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| 型号： | MAX1889ETE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 21/32页 |
| 文件大小： | 0K |
| 描述： | IC PWR SUP TRPL LCD 16-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 控制器，TFT LCD |
| 输入电压： | 2.7 V ~ 5.5 V |
| 输出数： | 3 |
| 输出电压： | 2.7 V ~ 13 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-WQFN 裸露焊盘 |
| 供应商设备封装： | 16-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
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Triple-Output TFT LCD Power Supply
with Fault Protection
N NEG =
C OUT ≥
N POS = PL DROPOUT IN
The number of negative charge-pump stages is given by:
-V NL + V DOPOUT
V MAIN - 2 × V D
where N NEG is the number of negative charge-pump
stages, V NL is the negative linear-regulator output,
V MAIN is the main step-up regulator output, V D is the
forward voltage drop of the charge-pump diode, and
V DROPOUT is the dropout margin for the linear regulator.
Use V DROPOUT = 2V.
The above equations are derived based on the
assumption that the first stage of the positive charge
pump is connected to V MAIN and the first stage of the
negative charge pump is connected to ground.
Sometimes fractional stages are more desirable for bet-
ter efficiency. This can be done by connecting the first
stage to V IN or another available supply.
If the first charge-pump stage is powered from V IN ,
then the above equations become:
V + V - V
V MAIN - 2 × V D
output voltage ripple is dominated by the capacitance
value. Use the following equation to approximate the
required capacitor value:
I LOAD
2 f OSC V RIPPLE
where V RIPPLE is the peak-to-peak value of the output
ripple.
Charge-Pump Rectifier Diodes
Use Schottky diodes with a current rating equal to or
greater than two times the average charge-pump input
current.
Linear-Regulator Controllers
Output Voltage Selection
Adjust the positive linear-regulator output voltage by
connecting a resistive voltage-divider from V PL to GND
with the center tap connected to FBP (Figure 1). Select
R13 in the range of 10k ? to 30k ? .
Calculate R12 with the following equation:
R12 = R13 [(V PL / V FBP ) - 1]
N NEG =
- V NL + V DROPOUT + V IN
V MAIN - 2 × V D
where V FBP = 1.25V.
Adjust the negative linear-regulator output voltage by
connecting a resistive voltage-divider from V NL to REF
Flying Capacitor
Increasing the flying capacitor (C X ) value increases the
output current capability. Increasing the capacitance
indefinitely has a negligible effect on output current
capability because the internal switch resistance and
the diode impedance limit the source impedance. A
0.1μF ceramic capacitor works well in most low-current
applications. The flying capacitor ’ s voltage rating must
exceed the following:
V CX > N × V MAIN
where N is the stage number in which the flying capaci-
with the center tap connected to FBN (Figure 1). Select
R10 in the range of 10k ? to 30k ? . Calculate R9 with the
following equation:
R9 = R10 [(V FBN - V NL ) / (V REF - V FBN )]
where V FBN = 125mV, V REF = 1.25V. Note that REF is
only guaranteed to source 50μA. Using a resistor less
than 20k ? for R10 results in higher bias current than
REF can supply. Connecting another resistor (R14)
from V MAIN to REF (Figure 1) can solve this problem
because the main output can supply part of the resis-
tor ’ s (R10) bias current. Use the following equation to
determine the value of R14:
? - 40 μ A
? V REF - V FBN ?
?
?
?
tor appears, and V MAIN is the main output voltage. For
example, the two-stage positive charge pump in the
typical application circuit (Figure 1) where V MAIN = 9V
contains two flying capacitors. The flying capacitor in
R 14 =
V MAIN - V REF
R 10
the first stage (C14) requires a voltage rating over 9V.
The flying capacitor in the second stage (C13) requires
a voltage rating over 18V.
Charge-Pump Output Capacitor
Increasing the output capacitance or decreasing the
ESR reduces the output ripple voltage and the peak-to-
peak transient voltage. With ceramic capacitors, the
Drawing only 40μA from REF leaves the remaining
10μA for other purposes.
Pass Transistor Selection
The pass transistor must meet specifications for current
gain ( β ), input capacitance, collector-emitter saturation
voltage, and power dissipation.
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| MAX1889EVKIT | 功能描述:电源管理IC开发工具 MAX1889 Eval Kit RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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