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參數(shù)資料
| 型號(hào)： | MAX1554ETA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 顯示驅(qū)動(dòng)器 |
| 英文描述： | High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs |
| 中文描述： | LED DISPLAY DRIVER, DSO8 |
| 封裝： | 3 X 3 MM, 0.80 MM HEIGHT, MO229WEEC, TDFN-8 |
| 文件頁(yè)數(shù)： | 8/11頁(yè) |
| 文件大?。?/td> | 347K |
| 代理商： | MAX1554ETA |
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
range for adjusting output current is 0 to 1.25V. Over
this range, the LED current is found from the following
equation:
BRT can be overdriven; however, applying a V
BRT
greater than 1.72V does not increase the output current
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:
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.
Inductor Selection
The MAX1553 has a 480mA inductor current limit and
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.
R
V
6 67
.
x I
BRT MAX
(
LED MAX
(
1
0 17
.
=
+
)
)
I
V
x R
LED
BRT
6 67
.
=
+
0 17
.
1
M
High-Efficiency, 40V Step-Up
Converters for 2 to 10 White LEDs
8
_______________________________________________________________________________________
LX
SS
R1
10
R3
10k
R2
330k
V
CC
FB
ON
OFF
BRT
GND
3.15V TO 5.5V
INPUT
C1
10
μ
F
C3
0.1
μ
F
C2
0.47
μ
F
50V
L1
22
μ
H
A915BY-220M
D1
CMDSH1-60M
OV
EN
D2
–
D11
WHITE
LEDs
PWM
OR
DC CONTROL
MAX1554
C4
3300pF
Figure 3. Circuit with the MAX1554 Driving 10 White LEDs
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1554ETA+ | 制造商:Maxim Integrated Products 功能描述:LED DRVR 10SEGMENT 3.15V TO 5.5V 8TDFN EP - Rail/Tube |
| MAX1554ETA+T | 功能描述:LED照明驅(qū)動(dòng)器 40V StepUp Converter for 2-10 White LEDs RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| 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照明驅(qū)動(dòng)器 40V StepUp Converter for 2-10 White LEDs RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| MAX1555EZK | 制造商:Maxim Integrated Products 功能描述:SOT-23 DUAL-INPUT USB/AC ADAPTER 1- - Cut Tape Product |
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