參數(shù)資料
型號(hào)： MAX1889
廠商： Maxim Integrated Products, Inc.
元件分類： 數(shù)字信號(hào)處理
英文描述： Fixed-Point Digital Signal Processor 256-BGA
中文描述： 三輸出TFT LCD電源，帶有故障保護(hù)
文件頁(yè)數(shù)： 21/32頁(yè)
文件大?。?/td> 796K
代理商： MAX1889
M
Triple-Output TFT LCD Power Supply
with Fault Protection
______________________________________________________________________________________
21
The number of negative charge-pump stages is given by:
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:
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:
where N is the stage number in which the flying capaci-
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
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
output voltage ripple is dominated by the capacitance
value. Use the following equation to approximate the
required capacitor value:
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]
where V
FBP
= 1.25V.
Adjust the negative linear-regulator output voltage by
connecting a resistive voltage-divider from V
NL
to REF
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:
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.
R
V
V
V
V
R
A
MAIN
-
REF
REF
FBN
14
10
40
=
μ
-
-
C
I
f
OUT
LOAD
OSC RIPPLE
≥
2
V
N V
CX
MAIN
>
N
V
V
V
V
V
N
V
V
V
V
V
POS
PL
DROPOUT
MAIN
DROPOUT
MAIN
IN
D
NEG
NL
IN
D
=
+
×
=
+
+
×
-
-
-
-
2
2
N
V
V
V
V
NEG
NL
MAIN
DOPOUT
×
-2
D
=
+
-
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參數(shù)描述
MAX1889EGE 制造商:Maxim Integrated Products 功能描述:
MAX1889EGE+ 制造商:Maxim Integrated Products 功能描述:TRIPLE-OUTPUT TFT LCD POWER SUPPLY WITH FAULT PROTECTION - Rail/Tube
MAX1889ETE 功能描述:LCD 驅(qū)動(dòng)器 RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時(shí)鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube
MAX1889ETE+ 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Quad-Output TFT LCD Power Supply RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
MAX1889ETE+T 功能描述:LCD 驅(qū)動(dòng)器 Quad-Output TFT LCD Power Supply RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時(shí)鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube
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