISET pin. Connect a resistor,
R ISET , between this pin and ground to set the reference current
level, I SET . The value of I SET (mA) is determined by:
Enable The IC turns on when a high signal is applied on the EN
pin, and turns off when this pin is pulled low. The LED current
sinks are turned on when both the EN and the PWM inputs are high.
Channel Selection The A8512 can be used to drive 1 to 6 LED
channels. During startup, the IC detects LED sink pins which are
shorted to ground, and disables the corresponding LED channel.
Therefore, any unused LED pins must be connected to ground,
otherwise the IC will go into overvoltage protection fault during
startup. LED pins can be paralleled together for higher cur-
rent. For example for a 3 parallel string configuration, connect
LED1-2, LED3-4, and LED5-6 together to deliver up to twice the
current per LED.
PWM Dimming The A8512 has a very wide range for PWM
signal input. It can accept a PWM signal from 100 Hz to 5 kHz.
When a PWM high signal is applied, the LEDx pins sink
I SET = 1.235 / R ISET (k Ω ) .
(1)
The resulting current is multiplied internally with a gain of 640
and mirrored on all enabled LEDx pins:
PWM
I LED = I SET × 640 . (2)
This sets the maximum current through each LEDx, referred as
the 100% Current . The LEDx current can be reduced from the
I LED
t D
100% Current value by applying an external PWM signal on the
PWM pin. Conversely, we can calculate R ISET according to the
Figure 13. Propagation delay from the PWM signal rising edge to I LEDx
reaching the 90% level
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
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| A8513KLPTR-T | 功能描述:IC LED DRVR AUTO BCKLGHT 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 特色产品:LM3445 TRIAC Dimmable LED Driver 标准包装:55 系列:PowerWise® 恒定电流:是 恒定电压:- 拓扑:PWM，降压（降压） 输出数:1 内部驱动器:无 类型 - 主要:- 类型 - 次要:高亮度 LED（HBLED） 频率:30kHz ~ 1MHz 电源电压:8 V ~ 12 V 输出电压:- 安装类型:表面贴装 封装/外壳:14-SOIC（0.154"，3.90mm 宽） 供应商设备封装:14-SOICN 包装:管件 工作温度:-40°C ~ 125°C 产品目录页面:1285 (CN2011-ZH PDF) 其它名称:LM3445M |
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