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| 型号： | LTC3208EUH#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 17/24页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVR QVGA DISPLAY 32-QFN |
| 标准包装： | 2,500 |
| 拓扑： | 升压（升压），切换式电容器（充电泵） |
| 输出数： | 17 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | RGB，白色 LED |
| 频率： | 600kHz ~ 1.2MHz |
| 电源电压： | 2.9 V ~ 4.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-QFN |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
LTC3208
APPLICATIO S I FOR ATIO
V RIPPLE P ? P =
3 f OSC CPO
(3)
V BAT , CPO Capacitor Selection
The value and type of capacitors used with the LTC3208
determine several important parameters such as regulator
control loop stability, output ripple, charge pump strength
and minimum start-up time.
To reduce noise and ripple, it is recommended that low
equivalent series resistance (ESR) ceramic capacitors are
used for both CV BAT and C CPO . Tantalum and aluminum
capacitors are not recommended due to high ESR.
The value of C CPO directly controls the amount of output
ripple for a given load current. Increasing the size of C CPO
will reduce output ripple at the expense of higher start-up
current. The peak-to-peak output ripple of the 1.5X mode
is approximately given by the expression
I OUT
? C
Where f OSC is the LTC3208 oscillator frequency or typically
900kHz and C CPO is the output storage capacitor.
The output ripple in 2x mode is very small due to the fact
that load current is supplied on both cycles of the clock.
Both value and type of output capacitor can signi?cantly
affect the stability of the LTC3208. As shown in the block
diagram, the LTC3208 uses a control loop to adjust the
strength of the charge pump to match the required output
current. The error signal of the loop is stored directly on the
output capacitor. The output capacitor also serves as the
dominant pole for the control loop. To prevent ringing or
instability, it is important for the output capacitor to maintain
at least 2.2μF of capacitance over all conditions.
In addition, excessive output capacitor ESR will tend to
degrade the loop stability. The closed loop output resis-
tance is about 80m . For a 100mA load current change,
the error signal will change by about 8mV. If the output
capacitor has 80m or more of ESR, the closed loop fre-
quency response will cease to roll off in a simple one-pole
fashion and poor load transient response or instability may
occur. Multilayer ceramic chip capacitors typically have
exceptional ESR performance. MLCCs combined with a
tight board layout will result in very good stability. As the
value of C CPO controls the amount of output ripple, the
value of CV BAT controls the amount of ripple present at
the input pin (V BAT ). The LTC3208 input current will be
relatively constant while the charge pump is either in 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 (~25ns), these missing “notches”
will result in only a small perturbation on the input power
supply line. Note that a higher ESR capacitor such as tan-
talum will have higher input noise due to the higher ESR.
Therefore, ceramic capacitors are recommended for low
ESR. Input noise can be further reduced by powering the
LTC3208 through a very small series inductor as shown
in Figure 6. 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 be fabricated on the PC board with about 1cm (0.4”)
of PC board trace.
V BAT
LTC3208
GND
3208 F06
Figure 6. 10nH Inductor Used for Input Noise Reduction
(Approximately 1cm of Board Trace)
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
LTC3208. Ceramic capacitors should always be used for
the ?ying capacitors.
The ?ying capacitors control the strength of the charge
pump. In order to achieve the rated output current it is
necessary to have 2.2μF of capacitance for each of the
?ying capacitors. 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
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
3208fa
17
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相关代理商/技术参数 |
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| LTC3209-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:600mA Main/Camera LED Controller |
| LTC3209-2 | 制造商:LINER 制造商全称:Linear Technology 功能描述:600mA Main/Camera LED Controller |
| LTC3209EUF-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:600mA Main/Camera LED Controller |
| LTC3209EUF-1#PBF | 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 |
| LTC3209EUF-1#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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