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| 型号： | LTC3208EUH#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/24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
OPERATIO
Soft-Start
For 2X mode, the available current is given by:
Initially, when the part is in shutdown, a weak switch con-
nects V BAT to CPO. This allows V BAT1,2 to slowly charge
the CPO output capacitor and prevent large charging
I OUT =
2V BAT – V CPO
R OL
(2)
currents to occur.
The LTC3208 also employs a soft-start feature on its charge
pump to prevent excessive inrush current and supply volt-
age droop when switching into the step-up modes. The
current available to the CPO pin is increased linearly over
a typical period of 150μs. Soft start occurs at the start of
both 1.5x and 2x mode changes.
Charge Pump Strength
When the LTC3208 operates in either 1.5x mode or 2x mode,
the charge pump can be modeled as a Thevenin-equivalent
circuit to determine the amount of current available from
the effective input voltage and effective open-loop output
resistance, R OL (Figure 1).
R OL is dependent on a number of factors including the
switching term, 1/(2f OSC ? C FLY ), internal switch resistances
Notice that the advantage voltage in the 2x case is
3.1V ? 2 – 3.8V – 0.1V = 2.3V. R OL is higher in 2x mode, but a
significant overall increase in available current is
achieved.
Typical values of R OL as a function of temperature are
shown in Figure 2 and Figure 3.
2.5
V BAT = 3V
V CPO = 4.2V
C2 = C3 = 2.2 μ F
2.3 C4 = 4.7 μ F
2.1
1.9
1.7
and the nonoverlap period of the switching circuit. However,
for a given R OL , the amount of current available will be
1.5
–40
–15
10 35
TEMPERATURE ( ° C)
60
85
directly proportional to the advantage voltage of 1.5V BAT
- CPO for 1.5x mode and 2V BAT -CPO for 2x mode. Consider
the example of driving white LEDs from a 3.1V supply. If
the LED forward voltage is 3.8V and the current sources
require 100mV, the advantage voltage for 1.5x mode is
3.1V ? 1.5 – 3.8V – 0.1V or 750mV. Notice that if the input
voltage is raised to 3.2V, the advantage voltage jumps to
900mV-a 20% improvement in available strength.
From Figure 1, for 1.5x mode the available current is
given by:
3208 F02
Figure 2. Typical 1.5x R OL vs Temperature
2.8
V BAT = 3V
V CPO = 4.8V
2.6 C2 = C3 = 2.2 μ F
C4 = 4.7 μ F
2.4
2.2
2.0
I OUT =
1.5V BAT – V CPO
R OL
(1)
1.8
1.6
R OL
+
–40
–15
10 35
TEMPERATURE ( ° C)
60
85
3208 F03
+
–
1.5V BAT OR 2V BAT
CPO
Figure 3. Typical 2x R OL vs Temperature
–
3208 F01
Figure 1. Charge Pump Thevenin–Equivalent Open-Loop Circuit
3208fa
10
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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