- 您现在的位置：买卖IC网 > Sheet目录340 > MAX1554ETA+T (Maxim Integrated)IC LED DVR WHITE BCKLGT 8TDFN
High-Efficiency, 40V Step-Up
Converters for 2 to 10 White LEDs
Adjusting the LED Current
Adjusting the output current changes the brightness of
the LEDs. The LED current is set by the voltage at BRT
(V BRT ) and the sense resistor (R1) at FB. The V BRT
3.15V TO 5.5V
INPUT
L1
22 μ H
A915BY-220M
D1
CMDSH1-60M
range for adjusting output current is 0 to 1.25V. Over
this range, the LED current is found from the following
equation:
C1
10 μ F
ON
OFF
V CC
EN
LX
OV
C2
0.47 μ F
50V
R2
330k ?
C4
3300pF
I LED =
V BRT + 0.17
6 . 67 x R 1
PWM
MAX1554
R3
10k ?
D2–D11
WHITE
LEDs
BRT can be overdriven; however, applying a V BRT
greater than 1.72V does not increase the output current
OR
DC CONTROL
C3
BRT
SS
FB
GND
R1
10 ?
above the level at 1.72V. See the LED Current vs. BRT
Voltage graph in the Typical Operating Characteristics
section. To set the maximum LED current, calculate R1
when V BRT is at its maximum, as follows:
0.1 μ F
Figure 3. Circuit with the MAX1554 Driving 10 White LEDs
R 1 =
V BRT(MAX ) + 0.17
6 . 67 x I LED ( MAX )
Inductor Selection
The MAX1553 has a 480mA inductor current limit and
where V BRT(MAX) is 1.72V if BRT is connected to any
value greater than 1.72V, such as V CC . Otherwise,
V BRT(MAX) is the maximum applied BRT control volt-
age. Power dissipation in R1 is typically less than 5mW;
therefore, power dissipation in a standard chip resistor
is not a concern.
PWM Dimming Control
The BRT input is also used as a digital input allowing
LED brightness control with a logic-level PWM signal
applied directly to BRT. The frequency range is from
100Hz to 10kHz, and the duty cycle range is 0 to 100%.
A 0% duty cycle corresponds to the minimum current,
and a 100% duty cycle corresponds to full current. See
the LED Current vs. BRT Duty Cycle graph in the
Typical Operating Characteristics section. The BRT
resistor and SS capacitor form a lowpass filter, so PWM
dimming results in DC current to the LEDs without the
need for additional RC filters.
Capacitor Selection
A 0.47μF ceramic output capacitor (C2) is recommend-
ed for most applications. For circuits driving six or
fewer LEDs, use a 4.7μF ceramic input capacitor (C1).
For circuits driving more than six LEDs, use a 10μF
input capacitor (C1). For best stability over a wide tem-
perature range, use capacitors with an X5R, X7R, or
better dielectric.
can drive up to six LEDs at 20mA or nine LEDs at
15mA. Inductor values from 4.7μH to 47μH work satis-
factorily. Larger values provide the best efficiency while
small inductor values allow the smallest inductor size. A
good choice for best efficiency is the TOKO D62 or
D62L series at 47μH. For smallest size, the Murata
LQH32C at 4.7μH works well.
The MAX1554 has a 970mA inductor current limit and
can drive up to 10 LEDs at 20mA. Inductor values from
4.7μH to 22μH work satisfactorily. A good choice for
high efficiency and small size when driving 9 or 10
LEDs is the TOKO D62 series at 22μH.
When large inductor values are used to optimize effi-
ciency, the MAX1553/MAX1554 operate with continuous
inductor current. With large inductor values (typically
greater than 10μH), stability, input, and output ripple
are improved by connecting a capacitor in parallel with
the LEDs (C4 in Figures 1, 2, and 3).
To prevent saturation, use an inductor with a current
rating that matches the device ’s LX current limit.
However, if size is particularly important, it is some-
times acceptable to operate the inductor 10% into satu-
ration. For best efficiency, the inductor’s DC resistance
should also be as low as possible.
Diode Selection
The MAX1553/MAX1554s ’ high switching frequency
demands a high-speed rectification diode (D1) for opti-
mum efficiency. A Schottky diode is recommended due
to its fast recovery time and low forward-voltage drop.
8
_______________________________________________________________________________________
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
MAX1570ETE+
IC LED DRVR WHITE BCKLGT 16-TQFN
MAX1573ETE+
IC LED DRVR WHITE BCKLGT 16-TQFN
MAX1574ETB+T
IC LED DRVR WHITE BCKLGT 10TDFN
MAX1575ETE+
IC LED DRVR WHITE BCKLGT 16-TQFN
MAX1576ETG+T
IC LED DRVR WHITE BCKLGT 24-TQFN
MAX1577ZETA+T
IC LED DRIVR BCKLGT FLASH 8-TDFN
MAX1582ETC+T
IC LED DRVR WHITE BCKLGT 12-TQFN
MAX1583ZETB+T
IC LED DRIVR PHOTO FLASH 10-TDFN
相关代理商/技术参数
MAX1554ETA+TG069
制造商:Maxim Integrated Products 功能描述:LED DRVR 10SEGMENT 3.15V TO 5.5V 8TDFN EP - Tape and Reel
MAX1554ETA-T
功能描述:LED照明驱动器 40V StepUp Converter for 2-10 White LEDs RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N
MAX1555EZK
制造商:Maxim Integrated Products 功能描述:SOT-23 DUAL-INPUT USB/AC ADAPTER 1- - Cut Tape Product
MAX1555EZK+
制造商:Maxim Integrated Products 功能描述:CHRGR LI-ION/LI-POL 280MA 4.2V 5PIN TSOT-23 - Rail/Tube
MAX1555EZK+T
功能描述:电池管理 Dual USB/AC 1-Cell Li+ Battery Charger
RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel
MAX1555EZK+T
制造商:Maxim Integrated Products 功能描述:CHARGER BATT LI+ USB/AC 5SOT23 制造商:Maxim Integrated Products 功能描述:CHARGER, BATT, LI+, USB/AC, 5SOT23 制造商:Maxim Integrated Products 功能描述:CHARGER, BATT, LI+, USB/AC, 5SOT23; Battery Type:Li-Ion, Li-Polymer; Input Voltage:7V; Battery Charge Voltage:4.2V; Charge Current Max:280mA; Battery IC Case Style:SOT-23; No. of Pins:5; No. of Series Cells:1; Operating Temperature ;RoHS Compliant: Yes
MAX1555EZK-T
功能描述:电池管理
RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel
MAX15561GTL+
功能描述:模数转换器 - ADC New RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32