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| 型号： | LTC3218EDDB#TRMPBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR FLASH TORCH 10DFN |
| 标准包装： | 500 |
| 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： | 闪灯/白光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 1MHz |
| 电源电压： | 2.9 V ~ 4.5 V |
| 输出电压： | 5.3V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 供应商设备封装： | 10-DFN-EP（3x2） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
LTC3218
APPLICATIONS INFORMATION
performance. MLCCs combined with a tight board layout
will yield very good stability. As the value of C CPO controls
the amount of output ripple, the value of C VIN controls the
amount of ripple present at the input pin (V IN ). The input
current to the LTC3218 will be relatively constant while
the charge pump is on either the input charging phase or
the output charging phase but will drop to zero during
the clock nonoverlap times. Since the nonoverlap time
is small (~15ns), these missing “notches” will result in
only a small perturbation on the input power supply line.
Note that a higher ESR capacitor such as tantalum will
have higher input noise due to the input current change
times the ESR. Therefore, ceramic capacitors are again
recommended for their exceptional ESR performance. Input
noise can be further reduced by powering the LTC3218
through a very small series inductor as shown in Figure 2.
A 10nH inductor will reject the fast current notches,
thereby presenting a nearly constant current load to the
input power supply. For economy, the 10nH inductor can
to 85°C whereas a Z5U or Y5V style capacitor will lose
considerable capacitance over that range. Z5U and Y5V
capacitors may also have a very poor voltage coef?cient
causing them to lose 60% or more of their capacitance when
the rated voltage is applied. Therefore, when comparing
different capacitors, it is often more appropriate to compare
the amount of achievable capacitance for a given case size
rather than comparing the speci?ed capacitance value. For
example, over rated voltage and temperature conditions,
a 1μF, 10V, Y5V ceramic capacitor in a 0603 case may not
provide any more capacitance than a 0.22μF, 10V, X7R
available in the same case. The capacitor manufacturer’s
data sheet should be consulted to determine what value
of capacitor is needed to ensure minimum capacitances
at all temperatures and voltages.
Table 1 shows a list of ceramic capacitor manufacturers
and how to contact them.
Table 1. Recommended Capacitor Vendors
be fabricated on the PC board with about 1cm (0.4 ? ) of
PC board trace.
AVX
Kemet
Murata
www.avxcorp.com
www.kemet.com
www.murata.com
10nH
V IN
Taiyo Yuden
Vishay
www.t-yuden.com
www.vishay.com
0.1μF
2.2μF
LTC3218
TDK
www.tdk.com
GND
3218 F02
Figure 2. 10nH Inductor Used for Input Noise Reduction
(Approximately 1cm of Wire)
Flying Capacitor Selection
Warning: Polarized capacitors such as tantalum or
aluminum should never be used for the ?ying capaci-
tors since their voltage can reverse upon start-up of the
LTC3218. Ceramic capacitors should always be used for
the ?ying capacitors.
The ?ying capacitor controls the strength of the charge
pump. In order to achieve the rated output current it is
necessary to have at least 1.6μF of actual capacitance for
the ?ying capacitor. Capacitors of different materials lose
their capacitance with higher temperature and voltage at
different rates. For example, a ceramic capacitor made of
X7R material will retain most of its capacitance from –40°C
Layout Considerations and Noise
Due to the high switching frequency and the transient
currents produced by the LTC3218, careful board layout
is necessary. A true ground plane and short connections
to all capacitors will improve performance and ensure
proper regulation under all conditions. An example of
such a layout is shown in Figure 3.
The ?ying capacitor pins, CP and CM, will have very high
edge rate waveforms. The large dv/dt on these pins can
couple energy capacitively to adjacent PCB runs. Magnetic
?elds can also be generated if the ?ying capacitors are
not close to the LTC3218 (i.e., the loop area is large).
To decouple capacitive energy transfer, a Faraday shield
may be used. This is a grounded PCB trace between the
sensitive node and the LTC3218 pins. For a high quality
AC ground, it should be returned to a solid ground plane
that extends all the way to the LTC3218.
3218fb
9
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| LTC3219EUD#TRPBF | 功能描述:IC LED DRIVR QVGA DISPLAY 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
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