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參數(shù)資料
| 型號： | LX1992CDU |
| 廠商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分類： | 顯示驅(qū)動器 |
| 英文描述： | High Efficiency LED Driver |
| 中文描述： | LED DISPLAY DRIVER, PDSO8 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 6/11頁 |
| 文件大小： | 335K |
| 代理商： | LX1992CDU |
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
Copyright
2000
Rev. 1.1b, 2005-03-03
W
M
.
C
LX1992
High Efficiency LED Driver
P
RODUCTION
D
ATA
S
HEET
TM
A P P L I C A T I O N I N F O R M A T I O N
formula for
V
DROOP
is:
(
)
(
)
0.5
V
I
I
C
L
V
IN
OUT
PK
OUT
DROOP
×
×
=
The output overshoot can be estimated as follows where the
0.5 value in the denominator is an estimate of the voltage
drop across the diode:
×
=
(
)
(
)
IN
OUT
V
2
OUT
PK
OUT
2
1
OVERSHOOT
V
V
0.5
I
I
C
L
+
×
D
ESIGN
E
XAMPLE
:
Determine the V
RIPPLE
where I
PK
equals 200mA, I
OUT
equals 12.8mA, L equals 47
μ
H, C
OUT
equals 4.7
μ
F, V
IN
equals 3.0V, and V
OUT
equals 13.0V:
(
)
(
0
)
mV
2
10
5
mA
8
12
mA
200
μ
F
7
μ
H
47
V
DROOP
×
×
=
(
)
(
)
mV
4
18
0
0.5
0
13
mA
8
12
mA
200
F
4.7
H
μ
47
V
2
2
1
OVERSHOOT
+
×
μ
×
=
Therefore
,
V
RIPPLE
=
10.2mV + 18.4mV + 10mV = 38.6mV
D
IODE
S
ELECTION
A Schottky diode is recommended for most applications
(e.g. Microsemi UPS5817). The low forward voltage drop
and fast recovery time associated with this device supports
the switching demands associated with this circuit
topology. The designer is encouraged to consider the
diode’s average and peak current ratings with respect to
the application’s output and peak inductor current
requirements. Further, the diode’s reverse breakdown
voltage characteristic must be capable of withstanding a
negative voltage transition that is greater than V
OUT
.
T
RANSISTOR
S
ELECTION
The LX1992 can source up to 100mA of gate current.
An N-channel MOSFET with a relatively low threshold
voltage, low gate charge and low R
DS(ON)
is required to
optimize overall circuit performance. The LXE1992
Evaluation Board uses a Fairchild FDV303. This NMOS
device was chosen because it demonstrates an R
DS_ON
of
0.33
and a total gate charge Q
g
of 1.64nC (typ.)
PCB
L
AYOUT
The LX1992 produces high slew-rate voltage and current
waveforms hence; the designer should take this into
consideration when laying out the circuit. Minimizing trace
lengths from the IC to the inductor, transistor, diode, input
and output capacitors, and feedback connection (i.e., pin 6)
are typical considerations. Moreover, the designer should
maximize the DC input and output trace widths to
accommodate peak current levels associated with this
topology.
E
VALUATION
B
OARD
The LXE1992 evaluation board is available from
Microsemi
for assessing overall circuit performance. The
evaluation board, shown in Figure 3, is 3 by 3 inches (i.e.,
7.6 by 7.6cm) square and programmed to drive 4 LEDs
(provided). Designers can easily modify circuit parameters
to suit their particular application by replacing R
CS
(as
described in this section) R
SET
(i.e., R4) and diode load.
Moreover, the inductor, FET, and switching diode are easily
swapped out to promote design verification of a circuit that
maximizes efficiency and minimizes cost for a specific
application. The evaluation board input and output
connections are described in Table 1.
The DC input voltage is applied to VBAT (not VCC)
however the LX1992 IC may be driven from a separate DC
source via the VCC input. The output current (i.e., LED
brightness) is controlled by adjusting the on-board
potentiometer. The designer may elect to drive the
brightness adjustment circuit from VBAT or via a separate
voltage source by selecting the appropriate jumper position
(see Table 2). Optional external adjustment of the output
LED current is achieved by disengaging the potentiometer
and applying either a DC voltage or a PWM-type signal to
the VADJ input. The PWM signal frequency should be
higher than 150KHz and contain a DC component les than
350mV.
The LX1992 exhibits a low quiescent current (I
Q
< 0.5
μ
A:
typ) during shutdown mode. The SHDN pin is used to
exercise the shutdown function on the evaluation board.
This pin is pulled-up to VCC via a 10K
resistor.
Grounding the SHDN pin shuts down the IC (not the circuit
output). The output voltage (i.e., voltage across the LED
string) is readily measured at the VOUT terminal and LED
current is derived from measuring the voltage at the VFDBK
pin and dividing this value by 15
(i.e., R4).
The factory installed component list for this must-have
design tool is provided in Table 3 and the schematic is shown
in Figure 4
A
P
P
L
I
C
A
T
I
O
N
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| LX1992CLM | High Efficiency LED Driver |
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| LX2203A | Li-Ion Battery Charger |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LX1992-CDU | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Driver |
| LX1992CDU-TR | 制造商:Microsemi Corporation 功能描述:LED DRVR 4SEGMENT 1.6V TO 6V 8MSOP IN TUBES - Bulk |
| LX1992CLM | 功能描述:IC LED DRIVR WT/CLR BCKLGT 8-MLP RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 恒定電流:- 恒定電壓:- 拓?fù)?PWM，切換式電容器（充電泵） 輸出數(shù):1 內(nèi)部驅(qū)動器:是 類型 - 主要:背光 類型 - 次要:白色 LED 頻率:642kHz 電源電壓:2.7 V ~ 5.5 V 輸出電壓:5V 安裝類型:表面貼裝 封裝/外殼:10-VFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:10-VSON 包裝:剪切帶 (CT) 工作溫度:-30°C ~ 85°C 產(chǎn)品目錄頁面:1371 (CN2011-ZH PDF) 其它名稱:BD1603NUV-E2CT |
| LX1992-CLM | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Driver |
| LX1992EVALKIT | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Driver |
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