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| 型号： | A8502KLPTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 26/35页 |
| 文件大小： | 0K |
| 描述： | IC LED DVR WHITE MULTI 16-TSSOP |
| 标准包装： | 8,000 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 2 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 车载，背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 580kHz ~ 2MHz |
| 电源电压： | 5 V ~ 40 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 供应商设备封装： | 16-TSSOP-EP |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 125°C |
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A8502
Design Example for Boost Configuration
Wide Input Voltage Range, High Efficiency
Fault Tolerant LED Driver
Application Information
Then the OVP resistor is:
This section provides a method for selecting component values
when designing an application using the A8502. The resulting
R OVP = ( V OUT(OVP) – V OVP(th) ) / I OVPH
(9)
design is diagrammed in figure 33.
Assumptions: For the purposes of this example, the following are
given as the application requirements:
? V BAT : 10 to 14 V
? Quantity of LED channels, # CHANNELS : 2
? Quantity of series LEDs per channel, # SERIESLEDS : 10
? LED current per channel, I LED : 120 mA
? LED V f at 120 mA: 3.2 V
? f SW : 2 MHz
? T A (max): 65°C
= (34.72 V – 8.1 V) / 199 μ A = 133.77 k Ω
where both I OVPH and V OVP(th) are taken from the Electrical
Characteristics table.
Chose a value of resistor that is higher value than the calculated
R OVP . In this case a value of 137 k Ω was selected. Below is the
actual value of the minimum OVP trip level with the selected
resistor:
V OUT(OVP) = 137 (k Ω ) × 199 ( μ A )+ 8.1 (V) = 35.36 V
Step 3b At this point a quick check must be done to determine if
the conversion ratio is acceptable for the selected frequency.
? PWM dimming frequency: 200 Hz, 1% duty cycle
D maxofboost = 1 – t SWOFFTIME × f SW
(10)
Procedure: The procedure consists of selecting the appropriate
configuration and then the individual component values, in an
ordered sequence.
Step 1 Connect LEDs to pins LED1 and LED2.
= 1 – 68 (ns) × 2 (MHz) = 86.4%
where the minimum off-time (t SWOFFTIME ) is found in the Electri-
cal Characteristics table.
The Theoretical Maximum V OUT is then calculated as:
Step 2 Determining the LED current setting resistor R ISET :
R ISET = ( V ISET × A ISET ) / I LED
(7)
V OUT (max) =
V IN (min)
1 – D maxofboost
– V d
(11)
= (1.003 (V) × 980) / 120 (mA) = 8.19 k Ω
Choose a 8.25 k Ω resistor.
=
10 (V)
1 – 0.864
– 0.4 (V) = 73.13 V
Step 3 Determining the OVP resistor. The OVP resistor is
connected between the OVP pin and the output voltage of the
converter.
Step 3a The first step is determining the maximum voltage based
on the LED requirements. The regulation voltage, V LED , of the
A8502 is 720 mV. A constant term, 2 V, is added to give margin
to the design due to noise and output voltage ripple.
where V d is the diode forward voltage.
The Theoretical Maximum V OUT value must be greater than the
value V OUT(OVP) . If this is not the case, the switching frequency
of the boost converter must be reduced to meet the maximum
duty cycle requirements.
Step 4 Selecting the inductor. The inductor must be chosen such
V OUT(OVP) = # SERIESLEDS × V f + V LED + 2 (V)
= 10 × 3.2 (V) + 0.720 (V) + 2 (V)
= 34.72 V
(8)
that it can handle the necessary input current. In most applica-
tions, due to stringent EMI requirements, the system must operate
in continuous conduction mode throughout the whole input volt-
age range.
26
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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相关代理商/技术参数 |
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| A8503 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:High Efficiency 6-Channel, 2 MHz, WLED/RGB Driver |
| A8503EECTR-T | 功能描述:IC LED DRVR WHT/RGB BCKLGT 26QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:1 系列:- 恒定电流:- 恒定电压:- 拓扑:PWM，切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:642kHz 电源电压:2.7 V ~ 5.5 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-VFDFN 裸露焊盘 供应商设备封装:10-VSON 包装:剪切带 (CT) 工作温度:-30°C ~ 85°C 产品目录页面:1371 (CN2011-ZH PDF) 其它名称:BD1603NUV-E2CT |
| A8503GECTR-T | 功能描述:IC LED DVR WHT/RGB BKLGT 26QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 恒定电流:- 恒定电压:- 拓扑:升压（升压），切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:625kHz ~ 875kHz 电源电压:2.7 V ~ 5.3 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-µMAX 包装:带卷 (TR) 工作温度:-40°C ~ 85°C |
| A8504 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:WLED/RGB Backlight Driver for Medium Size LCDs |
| A8504910100N | 功能描述:环形MIL规格后盖 Backshell, Envrn, EMI/RFI, Strt, Nickel, Size 48 RoHS:否 制造商:Amphenol PCD MIL 类型:MIL-DTL-38999 III, IV 系列:AS85049 产品类型:Environmental EMI/RFI Backshells 外壳类型:Straight 外壳大小:18 外壳材质:Aluminum Alloy |
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