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)： 25/32頁(yè)
文件大小： 796K
代理商： MAX1889
Additional Application Circuits
Operation with Output Voltage >13V
The maximum output voltage of the step-up regulator is
13V, which is limited by the absolute maximum rating of
the internal power MOSFET. To achieve higher output
voltage, an external N-channel MOSFET can be cas-
coded with the internal FET (Figure 9). Since the gate of
the external FET is biased from the input supply, use a
logic-level FET to ensure that the FET is fully enhanced
at the minimum input voltage. The current rating of the
FET needs to be higher than the internal current limit.
Changing Power-Up Sequence
The power-up sequencing of the linear regulators can be
controlled using external delays. Figure 10 shows an
application where the negative linear-regulator output
powers up with a certain delay after the positive linear
regulator reaches regulation. The resistors R1, R2, and
the capacitor C form an RC network that provides the
power-up delay. The time constant of this RC network is:
Select the ratio of R1 and R2 so that:
or:
With this R1/R2 ratio, the power-up delay can be calcu-
lated as:
where V
D
is the forward voltage drop of the diode and
0.125V is the FBN regulation point.
As a design example, assume the positive linear-regu-
lator output V
PL
is +20V, the negative charge-pump
output V
N
is -9V, and the required power-up delay time
t
D
is 4ms:
The ratio of R1 and R2 R
R
2
The required RC time constant is:
Choose C = 0.1μF, then R1//R2 = 16.8k
. Use stan-
dard resistor values: R1 = 56k
and R2 = 24k
.
Disabling Input MOSFET Switch
If the input protection MOSFET is not needed, disable
the input overcurrent comparator by connecting the
OCP pin to ground, the OCN pin to V
IN
. Leave the
GATE pin floating (Figure 11).
Generating Gamma Reference Voltage
The reference voltage for the Gamma correction resis-
tor string can be produced using the linear-regulator
controller. If the voltage difference between the main
boost voltage (V
MAIN
) and the Gamma reference volt-
age is 400mV or greater, the emitter of the PNP pass
transistor should be connected to V
MAIN
.
τ =
+
=
4
20
9
20
-
9
0 7 0 125
.
1 68
.
ms
ms
ln
.
1
9
20
=
τ
τ
D
PL
V
V
D
R
+
R
0 125
R
V
=
ln
.
1
1
2
-
R
R
V
V
N
PL
1
2
=
-
V
R
+
R
R
V
R
+
R
R
N
PL
2
1
2
1
1
2
0
+
=
τ =
×
+
R
R
R
R
C
1
1
2
2
M
Triple-Output TFT LCD Power Supply
with Fault Protection
______________________________________________________________________________________
25
STEP-UP
REGULATOR
LX
FB
PGND
MAX1889
V
N
V
P
V
MAIN
15V
V
IN
Figure 9. Operation with Output Voltage >13V Using Cascoded
MOSFET
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相關(guān)代理商/技術(shù)參數(shù)
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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