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参数资料
| 型号： | LTC3220IPF#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/20页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR QVGA DISPLAY 28UTQFN |
| 标准包装： | 91 |
| 拓扑： | 开路漏极，升压（升压），切换式电容器（充电泵） |
| 输出数： | 18 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | LED 闪烁器 |
| 频率： | 850kHz ~ 1.05MHz |
| 电源电压： | 2.9 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-UFQFN 裸露焊盘 |
| 供应商设备封装： | 28-UTQFN（4x4）裸露焊盘 |
| 包装： | 管件 |
| 工作温度： | -40°C ~ 125°C |
LTC3220/LTC3220-1
OPERATION
Power Management
The LTC3220/LTC3220-1 use a switched capacitor charge
pump to boost CPO as much as 2 times the input voltage
up to 5.1V. The part starts up in 1x mode. In this mode,
V IN is connected directly to CPO. This mode provides
maximum ef?ciency and minimum noise. The LTC3220/
LTC3220-1 will remain in 1x mode until an LED current
source drops out. Dropout occurs when a current source
voltage becomes too low for the programmed current
to be supplied. When dropout is detected, the LTC3220/
LTC3220-1 will switch into 1.5x mode. The CPO voltage
will then start to increase and will attempt to reach 1.5 ×
V IN up to 4.6V. Any subsequent dropout will cause the
part to enter the 2x mode. The CPO voltage will attempt
to reach 2 × V IN up to 5.1V.
A 2-phase non-overlapping clock activates the charge
pump switches. In the 2x mode the ?ying capacitors are
charged on alternate clock phases from V IN to minimize
CPO voltage ripple. In 1.5x mode the ?ying capacitors are
charged in series during the ?rst clock phase and stacked
in parallel on V IN during the second phase. This sequence
of charging and discharging the ?ying capacitors continues
at a constant frequency of 850kHz.
The current delivered by each LED current source is con-
trolled by an associated DAC. Each DAC is programmed
via the I 2 C port.
R OL
Soft-Start
Initially, when the part is in shutdown, a weak switch
connects V IN to CPO. This allows V IN to slowly charge the
CPO output capacitor and prevent large charging currents
from occurring.
The LTC3220/LTC3220-1 also employ a soft-start feature
on the charge pump to prevent excessive inrush current
and supply droop when switching into the step-up modes.
The current available to the CPO pin is increased linearly
over a typical period of 125μs. Soft-start occurs at the
start of both 1.5x and 2x mode changes.
Charge Pump Strength
When the LTC3220/LTC3220-1 operate in either 1.5x mode
or 2x mode, the charge pump can be modeled as a Theve-
nin-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 resis-
tances and the non-overlap period of the switching circuit.
However, for a given R OL , the amount of current available
will be directly proportional to the advantage voltage of
1.5V IN – CPO for 1.5x mode and 2V IN – CPO for 2x mode.
Consider the example of driving LEDs from a 3.1V supply.
+
–
+
1.5V IN OR
2V IN
CPO
–
3220 F01
Figure 1. Charge Pump Open-Loop Thevenin Equivalent Circuit
32201fc
8
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相关代理商/技术参数 |
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| LTC3220IPF-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:360mA Universal 18-Channel LED Driver |
| LTC3221 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower, Regulated Charge Pump in 2 】 2 DFN |
| LTC3221-3.3 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower, Regulated Charge Pump in 2 】 2 DFN |
| LTC3221-5 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower, Regulated Charge Pump in 2 】 2 DFN |
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