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參數(shù)資料
| 型號： | MAX1518B |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | DC/DC變換器 |
| 英文描述： | TFT-LCD DC-DC Converter with Operational Amplifiers |
| 中文描述： | TFT-LCD DC-DC轉(zhuǎn)換器，帶有運(yùn)算放大器 |
| 文件頁數(shù)： | 15/25頁 |
| 文件大?。?/td> | 1308K |
| 代理商： | MAX1518B |
M
TFT-LCD DC-DC Converter with
Operational Amplifiers
______________________________________________________________________________________
15
Gate-Off Linear-Regulator Controller, REG N
The gate-off linear-regulator controller (REG N) is an
analog gain block with an open-drain p-channel output.
It drives an external npn pass transistor with a 6.8k
base-to-emitter resistor (Figure 1). Its guaranteed base-
drive source current is at least 1mA. The regulator
including Q2 in Figure 1 uses a 0.47μF ceramic output
capacitor and is designed to deliver 50mA at -8V. Other
output voltages and currents are possible with the proper
pass transistor and output capacitor (see the
Pass-
Transistor Selection
and
Stability Requirements
sections).
REG N is typically used to provide the TFT-LCD gate
drivers’ gate-off voltage. A negative voltage can be
produced using a charge-pump circuit as shown in
Figure 1. REG N is enabled after the voltage on REF
exceeds 1.0V. Each time it is enabled, the control goes
through a soft-start routine that ramps down its internal
reference DAC from V
REF
to 250mV in 128 steps.
Operational Amplifiers
The MAX1518B has five operational amplifiers. The oper-
ational amplifiers are typically used to drive the LCD
backplane (VCOM) or the gamma-correction divider
string. They feature
±
150mA output short-circuit current,
13V/μs slew rate, and 12MHz bandwidth. The rail-to-rail
input and output capability maximizes system flexibility.
Short-Circuit Current Limit
The operational amplifiers limit short-circuit current to
approximately
±
150mA if the output is directly shorted to
SUP or to BGND. If the short-circuit condition persists, the
junction temperature of the IC rises until it reaches the
thermal-shutdown threshold (+160
°
C typ). Once the junc-
tion temperature reaches the thermal-shutdown threshold,
an internal thermal sensor immediately sets the thermal
fault latch, shutting off all the IC’s outputs. The device
remains inactive until the input voltage is cycled.
Driving Pure Capacitive Load
The operational amplifiers are typically used to drive
the LCD backplane (VCOM) or the gamma-correction
divider string. The LCD backplane consists of a distrib-
uted series capacitance and resistance, a load that can
be easily driven by the operational amplifier. However,
if the operational amplifier is used in an application with
a pure capacitive load, steps must be taken to ensure
stable operation.
As the operational amplifier’s capacitive load increases,
the amplifier’s bandwidth decreases and gain peaking
increases. A 5
to 50
small resistor placed between
OUT_ and the capacitive load reduces peaking but also
reduces the gain. An alternative method of reducing
peaking is to place a series RC network (snubber) in par-
allel with the capacitive load. The RC network does not
continuously load the output or reduce the gain. Typical
values of the resistor are between 100
and 200
, and
the typical value of the capacitor is 10nF.
MAX1518B
DRVP
FBP
V
MAIN
FROM CHARGE-PUMP
OUTPUT
NPN CASCODE
TRANSISTOR
PNP PASS
TRANSISTOR
V
GON
Figure 4. Using Cascoded npn for Charge-Pump Output
Voltages > 28V
MAX1518B
DRVP
FBP
V
GON
35V
LX
V
MAIN
13V
0.22
μ
F
0.1
μ
F
0.1
μ
F
0.47
μ
F
267k
1%
10.0k
1%
6.8k
Q1
Figure 5. The linear regulator controls the intermediate charge-
pump stage.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1518BETJ+ | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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 |
| MAX1518BETJ+T | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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 |
| MAX1518ETJ | 功能描述:LCD 驅(qū)動器 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 |
| MAX1518ETJ+ | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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 |
| MAX1518ETJ+T | 功能描述:LCD 驅(qū)動器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率: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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