- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385481 > LM3552SD (NATIONAL SEMICONDUCTOR CORP) 1A White LED Driver with Flash Timeout Protection PDF資料下載
參數(shù)資料
| 型號： | LM3552SD |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 顯示驅(qū)動器 |
| 英文描述： | 1A White LED Driver with Flash Timeout Protection |
| 中文描述： | LED DISPLAY DRIVER, QCC14 |
| 封裝： | 4 X 4 MM, LLP-24 |
| 文件頁數(shù)： | 12/15頁 |
| 文件大?。?/td> | 756K |
| 代理商： | LM3552SD |
Application Information
(Continued)
tance loss due to capacitor voltage coefficient. See the
capacitor manufacturer’s datasheet for DC bias perfor-
mance.
COMPENSATION
DC Gain and Open-Loop Gain
Since the control stage of the converter forms a complete
feedback loop with the power components, it forms a closed-
loop system that must be stabilized to avoid positive feed-
back and instability. A value for open-loop DC gain will be
required, from which you can calculate, or place, poles and
zeros to determine the crossover frequency and the phase
margin. A high phase margin (greater than 45) is desired for
the best stability and transient response. For the purpose of
stabilizing the LM3551/2, choosing a crossover point well
below where the right half plane zero is located will ensure
sufficient phase margin.
To ensure a bandwidth of
1
2
or less of the frequency of the
RHP zero, calculate the open-loop DC gain, A
. After this
value is known, you can calculate the crossover visually by
placing a 20dB/decade slope at each pole, and a +20dB/
decade slope for each zero. The point at which the gain plot
crosses unity gain, or 0dB, is the crossover frequency. If the
crossover frequency is less than
1
2
the RHP zero, the phase
margin should be high enough for stability. The equation for
A
DC
is given below with additional equations required for the
calculation:
mc
)
0.072 x fs (in V/s)
where R
is the minimum load resistance, fs is the switching
frequency, V
is the minimum input voltage, g
is the error
amplifier transconductance and R
is the power switch
on-resistance. The value for g
and R
DSON-S
are found in
the
Electrical Characteristics
table.
Right Half Plane Zero
A current mode control boost regulator has an inherent right
half plane zero (RHP zero). This zero has the effect of a zero
in the gain plot, causing an imposed +20dB/decade on the
rolloff, but has the effect of a pole in the phase, subtracting
another 90 in the phase plot. This can cause undesirable
effects if the control loop is influenced by this zero. To ensure
the RHP zero does not cause instability issues, the control
loop should be designed to have a bandwidth of less than
1
2
the frequency of the RHP zero. This zero occurs at a fre-
quency of:
where I
LOAD
is the maximum load current.
Compensation Components
The LM3551 and LM3552 provide a compensation pin (V
C
)
to customize the voltage loop feedback. It is recommended
that a series combination of R
C
and C
C
be used for the
compensation network, as shown in the typical application
circuit. For any given application, there exists a unique com-
bination of R
C
and C
C
that will optimize the performance of
the LM3551/2 circuit in terms of its transient response. The
series combination of R
and C
introduces a pole-zero pair.
The frequency of the pole created is determined by the
equation:
where R
is the output impedance of the error amplifier,
approximately 900k
. Since R
is generally much less than
R
, it has little effect on the above equation and can be
neglected until a value is chosen to set the zero f
. f
is
created to cancel the pole created by the output capacitor,
f
. The output capacitor pole will shift with different load
currents as shown by the equation, so setting the zero is not
exact. Determine the range of f
over the expected loads
and then set the zero f
to a point approximately in the
middle. The frequency of this zero is determined by:
Now R
can be chosen with the selected value for C
.
Check to make sure that the pole f
is still in the 10Hz to
500Hz range, and change each value slightly if needed to
ensure both component values are in the recommended
range. For both typical applications circuits shown on the
front page, the
Recommended value for C
C
is 4.7nF and
R
C
= 10k
for Lumiled applications. 10nF and 27k
are
recommended for Sharp applications.
RECOMMENDED MINIMUM COMPONENT
SPECIFICATIONS
Component
Value
Ratings
2.0A 30% I
SAT
Rating
10V X5R or
X7R
L1
4.7μH
C
IN
4.7μF (Sharp)
10μF (Lumiled)
4.7μF (Sharp)
10uF (Lumiled)
User
Determined
C
OUT
16V X5R or
X7R
6.3V X5R or
X7R
C
FTO
L
www.national.com
12
相關PDF資料 |
PDF描述 |
|---|---|
| LM3552SDX | 1A White LED Driver with Flash Timeout Protection |
| LM3552 | 1A White LED Driver with Flash Timeout Protection |
| LM3551 | 1A White LED Driver with Flash Timeout Protection |
| LM3595 | The LM3595 is a parallel white-LED driver that is capable of driving four white LEDs. |
| LM3595LD | The LM3595 is a parallel white-LED driver that is capable of driving four white LEDs. |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM3552SD/NOPB | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| LM3552SDEV | 功能描述:電源管理IC開發(fā)工具 LM3552SD EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| LM3552SDX | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| LM3552SDX/NOPB | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| LM3553 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1.2A Dual Flash LED Driver System with I2C Compatible |
發(fā)布緊急采購，3分鐘左右您將得到回復。