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参数资料
| 型号： | LTC3203EDD-1#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BOOST SWITCHED CAP 10DFN |
| 标准包装： | 121 |
| 类型： | 升压（升压），切换电容（充电泵） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 4.5V |
| 输入电压： | 2.7 V ~ 5.5 V |
| PWM 型： | Burst Mode? |
| 频率 - 开关： | 900kHz，1MHz |
| 电流 - 输出： | 500mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 10-DFN（3x3） |
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
APPLICATIO S I FOR ATIO
V IN MODEL ? ? MODE 1 + 1 ?
= V
1 . 5 ? V MODEL ? ? MODE 1 + 1 ?
resistorR X .Thus,thisconfigurationwillhavethehighest
loop gain giving it the lowest closed-loop output resis-
tance. Likewise it will also require the largest amount of
output capacitance to preserve stability.
Effective Open Loop Output Resistance (R OL )
The effective open loop output resistance (R OL ) of a
charge pump is a very important parameter, which deter-
mines its strength. The value of this parameter depends on
many factors such as the oscillator frequency (f OSC ), the
value of the flying capacitor (C FLY ), the non-overlap time,
the internal switch resistances (R S ), and the ESR of the
external capacitors.
Maximum Available Output Current
Figure 3 shows how the LTC3203/LTC3203-1/LTC3203B/
LTC3203B-1 can be modeled as a Thevenin-equivalent
circuit.
Thus the maximum available output current and voltage
can be calculated from the effective open-loop output
resistance, R OL , and the effective output voltage, 1.5V IN
(in 1.5x mode) or 2V IN (in 2x mode). From Figure 3, the
available current is given by:
Programming the MODE Pin
By connecting a resistor divider to the MODE pin, the V IN
voltage at which the chip switches modes can be accu-
rately programmed.
When V IN ramps up, the voltage at the MODE pin crosses
V MODEH and the chip switches from 2x mode to 1.5x mode.
When V IN starts to drop, the voltage at the MODE pin
crosses V MODEL and the chip switches back to 2x mode.
The MODE pin resistor ratio must be selected such that at
the switch point the output is still able to maintain regula-
tion at maximum I OUT :
1.5 ? V IN(1.5x) – V OUT > I OUT ? R OL(1.5X)
The minimum V IN operating in 1.5x mode occurs at the
switch point where:
? R ?
? R MODE 2 ?
therefore:
? R ?
? R MODE 2 ?
R MODE 1 V OUT ( M I N ) + R OL ( 1 . 5 x )( MAX ) ? I OUT ( MAX )
I OUT =
I OUT =
1.5 V IN ? V OUT
R OL
2 V IN ? V OUT
R OL
In 1 . 5 x mod e
In 2 x mod e
> R OL ( 1 . 5 X )( M A X ) ? I OUT ( MAX ) + V OUT ( MIN )
>
R MODE 2 1 . 5 ? V MODEL
– 1
As evident from the above two equations, with the same
V IN and R OL , the 2x mode will give more output current
than the 1.5x mode.
V IN
LTC3203/
LTC3203B
MODE
7
6
R MODE1
C IN
R MODE2
1.5V IN
OR
2V IN
+
–
R OL
+
V OUT
GND
9, 11
Figure 4
3203 F04
–
3203 F03
Figure 3. Charge Pump Open-Loop Thevenin-Equivalent Circuit
32031fa
11
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| LTC3204 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low Noise Regulated Charge Pump in 2 X 2 DFN |
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